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Purpose: The purpose of this study was to determine magnitudes of differences for anthropometric and athletic performance scores between high school and elite college-level American football players. Method: Participants included high school-age (n = 3,666) athletes who participated in American football combines, as well as elite college-level (n = 5,537) athletes who participated in the National Football League (NFL) scouting combine. Combine data included position; height; weight; 10-, 20-, and 40-yard dash; pro-agility (PA); L-cone drill (LC); vertical jump (VJ); and broad jump (BJ). Athletes were separated into their respective position group, defensive back (DB), wide receiver (WR), linebacker (LB), quarterback (QB), running back (RB), tight end (TE), defensive line (DL), and offensive line (OL) for analysis of performance differences. Percent differences for each dependent variable were calculated to quantify magnitudes of differences. Results: NFL combine participants scored 3% to 25% better on all measurements, with the largest differences between weight and VJ (14%-25%). Conclusion: The largest measurement-specific differences between high school-age and elite college-level American football players were body size and power. Although it may seem intuitive that elite college-level players would perform better, these data provide a unique perspective to high school players, parents, and coaches, giving new information to use when designing measurement-specific athletic development programs. Thus, strength and conditioning professionals may benefit from emphasizing increases in muscle mass and power output in strength and conditioning programs.

Shoemaker, ME, Smith, CM, Gillen, ZM, and Cramer, JT. Sex differences in test-retest reliability of near-infrared spectroscopy during postocclusive reactive hyperemia of the vastus lateralis. J Strength Cond Res 38(2): e40-e48, 2024--The purpose of this study was to determine test-retest reliability for vascular reactivity measures and ranges for normalization of near-infrared spectroscopy (NIRS) variables from the vastus lateralis using postocclusive reactive hyperemia (PORH) procedure in male subjects, female subjects, and combined. Concentrations of oxygenated hemoglobin (Hb) + myoglobin (Mb) (O2Hb) and deoxygenated Hb + Mb (HHb) to derive total Hb + Mb (THb), difference in Hb + Mb signal (Hbdiff), and muscle tissue oxygen saturation (StO2) from the vastus lateralis were measured during the PORH in 12 male subjects (age: 23.17 6 1.77 years; stature: 180.88 6 4.59 cm; and mass: 81.4769.68 kg) and 10 female subjects (age: 23.8062.07 years; stature: 165.9564.92 cm; and mass: 70.93610.55 kg) on 2 separate days. Adipose tissue thickness at the NIRS site was measured with ultrasonography. There were no significant differences between the mean values from visit 1 to visit 2 (p. 0.076-0.985). In the composite sample, intraclass correlation coefficient (ICC) and coefficient of variation (CV) ranged from 0.35 to 0.91 and 4.74 to 39.18%, respectively. In male subjects, ICC and CV values ranged from 0.57 to 0.89 and 2.44 to 28.55%, respectively. In female subjects, ICC and CV values ranged from 2 0.05 to 0.75 and 7.83 to 61.19%, respectively. Although NIRS variables were overall reliable during PORH, when separated by sex, reliability in male subjects generally increased, whereas female subjects were not reliable, suggesting adipose tissue thickness may be a contributing factor. Understanding sex differences in reliability is important when using this technique for normalization or examining vascular reactivity during athletic performance. With greater utilization of NIRS monitoring in athletes to examine training adaptations, it is important for practitioners to understand the capabilities and potential limitations of the tool. [ABSTRACT FROM AUTHOR]

The purpose of this trial was to examine the effects of self-selected exercise intensities plus either whey protein or placebo supplementation on vital signs, body composition, bone mineral density, muscle strength, and mobility in older adults. A total of 101 participants aged 55 years and older (males [n = 34] and females [n = 67]) were evaluated before and after 12 weeks of self-selected, free-weight resistance exercise plus 30 min of self-paced walking three times per week. The participants were randomized into two groups: whey protein (n = 46) or placebo (n = 55). Three-way mixed factorial analyses of variance were used to test for mean differences for each variable. The 12 weeks of self-selected, self-paced exercise intensities improved resting heart rate, fat-free mass, percent body fat, handgrip strength, bench press strength, leg press strength, and all mobility measurements (p <.05) in males and females despite supplementation status. This suggests that additional protein in well-fed healthy older adults does not enhance the benefit of exercise. [ABSTRACT FROM AUTHOR]

This study measured peak force (PF), peak rate of force development (PRFD), peak power (PP), concentric impulse, and eccentric impulse during static jump (SJ), countermovement jump (CMJ), and drop jump (DJ) in youth athletes to examine changes in vertical jump power with progressively greater eccentric preloading in relation to age, maturity, and muscle mass. Twenty-one males ranging from 6 to 16 years old performed the following vertical jumps in a random order: SJ, CMJ, and DJ from drop heights of 20, 30, and 40 cm (DJ20, DJ30, and DJ40, respectively). Measurements included PF, PRFD, PP, eccentric impulse, and concentric impulse for each vertical jump condition. Maturity offset was calculated, while ultrasound images quantified thigh muscle cross-sectional area (CSA). PF and PRFD increased from CMJ to DJ20. PP increased from SJ to CMJ. Concentric impulse remained unchanged, but eccentric impulse increased systematically from across jumps. The change in PP from SJ to CMJ was correlated with age, height, weight, maturity offset, and CSA. The CMJ resulted in the greatest concentric PP with the least amount of eccentric preloading. The inability of young athletes to translate the energy absorbed during the eccentric phase of the stretch-shortening cycle of DJs may be influenced by growth and development. [ABSTRACT FROM AUTHOR]

Furthermore, substrate utilization and fuel adaptability are positively associated with exercise performance [[6]], while numerous dietary and training interventions have been explored to either quantify or manipulate these outcome variables [[7], [9]]. Metabolic flexibility can be defined as the ability of the skeletal muscle to adjust its utilization of substrate pathways [[1]]. Thus, to appropriately adjust substrate utilization in response to nutritional and/or exercise stress (i.e., glucose mobilization via insulin), increasing skeletal muscle quality and/or quality should be prioritized. Skeletal muscle is necessary for movement and exercise; however, it also has an important role in metabolism, as skeletal muscle accounts for 60-80% of the response of glucose to insulin [[1], [5]]. [Extracted from the article]

There is conflicting evidence of the roles vitamin D and iron have in isolation and combined in relation to muscle health. The purpose of this narrative review was to examine the current literature on the roles that vitamin D and iron have on skeletal muscle mass, strength, and function and how these nutrients are associated with skeletal muscle health in specific populations. Secondary purposes include exploring if low vitamin D and iron status are interrelated with skeletal muscle health and chronic inflammation and reviewing the influence of animal-source foods rich in these nutrients on health and performance. PubMed, Scopus, SPORT Discus, EMBAE, MEDLINE, and Google Scholar databases were searched to determine eligible studies. There was a positive effect of vitamin D on muscle mass, particularly in older adults. There was a positive effect of iron on aerobic and anaerobic performance. Studies reported mixed results for both vitamin D and iron on muscle strength and function. While vitamin D and iron deficiency commonly occur in combination, few studies examined effects on skeletal muscle health and inflammation. Isolated nutrients such as iron and vitamin D may have positive outcomes; however, nutrients within food sources may be most effective in improving skeletal muscle health. [ABSTRACT FROM AUTHOR]

Lamont, HS, Cramer, JT, Bemben, DA, Shehab, RL, Anderson, MA, and Bemben, MG. The acute effect of whole-body low-frequency vibration on countermovement vertical jump performance in college-aged men. J Strength Cond Res 24(12): 3433-3442, 2010--The purpose of this study was to examine the acute effects of whole-body vibration on jump performance. A total of 21 college-aged men, 18-30 years, recreationally resistance trained, were exposed to a total of 4 different acute whole-body low-frequency vibration (WBLFV) protocols (conditions 1-4), performing 2 protocols per testing session in random order. Exposures were all performed using high-amplitude (peak-peak 4-6 mm) and either 30 or 50 Hz for 30 continuous seconds, or 3 exposures of 10 seconds with 1 minute between exposures. Three countermovement vertical jumps (CMVJs) were performed before vibration (testing phase 1 or Tp1 and J1 the highest of 3 attempts) and at 3 separate time points postvibration (Tp2-4). Jump height (cm), peak power ([P.sub.max]), peak power per kilogram of body mass ([P.sub.max] [kg.sub.-1]), mean power ([P.sub.av]), and mean velocity ([V.sub.av]) were recorded. Repeated measures analysis of variance and analysis of covariance revealed no significant condition (C) or jump (J) differences for CMVJ height (cm) (p > 0.05). Analysis of percent change ([DELTA]%) for CMVJ height (cm) revealed a significant Condition x Jump interaction, C4, J3 > C1, J3 (p = 0.009, mean diff 4.12%). Analysis of [P.sub.max] and [P.sub.max] [kg.sup.-1] revealed no significant Condition, Jump, or Condition x Jump interaction for the raw data or percent change (p > 0.05). Analysis of Pay (W) revealed significant differences for Condition (p = 0.031) but not for Jump (p = 0.226). There was a strong trend toward significance for Condition x Jump interaction (p = 0.059). C4 > C3 (p = 0.043, mean diff 23.78 W) and C1 (p = 0.038, mean diff 32.03 W). Analysis of [V.sub.av] (m x [s.sup.-1]) revealed no significant main effects for Condition or Jump (p > 0.05) but found a significant Condition x Jump interaction (p = 0.007). C4, J6 > C2, J6 (p = 0.014, mean diff 0.05 m x [s.sup.-1]), and C3, J6 (p = 0.020, 0.05 m x [s.sup.-1]). WBLFV applied intermittently using 50 Hz appears to be more effective than other protocols using 30 and 50 Hz in facilitating select measures of CMVJ performance over a 17-minute time period post-WBLFV exposure. Practical manipulation of such a WBLFV 'dose' may be beneficial to strength and conditioning practitioners wanting to acutely facilitate CMVJ and slow stretch shortening cycle performance while minimizing exposure time. KEY WORDS stretch shortening cycle, jump performance, postactivation potentiation

The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean [+ or -] SD age = 21 [+ or -] 2 years; body mass = 79 [+ or -] 15 kg; and height = 1 77 [+ or -] 7 cm) and 19 women (21 [+ or -] 3 years; 61 [+ or -] 9 kg; 165 [+ or -] 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means [+ or -] SD pre to post: 109.39[degrees] [+ or -] 10.16[degrees] to 116.63[degrees] [+ or -] 9.63[degrees]; p [less than or equal to]-< 0.05) but not for the men (111.79[degrees] -+ 6.84[degrees] to 113.93[degrees] [+ or -] 8.15[degrees]; p > 0.05). There were no stretching-induced changes in MTS (women's pre to postchange in MTS: -0.35 [+ or -] 0.38; men's MTS: +0.1 7 [+ or -] 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 4 [+ or -] 0.41 vs. 0.97 [+ or -] 0.38; p [less than or equal to] 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p [less than or equal to] 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS. KEY WORDS constant torque, viscoelastic properties, electromyography

DeFreitas, JM, Beck, TW, Stock, MS, Dillon, MA, Sherk, VD, Stout, JR, and Cramer, JT. A comparison of techniques for estimating training-induced changes in muscle cross-sectional area. J Strength Cond Res 24(9): 2383-2389, 2010--The ability to accurately estimate changes in muscle cross-sectional area (CSA) could be a useful tool for strength and conditioning practitioners to assess the effectiveness of a resistance training program. The purpose of this study was twofold: (a) to compare the reliability of 2 separate anthropometric-based field estimations of thigh muscle CSA with that of a more accurate, sophisticated imaging technique (peripheral quantitative computed tomography [pQCT] scanner) and (b) to determine if the field methods would be sensitive enough to detect changes in CSA during a resistance training program. Twenty-five healthy, untrained men completed 8 weeks of resistance training. Cross-sectional area testing occurred twice before the start of training, for reliability and again every 2 weeks during the study. Testing consisted of a pQCT scan of the right thigh followed by circumference and skinfold measurements. Two separate equations (Moritani and deVries [M + D] and Housh multiple regression [HMR]) were used to estimate CSA from the anthropometric data. The M + D and HMR methods demonstrated intraclass correlations of 0.983 and 0.961, respectively, but both significantly underestimated thigh muscle CSA when compared to the pQCT. This error was consistent, however, and consequently, the field methods were able to demonstrate increases in muscle CSA with a pattern similar to those from the pQCT. Thus, these equations can be useful tools to evaluate an athlete's progress toward the goal of increasing muscle CSA. It is the authors' hope that the present study will increase awareness among practitioners of these useful field methods for estimating training-induced changes in muscle CSA. KEY WORDS anthropometry; pQCT, hypertrophy

Energy drink use has grown despite limited research to support efficacy or safety and amid concerns when combined with exercise. The purpose of this study was to assess the effects of 10 weeks of once-daily energy drink consumption or energy drink consumption with exercise on measures of body composition, cardiorespiratory fitness, strength, mood, and safety in previously sedentary males. Thirty-eight males were randomly assigned to energy drink + exercise (EX-A), energy drink (NEX-A), placebo + exercise (EX-B), or placebo (NEX-B). All participants consumed 1 drink per day for 10 weeks; EX-A and EX-B participated in 10 weeks of resistance and endurance exercise. Testing was performed before (PRE) and after (POST) the 10-week intervention. No significant (p > 0.05) changes were observed for body composition, fitness, or strength in NEX-A; however, significantly greater decreases in fat mass and percentage body fat and increases in [VO.sub.2]peak were observed in EX-A versus EX-B. Ventilatory threshold (VT), minute ventilation, [[??]O.sub.2] at VT, and power output at VT improved significantly PRE to POST in EX-A but not in EX-B or nonexercising groups. Clinical markers for hepatic, renal, cardiovascular, and immune function, as determined by PRE and POST blood work revealed no adverse effects in response to the energy drink. Mood was not affected by energy drink use. Absent energy restriction or other dietary controls, chronic ingestion of a once-daily low-calorie energy drink appears ineffective at improving body composition, cardiorespiratory fitness, or strength in sedentary males. However, when combined with exercise, preworkout energy drink consumption may significantly improve some physiological adaptations to combined aerobic and resistance training. KEY WORDS caffeine, thermogenic, body composition, taurine, EGCG, green tea

Creatine (Cr) loading consists of short-term, high-dosage Cr supplementation and has been shown to increase intramuscular total Or content. Increases in body weight (BW) have been shown to result from Cr loading, with differences by gender, and increased BW may impact weight-bearing exercise. The critical velocity (CV) test is used to quantify the relationship between total running distance and time to exhaustion. The CV test provides the variable, anaerobic running capacity (ARC), which is an estimate of the anaerobic energy reserves in muscle. The purpose of this study was to examine the effects of gender and Cr loading on ARC. Fifty moderately trained men and women volunteered to participate in this randomized, double-blinded, placebo (PL)controlled, repeated-measures study. After a familiarization session, a 3-day testing procedure was conducted. A maximal oxygen consumption test ([[??]o.sub.2]max) on a treadmill was performed on day 1 to establish the maximum velocity (Vmax) at [[??]o.sub.2]max and to record BW. Days 2 and 3 involved treadmill running at varying percentages of Vmax. Participants were randomly assigned to either the Cr or PL group and received 20 packets of the Cr supplement (1 packet = 5 g Cr citrate, 18 g dextrose) or 20 packets of the PL (1 packet = 18 g dextrose). After consuming 4 packets daily for 5 consecutive days, the 3-day testing procedure was repeated. The male Cr loading group exhibited a 23O/o higher (p = 0.003) ARC compared to the PL group. Nonsignificant BW increases were found for the Cr groups. These findings suggest that Cr loading may be an effective strategy for improving ARC in men, but not in women, and revealed only nonsignificant increases in BW. Creatine loading may be used before competition by athletes to provide improvements in high-intensity, short-duration activities. KEY WORDS ergogenic aids, treadmill running, sprint performance, body weight, high-intensity activity, critical velocity

The purpose of the present study was to evaluate the effects of cycle ergometry high-intensity interval training (HIIT) with and without [beta]-alanine supplementation on maximal oxygen consumption rate ([[??]o.sub.2]peak), cycle ergometer workload at the ventilatory threshold ([VT.sub.w]), and body composition. Forty-four women (mean [+ or -] SD age = 21.8 [+ or -] 3.7 years; height = 166.5 [+ or -] 6.6 cm; body mass (BM) = 65.9 [+ or -] 10.8 kg; [[??]o.sub.2]peak = 31.5 [+ or -] 6.2 ml x [kg.sup.-1] x [min.sup.-1]) were randomly assigned to 1 of 3 groups: [beta]-alanine (BA, n = 14) 1.5 g + 15 g dextrose powder; placebo (PL, n = 19) 16.5 g dextrose powder; or control (CON, n = 11 ). Testing was conducted at baseline (week 0), after 3 weeks (week 4), and after 6 weeks (week 8). [[??]o.sub.2]peak (ml x [kg.sup.-1] x [min.sup.-1]) and [VT.sub.w] were measured with a metabolic cart during graded exercise tests on a corival cycle ergometer, and body composition (percent fat = % fat and fat-free mass = FFM) were determined by air displacement plethysmography. High-intensity interval training was performed on a corival cycle ergometer 3 times per week with 5 2-minute work intervals and 1-minute passive recovery with undulating intensities (90-110% of the workload recorded at [[??]o.sub.2]peak) during each training session. [[??]o.sub.2]peak increased (p [less than or equal to] 0.05) in the BA and PL groups at weeks 4 and 8, but did not change (p > 0.05) for the CON group. [VT.sub.w] increased (p [less than or equal to] 0.05) for all groups at weeks 4 and 8. Body mass increased (p [less than or equal to] 0.05) only for the BA group at weeks 4 and 8, whereas %fat decreased (p [less than or equal to] 0.05) and FFM increased (p [less than or equal to] 0.05) at weeks 4 and 8 for all groups (BA, PL, and CON). Although it is unclear why [beta]-alanine supplementation increased BM, there was no additive effects for increasing [[??]o.sub.2]peak beyond the PL. Overall, these results suggested that HIlT may be an effective and time-efficient method of training to improve maximal oxygen uptake. KEY WORDS cycle ergometry, [[??]o.sub.2]peak, HIIT

J Strength Cond Res 24(1): 171-183, 2010--Resistance training interventions aimed at increasing lower-body power and rates of force development have produced varying results. Recent studies have suggested that whole-body low-frequency vibration (WBLFV) may elicit an acute postactivation potentiation response, leading to acute improvements in power and force development. Potentially, the use of WBLFV between sets of resistance training rather than during training itself may lead to increased recruitment and synchronization of high-threshold motor units, minimize fatigue potential, and facilitate the chronic adaptation to resistance exercise. The purpose of this study was to determine the effects of applying TriPlaner, WBLFV, prior to and then intermittently between sets of Smith machine squats on short-term adaptations in explosive isometric force expression. Thirty recreationally resistance trained men aged 18-30 were randomly assigned to 1 of 3 groups: resistance training only (SQT, n = 11), resistance plus whole-body vibration (SQTV, n = 13), or active control (CON, n = 6). An isometric squat test was performed prior to and following a 6-week periodized Smith machine squat program. Whole-body low-frequency vibration was applied 180 seconds prior to the first work set (50 Hz, 2-4 mm, 30 seconds) and intermittently (50 Hz, 4-6 mm, 3 x 10 seconds, 60 seconds between exposures) within a 240-second interset rest period. Subjects were instructed to assume a quarter squat posture while positioning their feet directly under their center of mass, which was modified using a handheld goniometer to a knee angle of 135 [+ or -] 5[degrees]. Instructions were given to subjects to apply force as fast and as hard as possible for 3.5 seconds. Isometric force (N) and rates of force development (N x [s.sup.-1]) were recorded from the onset of contraction ([F.sub.o]) to time points corresponding to 30, 50, 80, 100, 150, and 250 milliseconds, as well as the peak isometric rate of force development (PISORFD), and rate of force development to initial peak in force (RFDinitial). Repeated measures analysis of variance and analysis of covariance revealed no significant group by trial interactions for isometric rate of force development (ISORFD) between 0-30, 0-50, 0-80, 0-100, 0-150, and 0-250 milliseconds and PISORFD (p > 0.05). A significant group x trial interaction was seen for RFDinitial with SQTV >CG (p = 0.04, mean difference 997.2 N x [s.sup.-1]) and SQTV >SQT (p = 0.04, mean difference 1,994.22 N x [s.sup.-1]). Significant trial by covariate interactions (week one measures for ISORFD) and main effects for trial were observed for ISORFD between 0-80, 0-100, 0-and 150 milliseconds; PISORFD; and RFDinitial (p < 0.01). A significant trial effect was seen for Finitial (%) when expressed as a relative percentage of maximal voluntary contraction (MVC) (MVC = 100%) (p = 0.015; week 1 > week 7, mean difference, 5.82%). No significant differences were seen for any other force variables from the onset of contraction to MVC between weeks 1 and 7 (p > 0.05). The data suggest that there was a significant benefit afforded by adding WBLFV to a short-term resistance training protocol with regard to 'explosive' strength expression. The addition of vibration prior to and between sets of resistance exercise may be a viable alternative to vibration applied during resistance exercise when trying to improve 'explosive' isometric strength. KEY WORDS explosive strength, low-frequency vibration, potentiation, rate of force development, resistance training

J Strength Cond Res 24(1): 109-113, 2010--The submaximal electromyographic fatigue threshold test ([EMG.sub.FT]) has been shown to be highly correlated to ventilatory threshold (VT) as determined from maximal graded exercise tests (GXTs). Recently, a prediction equation was developed using the [EMG.sub.FT] value to predict VT. The aim of this study, therefore, was to determine if this new equation could accurately track changes in VT after high-intensity interval training (HILT). Eighteen recreationally trained men (mean [+ or -] SD; age 22.4 [+ or -] 3.2 years) performed a GXT to determine maximal oxygen consumption rate ([Vo.sub.2]peak) and VT using breath-by-breath spirometry. Participants also completed a discontinuous incremental cycle ergometer test to determine their [EMG.sub.FT] value. A total of four 2-minute work bouts were completed to obtain 15-second averages of the electromyographic amplitude. The resulting slopes from each successive work bout were used to calculate [EMG.sub.FT]. The [EMG.sub.FT] value from each participant was used to estimate VT from the recently developed equation. All participants trained 3 days a week for 6 weeks. Training consisted of 5 sets of 2-minute work bouts with 1 minute of rest in between. Repeated-measures analysis of variance indicated no significant difference between actual and predicted VT values after 3 weeks of training. However, there was a significant difference between the actual and predicted VT values after 6 weeks of training. These findings suggest that the EMGFT may be useful when tracking changes in VT after 3 weeks of HIIT in recreationally trained individuals. However, the use of [EMG.sub.FT] to predict VT does not seem to be valid for tracking changes after 6 weeks of HILT. At this time, it is not recommended that [EMG.sub.FT] be used to predict and track changes in VT. KEY WORDS cardiorespiratory fitness, muscle fatigue, interval training, cycling