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During sustained or repeated maximal voluntary efforts, muscle fatigue (acute strength loss) is not linear. After a large initial decrease, muscle strength plateaus at approximately 40% of baseline. This plateau, which likely reflects muscle strength preservation, has been observed in sustained maximal isometric and repeated maximal isokinetic contractions. Whether this pattern of fatigue occurs with traditional resistance exercise repetitions with free weights and weight stack machines has not been overviewed. Here, the aim was to determine whether the number of repetitions completed across 4 or more consecutive repetitions-to-failure tests exhibits the same nonlinear pattern of muscle fatigue. A secondary analysis was applied to data extracted as part of a recent meta-analysis on repetitions-to-failure tests. Studies were eligible if they reported mean number of repetitions completed in 4-6 consecutive repetitions-to-failure tests at a given relative load. Twenty-nine studies were included. Overall, the results show that the number of repetitions completed in consecutive repetitions-to-failure tests at a given load generally decreases curvilinearly. The numbers of repetitions completed in sets 2, 3, 4, 5, and 6 were equal to approximately 70, 55, 50, 45, and 45% of the number of repetitions completed in set 1, respectively. Longer interset rest intervals typically attenuated repetition loss, but the curvilinear pattern remained. From the results, a chart was created to predict the number of repetitions across 6 sets of resistance exercise taken to failure based on the number of repetitions completed in set 1. The chart is a general guide and educational tool. It should be used cautiously. More data from a variety of exercises, relative loads, and interset rest intervals are needed for more precise estimates of number of repetitions completed during repeated sets of fatiguing resistance exercise. [ABSTRACT FROM AUTHOR]

Context: Localized and widespread hyperalgesia has been observed in patients with patellofemoral pain. Diacutaneous fibrolysis (DF) has shown to be effective in reducing pain in several musculoskeletal conditions including patellofemoral pain syndrome, but no studies have evaluated the effects of this technique in reducing localized and widespread hyperalgesia. Objective: To assess the effect of DF on the pressure pain threshold and muscle length tests in patients with patellofemoral pain syndrome. Design: A single-group, pretest–posttest clinical trial. Setting: University of Zaragoza. Participants: Forty-six subjects with patellofemoral pain (20 males and 26 females: age 27.8 [6.9] y). Intervention: Three sessions of DF. Main OutcomeMeasures: Pressure pain threshold using a handheld pressure algometer (4 sites around the knee, on tibialis anterior muscle, and one remote site on the upper contralateral limb); muscle length test of the iliotibial band, rectus femoris, and hamstring muscles; and patient-perceived treatment effect score. Results: The application of 3 sessions of DF significantly increased the pressure pain threshold in all sites at posttreatment evaluation (P <.001) and at a 1-week follow-up (P <.001). A significant increase in muscle length was also observed at the posttreatment evaluation (P <.001) and 1-week follow-up (P <.001). Ninety-seven percent of the patients reported subjective improvement at posttreatment and at 1-week follow-up. Conclusion: This study found that local and widespread hyperalgesia was significantly reduced after 3 sessions of diacutaneous fibrolysis and at the 1-week follow-up. A significant improvement on muscle length tests was also observed, with high clinical satisfaction among patients. [ABSTRACT FROM AUTHOR]

Background: Knee joint position sense (JPS) might be negatively affected after injuries to the anterior cruciate ligament (ACL). Recent systematic reviews suggest further investigation of psychometric properties, including validity, of knee JPS tests following ACL reconstruction (ACLR). This study investigated the known-group validity by comparing knee JPS errors between individuals who underwent unilateral ACLR and healthy controls. Methods: This cross-sectional study involved 36 men, including 19 after ACLR (ACLR group) and 17 healthy controls (control group). In both groups, the absolute error (AE), constant error (CE) and variable error (VE) of passive knee JPS were calculated in the flexion and extension directions, for two target angles (30° and 60° flexion) per direction. Discriminative validity was evaluated by comparing JPS errors between the operated and non-operated knees in the ACLR group. Known-group validity was evaluated by comparing JPS errors between the operated knees in the ACLR group and the asymptomatic non-dominant knees of healthy controls. Results: Mean AE, CE and VE for all tests were 4.1°, − 2.3° and 3.6° for the operated knees in the ACLR group, 5.5°, − 2.6° and 3.3° for the non-operated knees in the ACLR group and 4.6°, − 2.6° and 3.3° for the non-dominant knees in the control group, respectively, regardless of the test direction and target angle. The operated knees in the ACLR group did not show significantly greater JPS errors compared to the contralateral knees in the ACLR group and to the non-dominant knees in the control group (p ≥ 0.05). On the other hand, the non-operated knees showed significantly greater AE for the 0°–60° flexion test (p = 0.025) and CE for the 0°–30° flexion test (p = 0.024) than the operated knees in the ACLR group. JPS errors did not significantly differ in the operated knees in the ACLR group based on the direction of movement and the target angle. However, the errors were significantly higher when the knee was moved through a greater range compared to that of a lesser range between the starting and target angles. Conclusion: The ACLR knees did not show greater passive JPS errors than the contralateral or control knees. The direction of movement and target angle did not influence the JPS acuity after ACLR. However, higher JPS errors were evident when the knee was moved through a greater range compared to a lesser range of motion. Further studies investigating the psychometric properties of standardized JPS tests following ACLR are warranted. [ABSTRACT FROM AUTHOR]

BACKGROUND: Although proprioceptive impairment is observed in about half of patients with stroke and is a factor affecting functional recovery and length of hospital stay, there is a discrepancy in terms of its measurement methods between physiotherapy research and the clinical field. This study aimed to examine the concurrent validity and reliability of knee proprioception using an electrogoniometer and a mobile app in patients with stroke. METHODS: In this cross-sectional study, we conducted proprioception tests with an electrogoniometer (custom-made device; Unimec, Japan) and an app (Goniometer Pro; 5fuf5, Bloomfield, NJ) in 28 hospitalized patients with stroke, with an average of 11.21 days (range 2–4 days) from the onset of stroke. Threshold to detect passive motion (TDPM), TDPM+muscle tendon vibration (MTV), and joint position sense (JPS) were used for proprioception tests. These tests were performed three times each in a random order, and the intraclass correlation coefficient, correlation, and absolute reliability for the electrogoniometer and the app were analyzed. RESULTS: Both TDPM and TDPM+MTV measured by the electrogoniometer and the app showed high correlation and "good" to "excellent" reliability regarding the variation in measured values, indicating that the two instruments are compatible, while JPS showed "poor" to "moderate" reliability and weak correlation for the electrogoniometer and the app. CONCLUSIONS: In conclusion, in patients with stroke, TDPM and TDPM+MTV measurements using the Goniometer Pro app can replace measurements with an electrogoniometer. [ABSTRACT FROM AUTHOR]

The congenital heart disease (CHD) population now comprises an increasing number of older persons in their 6th decade of life and beyond. We cross-sectionally evaluated patient-reported outcomes (PROs) in persons with CHD aged 60 years or older, and contrasted these with PROs of younger patients aged 40–59 years and 18–39 years. Adjusted for demographic and medical characteristics, patients ≥60 years had a lower Physical Component Summary, higher Mental Component Summary, and lower anxiety (Hospital Anxiety and Depression Scale-Anxiety) scores than patients in the two younger categories. For satisfaction with life, older persons had a higher score than patients aged 40–59 years. Registration: ClinicalTrials.gov NCT02150603. [ABSTRACT FROM AUTHOR]

Background: Currently, invasive dynamic intracompartmental pressure (ICP) measurements are considered the gold standard for diagnosis of chronic exertional compartment syndrome (CECS). During recent years, different noninvasive imaging modalities have been presented as a possible replacement for ICP measurement. Purpose: To provide an overview of the current state of evidence and possibilities regarding noninvasive diagnostic methods for CECS. Study Design: Scoping review; Level of evidence, 4. Methods: The PubMed (MEDLINE) and Embase databases were searched using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Full-text articles were included if they reported on noninvasive diagnostic methods for CECS, included ≥5 patients with CECS, and were published between 1994 and 2022. Articles not written in English were excluded. Systematic reviews, letters to the editor, and case reports were not eligible for inclusion. Out of 961 articles identified in the initial search, 25 studies (N = 1257 participants) were included. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies–Comparative (QUADAS-C) tool for comparative studies and the QUADAS-2 tool for noncomparative studies. Narrative synthesis was used to present results. Results: The level of evidence for the 25 studies ranged from 2 to 4. Four studies were classified as having a low risk of bias, 21 studies were classified as being at risk of bias. The following noninvasive diagnostic tools for CECS were reported: magnetic resonance imaging/diffusion tensor imaging (n = 8), near-infrared spectroscopy (n = 6), electromyography (n = 4), single-photon emission computed tomography (n = 5), ultrasound (n = 2), myotonometry (n=1) and predictive clinical model (n = 1). There was insufficient evidence in the literature to support the use of any of these noninvasive diagnostic tools as a gold standard for CECS. Conclusion: Despite the need to replace the controversial use of ICP for the diagnosis of CECS, our review indicated a lack of validity on all discussed noninvasive diagnostic tools as a replacement. [ABSTRACT FROM AUTHOR]

Purpose: This study examined tissue oxygen saturation (StO2) of the vastus lateralis (VL) muscles of chronic stroke survivors during a graded exercise test (GXT). We hypothesized that the reduction in StO2 will be blunted in the paretic versus nonparetic VL during a maximum effort GXT. Methods: Chronic stroke survivors performed a GXT, and StO2 of the VL in each leg was measured using near-infrared spectroscopy. Twenty-six stroke survivors performed a GXT. Results: At rest, there was no difference in StO2 between the paretic and nonparetic VL (65 ± 9% vs 68 ± 7%, respectively, P =.32). The maximum change in StO2 from rest during the GXT was greater in the nonparetic versus the paretic VL (−16 ± 14% vs −9 ± 10%, respectively, P <.001). The magnitude of the oxygen resaturation response was also greater in the nonparetic versus the paretic VL (29 ± 23% vs 18 ± 15%, respectively, P <.001). VO2 peak was associated with the magnitude of the VL StO2 change during (r2 = 0.54, P <.0001) and after (r2 = 0.56, P <.001) the GXT. Conclusion: During a GXT, there is a blunted oxygen desaturation response in the paretic versus the nonparetic VL of chronic stroke survivors. In the paretic VL, there was a positive correlation between the oxygen desaturation response during the GXT and VO2 peak. [ABSTRACT FROM AUTHOR]

BACKGROUND: Electronic media have become integral parts of modern life, in which prolonged screen viewing time (SVT) by children is nearly unavoidable. Prolonged use of smartphones could lead to musculoskeletal problems. OBJECTIVES: To investigate the effect of SVT on head and neck posture during and after using smartphones for various periods of time in either standing or sitting postures. METHODS: This observational study included 34 male children aged 5–12 years who were assigned to one of two groups based on average smartphone use duration per day: group A comprised 18 children averaging > 4 hours per day (h/day) of smartphone use, and group B comprised 16 children with < 4 h/day of smartphone use. The children's postures were photographed in standing and sitting positions while using a smartphone and 30 min after ceasing smartphone use. The head flexion, neck flexion, gaze, and craniocervical angles were measured using the software program Kinovea. RESULTS: Significant increases were found in head flexion, neck flexion, and gaze angles. Furthermore, both groups saw a significant decrease in craniocervical angle when sitting compared to when standing, both during and 30 min after smartphone use. The head flexion, neck flexion, and gaze angles of group A were significantly higher than those of group B, and the craniocervical angle of group A was significantly lower than that of group B in both postures (p < 0.05). CONCLUSION: SVT is associated with increased neck and head flexion posture in children, especially in a sitting position. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of sustained abdominal exercises--pelvic tilt and twist curl-up--on the magnitude of abdominalmuscle activation andmaximal expiratory pressure (MEP) in healthymen andwomen. It was hypothesized that the activation would differ between men and women during these 3 exercisemaneuvers. Methods: Using a cross-sectional design, 10 healthy men and 10 women sustained pelvic tilt and twist curl-up exercises until task failure. Baseline MEP was compared with MEP immediately after both exercises. The root mean square of the internal oblique, rectus abdominis, external oblique, and transverse abdominis were evaluated during pelvic tilt, twist curl-up, andMEP. Results: Pelvic tilt and twist curl-upwere sustained for similar durations. Twist curl-up induced higher activations andmore shifts to lowermedian frequency inall 4 abdominals compared with pelvic tilt. Although internal oblique activation was highest during MEP and lowest during pelvic tilt in women, these comparisons did not differ in men. Maximal expiratory pressure tended to decrease after sustained pelvic tilt inwomen but did not change inmen. Conclusions: Twist curl-up activated abdominalmuscles more so than pelvic tilt. Some sex differences were shown that should be considered in future research of abdominal muscle exercise prescription. [ABSTRACT FROM AUTHOR]

Background: Eccentric exercise may be considered as an attractive alternative to conventional exercise in pulmonary rehabilitation (PR) for patients with chronic obstructive pulmonary disease (COPD). However, due to muscle damage associated with eccentric exercise, there has been reluctance in using this exercise form in PR. Objective: The aim of the present study was to investigate the effect of eccentric exercise on markers of muscle damage in patients with COPD. Methods: We analyzed 14 patients with moderate-severe COPD and 14 age-matched healthy controls. Both groups performed submaximal eccentric exercise of the elbow flexors. Muscle soreness (MS), maximum voluntary isometric contraction (MVC) of the elbow flexors, elbow range of motion (ROM), upper arm circumference (CIR), and biochemical markers such as creatine Kinase (CK) and lactate Dehydrogenase (LDH) were measured at pre-exercise, 24 h, 48 h, and 72 h following submaximal eccentric exercise. Results: There was a significant difference in markers of muscle damage, MS (p =.002), MVC (p <.001), ROM (p =.010), CIR (p <.001), and LDH (p =.001). However, no significant differences were observed in the activity of CK (p =.261) between COPD and control group following eccentric exercise which indicates greater degree of muscle damage in COPD as compared with control. Conclusion: Sub-maximal eccentric exercise causes significantly greater muscle damage in elderly COPD patients than healthy controls. Therefore, initial exercise should be progressed with lower intensities to prevent undue muscle damage in these patients. [ABSTRACT FROM AUTHOR]

To study the long-term evolution of patients with lower-limb Complex Regional Pain Syndrome (CRPS), focusing on functional and proprioceptive aspects and quality of life. In 20 patients suffering from chronic distal lower-limb CRPS diagnosed using Budapest criteria, we assessed joint position sense and strength of the knee muscles at the CRPS and unaffected leg, functional exercise capacity, pain, CRPS severity score, quality of life and kinesiophobia. Similar assessments were performed in 20 age-matched controls. The joint position performance (at 45°) was significantly lower for the CRPS leg as compared to controls. The knee extensor strength of the CRPS leg was significantly reduced as compared to the unaffected leg (−27%) and controls (−42%). CRPS patients showed significantly reduced performance at the 6 min-walk test as compared to their age group predicted value and controls. Patients suffering from CRPS for 3.8 years in average still exhibit high pain, severity and kinesiophobia scores. Long-term deficits in strength and proprioceptive impairments are observed at the knee joint of the CRPS leg. This persistent functional disability has significant repercussions on the quality of life. We highlight the importance of including strength and proprioceptive exercises in the therapeutic approaches for CPRS patients. The long-term evolution of patients suffering from lower-limb Complex Regional Pain Syndrome is associated with persistent disability, pain and impacts the quality of life. Strength, proprioceptive, functional and subjective assessments are necessary to better identify deficits. Rehabilitation should focus on the overall deficit of the affected and contralateral limb. [ABSTRACT FROM AUTHOR]

BACKGROUND: Various cupping sizes of cupping therapy have been used in managing musculoskeletal conditions; however, the effect of cupping sizes on skin blood flow (SBF) responses is largely unknown. OBJECTIVE: The objective of this study was to compare the effect of three cupping sizes of cupping therapy on SBF responses. METHODS: Laser Doppler flowmetry (LDF) was used to measure SBF on the triceps in 12 healthy participants in this repeated measures study. Three cup sizes (35, 40 and 45 mm in diameter) were blinded to the participants and were tested at - 300 mmHg for 5 minutes. Reactive hyperemic response to cupping therapy was expressed as a ratio of baseline SBF. RESULTS: All three sizes of cupping cups resulted in a significant increase in peak SBF (p < 0.001). Peak SBF of the 45 mm cup (9.41 ± 1.32 times) was significantly higher than the 35 mm cup (5.62 ± 1.42 times, p < 0.05). Total SBF of the 45 mm cup ((24.33 ± 8.72) × 10 3 times) was significantly higher than the 35 mm cup ((8.05 ± 1.63) × 10 3 times, p < 0.05). Recovery time of the 45 mm cup (287.46 ± 39.54 seconds) was significantly longer than the 35 mm cup (180.12 ± 1.42 seconds, p < 0.05). CONCLUSIONS: Our results show that all three cup sizes can significantly increase SBF. The 45 mm cup is more effective in increasing SBF compared to the 35 mm cup. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to examine the acute effects of equal volumes of fatiguing high- vs. low-intensity eccentric muscle actions on changes in muscle thickness, echo intensity, muscle blood flow, and adipose thickness. Eighteen men (mean ± SD = 23.2 ± 3.0 years) performed eccentric peak torque (PT) and maximal voluntary isometric contraction (MVIC) trials before (pretest), immediately after (posttest), and 5 minutes after (recovery) performing randomly ordered fatiguing eccentric, isokinetic (180°⋅s-1) muscle actions of the elbow flexors at 40% (72 repetitions) or 80% (36 repetitions) of eccentric PT. Muscle thickness, exercise-induced edema, muscle blood flow, and adipose thickness were also assessed via ultrasound at pretest, posttest, and recovery. There were no intensity-specific effects on the patterns of responses for eccentric PT, MVIC, muscle thickness, echo intensity, muscle blood flow, or adipose thickness. There were, however, effects across time that decreased from pretest to posttest and from pretest to recovery for eccentric PT (21.5 and 13.0%), MVIC (14.6 and 5.8%), and adipose thickness (10.0 and 6.0%), but increased for muscle thickness (7.6 and 5.9%), echo intensity (13.7 and 9.9%), and muscle blood flow (129.6 and 90.1%) (collapsed across 40 and 80%). These findings indicated that when matched for exercise volume, there were no intensity-related effects on the increases in muscle thickness, echo intensity, muscle blood flow, or the decreases in eccentric PT, MVIC, and adipose thickness after fatiguing eccentric muscle actions. Therefore, exercise volume, independent of exercise intensity and number of repetitions, may be a mediating factor of muscle fatigue and performance during eccentric muscle actions. [ABSTRACT FROM AUTHOR]

BACKGROUND: A high prevalence of work-related musculoskeletal disorders (WMSDs) has been reported among flight attendants. Identifying the root causes of these disorders may improve the health conditions of flight attendants and further improve flight safety and service quality. OBJECTIVE: In this study, we aimed to identify WMSD risk factors for a specific population, namely Chinese female flight attendants. METHODS: A two-stage survey including an online questionnaire (46 flight attendants) and a semi-structured interview (16 flight attendants) was used to assess the WMSDs of Chinese female flight attendants. Text analysis tools in NVivo 11 were used to identify the main concerns and risk factors for WMSDs of Chinese flight attendants. RESULTS: In the online questionnaire, more than 86% of the participants reported discomfort in at least one body part. Biomechanical factors, work organizational factors, and psychosocial factors were reported by participants in this study. Chinese passengers were found to have an effect on WMSD development in Chinese flight attendants. CONCLUSIONS: The results of this study suggested that WMSDs are severe problems among Chinese flight attendants. General factors as well as the passenger-relevant factor were identified as the most influential causes of WMSDs. [ABSTRACT FROM AUTHOR]

GÓmez-Carmona, CD, Bastida-Castillo, A, Rojas-Valverde, D, de la Cruz Sánchez, E, Garcia-Rubio, J, Ibáñez, SJ, and Pino-Ortega, J. Lower-limb dynamics of muscle oxygen saturation during the back-squat exercise: effects of training load and effort level. J Strength Cond Res 34(5): 1227-1236, 2020 The aim of this study was to analyze the effect of strength training on lower limb muscle oxygenation. The sample consisted of 12 male subjects (22.4 ± 1.73 years; 1.81 ± 0.08 cm height and 77.76 ± 8.77 kg body mass). Six different strength training stimuli were analyzed, based on the training variables: load (60-75% 1 repetition maximum [1RM]) and level of effort (LE) (E1: 4 × 8 [20RM], E2: 4 × 12 [20RM], E3: 4 × 16 [20RM], E4: 4 × 4 [10RM], E5: 4 × 6 [10RM], and E6: 4 × 8 [10RM]) in the squat exercise up to 90° with a 2-second stop between repetitions to avoid the myotatic reflex. Oxygen saturation at the beginning of the series (SmO2start), oxygen saturation at the end of the series (SmO2stop), percentage of oxygen saturation loss (▿ %SmO2), and reoxygenation time (SmO2recT) were assessed using a near-infrared spectroscopy device. In addition, the percentage of mean propulsive velocity loss (%MPVL) was recorded using a linear transducer. The results suggested an influence of LE and training load on muscle oxygenation. A greater LE was directly associated with SmO2recT (r =0.864), ▿ %SmO2 (r=0.873), and %MPVL (r=0.883) and inversely with SmO2stop (r =−0.871). When the same LE was used (E1 vs. E4, E2 vs. E5, and E3 vs. E6), it was found that the stimuli with a higher load had a lower SmO2recT, ▿ %SmO2, and %MPVL and a higher SmO2stop. Muscle oxygen saturation was found to be minimal (%SmO2 =0) in stimuli with a LE greater than 60% (E3 and E6). The SmO2 variables studied in the present research could be considered as an easier and more useful method for understanding skeletal muscle fatigue during resistance training [ABSTRACT FROM AUTHOR]

BACKGROUND: The health implication of backpack carriage among school-aged children is a topic of growing research and public health interest. Low weighing backpacks may decrease the risk of musculoskeletal discomforts (MSDs). OBJECTIVE: To investigate MSDs and their association with backpack carriage practices among secondary school students in eastern Nigeria. METHOD: Across-sectional study of 404 (243 females and 161 males) secondary school students aged thirteen to seventeen who were residents of Enugu State, Nigeria was conducted. The Modified Standard Nordic Musculoskeletal Questionnaire was adapted and used to collect information onstudents' demographics, musculoskeletal painand backpack carriage. Descriptive statistics (frequencies and percentages) were utilized to summarize results. Chi-square test was used to explore the association between MSD prevalence and backpack carriage practices. Data were analysed using SPSS version 20.0. Alpha level was kept at 0.05. RESULTS: The average backpack weight carried by the students in this study was 2.49 kg. Shoulder (185, 45.8%), neck (121, 30.0%), upper back (91, 22.6%) and lower back (22, 5.5%) in that order were the body regions most affected by MSDs within the last 12 months. More females than males reported MSDs (60.5% vs 45.2%; x2 = 8.09, p = 0.04). Other students'characteristics and backpack carriage related factors were not associated with MSDs. CONCLUSION: There is a high prevalence of MSDs among secondary school students in this study but it is not related to backpack carriage. Further research is required to identify the factors responsible for the MSDs, as well as suitable interventions to reduce its impact in this population. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare effects of newly designed double-chamber cuff with asymmetric pressure (APC) distribution and standard single-chamber cuff with symmetric pressure (SPC) distribution on muscle perfusion and volitional activation. First, the 2 cuffs were compared bilaterally on resting thigh muscles of 17 healthy volunteers at 4 cuff pressures (120, 160, 200, and 240 mm Hg). Then, the subjects performed the isometric endurance test of knee extensor muscles to volitional failure at 40% of maximal volitional isometric action in both free-flow and blood flow restricted condition. Changes in hemoglobin kinetics in vastus lateralis muscle (near-infrared spectroscopy), surface electromyography of vastus medialis muscle, and pain intensity (visual analogue scale [VAS]) were continuously recorded. At rest, a significant difference (p = 0.009) in velocity of change in total hemoglobin concentration was noted between the cuffs at 160 mm Hg (APC = 0.028 µM·s-1 and SPC = 0.056 µM⋅s-1). The VAS scores significantly increased (p = 0.031) at pressures ≥200 mm Hg, with no difference between the cuffs. Duration of isometric action with blood flow restriction was 12% shorter (p = 0.003) than in free-flow condition, with no difference between the cuffs. There were no significant differences in muscle activation or hemoglobin kinetics between the exercise conditions or cuff types. The results show that APC reduces blood flow in quadriceps femoris muscle at rest at lower pressure than SPC, which suggests its enhanced efficiency for blood flow restriction. Given that application of either type of cuff during sustained isometric action had only minor impact on muscle endurance and oxygen kinetics, future research must focus primarily on dynamic muscle actions. [ABSTRACT FROM AUTHOR]

The mechanisms underlying velocity-specific decreases in torque production during eccentric muscle actions remain unclear. Therefore, the purpose of the present study was to examine electrical efficiency at 60 and 180° · s-1 during fatiguing, maximal eccentric isokinetic muscle actions of the leg extensors. Thirteen men visited the lab on two occasions and randomly performed 30 repeated maximal eccentric isokinetic muscle actions of the leg extensors at 60 and 180° · s-¹ through a 90° range of motion. Polynomial regression analyses and separate repeated measures ANOVAs were used to examine the composite patterns of responses for electromyographic amplitude, eccentric torque, and electrical efficiency across the 60 and 180° ⋅ s-¹ protocols. Eccentric torque remained unchanged across the 30 maximal eccentric muscle actions performed at 60 and 180° ⋅ s-1. Electromyographic amplitude and electrical efficiency, however, increased linearly across the 180° ⋅ s-1 protocol, but there were no changes for either electromyographic amplitude or electrical efficiency during the 60° · s-1 fatiguing protocol. These findings indicated that performing eccentric muscle actions at a fast velocity (i. e., 180° ⋅ s-1) was characterized by greater efficiency (i. e., decreased electrical efficiency) compared to eccentric muscle actions performed at a slow velocity (i. e., 60° ⋅ s-1). Thus, it is possible that eccentric muscle actions performed at fast velocities are more robust to fatigue due, in part, to greater effi- ciency compared to slow-velocity eccentric muscle actions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wrist disorders are common in force demanding industrial repetitive work. Visual assessment of force demands have a low reliability, instead surface electromyography (EMG) may be used as part of a risk assessment for work-related wrist disorders. For normalization of EMG recordings, a power grip (hand grip) is often used as maximal voluntary contraction (MVC) of the forearm extensor muscles. However, the test-retest reproducibility is poor and EMG amplitudes exceeding 100% have occasionally been recorded during work. An alternative MVC is resisted wrist extension, which may be more reliable. OBJECTIVE: To compare hand grip and resisted wrist extension MVCs, in terms of amplitude and reproducibility, and to examine the effect of electrode positioning. METHODS: Twelve subjects participated. EMG from right forearm extensors, from four electrode pairs, was recorded during MVCs, on three separate occasions. RESULTS: The group mean EMG amplitudes for resisted wrist extension were 1.2–1.7 times greater than those for hand grip. Resisted wrist extension showed better reproducibility than hand grip. CONCLUSIONS: The results indicate that the use of resisted wrist extension is a more accurate measurement of maximal effort of wrist extensor contractions than using hand grip and should increase the precision in EMG recordings from forearm extensor muscles, which in turn will increase the quality of risk assessments that are based on these. [ABSTRACT FROM AUTHOR]

Background: Low-load resistance training (< 50% of one-repetition maximum [1RM]) associated with blood-flow restriction (BFR-RT) has been thought to promote increases in muscle strength and mass. However, it remains unclear if the magnitude of these adaptations is similar to conventional high-load resistance training (> 65% 1RM; HL-RT). Objective: To compare the effects of HL- versus BFR-RT on muscle adaptations using a systematic review and meta-analysis procedure. Methods: Studies were identified via electronic databases based on the following inclusion criteria: (a) pre- and post-training assessment of muscular strength; (b) pre- and post-training assessment of muscle hypertrophy; (c) comparison of HL-RT vs. BFR-RT; (d) score ≥ 4 on PEDro scale; (e) means and standard deviations (or standard errors) are reported from absolute values or allow estimation from graphs. If this last criterion was not met, data were directly requested from the authors. Results: The main results showed higher increases in muscle strength for HL- as compared with BFR-RT, even when considering test specificity, absolute occlusion pressure, cuff width, and occlusion pressure prescription. Regarding the hypertrophic response, results revealed similar effects between HL- and BFR-RT, regardless of the absolute occlusion pressure, cuff width, and occlusion pressure prescription. Conclusions: Based on the present data, maximum muscle strength may be optimized by specific training methods (i.e., HL-RT) while both HL- and BFR-RT seem equally effective in increasing muscle mass. Importantly, BFR-RT is a valid and effective approach for increasing muscle strength in a wide spectrum of ages and physical capacity, although it may seem particularly of interest for those individuals with physical limitations to engage in HL-RT. [ABSTRACT FROM AUTHOR]

Several studies have confirmed the efficacy of flywheel paradigm training for improving or benefiting muscle volume and force. A meta-analysis of 13 studies with a total of 18 effect sizes was performed to analyse the role of various factors on the effectiveness of flywheel paradigm training. The following inclusion criteria were employed for the analysis: (a) randomized studies; (b) high validity and reliability instruments; (c) published in a high quality peer-reviewed journal; (d) healthy participants; (e) studies where the eccentric programme were described; and (f) studies where increases in muscle volume and force were measured before and after training. Increases in muscle volume and force were noted through the use of flywheel systems during short periods of training. The increase in muscle mass appears was not influenced by the existence of eccentric overload during the exercise. The increase in force was significantly higher with the existence of eccentric overload during the exercise. The responses identified in this analysis are essential and should be considered by strength and conditioning professionals regarding the most appropriate dose response trends for flywheel paradigm systems to optimize the increase in muscle volume and force. [ABSTRACT FROM AUTHOR]

BACKGROUND: Range of Motion (ROM) and passive torque have been widely used to evaluate flexibility stretching protocols, but little attention has been given to the reliability of these measurements. OBJECTIVE: To verify the interday reliability of isokinetic dynamometer for assessing ROM measures based on discomfort perception (initial and maximum), static and dynamic measures of passive torque during a leg extension movement on a young adult sample. METHODS: Twenty students (13 men; 7 women) aged between 18 and 30 years attended the laboratory to perform the test and retest with 2-7 days interval. The evaluations included: Initial Discomfort Angle (IDA), Passive dynamic torque (Stiffness), Passive static torque (Viscoelastic Stress Relaxation-VSR) and Maximal Discomfort Angle (MDA). Reliability was tested by the Intraclass Correlation Coefficient (ICC), one-sample t-test and Bland-Altman charts. RESULTS: Stiffness (ICC = 0.93), IDA (ICC = 0.90) and MDA (ICC = 0.87) showed excellent reliability values, while VSR had moderate ones (ICC = 0.59). Bland-Altman plots indicated bias close or equal to zero. The one-sample t-test for all measures reinforced the absence of a systematic error. CONCLUSIONS: Dynamic and static stiffness measures and ROM based on the subject's discomfort perception may be applied to relevant clinical issues. [ABSTRACT FROM AUTHOR]

The present study aimed to analyze and compare the effects of four different interval-training protocols on aerobic fitness and muscle strength. Thirty-seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low-intensity interval training with ( BFR, n = 10) or without ( LOW, n = 7) blood flow restriction, high-intensity interval training ( HIT, n = 10), and combined HIT and BFR ( BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake ( VO2max), maximal power output ( Pmax), onset blood lactate accumulation ( OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA ( BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO2max and Pmax improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to examine the effects of hyperbaric oxgen (HBO) on muscle fatigue after maximal intermittent plantar flexion exercise. The study includes 20 healthy male volunteers who were randomly assigned to either HBO or normoxic group and were blined to their treatment and group assignment. The study results suggests that HBO can contribute to the prevetion of excess fatigue of agonist muscles for specific exercises that involve repeated jumping.

The article offers information on the assessment of peristaltic pulse dynamic compression (PPDC) that reduces stiffness of muscles in athletes of Olympic training center. Topics discussed include symptoms of muscle microtrauma and stiffness, strategies to recover athletes' health and the statistical results based on gender differences.

The article discusses a study analyzing impact of unusual eccentric exercise (ECC) bouts on blood flow of muscles and electromyographic (EMG) signal from exercises of anterior muscle. Topics discussed include measurements of changes in blood flow to muscles while performing, ECC on tibialis anterior muscle, and changes in pattern of blood flow as a result of vasodilation of muscular veins and oxygen content.

The article focuses on a study which is aimed at comparative analysis of the effects of low-resistance training coupled with blood flow restriction (LRT-BFR) and high-intensity resistance training (HRT) on the quadriceps muscle strength and mass when performed in healthy elderly age group. Various tests were performed including one repetition maximum test in which leg press strength was assessed, determination of cross-sectional area of quadriceps and determination of blood flow restriction.

In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD) or a carbohydrate group (PLA). Subjects completed 12 weeks maximal knee extensor training with one leg using eccentric contractions and the other using concentric contractions. Before and after training cross-sectional area (CSA) of m. quadriceps and patellar tendon CSA was quantified with magnetic resonance imaging and a isometric strength test was used to assess maximal voluntary contraction (MVC) and rate of force development (RFD). Quadriceps CSA increased by 7.3 ±1.0% (P< 0.001) in WHD and 3.4 ± 0.8% (P< 0.01) in PLA, with a greater increase in WHD compared to PLA (P<0.01). Proximal patellar tendon CSA increased by 14.9 ± 3.1% (P< 0.001) and 8.1 ± 3.2% (P = 0.054) for WHD and PLA, respectively, with a greater increase in WHD compared to PLA (P < 0.05), with no effect of contraction mode. MVC and RFD increased by 15.6 ± 3.5% (P< 0.001) and 12-63% (P<0.05), respectively, with no group or contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training - irrespective of contraction mode. [ABSTRACT FROM AUTHOR]

The article discusses research investigating the effects and mechanisms of normobaric hyperoxia on the recovery of local muscle fatigue in male research subjects. Topics include measurements of maximum voluntary isometric contraction (MVIC), endurance time to exhaustion, blood lactate levels, and perceived exertion measured by a visual analog scale (VAS). Various factors encompassing local muscle fatigue, metabolic acidosis, and the study's experimental design are discussed.

Purpose Chronic neck/shoulder pain ( CNSP) is one of the most common pain conditions. The understanding of mechanisms, including the peripheral balance between nociceptive and antinociceptive processes, is incomplete. N-acylethanolamines ( NAEs) are a class of endogenous compounds that regulate inflammation and pain. The aim of this study was to investigate the levels of two NAEs: the peroxisome proliferator-activated receptor type-α ligand palmitoylethanolamide ( PEA) and stearoylethanolamide ( SEA) in the muscle interstitium of the trapezius muscle in women with CNSP randomized to two different neck specific training programs and in a healthy pain-free control group ( CON). Materials and Methods Fifty-seven women with CNSP were randomized to strength + stretch or stretch alone exercise programs. Twenty-nine subjects underwent microdialysis procedure before and after 4-6 months of exercise. Twenty-four CON subjects underwent microdialysis procedure before and after 4-6 months without any intervention in between. Microdialysate samples were collected from the trapezius muscle and analyzed by mass spectrometry for PEA and SEA levels. Results PEA and SEA levels were significantly higher in CNSP patients compared with CON. PEA was significantly higher in CNSP than in CON after both training programs. SEA was significantly higher in CNSP than in CON after stretch alone but not after strength + stretch training. A significant positive correlation was found between changes in pain intensity and in SEA levels in the strength + stretch group, but not in the stretch alone group. Conclusion Our results indicate that exercise interventions differentially affect the levels of the bioactive lipids PEA and SEA in the interstitium of the trapezius muscle in women with CNSP. [ABSTRACT FROM AUTHOR]

Objective. This study evaluated the effect of different types of activities during rest-break interventions on neck and shoulder muscle activity, muscle discomfort and productivity among symptomatic video display unit (VDU) operators performing prolonged computer terminal work. Study design and setting. Randomized controlled trial was used. Thirty symptomatic VDU operators were randomly assigned to 2 active break groups (stretching and dynamic movement) and a reference group. The subjects performed the same typing task for 60 min and received 3-min breaks after each 20 min of work. Root mean square and median frequency were calculated for neck and shoulder muscle activity. Muscle discomfort was measured with Borg's CR-10 scale. Productivity was measured by counting words. Results. There were no significant differences between the types of activities during breaks on neck and shoulder muscle activity, muscle discomfort or productivity. However, there was a significant difference in the level of muscle discomfort over time. Conclusions. Three types of activity during breaks showed a favourable effect on neck and shoulder muscle activity and productivity, and a positive effect on muscle discomfort in symptomatic VDU operators. [ABSTRACT FROM AUTHOR]

Previous findings, during chewing, that boluses of larger size and harder texture result in larger amplitudes of both mandibular and head-neck movements suggest a relationship between increased chewing load and incremental recruitment of jaw and neck muscles. The present report evaluated jaw (masseter and digastric) and neck [sternocleidomastoid ( SCM) and trapezius] muscle activity during the chewing of test foods of different sizes and textures by 10 healthy subjects. Muscle activity was recorded by surface electromyography and simultaneous mandibular and head movements were recorded using an optoelectronic technique. Each subject performed continuous jaw-opening/jaw-closing movements whilst chewing small and large boluses of chewing gum and rubber silicone (Optosil). For jaw opening/jaw closing without a bolus, SCM activity was recorded for jaw opening concomitantly with digastric activity. During chewing, SCM activity was recorded for jaw closing concomitantly with masseter activity. Trapezius activity was present in some, but not all, cycles. For the masseter and SCM muscles, higher activity was seen with larger test foods, suggesting increased demand and recruitment of these muscles in response to an increased chewing load. This result reinforces the previous notion of a close functional connection between the jaw and the neck motor systems in jaw actions and has scientific and clinical significance for studying jaw function and dysfunction. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to investigate the impact three weeks of eccentric training combined with overspeed exercises had on power and running speed performance gains in trained athletes. Researchers evaluated 20 team sports athletes. They found that the training and exercises led to enhanced power and running speed performance gains in the athletes.

The effect of contraction intensity (100%-, 75%-, 50%-, and 25%-maximum voluntary contraction [MVC]) and movement velocity (0°, 100°, 200°, 300°, and 400°/s) on the root mean square amplitude (SEMG-RMS) and median frequency power spectrum (SEMG-MPF) of the surface electromyography of the vastus medialis (VM) and rectus femoris (RF) muscles during isokinetic extension movements was investigated. Eight healthy female university students (age=23.1 ± 2.6 yrs., mean height=161.8 ± 6.8 cm, mean weight=64.6 ± 6.1 kg) with no known knee pathologies participated in the study. Peak moment (PM), SEMG-MPF, and SEMG-RMS were analyzed using separate repeated measures analysis of variance (ANOVA). Results indicated (p&les; 0.05): (1) an inverse relationship between PM and movement velocity, which was consistent with the literature and the force-velocity curve; (2) an increase in VM and RF SEMG-RMS across all isovelocity movements compared to isometric, with highest values occurring at 200°/s; (2) a linear increase in SEMG-RMS as force levels increased from 25%-MVC to 100%-MVC; and, (3) an increase in SEMG-MPF values during isovelocity movements compared to that found during isometric contractions, with highest values at 50°/s, suggesting isovelocity movements facilitated a greater recruitment of fast-twitch fibers. It appears that the degree to which the central nervous system activates muscle is based on the interplay of both contraction intensity and velocity needed to complete the required motor task. [ABSTRACT FROM AUTHOR]