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The purpose of this investigation was to determine the effect of an acute bout of high-volume, full-body resistance training with an eccentric concentration on resting energy expenditure (REE) and indicators of delayed-onset muscle soreness (DOMS). Eight resistance trained (RT) and eight untrained (UT) participants (mean: age = 23.5 years; height = 180.76 cm; weight = 87.58 kg; body fat = 19.34%; lean mass = 68.71 kg) were measured on four consecutive mornings for REE and indicators of DOMS: creatine kinase (CK) and rating of perceived muscle soreness (RPMS). Delayed-onset muscle soreness was induced by performing eight exercises, eight sets, and six repetitions using a 1-second concentric and 3-second eccentric muscle action duration. A two-factor repeated-measures analysis of variance revealed that REE was significantly (p < 0.05) elevated at 24, 48, and 72 hours post compared with baseline measures for both UT and RT groups. Ratings of perceived muscle soreness were significantly elevated within groups for UT and RT at 24 and 48 hours post and for UT only at 72 hours post compared with baseline (p < 0.05). Nonparametric analyses revealed that CK was significantly increased at 24 hours post for both UT and RT and at 48 and 72 hours post for UT only compared with baseline (p < 0.05). Resting energy expenditure and indicators of DOMS were higher in UT compared with RT on all measures, but no significant differences were determined. The main finding of this investigation is that full-body resistance training with an eccentric concentration significantly increased REE up to 72 hours postexercise in UT and RT participants. [ABSTRACT FROM AUTHOR]

Electronic handgrip dynamometry allows for multiple muscle function aspects to be feasibly measured, yet their relationship with lower extremity muscle function is unknown. We sought to determine the relationships between upper and lower extremity mechanical isometric muscle strength, rate of force development (RFD), and endurance by limb dominance in resistance trained adults. The analytic sample included 30 adults aged 32.1 ± 13.5 years. An electronic handgrip dynamometer ascertained upper extremity strength capacity, RFD, and endurance. Lower extremity strength, RFD, and endurance were collected with the isometric feature on an isokinetic knee dynamometer. Limb dominance was self-reported. Pearson correlations were used for the analyses. Each muscle function attribute on the dominant limb of the upper and lower extremities were correlated: r = 0.76 ( p < 0.01) for strength, r = 0.37 ( p = 0.04) for RFD, and r = -0.48 ( p < 0.01) for endurance. Although strength from the non-dominant limbs were correlated ( r = 0.67; p < 0.01), no significant correlations were observed for RFD ( r = 0.20; p = 0.29) and endurance ( r = -0.21; p = 0.26). For adults aged 18-34 years, only upper and lower extremity strength was correlated on the dominant ( r = 0.69; p < 0.01) and non-dominant limbs ( r = 0.75; p < 0.01); however, strength ( r = 0.88; p < 0.01) and endurance ( r = -0.68; p = 0.01) were correlated in adults aged 35-70 years. Upper and lower extremity fatigability was likewise correlated in females ( r = -0.56; p = 0.01). Our findings suggest that electronic handgrip dynamometry derived strength, RFD, and endurance could be a whole-body indicator of these muscle function attributes given their relationships with the lower extremities. These findings underscore the promise of handgrip dynamometry in routine muscle function assessments across different age groups.

Disuse is associated with reduced muscle oxygen saturation (SmO 2 ). Improving oxygen delivery to tissues is important for healing, preventing muscle atrophy, and reducing the risk of deep vein thrombosis. Mobility devices are used during disuse periods to ambulate and protect the injured limb. This study examined SmO 2 in walking and ambulation with various mobility devices. Thirty-eight participants randomly completed four, ten-minute trials which included: (1) walking, (2) medical kneeling scooter (MKS), (3) hands-free crutch (HFC), and (4) axillary crutch (AC). During each trial, near infrared spectroscopy sensors were placed on the vastus lateralis (VL), biceps femoris (BF), and lateral gastrocnemius (LG) of the right limb. Compared to walking, all mobility devices showed a decline in SmO 2 in the VL of ∼10% (mean ± SD; 75% ± 12%-65% ± 17%, P  < 0.05). In the BF, SmO 2 declined ∼9% in AC compared to walking (76% ± 12%-67% ± 17%, P  = 0.025). In the LG, SmO 2 declined in AC (64% ± 16%) compared to MKS (70% ± 15%, P  = 0.005). There were no differences in LG SmO 2 compared to walking (69% ± 13%) in MKS ( P  > 0.05) or HFC (65% ± 15%, P  > 0.05). In young, healthy volunteers, the use of mobility devices altered muscle oxygenation in several muscles. AC reduced muscle oxygenation in the VL, BF, and LG; while MKS and HFC maintained BF and LG muscle oxygenation at a level consistent with ambulatory walking., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Bradley, Roehl, Smith, McGrath and Hackney.)

Abstract: McGrath, R, FitzSimmons, S, Andrew, S, Black, K, Bradley, A, Christensen, BK, Collins, K, Klawitter, L, Kieser, J, Langford, M, Orr, M, and Hackney, KJ. Prevalence and trends of weakness among middle-aged and older adults in the United States. J Strength Cond Res 37(12): 2484-2490, 2023-Muscle weakness, which is often determined with low handgrip strength (HGS), is associated with several adverse health conditions; however, the prevalence and trends of weakness in the United States is not well-understood. We sought to estimate the prevalence and trends of weakness in Americans aged at least 50 years. The total unweighted analytic sample included 22,895 Americans from the 2006-2016 waves of the Health and Retirement Study. Handgrip strength was measured with a handgrip dynamometer. Men with weakness were below at least one of the absolute or normalized (body mass, body mass index) cut points: <35.5 kg, <0.45 kg/kg, <1.05 kg/kg/m 2 . The presence of any weakness in women was also identified as being below one of the absolute or normalized HGS cut points: <20.0 kg, <0.34 kg/kg, or <0.79 kg/kg/m 2 . There was an increasing trend in the prevalence of any weakness over time ( p < 0.001). The prevalence of weakness was 45.1% (95% confidence interval [CI]: 44.0-46.0) in the 2006-2008 waves and 52.6% (CI: 51.5-53.7) in the 2014-2016 waves. Weakness prevalence was higher for older (≥65 years) Americans (64.2%; CI: 62.8-65.5) compared with middle-aged (50-64 years) Americans (42.2%; CI: 40.6-43.8) in the 2014-2016 waves. Moreover, the prevalence of weakness in the 2014-2016 waves was generally higher in women (54.5%; CI: 53.1-55.9) than in men (50.4%; CI: 48.7-52.0). Differences existed in weakness prevalence across races and ethnicities. The findings from our investigation suggest that the prevalence of weakness is overall pronounced and increasing in Americans. Efforts for mitigating and better operationalizing weakness will elevate in importance as our older American population grows., (Copyright © 2023 National Strength and Conditioning Association.)

Background: Recently developed absolute and body size normalized handgrip strength (HGS) cut-points could be used individually and collectively to predict mobility problems and falls., Aims: We examined the associations of (1) each absolute and normalized weakness cut-point, (2) collective weakness categories, and (3) changes in weakness status on future falls in older Americans., Methods: The analytic sample included 11,675 participants from the 2006-2018 waves of the Health and Retirement Study. Falls were self-reported. Men were classified as weak if their HGS was < 35.5-kg (absolute), < 0.45 kg/kg (body mass normalized), or < 1.05 kg/kg/m 2 (body mass index normalized). While, women were considered weak if their HGS was < 20.0-kg, < 0.337 kg/kg, or < 0.79 kg/kg/m 2 . Collective weakness categorized those below 1, 2, or all 3 cut-points. The collective weakness categories were also used to observe changes in weakness status over time., Results: Older Americans below each absolute and normalized cut-point had greater odds for future falls: 1.23 (95% confidence interval (CI): 1.15-1.32) for absolute weakness, 1.20 (CI 1.11-1.29) for body mass index normalized weakness, and 1.26 (CI 1.17-1.34) for body mass normalized weakness. Persons below 1, 2, or all 3 weakness cut-points had 1.17 (CI 1.07-1.27), 1.29 (CI 1.18-1.40), and 1.36 (CI 1.24-1.48) greater odds for future falls, respectively. Those in some changing weakness categories had greater odds for future falls: 1.26 (CI 1.08-1.48) for persistent and 1.31 (CI 1.11-1.55) for progressive., Discussion: Collectively using these weakness cut-points may improve their predictive value., Conclusion: We recommend HGS be evaluated in mobility and fall risk assessments., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Abstract: Lillquist, T, Mahoney, SJ, Kotarsky, C, McGrath, R, Jarajapu, Y, Scholten, SD, and Hackney, KJ. The effect of direct and remote postexercise ischemic conditioning on muscle soreness and strength 24 hours after eccentric drop jumps. J Strength Cond Res 37(9): 1870-1876, 2023-Strategic limb occlusion applied after exercise may facilitate recovery, not only in directly targeted tissue but also in remote areas of the body. The purpose of this study was to determine if postexercise ischemic conditioning (PEIC) applied directly to one leg facilitated recovery in the targeted leg and the contralateral leg that did not receive direct PEIC. Twenty active men participated in a single-blind, randomized, crossover design. Subjects completed 2 paired testing sessions (PEIC and control-SHAM) that included pre-assessments and 24-hour postassessments. Each paired testing session included an eccentric drop jump task, which has been shown to increase lower-body muscle soreness and decrease strength. After each drop jump task, occlusion cuffs were immediately applied. In the PEIC session, ∼198 mm Hg was applied directly to one leg (PEIC-Direct), whereas the contralateral leg received a nonphysiological stimuli of 20 mm Hg (PEIC-Remote). In the control-SHAM session, both legs directly and remotely received the 20 mm Hg pressure. Unilateral pre-assessments and 24-hour postassessments included muscle soreness using a visual analog scale and strength via peak torque assessment across the force-velocity spectrum (flexion/extension 60/60, 120/120, 180/180, 240/240, 300/300 °·s -1 ), and a maximal eccentric extension (30/30 °·s -1 ). Muscle soreness was significantly increased ( p < 0.05) at 24 hours compared with pretreatment except for PEIC-Direct (1.19 ± 0.78 vs. 2.32 ± 1.48, p = 0.096). Across the force-velocity spectrum, there were no significant differences observed between any associated pretest and posttest ( p > 0.05). PEIC applied directly to target leg after eccentric drop jumps attenuated perceived quadriceps muscle soreness 24 hours post; however, there was no effect on muscle strength., (Copyright © 2023 National Strength and Conditioning Association.)

Abstract: Klawitter, LA, Hackney, KJ, Christensen, BK, Hamm, JM, Hanson, M, and McGrath, R. Using electronic handgrip dynamometry and accelerometry to examine multiple aspects of handgrip function in master endurance athletes: A Pilot Study. J Strength Cond Res 37(9): 1777-1782, 2023-Electronic handgrip dynamometry and accelerometry may provide novel opportunities to comprehensively measure muscle function for human performance, especially for master athletes. This investigation sought to determine the multivariate relationships between maximal strength, asymmetry, rate of force development, fatigability, submaximal force control, bimanual coordination, and neuromuscular steadiness to derive one or more handgrip principal components in master-aged endurance athletes. We included n = 31 cyclists and triathletes aged 35-70 years. Maximal strength, asymmetry, rate of force development, fatigability, submaximal force control, bimanual coordination, and neuromuscular steadiness were measured twice on each hand using electronic handgrip dynamometry and accelerometry. The highest performing measures were included in the analyses. A principal component analysis was conducted to derive a new collection of uncorrelated variables from the collected handgrip measurements. Principal components with eigenvalues >1.0 were kept, and individual measures with a factor loading of |>0.40| were retained in each principal component. There were 3 principal components retained with eigenvalues of 2.46, 1.31, and 1.17. The first principal component, "robust strength," contained maximal strength, rate of force development, submaximal force control, and neuromuscular steadiness. The second principal component, "bilateral synergy," contained asymmetry and bimanual coordination, whereas the third principal component, "muscle conditioning," contained fatigability. Principal components 1, 2, and 3 explained 44.0, 31.6, and 24.4% of the variance, respectively. Different dimensions of muscle function emerged from our findings, suggesting the potential of a muscle function battery. Further research examining how these measures are associated with appropriate human performance metrics and lower extremity correlates is warranted., Competing Interests: This research was funded by an intramural pilot mechanism at North Dakota State University. The results of this study do not constitute endorsement of the product by the authors or the NSCA. The authors report no conflicts of interest., (Copyright © 2023 National Strength and Conditioning Association.)

Introduction: Police officers must perform various tasks in unpredictable work environments and potentially volatile situations. This study aimed to determine if cardiovascular fitness, body composition, and physical activity levels could predict performance in a Midwest Police Department's Physical Readiness Assessment (PRA)., Methods: Researchers collected data from thirty incumbent police officers (33.9 ± 8.3 years, female = 5). Anthropometric data included height, body mass, body fat percentage (BF%), fat-free mass (FFM), and maximal hand grip strength. The police officers also completed a physical activity rating (PA-R) scale to estimate maximal oxygen consumption ( V ˙ O 2max ) and the International Physical Activity Questionnaire (IPAQ). Police officers then conducted their department's PRA. Stepwise linear regression analyses were used to determine the relationship between predictor variables and PRA performance. Pearson's product-moment correlations investigated relationships between anthropometric, physical fitness, and physical activity variables and PRA performance using SPSS (v.28). The significance level was set at p  < 0.05., Results: Descriptive data for the sample includes BF%: 27.85 ± 7.57%, FFM: 65.73 ± 10.72 kg, hand grip strength: 55.51 ± 11.07 kg, weekday sedentary time (WST): 328 ± 28.26 min, weekend day sedentary time (WDST): 310 ± 28.92 min, daily moderate-to-vigorous physical activity (MVPA): 29.02 ± 39.41 min, PRA: 273.6 ± 51.4 s and estimated V ˙ O 2max : 43.26 ± 6.35 mL kg -1 min -1 . The stepwise regression analyses indicated that BF% was predictive of PRA time ( R 2  = 0.32, p  < 0.01); estimated V ˙ O 2max predictive of PRA time ( R 2  = 0.45, p  < 0.001). There were significant correlations between BF % and PRA time ( r  = 0.57, p  < 0.001), PA-R and MVPA ( r  = 0.71, p  < 0.001), %BF % and WDST ( r  = -0.606, p  < 0.001), hand grip and FFM ( r  = 0.602, p  < 0.001) and PA-R and PRA time ( r  = -0.36, p  < 0.05)., Discussion: The results of this exploratory study highlight that higher estimated V ˙ O 2max and lower BF% were the best predictors for faster PRA completion times, accounting for 45% and 32% of the variance, respectively. The findings of this study support the need for wellness and fitness initiatives in law enforcement agencies focused on increasing cardiovascular fitness and physical activity while decreasing BF% to ensure optimal performance in policing and overall health., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Dicks, Shoemaker, DeShaw, Carper, Hackney and Barry.)

Body composition tools vary in reliability, portability, and accessibility. The purpose of this study was to evaluate test-retest reliability of MuscleSound® (MS) and dual-energy x-ray absorptiometry (DXA) for both two compartment (region) and three compartment (tissue) models. A secondary aim was to compare body composition values produced by both devices. Fifty participants ( n = 25 male, n = 25 female) aged 18-39 years completed two body composition assessments, twice in a single session. Participants arrived at the lab after a 12-hour fast. DXA required participants to lay supine for 10-15 minutes during the scanning process. Thereafter, MS was utilized to measure subcutaneous adipose tissue thickness at seven sites: chest, subscapula, triceps, axilla, suprailium, abdomen, and mid-thigh. MS automatically estimated body composition utilizing a modified Jackson-Pollock equation and the Siri equation within the software. The sequence of assessments was then repeated. Statistical analysis included paired T-tests with Pearson correlations, intraclass correlation coefficients (ICC), and least significant change (LSC). Both methods were strongly reliable (ICC MS = .997, ICC DXA-region = .999, ICC DXA-tissue = .999). MS and DXA-region body fat percentages were significantly different (mean difference (%): 2.60 ± 1.32, p < .001) but highly correlated ( r = .928, p < .001). Notably, the mean difference was within DXA-region's calculated least significant change of 3.24%. MS is reliable for assessing body fat percentage in young and middle-aged adults and operators can utilize MS to collect body composition data in the field.

The current study aimed to investigate exercise with blood flow restriction (BFR) as a low-intensity conditioning strategy in tactical professionals with load carriage. During the low-intensity exercise, researchers examined the acute metabolic responses from low-intensity BFR walking, walking with load carriage, and walking with BFR and load carriage. Twelve healthy adult males (age = 21.8 ± 1.5 yrs, height = 181.3 ± 7.2 cm, body mass = 84.4 ± 11.1 kg and BMI = 25.6 ± 2.6 kg·m 2 ) completed five bouts of 3-min treadmill walking at 4.8 km·h -1 with 1-min rest interval under three different conditions: 1) blood flow restriction (BFR), 2) loaded with 15% of body mass (LOAD) and 3) loaded with 15% of body mass with blood flow restriction (BFR-LOAD). Oxygen consumption (V̇O 2 ), heart rate, and local muscle oxygen saturation was measured during the exercise bouts. V̇O 2 increased by 7% during the BFR- LOAD ( p = 0.001) compared with BFR or LOAD alone. There were no differences in V̇O 2 between BFR and LOAD ( p = 0.202). BFR-LOAD showed significantly lower (-9%) muscle oxygen saturation ( p = 0.044) and deoxygenated hemoglobin ( p = 0.047) compared to LOAD. Low-intensity walking with the addition of BFR shares acute metabolic characteristics similar to walking with a load. These characteristics suggest there is potential for the use of BFR to increase exercise intensity for individuals training with load carriage.

Background: Ambulation devices may differ in their utility, muscle activation patterns, and how they affect regional blood flow. This study aimed to evaluate popliteal blood flow and vessel dimensions in response to ambulation with a hands-free crutch (HFC), axillary crutches (AC), a medical kneeling scooter (MKS), and regular walking in healthy adults., Methods: HFC, AC, MKS, and regular walking were completed in a random order by 40 adults aged 18-45 years. Participants ambulated at a comfortable pace for 10 minutes with each device. At baseline and immediately following each trial, a trained operator used diagnostic ultrasonography to capture popliteal vein and artery dimensional and flow characteristics., Results: Significant increases were observed from baseline (0.65 ± 0.23 cm) in venous diameter following walking (0.71 ± 0.21 cm, P = .012) and MKS (0.73 ± 0.21 cm, P = .003). Venous blood flow was also significantly different between conditions ( P = .009) but was only greater following walking (124 ± 79 mL/min) compared to MKS (90 ± 64 mL/min, P = .021). No differences were observed in arterial dimensions between ambulation conditions. Significant increases were found in arterial blood flow from baseline (107 ± 69 mL/min) following walking (184 ± 97 mL/min, P < .001) and HFC (163 ± 86 mL/min, P < .001). Arterial blood flow following walking was greater than AC (132 ± 72 mL/min, P = .016) and MKS (128 ± 74 mL/min, P = .003)., Conclusion: We found an average decrease in venous time-averaged mean velocity between walking and use of the MKS, but no such decrease with either HFCs or use of ACs in this healthy experimental cohort., Level of Evidence: Level III, diagnostic comparative study., Competing Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Adam P. Bradley, MS, Alexis S. Roehl, and Kyle J. Hackney, PhD, report research grant from IwalkFree, Inc, grant to institution (North Dakota State University [NDSU]); medical knee scooter, axillary crutches, and IwalkFree devices were provided for study via grant (1), and devices provided to institution (NDSU). ICMJE forms for all authors are available online., (© The Author(s) 2022.)

Background: A Hands-Free crutch (HFC) is a relatively new device that can be used during the nonweightbearing period to increase mobility. The primary aim of this investigation was to examine aerobic oxygen consumption (V.o 2 ) and substrate utilization with HFC compared to conventional ambulation devices as well as normal ambulation. A secondary purpose was to quantify perceived exertion, pain, and performance during each ambulation condition., Methods: Forty participants completed 4 separate 10-minute ambulation conditions around a rectangular course. The order of the ambulation conditions was randomized and consisted of (1) walking, (2) medical knee scooter (MKS), (3) HFC, and (4) axillary crutch (AC). Indirect calorimetry was used to determine V.o 2 and the respiratory exchange ratio (RER), an indicator of substrate utilization. Perceived exertion and pain were also assessed using questionnaires., Results: All mobility devices significantly elevated V.o 2 (+35%) compared to walking (13.14 ± 1.70 mL/kg/min; P < .001). AC had significantly greater V.o 2 requirements (20.26 ± 2.62 mL/kg/min) compared to both the MKS (15.28 ± 2.29 mL/kg/min; P < .001) and HFC (15.88 ± 2.03 mL/kg/min; P < .001). There was no difference in average V.o 2 between MKS and HFC ( P = .368). Compared to walking (0.78 ± 0.43), RER was significantly elevated in MKS (0.81 ± 0.05, P < .001) and AC (0.84 ± 0.06, P < .001), but not in HFC (0.79 ± 0.04, P = .350). RPE and pain were elevated in all ambulatory conditions (all P values <.001). Pain was significantly greater in AC compared with MKS ( P < .001) and HFC ( P < .001)., Conclusion: HFC and MKS share similar V.o 2 requirements over a 10-minute ambulation interval and are below those needed in AC. Substrate utilization in HFC was similar to regular walking with a greater reliance on lipid utilization for energy as evidenced by a lower RER. Exertion and pain scores were the most tolerable in HFC and MKS., Level of Evidence: Level II, prospective comparative study., Competing Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Kyle J. Hackney, PhD, Adam P. Bradley, MS, and Alexis S. Roehl report reseach grant from IwalkFree, Inc, grant to institution (NDSU; FAR0034987), as well as receipt of, medical knee scooter, axillary crutches, and iwalkfree devices with consultation on proper fitting provided for study via grant (devices provided to institution [NDSU]). ICMJE forms for all authors are available online., (© The Author(s) 2022.)

Weight loss through dietary and exercise intervention is commonly prescribed but is not effective for all individuals. Recent studies have demonstrated that circulating microRNA (miR) biomarkers could potentially be used to identify individuals who will likely lose weight through diet and exercise and attain a healthy body weight. However, accurate detection of miRs in clinical samples is difficult, error-prone, and expensive. To address this issue, we recently developed iLluminate -a low-cost and highly sensitive miR sensor suitable for point-of-care testing. To investigate if miR testing and iLluminate can be used in real-world obesity applications, we developed a pilot diet and exercise intervention and utilized iLluminate to evaluate miR biomarkers. We evaluated the expression of miRs-140, -935, -let-7b, and -99a, which are biomarkers for fat loss, energy metabolism, and adipogenic differentiation. Responders lost more total mass, tissue mass, and fat mass than non-responders. miRs-140, -935, -let-7b, and -99a, collectively accounted for 6.9% and 8.8% of the explained variability in fat and lean mass, respectively. At the level of the individual coefficients, miRs-140 and -935 were significantly associated with fat loss. Collectively, miRs-140 and -935 provide an additional degree of predictive capability in body mass and fat mass alternations.

Objective: Identify contributors to differences in the muscle size and strength of sedentary and active young and middle-aged adults., Methods: This cross-sectional study included 98 participants aged 20-65 years. Participants were categorized based on age and self-reported physical activity (PA) habits. Participants completed a strength assessment of knee extensors (KEPT), knee flexors (KFPT), plantar flexors (PFPT), and dorsiflexors (DFPT), a 3-day dietary intake log, 7-day accelerometry, and a magnetic resonance imaging (MRI) scan for muscle cross-sectional area analysis of the right quadriceps (CSAq)., Results: There were significant age and activity-related group effects for relative protein intake (p<0.001), relative energy intake (p=0.04), KEPT (p=0.01), CSAq (p=0.002), PFPT (p=0.004) and DFPT (p=0.003). Moderate, moderate-to-vigorous, and vigorous PA were positively associated with CSAq (R 2 =0.69- 0.71; p<0.05), KEPT (R 2 =0.61-0.63; p<0.05), and PFPT (R 2 =0.31-0.36; p<0.05). Relative protein intake and daily leucine intake were significantly and positively associated with CSAq (R 2 =0.70 and 0.67 respectively; p<0.05), KEPT (R 2 =0.62 and 0.65 respectively; p<0.05), and PFPT (R 2 =0.29 and 0.28 respectively; p<0.05)., Conclusion: Muscle size and strength were lower in middle age relative to younger age, but increased PA, protein intake, and leucine intake was associated with the preservation of muscle size and strength in larger muscle groups of the lower body., (Copyright: © 2022 Hylonome Publications.)

Background: Metabolic syndrome (MetS) increases risk for morbidity and premature mortality. Blood pressure, waist circumference, and fasting triglycerides (TG), blood glucose (BG), and high-density lipoprotein cholesterol (HDL) are factors for determining MetS. The Simple Method for Quantifying Metabolic Syndrome (siMS) score and risk score estimate risk of MetS. The purpose for this study was to exam the relationship of animal-based (ABP) and plant-based protein (PLP) with MetS as estimated by siMS score and risk score. Physical activty is another important consideration in MetS as it can reduce blood pressure, waist circumference and blood glucose, and affect blood lipid and lipoprotein concentrations., Methods: A cross-sectional study examined whether physical activity (PA) level and dietary protein source (i.e., animal- or plant-based) among young (18-24 years) and middle-aged (45-60 years) females were associated with siMS score and siMS risk score. Average time spent in sedentary, light, and moderate-to-vigorous PA (MVPA; min/wk), steps (steps/day), energy intake (kcal/day), percent dietary protein to total energy intake, ABP and PLP dietary intake, and ABP:PLP ratio (g/day) were included in the analysis. Volunteers were recruited from North Dakota and Minnesota from 2017 to 2019., Results: Eighty-one female participants (mean ± SD; young, n = 38, 20.4 ± 1.7 years, middle-aged, 52.5 ± 4.8 years) were included in the independent t -tests used to examine group differences in age, body mass index, HDL, BG, TG, systolic blood pressure, waist circumference, energy intake, energy intake percentage of total carbohydrates, fat, protein, ABP, and PLP, ABP:PLP, siMS score, and siMS risk score. Stepwise linear regressions were used to evaluate whether PA level and dietary protein source were predictors of siMS score and siMS risk score among young and middle-aged adult females. There was an inverse relationship between PLP intake and siMS score. The model explained 6.9% of the variance in siMS risk score (F 1, 80  = 5.93). Plant-based protein intake was inversely related to siMS risk score while light PA was positively associated with siMS risk score. The model explained 16% of the variance in siMS risk score (F 1, 80  = 7.53). Animal-based dietary protein intake did not impact siMS score ( p  = 0.180) and siMS risk score ( p  = 0.283)., Conclusions: Plant-based protein intake was associated with a lower risk of MetS via siMS scores, while ABP was not associated. Given the nature of the cross-sectional design of this study, no causal relationship can be determined, but longitudinal studies or randomized control trials to confirm the results from this study are needed in the future., Competing Interests: Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2022.)

Background: Evenness of protein intake is associated with increased lean mass, but its relationship with muscle strength and performance is uncertain., Objectives: We determined the association of evenness of protein intake with lean mass, muscle strength and endurance, and functional ability., Design: This was a cross-sectional study., Setting: Data were collected at a research university in the upper midwestern United States., Participants: One hundred ninety-two healthy women, aged 18 to 79 years, mean ± SEM 41.9 ± 1.3, completed the study., Measurements: Dietary intake was assessed using 3-day food diaries verified with food frequency questionnaires. To assess evenness of protein intake, the day was divided into 3 periods: waking to 11:30, 11:31 to 16:30, and after 16:30. Lean mass was measured with dual energy X-ray absorptiometry. Lower-body muscle strength and endurance were determined using isokinetic dynamometry. Upper-body muscle strength was maximal handgrip strength. Functional ability was assessed using 6-m gait speed and 30-second chair stand tests. Accelerometry measured physical activity., Results: Intakes of 25 g or more of protein at 1 or more of the 3 periods was positively associated with lean mass (β ± S.E.; 1.067 ± 0.273 kg, P  < .001) and upper-body (3.274 ± 0.737 kg, P  < .001) and lower-body strength (22.858 ± 7.918 Nm, P  = .004) when controlling for age, body mass index, physical activity, and energy and protein intakes. Consuming at least 0.24 g/kg/period for those under 60 years and 0.4 g/kg/period for those 60 years and older was related to lean mass (0.754 ± 0.244 kg, P  = .002), upper-body strength (2.451 ± 0.658 kg, P  < .001), and lower-body endurance (184.852 ± 77.185 J, P  = .018), controlling for the same variables., Conclusions: Evenness of protein intake is related to lean mass, muscle strength, and muscular endurance in women. Spreading protein intake throughout the day maximizes the anabolic response to dietary protein, benefiting muscle mass and performance., Competing Interests: Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: This project was funded by Beef Checkoff; this funder was not involved in data collection or analysis and did not affect, or in any way determine the contents of this manuscript., (© The Author(s) 2022.)

Purpose: Individuals in the emerging adult age group (18-30 years) with type 1 diabetes (T1DM) have unique medical and social needs. The purpose of this study was to observe barriers and strategies for diabetes management among emerging adults with T1DM., Methods: A qualitative grounded theory model was utilized. An open-ended approach with a telephone interview was designed to allow a deeper understanding of the T1DM experience. The participants were from a larger survey-volunteer participant group and were asked to complete 1 interview in spring 2020 (n = 21, diagnosed age: mean 15.00 ± 8.00, females, n = 19). The data were analyzed for cohesive themes using grounded theory., Results: Participants indicated three main barrier themes (physiology, environment, and insurance) and 3 barrier subthemes (mental health, lack of social support, and weather). Three main strategy themes to diabetes management were recognized (medical technology, access to social support, and physical activity). There were 2 strategy subthemes (social media and social accountability)., Conclusions: Regular use of social media can be a key tool for social accountability while lack of social support and physiological shifts can be barriers to management of T1DM. Physical activity should be considered as part of an individualized plan for management of diabetes., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2022.)

This investigation sought to determine the associations between handgrip strength (HGS) asymmetries and limitations in individual activities of daily living (ADL). The analytic sample included 18,468 participants from the 2006 to 2016 waves of the Health and Retirement Study. Those with HGS >10% stronger on either hand had any HGS asymmetry. Individuals with HGS >10% stronger on their dominant or non-dominant hand had dominant or non-dominant HGS asymmetry, respectively. ADL abilities were self-reported. Those with any HGS asymmetry had 1.21 (95% confidence interval [CI] = [1.01-1.46]) greater odds for a toileting limitation and 1.25 (CI = [1.03-1.52]) greater odds for a transferring limitation. Individuals with dominant HGS asymmetry had 1.24 (CI = [1.01-1.53]) greater odds for a transferring limitation. Those with non-dominant HGS asymmetry had 1.39 (CI = [1.01-1.93]) and 1.44 (CI = [1.05-1.96]) greater odds for a bathing and toileting limitation, respectively. HGS asymmetries could help to identify future limitations in specific ADLs.

Background: Older adults with a cognitive impairment, including those not yet diagnosed, may have deficits in their physical function., Objective: We sought to determine the associations of cognitive impairment consistent with dementia (CICD) diagnosis status on handgrip strength, gait speed, and functional disability in older adults., Methods: The analytical sample included 8,383 adults aged ≥65-years without history of stroke, cancers, neurological conditions, or brain damage who participated in at least one-wave of the 2010-2016 waves of the Health and Retirement Study. A handgrip dynamometer measured handgrip strength. Men with handgrip strength &lt;26 kg and women &lt;16 kg were weak. Gait speed was timed across a 2.5-m course and those with slowness had gait speed &lt;0.8 m/s. Participants with difficulty or an inability in completing any basic activities of daily living had a functional disability. The adapted Telephone Interview of Cognitive Status evaluated cognitive function. Persons with scores &lt;7 had a CICD. Healthcare provider dementia-related diagnosis was self-reported. Undiagnosed CICD was defined as no reported dementia-related diagnosis but had CICD, while diagnosed CICD was classified as reporting a dementia-related diagnosis. Covariate-adjusted logistic models were used for the analyses., Results: Persons with undiagnosed CICD had 1.37 (95% confidence interval (CI): 1.04-1.80) greater odds for weakness and 2.02 (CI: 1.39-2.94) greater odds for slow gait speed. Older adults with diagnosed CICD had 2.29 (CI: 1.32-3.97) greater odds for slowness and 1.85 (CI: 1.19-2.90) greater odds for functional disability., Conclusion: Screening for CICD could be recommended when defects in physical function are observed in older adults.

INTRODUCTION: During spaceflight missions, astronauts work in an extreme environment with several hazards to physical health and performance. Exposure to microgravity results in remarkable deconditioning of several physiological systems, leading to impaired physical condition and human performance, posing a major risk to overall mission success and crew safety. Physical exercise is the cornerstone of strategies to mitigate physical deconditioning during spaceflight. Decades of research have enabled development of more optimal exercise strategies and equipment onboard the International Space Station. However, the effects of microgravity cannot be completely ameliorated with current exercise countermeasures. Moreover, future spaceflight missions deeper into space require a new generation of spacecraft, which will place yet more constraints on the use of exercise by limiting the amount, size, and weight of exercise equipment and the time available for exercise. Space agencies are exploring ways to optimize exercise countermeasures for spaceflight, specifically exercise strategies that are more efficient, require less equipment, and are less time-consuming. Blood flow restriction exercise is a low intensity exercise strategy that requires minimal equipment and can elicit positive training benefits across multiple physiological systems. This method of exercise training has potential as a strategy to optimize exercise countermeasures during spaceflight and reconditioning in terrestrial and partial gravity environments. The possible applications of blood flow restriction exercise during spaceflight are discussed herein. Hughes L, Hackney KJ, Patterson SD. Optimization of exercise countermeasures to spaceflight using blood flow restriction . Aerosp Med Hum Perform. 2021; 93(1):32-45.

Maximal handgrip strength (HGS) is a convenient and reliable, but incomplete, assessment of muscle function. Although low HGS is a powerful predictor of poor health, several limitations to maximal HGS exist. The predictive value of HGS is restricted because low HGS is associated with a wide range of unspecified health conditions, and other characteristics of muscle function aside from strength capacity are not evaluated. Current HGS protocol guidelines emphasize the ascertainment of maximal force, which is only a single muscle function characteristic. Muscle function is intrinsically multivariable, and assessing other attributes in addition to strength capacity will improve screenings for age-related disabilities and diseases. Digital handgrip dynamometers and accelerometers provide unique opportunities to examine several aspects of muscle function beyond strength capacity, while also maintaining procedural ease. Specifically, digital handgrip dynamometry and accelerometry can assess the rate of force development, submaximal force steadiness, fatigability, and task-specific tremoring. Moreover, HGS protocols can be easily refined to include an examination of strength asymmetry and bilateral strength. Therefore, evaluating muscle function with new HGS technologies and protocols may provide a more comprehensive assessment of muscle function beyond maximal strength, without sacrificing feasibility. This Special Article introduces a novel framework for assessing multiple attributes of muscle function with digital handgrip dynamometry, accelerometry, and refinements to current HGS protocols. Such framework may aid in the discovery of measures that better predict and explain age-related disability, biological aging, and the effects of comorbid diseases that are amenable to interventions. These additional HGS measures may also contribute to our understanding of concepts such as resilience. Using sophisticated HGS technologies that are currently available and modernizing protocols for developing a new muscle function assessment may help transform clinical practice by enhancing screenings that will better identify the onset and progression of the disabling process., (Copyright © 2021 AMDA — The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.)

This study examined the associations between asymmetric handgrip strength (HGS) and multimorbidity in American adults. Secondary analyses of data from persons aged at least 40 years from the 2011-2012 and 2013-2014 waves of the National Health and Nutrition Examination Survey were conducted. A handheld dynamometer collected HGS on each hand and persons with a strength imbalance >10% between hands were classified as having asymmetric HGS. Adults with the presence of ≥2 of the following conditions had multimorbidity: cardiovascular disease, chronic obstructive pulmonary disease, chronic kidney disease, asthma, arthritis, cancer, obesity, stroke, hypertension, high cholesterol, and diabetes. Of the n = 3483 participants included, n = 2700 (77.5%) had multimorbidity. A greater proportion of adults with multimorbidity had HGS asymmetry ( n = 1234 (45.7%)), compared to persons living without multimorbidity ( n = 314 (40.1%); p < 0.05). Relative to individuals without asymmetry, adults with asymmetric HGS had 1.31 (95% confidence interval (CI): 1.03-1.67) greater odds for multimorbidity. Moreover, persons with HGS asymmetry had 1.22 (CI: 1.04-1.44) greater odds for accumulating morbidities. Asymmetric strength, as another indicator of diminished muscle function, is linked to chronic morbidity status. Healthcare providers should recommend healthy behaviors for reducing asymmetries to improve muscle function and mitigate morbidity risk after completing asymmetry screenings.

Background: Physical inactivity during the COVID-19 pandemic is a public health concern for older adults. Telehealth presents a safe platform for conducting health-related interventions that may have additional benefits such as widespread reach. Our pilot study sought to examine how a telehealth intervention changed activity profiles in older adults during the COVID-19 pandemic., Methods: There were n =13 adults aged 70.6 ± 4.5 years that participated in a 6 week telehealth intervention during the COVID-19 pandemic. The didactic intervention contents were shared online, and participants worked with trained interviewers over the telephone to discuss physical activity. At baseline and post-intervention, the Multimedia Activity Recall for Children and Adults examined activity profiles, while accelerometry estimated time spent sedentary and in physical activity., Results: Relative to the baseline measures, there was an 88 min/day (95% confidence interval (CI): 39, 137) increase in computer time and 36 min/day (CI: 10, 62) reduction in time spent in active transport at post-intervention. Moderate-to-vigorous physical activity participation also increased by an estimated 2 min/day (CI: -21, 26) and 12 min/week (CI: -154, 180), but this trend was not statistically significant., Conclusion: We recommend that support be provided to older adults transitioning to telehealth, especially as migration to telehealth progresses., Competing Interests: The authors declare no conflict of interest.

The purpose of this study was to evaluate the effects of using the critical velocity (CV) concept to prescribe two separate high-intensity interval training (HIT) exercise programs aimed at enhancing CV and load carriage performance. 20 young adult participants (male = 15, female = 5) underwent a 4-week training period where they exercised 2 d   wk -1 . Participants were randomly assigned into two groups: (1) HIT or (2) Load Carriage-HIT (LCHIT). Pre- and post-training assessments included running 3-minute All-Out Test (3MT) to determine critical velocity (CV) and distance prime ( D ') and two load carriage tasks (400 and 3200 m). There were significant increases in CV ( p  = 0.005) and velocity at V ˙ O 2max ( v V ˙ O 2max ) ( p  = 0.037) among the sample but not between training groups. Improvements were observed in 3200 m load carriage performance time ( p  < 0.001) with a 9.8 and 5.4% decrease in the LCHIT and HIT groups, respectively. Practitioner summary: Critical velocity has shown efficacy as a marker for performance in tactical populations. With the addition of load carriage, there is a reduction in the individual's CV. The CV-concept-prescribed exercises (HIT and LCHIT) 2 days per week for 4 weeks showed improvements in CV, v V ˙ O 2max and load carriage performance. The use of the CV concept provides a method to prescribe HIT to increase running and load carriage performances in tactical populations.

The purpose of this study was to determine whether time-restricted eating (TRE), also known as time-restricted feeding, was an effective dietary strategy for reducing fat mass and preserving fat-free mass while evaluating changes in cardiometabolic biomarkers, hormones, muscle performance, energy intake, and macronutrient intake after aerobic and resistance exercise training in physically inactive and overweight or obese adults. This study was a randomized, controlled trial. Overweight and obese adults (mean ± SD; age: 44 ± 7 years; body mass index [BMI]: 29.6 ± 2.6 kg/m 2 ; female: 85.7%) were randomly assigned to a TRE or normal eating (NE) dietary strategy group. The TRE participants consumed all calories between 12:00 p.m. and 8:00 p.m., whereas NE participants maintained their dietary habits. Both groups completed 8 weeks of aerobic exercise and supervised resistance training. Body composition, muscle performance, energy intake, macronutrient intake, physical activity, and physiological variables were assessed. A total of 21 participants completed the study (NE: n = 10; TRE: n = 11). A mild energy restriction was observed for TRE (~300 kcal/day, 14.5%) and NE (~250 kcal/day, 11.4%). Losses of total body mass were significantly greater for TRE (3.3%) relative to NE (0.2%) pre- to post-intervention, of which TRE had significantly greater losses of fat mass (9.0%) compared to NE (3.3%). Lean mass increased during the intervention for both TRE (0.6%) and NE (1.9%), with no group differences. These data support the use of TRE and concurrent exercise training as a short-term dietary strategy for reducing fat mass and increasing lean mass in overweight and obese adults., (© 2021 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Over the last decade, more than 50,000 pregnancy discrimination claims were filed in the United States (United States Equal Employment Opportunity Commission [U.S. EEOC], 2018a). While pregnancy discrimination claims remain prevalent, research examining the effects of pregnancy discrimination on the well-being and health of working mothers and their babies is lacking. As such, we aim to examine the role of perceived pregnancy discrimination in the workplace on health outcomes for mothers and their babies via mother's stress. We draw on the occupational stress literature and medical research to propose that perceived pregnancy discrimination indirectly relates to mother and baby health via the mother's perceived stress. In our first study, we examine the effects of perceived pregnancy discrimination on mothers' postpartum depressive symptoms via perceived stress. In our second study, we replicate and extend our first study and examine the effects of perceived pregnancy discrimination on mothers' postpartum depressive symptoms and babies' gestational age, Apgar scores, birth weight, and number of doctors' visits, through the mechanism of perceived stress. We find that perceived pregnancy discrimination indirectly relates to increased levels of postpartum depressive symptoms for the mothers, and lower birth weights, lower gestational ages, and increased number of doctors' visits for the babies, via perceived stress of the mothers during pregnancy. Implications for theory and practice, limitations, and future research are discussed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Ultrasonography advantageously measures skeletal muscle size and quality, but some muscles may be too large to capture with standardized brightness mode (B-mode) imaging. Panoramic ultrasonography can capture more complete images and may more accurately measure muscle size. We investigated measurements made using panoramic compared to B-mode ultrasonography images of the rectus femoris with muscular performance. Concurrently, protein intake plays an important role in preventing sarcopenia; therefore, we also sought to investigate the association between animal-based protein intake (ABPI) and muscular performance. Ninety-one middle-aged adults were recruited. Muscle cross-sectional area (CSA) and thickness were obtained using B-mode and panoramic ultrasound and analyzed with Image J software. Muscular performance was assessed using isokinetic dynamometry, a 30-s chair test, and handgrip strength. Three-day food diaries estimated dietary intakes. Linear regression models determined relationships between measures from ultrasonography and muscular performance. Mixed linear models were used to evaluate the association between ABPI and muscular performance. Muscle CSA from panoramic ultrasonography and ABPI were positively associated with lower-body strength (β ± S.E.; CSA, 42.622 ± 20.024, p = 0.005; ABPI, 65.874 ± 19.855, p = 0.001), lower-body endurance (β ± S.E.; CSA, 595 ± 200.221, p = 0.001; ABPI, 549.944 ± 232.478, p = 0.020), and handgrip strength (β ± S.E.; CSA, 6.966 ± 3.328, p = 0.004; ABPI, 0.349 ± 0.171, p = 0.045). Panoramic ultrasound shows promise as a method for assessing sarcopenia. ABPI is related to better muscular performance.

Background: Evaluating handgrip strength (HGS) asymmetry may help to improve the prognostic value of HGS. This study sought to determine the associations of HGS asymmetry and weakness on future activities of daily living (ADL) disability in a national sample of aging Americans., Methods: The analytic sample included 18,468 Americans aged ≥50 years from the 2006-2016 waves of the Health and Retirement Study. A handgrip dynamometer measured HGS. Those with HGS >10% stronger on either hand were considered as having any HGS asymmetry. Individuals with HGS >10% stronger on their dominant hand were considered as having dominant HGS asymmetry, while those with HGS >10% stronger on their nondominant hand were classified as having nondominant HGS asymmetry. Men with HGS <26 kg and women with HGS <16 kg were considered weak. ADLs were self-reported. Generalized estimating equations were used for analyses., Results: Relative to those with symmetric HGS and no weakness, each HGS asymmetry and weakness group had increased odds for future ADL disability: 1.11 (95% confidence interval [CI]: 1.02-1.20) for any HGS asymmetry alone, 1.42 (CI: 1.16-1.74) for weakness alone, and 1.81 (CI: 1.52-2.16) for both any HGS asymmetry and weakness. Most weakness and HGS asymmetry dominance groups had increased odds for future ADL disability: 1.30 (CI: 1.13-1.50) for nondominant HGS asymmetry alone, 1.42 (CI: 1.16-1.74) for weakness alone, 1.72 (CI: 1.29-2.29) for both weakness and nondominant HGS asymmetry, and 1.86 (CI: 1.52-2.28) for both weakness and dominant HGS asymmetry., Conclusions: HGS asymmetry and weakness together may increase the predictive utility of handgrip dynamometers., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Handgrip dynamometers are used to assess handgrip strength (HGS), and low HGS is linked to poor cognitive function. Although HGS is a reliable measure of muscle function, it is only measuring maximal grip force. Other aspects of muscle function such as force control, fatigability, and steadiness are unaccounted for in current HGS protocols. This pilot study sought to determine the role of maximal HGS, submaximal HGS force control, HGS fatigability, and HGS neuromuscular steadiness on cognitive function in older adults. Our findings indicate that these additional HGS measurements could factor into detecting poorer cognitive functioning, while also evolving HGS protocols., Competing Interests: The authors have no conflict of interest to report., (© 2020 – IOS Press and the authors. All rights reserved.)

Objectives: Assessing handgrip strength (HGS) asymmetry may provide insights into HGS as a prognostic assessment of strength capacity and vitality. This study sought to determine the associations of HGS asymmetry and weakness on time to mortality in aging Americans., Design: Longitudinal panel., Setting: Secondary analyses of data from participants aged ≥50 years from the 2006‒2014 waves of the Health and Retirement Study., Participants: The analytic sample included 19,325 Americans who identified hand dominance and had measures of HGS for both hands in a single wave., Measures: A handgrip dynamometer was used to measure HGS. Men and women who were considered weak had HGS <26 kg and <16 kg, respectively. The highest HGS values from the dominant and nondominant hands were used to calculate HGS ratio: (nondominant HGS/dominant HGS). Those with HGS ratio <0.90 or >1.10 had any HGS asymmetry. Moreover, participants with HGS ratio <0.90 had dominant HGS asymmetry, whereas those with HGS ratio >1.10 had nondominant HGS asymmetry. The National Death Index and postmortem interviews verified date of death. Covariate-adjusted Cox models were used for analyses., Results: Those with any HGS asymmetry had a 1.10 [95% confidence interval (CI) 1.03‒1.17] higher hazard for mortality, while those with weakness had a 1.44 (CI 1.32‒1.58) higher hazard for mortality. Likewise, participants with dominant HGS asymmetry had a 1.11 (CI 1.03‒1.18) higher hazard for mortality, and those with weakness had a 1.45 (CI 1.32‒1.58) higher hazard for mortality; however, the association was not significant for those with nondominant HGS asymmetry (hazard ratio: 1.07; CI 0.96‒1.18)., Conclusions and Implications: HGS asymmetry and weakness are markers of impaired strength capacity that independently accelerate time to mortality, but the magnitude of these associations was more prominent for weakness. Nevertheless, assessments of asymmetric HGS are a simple adjunct analysis that may show promise for increasing the prognostic value of handgrip dynamometers., (Copyright © 2020 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.)

Objectives: The time course and magnitude of atrophic remodeling and the effects of an acute rehabilitation program on muscle atrophy are unclear. We sought to characterize bed rest-induced leg muscle atrophy and evaluate the safety and efficacy of an acute rehabilitation program., Design: Prespecified analysis of a randomized controlled trial., Setting: Single-center urban hospital., Patients: Adults (24-55 yr) randomized to 70 days of sedentary bed rest., Interventions: The 11-day post-bed rest rehabilitation program consisted of low intensity exercise and progressed to increased aerobic exercise duration, plyometric exercises, and higher intensity resistance exercise., Measurements and Main Results: Upper (rectus femoris, vastus lateralis, quadriceps, hamstrings, adductors) and lower leg (medial gastrocnemius, lateral gastrocnemius, and soleus) MRI scans were obtained once before, nine times during, and three times after bed rest to assess muscle cross-sectional area. The magnitude and rate of muscle atrophy and recovery were determined for each muscle. Nine participants completed 70 days of sedentary bed rest and an 11-day rehabilitation program. A total of 11,588 muscle cross-sectional area images were quantified. Across all muscles except the rectus femoris (no change), there was a linear decline during bed rest, with the highest atrophic rate occurring in the soleus (-0.33%/d). Following rehabilitation, there was rapid recovery in all muscles; however, the quadriceps (-3.74 cm 2 ; 95% CI, -7.36 to -0.12; p = 0.04), hamstrings (-2.30 cm 2 ; 95% CI, -4.07 to -0.54; p = 0.01), medial gastrocnemius (-0.62 cm 2 ; 95% CI, -1.10 to -0.14; p = 0.01), and soleus (-1.85 cm 2 ; 95% CI, -2.90 to -0.81; p < 0.01) remained significantly lower than baseline., Conclusions: Bed rest results in upper and lower leg muscle atrophy in a linear pattern, and an 11-day rehabilitation program was safe and effective in initiating a rapid trajectory of muscle recovery. These findings provide important information regarding the design and refinement of rehabilitation programs following bed rest., Competing Interests: Dr. Scott is supported by research grants from AKTIV Against Cancer and the Memorial Sloan Kettering Cancer Center Support Grant/Core Grant (P30 CA008748). The remaining authors have disclosed that they do not have any potential conflicts of interest.

Background : Maximal handgrip strength (HGS) could be an incomplete and unidimensional measure of muscle function. This pilot study sought to examine the relationships between maximal HGS, radial and ulnar digit grip strength, submaximal HGS force control, HGS fatigability, neuromuscular HGS steadiness, and HGS asymmetry in older adults. Methods: A digital handgrip dynamometer and accelerometer was used to collect several HGS measurements from 13 adults aged 70.9 ± 4.0 years: maximal strength, radial and ulnar digit grip strength, submaximal force control, fatigability, neuromuscular steadiness, and asymmetry. Pearson correlations determined the relationships between individual HGS measurements. A principal component analysis was used to derive a collection of new uncorrelated variables from the HGS measures we examined. Results: The individual HGS measurements were differentially correlated. Maximal strength (maximal HGS, radial digit strength, ulnar digits strength), contractile steadiness (maximal HGS steadiness, ulnar digit grip strength steadiness), and functional strength (submaximal HGS force control, HGS fatigability, HGS asymmetry, HGS fatigability steadiness) emerged as dimensions from the HGS measurements that we evaluated. Conclusion : Our findings suggest that these additional measures of muscle function may differ from maximal HGS alone. Continued research is warranted for improving how we assess muscle function with more modern technologies, including handgrip dynamometry and accelerometry.

Objective: We sought to determine whether daily protein intake and protein distribution across eating occasions were associated with functional disability in a national sample of older Americans. Methods : Data from 8,070 adults aged ≥60 years from the 2007-2016 waves of the National Health and Nutrition Examination Survey were included. Protein intake and functional capacity was self-reported. A daily protein recommendation of ≥1.0 g/kg/day was utilized. The daily protein recommendation was then spread-out across four meals, whereby a ≥0.25 g/kg/meal threshold was used. Results : Those meeting the daily protein recommendation had 0.78 (95% confidence interval [CI] = [0.65, 0.93]) decreased odds for functional disability. Persons meeting the protein intake threshold per eating occasion for one, two, three, and four occasions had 0.60 (CI = [0.38, 0.95]), 0.48 (CI = [0.30, 0.77]), 0.47 (CI = [0.29, 0.77]), and 0.39 (CI = [0.20, 0.75]) decreased odds for functional disability, respectively. Discussion : Protein consumption seems to be important for preserving function in older Americans.

Background: Discovering how certain health factors contribute to functional declines may help to promote successful aging., Aims: To determine the independent and joint associations of handgrip strength (HGS) and cognitive function with instrumental activities of daily living (IADL) and activities of daily living (ADL) disability decline in aging Americans., Methods: Data from 18,391 adults aged 50 years and over who participated in at least one wave of the 2006-2014 waves of the Health and Retirement Study were analyzed. A hand-held dynamometer assessed HGS and cognitive functioning was examined with a modified version of the Telephone Interview of Cognitive Status. IADL and ADL abilities were self-reported. Participants were stratified into four distinct groups based on their HGS and cognitive function status. Separate covariate-adjusted multilevel models were conducted for the analyses., Results: Participants who were weak, had a cognitive impairment, and had both weakness and a cognitive impairment had 1.70 (95% confidence interval (CI) 1.57-1.84), 1.97 (CI 1.74-2.23), and 3.13 (CI 2.73-3.59) greater odds for IADL disability decline, respectively, and 2.26 (CI 2.03-2.51), 1.26 (CI 1.05-1.51), and 4.48 (CI 3.72-5.39) greater odds for ADL disability decline, respectively., Discussion: HGS and cognitive functioning were independently and jointly associated with IADL and ADL disability declines. Individuals with both weakness and cognitive impairment demonstrated substantially higher odds for functional decline than those with either risk factor alone., Conclusions: Including measures of both HGS and cognitive functioning in routine geriatric assessments may help to identify those at greatest risk for declining functional capacity.

Adult CD34 + hematopoietic stem/progenitor cells (HSPC) in the systemic circulation are bone marrow-derived and have the propensity of maintaining cardiovascular health. Activation of angiotensin-converting enzyme-2 (ACE2)-angiotensin-(1-7)-Mas receptor pathway, the vascular protective axis of the renin-angiotensin system (RAS), stimulates vasculogenic functions of HSPCs. In a previous study, exposure to hypoxia increased the expressions of ACE2 and Mas, and stimulated ACE2 shedding. The current study tested if blood flow restriction exercise (BFR)-induced regional hypoxia recapitulates the in vitro observations in healthy adults. Hypoxia was induced by 80% limb occlusion pressure (LOP) via inflation cuff. Muscle oxygen saturation was determined using near-infrared spectroscopy. Peripheral blood was collected 30 min after quiet sitting (control) or after BFR. Lin - CD45 low CD34 + HSPCs were enumerated by flow cytometry, and ACE and ACE2 activities were determined in plasma and cell lysates and supernatants. Regional hypoxia resulted in muscle oxygen saturation of 17.5% compared with 49.7% in the control condition ( P < 0.0001, n = 9). Circulating HSPCs were increased following BFR (834.8 ± 62.1/mL) compared with control (365 ± 59, P < 0.001, n = 7), which was associated with increased stromal-derived factor 1α and vascular endothelial growth factor receptor levels by four- and threefold, respectively ( P < 0.001). ACE2 activity was increased in the whole cell lysates of HSPCs, resulting in an ACE2-to-ACE ratio of 11.7 ± 0.5 in BFR vs 9.1 ± 0.9 in control ( P < 0.05). Cell supernatants have threefold increase in the ACE2-to-ACE ratio following BFR compared with control ( P < 0.001). Collectively, these findings provide strong evidence for the upregulation of ACE2 by acute regional hypoxia in vivo. Hypoxic exercise regimens appear to be promising means of enhancing vascular regenerative capacity. NEW & NOTEWORTHY Although many studies have explored the mechanisms of skeletal muscle growth and adaptation with hypoxia exercise interventions, less attention has been given to the potential for vascular adaptation and regenerative capacity. This study shows for the first time an acute upregulation of the angiotensin-converting enzyme 2 and increase in CD34 + vasculogenic cells following an acute bout of blood flow restriction with low-intensity exercise. These rapid changes collectively promote skeletal muscle angiogenesis. Therefore, this study supports the potential of hypoxic exercise interventions with low intensity for vascular and muscle health.

Objectives: Quantifying the association between muscle weakness and mortality with carefully matched cohorts will help to better establish the impact of weakness on premature death. We used a matched cohort analysis in a national sample of older Americans to determine if those who were weak had a higher risk for mortality compared with control groups with incrementally higher strength capacities., Design: Longitudinal panel., Setting: Detailed interviews that included physical measures were conducted in person, whereas core interviews were often performed over the telephone., Participants: Data from 19,729 Americans aged at least 50 years from the 2006-2014 waves of the Health and Retirement Study were analyzed., Measures: A handgrip dynamometer was used to assess handgrip strength (HGS) in each participant. Men with HGS <26 kg were considered weak, ≥26 kg were considered not weak, and ≥32 kg were considered strong. Women with HGS <16 kg were classified as weak, ≥16 kg were classified as not-weak, and ≥20 kg were classified as strong. The National Death Index and postmortem interviews determined the date of death. The greedy matching algorithm was used to match cohorts., Results: Of the 1077 weak and not-weak matched pairs, 401 weak (37.2%) and 296 not-weak (27.4%) older Americans died over an average 4.4 ± 2.5-year follow-up. There were 392 weak (37.0%) and 243 strong (22.9%) persons who died over a mean 4.5 ± 2.5-year follow-up from the 1057 weak and strong matched pairs. Those in the weak cohort had a 1.40 [95% confidence interval (CI) 1.19, 1.64] and 1.54 (CI 1.30, 1.83) higher hazard for mortality relative to persons in the not-weak and strong control cohorts, respectively., Conclusions and Implications: Our findings may indicate a causal association between muscle weakness and mortality in older Americans. Health care providers should include measures of HGS as part of routine health assessments and discuss the health risks of muscle weakness with their patients., (Copyright © 2019 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.)

Objectives: Factors that are responsible for age-related neurologic deterioration of noncognitive and cognitive processes may have a shared cause. We sought to examine the temporal, directional associations of handgrip strength and cognitive function in a national sample of aging Americans., Design: Longitudinal panel., Setting: Enhanced interviews that included physical, biological, and psychosocial measures were completed in person. Core interviews were often conducted over the telephone., Participants: The analytic sample included 14,775 Americans aged at least 50 years who participated in at least 2 waves of the 2006-2016 waves of the Health and Retirement Study., Measures: Handgrip strength was measured with a hand-held dynamometer. Participants were considered cognitively intact, mildly impaired, or severely impaired according to the Telephone Interview of Cognitive Status questionnaire. Separate lagged general estimating equations analyzed the directional associations of handgrip strength and cognitive function., Results: The overall time to follow-up was 2.1 ± 0.4 years. Every 5 kg higher handgrip strength was associated with 0.97 [95% confidence interval (CI) 0.93, 0.99] lower odds for both future cognitive impairment and worse cognitive impairment. Those who were not weak had 0.54 (CI 0.43, 0.69) lower odds for future cognitive impairment and 0.57 (CI 0.46, 0.72) lower odds for future worse cognitive impairment. Conversely, any (β = -1.09; CI -1.54, -0.64), mild (β = -0.85; CI -1.34, -0.36), and severe cognitive impairment (β = -2.34; CI -3.25, -1.42) predicted decreased handgrip strength. Further, the presence of any, mild, and severe cognitive impairment was associated with 1.82 (CI 1.48, 2.24), 1.65 (CI 1.31, 2.08), and 2.53 (CI 1.74, 3.67) greater odds for future weakness, respectively., Conclusions/implications: Strength capacity and cognitive function may parallel each other, whereby losses of functioning in 1 factor may forecast losses of functioning in the other. Handgrip strength could be used for assessing cognitive status in aging Americans and strength capacity should be monitored in those with cognitive impairment., (Copyright © 2019 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.)

Measures of handgrip strength can be used to conveniently assess overall muscle strength capacity. Although stand-alone measures of handgrip strength provide robust health information, the clinical meaningfulness to determine prevention and treatment options for weakness remains limited because the etiology of muscle weakness remains unclear. Moreover, clinical outcomes associated with handgrip strength are wide-ranging. Therefore, disentangling how handgrip strength is associated with health conditions that are metabolically or neurologically driven may improve our understanding of the factors linked to handgrip strength. The purpose of this topical review was to highlight and summarize evidence examining the associations of handgrip strength with certain health outcomes that are metabolically and neurologically driven. From this perusal of the literature, we posit that stand-alone handgrip strength be considered an umbrella assessment of the body systems that contribute to strength capacity, and a panoptic measurement of muscle strength that is representative of overall health status, not a specific health condition. Recommendations for future strength capacity-related research are also provided., Competing Interests: Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2020.)

Proper warm-up is important for facilitating peak athletic performance and reducing injury risk; yet, warm-up procedures vary considerably amongst coaches and athletes. The purpose of this study was to assess the effect of a static stretching, medicine-ball, and mini-band warm-ups relative to a light jogging warm-up only on athletic ability test performance. It was hypothesized that static stretching would negatively affect performance, while medicine-ball and mini-band warm-ups would positively affect performance relative to light jogging only. Twelve female collegiate soccer players (19.3 ± 1.2y, 65.2 ± 7.5kg, 1.67 ± 0.07m) participated in this study. Athletes completed each warm-up protocol and all of the athletic performance tests over four sessions in a semi-randomized, counterbalanced order. An omnibus MANOVA with vertical jump height, medicine ball throw distance, 10m and 20m sprint time, and T-test time as the dependent variables was not significant indicating that warm up did not have an effect on subsequent athletic ability test performance [Wilks' λ = 0.64, F(15,110) = 1.28, p = 0.23, η 2 = 0.14]. Static stretching warm-up did not negatively influence athletic potential compared to mini-band and medicine ball warm-ups, though the most optimal warm-up is likely athlete specific.

Few studies have measured the effects of multi-ingredient pre-workout supplements on blood flow or heart rate variability or have compared a multi-ingredient pre-workout supplement to a matched single ingredient. This study examined the effects of a multi-ingredient pre-workout supplement, an equivalent amount of caffeine, and placebo on markers of resistance training performance, blood flow, blood pressure, and heart rate variability. The study utilized a randomized, placebo-controlled, repeated-measures, crossover design. Twelve resistance-trained males (22.75 ± 4.51 yrs; 183.4 ± 7.37 cm; 91.05 ± 17.77 kg) completed the study. Resistance exercise performance was defined as total work performed during elbow flexion and extension on an isokinetic dynamometer. Blood flow was calculated using time-averaged mean velocity and blood vessel diameter of the right brachial artery, which were measured via Doppler ultrasound. Heart rate was recorded using an electrocardiogram. Neither a multi-ingredient pre-workout supplement nor caffeine alone improved upper-body resistance exercise performance or markers of blood flow relative to placebo. No differences in heart rate variability were observed across treatments. A multi-ingredient pre-workout supplement was not effective at improving performance or blood flow and did not alter autonomic nervous system function.

Background: Gender and ethnicity are factors which influence strength, and hand dominance could be a critical component of handgrip strength (HGS) testing. Providing such HGS percentiles across the lifespan may help to identify weakness-related health concerns. We sought to generate growth charts and curves for HGS by gender and ethnicity in a nationally-representative sample of Americans aged 6-80 years., Methods: Data from 13,617 participants in the 2011-2012 and 2013-2014 waves of the National Health and Nutrition Examination Survey were analyzed. HGS was measured with a handgrip dynamometer. Age, gender, ethnicity, and hand dominance were self-reported. Body Mass Index (BMI) was calculated from height and body mass. Measures of absolute HGS and HGS normalized to BMI were separately included in parametric quantile regression analyses for determining the 10th-90th percentiles across ages by gender and ethnicity. Similar models were also conducted by hand dominance., Results: Differences in absolute HGS and HGS normalized to BMI quantiles across ages existed for each ethnicity regardless of gender. In men, absolute HGS generally increased until about 25 years of age, began to decline around age 30 years, and regressed into older adulthood. In women, absolute HGS appeared to rise starting at age 6 years, peaked between 20 and 30 years of age, but was maintained into mid-life before declining in older adulthood. Similar results were found for HGS normalized to BMI., Conclusions: Our findings provide percentile charts for HGS capacity that could be utilized for comparing individual measures of HGS to those from a United States population-representative sample.

Background: Measures of handgrip strength have not only emerged as a clinically viable screening tool for determining risk for morbidity, functional disability, and early mortality, but also for helping to identify cognitive deficits. However, the phenomena that links low handgrip strength with cognitive decline remains unclear. The role of the muscular and neural systems, and their adaptations to muscle strengthening activities over the life course, may provide important information for how age-related changes to muscle mass, strength, and neural capacity influence cognition. Moreover, disentangling how handgrip strength and cognitive function are associated may help to inform healthcare providers working with aging adults and guide targeted interventions aiming to preserve muscle and cognitive functioning., Objective: To 1) highlight and summarize evidence examining the associations of handgrip strength and cognitive functioning, and 2) provide directions for future research in this area., Methods: Articles from the PubMed database were searched from November 2018-May 2019. The search term algorithm, inclusion and exclusion criteria were pre-specified by investigators., Results: Several cross-sectional and longitudinal studies have revealed that measures of handgrip strength were associated with cognitive declines regardless of age demographics and the presence of comorbidities., Conclusion: Handgrip strength can be used in clinical and epidemiological settings for helping to determine the onset and progression of cognitive impairment. Future research should continue to examine how handgrip strength and cognitive function are linked.

Background: The use of magnetic resonance imaging (MRI) derived functional cross-sectional area (FCSA) and intramuscular adipose tissue (IMAT) to define skeletal muscle quality is of fundamental importance in order to understand aging and inactivity-related loss of muscle mass., Objectives: This study examined factors associated with lower-extremity skeletal muscle quality in healthy, younger, and middle-aged adults., Design: Cross-sectional study., Setting and Participants: Ninety-eight participants (53% female) were classified as younger (20-35 years, n=50) or middle-aged (50-65 years, n=48) as well as sedentary (≤1 day per week) or active (≥3 days per week) on self-reported concurrent exercise (aerobic and resistance)., Measurements: All participants wore an accelerometer for seven days, recorded a three-day food diary, and participated in magnetic resonance imaging (MRI) of the lower limbs. Muscle cross-sectional area (CSA) was determined by tracing the knee extensors (KE) and plantar flexors, while muscle quality was established through the determination of FCSA and IMAT via color thresholding., Results: One-way analysis of variance and stepwise regression models were performed to predict FCSA and IMAT. KE-IMAT (cm2) was significantly higher among sedentary (3.74 ± 1.93) vs. active (1.85 ± 0.56) and middle-aged (3.14 ± 2.05) vs. younger (2.74 ± 1.25) (p < 0.05). Protein intake (g•kg•day-1) was significantly higher in active (1.63 ± 0.55) vs. sedentary (1.19 ± 0.40) (p < 0.05). Sex, age, concurrent exercise training status, and protein intake were significant predictors of KE FCSA (R2 = 0.71, p < 0.01), while concurrent exercise training status and light physical activity predicted 33% of the variance in KE IMAT (p < 0.01)., Conclusion: Concurrent exercise training, dietary protein intake, and light physical activity are significant determinants of skeletal muscle health and require further investigation to mitigate aging and inactivity-related loss of muscle quality., Competing Interests: There are no conflicts of interest.

Objective: To examine associations among objectively measured physical activity (PA), body mass index (BMI), waist circumference (WC), and cardiorespiratory fitness (CRF) in firefighters., Methods: Career firefighters (n = 29; male = 100%) wore accelerometers to assess PA. BMI and WC classified obesity. Each participant completed a stage-graded exercise test to determine maximal oxygen uptake ((Equation is included in full-text article.))., Results: Two linear regression models were used to investigate whether PA intensities, step count, BMI, or WC were predictive of "true" (Equation is included in full-text article.). Vigorous physical activity (VPA) was predictive of "true" (Equation is included in full-text article.)(F[1,27] = 7.89, R = 0.23, P < 0.01). Additionally, when BMI and WC were added, only WC was predictive of "true" (Equation is included in full-text article.)(F[1,27] = 11.76, R = 0.30, P < 0.01)., Conclusion: Fire departments should be cognizent of ways to increase PA levels, decrease excess weight gain, and maintain CRF to adequately perform job-specific tasks.

Introduction: The purpose of the current study was to examine if isometric peak force and rate of force development (RFD) were related to the ability to successfully perform a simulated casualty evacuation task in both unweighted and weighted conditions., Methods: Eighteen male participants from Army Reserve Officers' Training Corps (ROTC) completed a maximum isometric deadlift on a force plate (IRB#HE16227). Isometric peak force and RFD were calculated from ground reaction force. Two simulated casualty evacuation performance trials were then completed. The unweighted trial consisted of lifting and carrying a 75 kg dummy as quickly as possible for 50 m. The weighted trial was similar except 9 kg vests were added to both the simulation dummy and the participant to represent 18 kg of duty gear. Independent sample t-tests and Pearson correlations were performed to compare the characteristics of those who passed and failed the weighted trial., Results: All of the participants (n = 18) completed the unweighted casualty evacuation trial, while 72% (n = 13) were able to complete the weighted casualty evacuation trial. The participants that successfully completed the weighted evacuation trial had significantly (p < 0.05) greater isometric peak force (1420 ± 165 vs. 1076 ± 256 N) and lean mass (74.18 ± 3.89 vs. 65.34 ± 3.89 kg) when compared to participants (n = 5) that could not complete the weighted evacuating task trial. Additionally, greater Army Physical Fitness Test scores (288 ± 13 vs. 269 ± 16 arbitrary units) and significantly faster (30.34 ± 4.41 vs. 44.92 ± 10.62 seconds) unweighted evacuation trial times were observed in participants that could complete the weighted evacuation task. Peak force was also significantly correlated with lean mass (r = 0.51, p < 0.05). There was no relationship between RFD and performance of the unweighted or weight trial., Conclusion: Isometric deadlift peak force represents an important determinant for the success of a simulated casualty evacuation task and may be a useful marker to include in periodic fitness evaluations of military personnel., (© Association of Military Surgeons of the United States 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Impairments in specific tasks that are necessary for independent living may identify future self-care limitations, and the use of time-varying covariates can better capture the fluidity in functional capacity trajectories over time. The purpose of this study was to determine the associations between individual instrumental activities of daily living (IADL) impairments and time to activities of daily living (ADL) disability for middle-aged and older adults in the United States., Design: Longitudinal panel., Setting: Detailed interviews that included physical, biological, and psychosocial measures were completed in person. The core interview was typically completed over the telephone., Participants: A nationally representative sample of 15,336 adults aged at least 50 years from the 2006 wave of the Health and Retirement Study was followed for 8 years., Measures: Ability to perform IADL and ADL were self-reported at each wave. Separate covariate-adjusted Cox models were used to examine the time-varying associations between individual IADL impairments and time to ADL disability., Results: The presence of each IADL impairment was associated with a higher hazard ratio for an ADL disability for the following functions: 2.52 [95% confidence interval (CI) 2.35, 2.70] for grocery shopping, 1.91 (CI 1.77, 2.06) for preparing hot meals, 1.55 (CI 1.37, 1.76) for taking medications, 1.48 (CI 1.36, 1.61) for managing money, 1.41 (CI 1.27, 1.57) for using a telephone, and 1.38 (CI 1.29, 1.48) for using a map., Conclusions/implications: Our findings provide insights into the disabling process by revealing how impairments in each IADL are differentially associated with time to ADL disability. Interventions aiming to retain function during aging should be informed by fluctuations in IADL performance and how specific IADL impairments may exacerbate functional capacity declines more so than others., (Copyright © 2018 AMDA – The Society for Post-Acute and Long-Term Care Medicine. All rights reserved.)

The purpose of this study was to examine the acute endothelial, cardiovascular, and performance responses to L-arginine intake by assessing flow-mediated dilation (FMD) and various indicators (e.g., heart rate, heart rate variability (HRV), blood pressure, torque) both before and after resistance exercise. Thirty (15 male, 15 female) physically active participants (mean ± SD: age 20.4 ± 1.8 years, height 176.9 ± 10.2 cm, body mass 76.0 ± 12.2 kg) volunteered for a randomized, cross-over, double-blind, placebo-controlled clinical trial. Participants completed five sets of elbow extension-flexion exercise after consumption of either 3 g L-arginine or 3 g of placebo. There was a significant decline in post-exercise elbow extension ( p = 0.014) and flexion peak torque ( p < 0.001). FMD response after exercise was ~5.8% less than before resistance exercise (L-arginine and placebo data pooled, p < 0.001). Baseline brachial artery diameter significantly increased post-FMD ( p < 0.001), post-resistance exercise ( p < 0.001), and post-resistance exercise FMD ( p < 0.001). There were significant time effects for HRV when expressed as the square root of the mean of the sum of squares of differences between adjacent RR intervals (RMSSD) or the proportion of differences between adjacent normal (NN) RR intervals that exceed 50 ms (pNN50) (all p -values < 0.05), but there were no treatment or interaction effects (all p -values > 0.05). We conclude the increased vasodilation due to acute resistance exercise was not enhanced by acute supplementation with L-arginine nor was exercise performance augmented. Further, the relative contribution of sympathetic nervous system input increased with resistance exercise but was not influenced by the addition of L-arginine.

Objective: The aim of this study was to validate a (Equation is included in full-text article.)O2max protocol designed specifically for the occupational demands of firefighters by incorporating the use of personal protective equipment (PPE)., Methods: Career firefighters completed a stage-graded exercise test (GXT) with submaximal square-wave verification bout while wearing PPE (pants and boots) to determine (Equation is included in full-text article.)O2max. Using the self-reported Physical Activity-Rating (PA-R) scale and an estimated nonexercise regression equation of (Equation is included in full-text article.)O2max for comparison to measured., Results: Twenty-eight male, career firefighters performed the GXT and square-wave bout. (Equation is included in full-text article.)O2 values (mean ± SD) from the GXT and the square-wave verification bout were 41.04 ± 6.98 and 39.74 ± 6.42 mL/kg/min, respectively (ICC = 0.98, typical error = 0.96 mL/kg/min, CV = 2.4%)., Conclusion: Our data suggest an incremental treadmill protocol that incorporates PPE and square-wave verification as an occupational-specific tool to measure cardiovascular fitness in firefighters.