Differing hypertrophy patterns from open and closed kinetic chain training affect quadriceps femoris center of mass and moment of inertia.

Purpose: To determine whether kinetic chain pattern during knee extensor strength training influences quadriceps femoris center of mass and moment of inertia about the hip in a predictable manner as such changes can affect running economy. Methods: Twelve participants completed 8 weeks of both unilateral open (OKC) and closed (CKC) kinetic chain resistance training on opposing legs. Changes in quadriceps femoris muscle volume (VOLQF), center of mass location (CoMQF), and moment of inertia (I QF) about the hip were determined from magnetic resonance images scans. Regional hemodynamics of the vastus lateralis taken at 30% and 70% of muscle length during OKC and CKC bouts early in the training program were measured using near-infrared spectroscopy (NIRS) and used post hoc to predict changes in CoMQF. Results: While increases in VOLQF were similar between OKC (Δ79.5 ± 87.9 cm3) and CKC (Δ60.2 ± 110.5 cm3, p = 0.29), the patterns of hypertrophy differed; a distal shift in CoMQF (Δ2.4 ± 0.4 cm, p < 0.001) and increase in I QF (Δ0.017 ± 0.014 kg m2, p < 0.001) occurred in OKC but not in CKC (CoMQF: Δ-2.2 ± 2.0 cm, I QF: Δ-0.022 ± 0.020 kg m2, p > 0.05). Regional hemodynamics assessed by NIRS during a single training session displayed similar exercise and regional differences and predicted 39.6% of observed changes in CoMQF. Conclusions: Exercise selection influences muscle shape sufficiently to affect CoMQF and I QF, and these changes may be predicted in part from NIRS measurements during a single workout. Given I QF is inversely related to running economy and since CKC exercise provides a more proximal pattern of hypertrophy than OKC, it may be more preferential for running. The results from the present study also highlight the potential of NIRS as a tool for predicting patterns of hypertrophy between different exercises and exercise conditions.

Contrast With Compression Therapy Enhances Muscle Function Recovery and Attenuates Glycogen Disruption After Exercise.

BACKGROUND: Exercise-associated muscle damage (EAMD) temporally impairs muscle function and intramuscular glycogen storage. Contrast with compression (CwC) therapy provides localized EAMD treatment with minimal changes in core/tissue temperature that can impair glycogen resynthesis. HYPOTHESIS: CwC will enhance the recovery of strength, power, and joint mobility, reduce markers of EAMD, and attenuate the disruption of glycogen storage observed after damaging exercise. STUDY DESIGN: Randomized controlled trial with crossover design. LEVEL OF EVIDENCE: Level 2. METHODS: Ten men completed 2 bouts of eccentric elbow flexor exercise, separated by 1 week, using contralateral arms. After each bout, participants received either CwC therapy (at 0, 24, and 48 h postexercise) or no therapy with intervention order and limb randomly assigned. Prior to (pre-exercise) and 1, 24, 48, and 72 h after each exercise bout, muscular strength, muscular power, intramuscular glycogen, creatine kinase, muscle thickness, muscle soreness, pressure pain threshold, active elbow flexion, passive elbow extension, and dietary intake were assessed. Comparisons were made between conditions over time (interaction effects) using separate repeated-measures analyses of variance/multivariate analyses of variance and effect sizes (Cohen d) to describe treatment effect at each time point. RESULTS: Significant interaction effects were observed for muscular strength (d = 0.67-1.12), muscular power (d = 0.20-0.65), intramuscular glycogen (d = 0.29-0.81), creatine kinase (d = 0.01-0.96), muscle thickness (d = 0.35-0.70), muscle soreness (d = 0.18-0.85), and active elbow flexion (d = 0.65-1.17) indicating a beneficial effect of CwC over time (P ≤ 0.05). In contrast, no significant interaction effect was observed for pressure pain threshold or passive elbow extension (P > 0.05). CONCLUSION: These results support the use of CwC for the recovery of muscle function after damaging exercise in male patients and indicate that CwC attenuates, but does not remove, the disruption of intramuscular glycogen stores observed after intense eccentric exercise. CLINICAL RELEVANCE: Glycolysis-dependent athletes may benefit from CwC therapy after training/competition that causes EAMD.

Effect of a Neoprene Knee Sleeve on Performance and Muscle Activity in Men and Women During High-Intensity, High-Volume Resistance Training.

ABSTRACT: Hatfield, DL, Stranieri, AM, Vincent, LM, and Earp, JE. Effect of a neoprene knee sleeve on performance and muscle activity in men and women during high-intensity, high-volume resistance training. J Strength Cond Res 35(12): 3300-3307, 2021-The purpose of this study was to assess the effects of a commercially available neoprene knee sleeve (KS) on exercise performance and muscle activity during an exhaustive leg press exercise. Twenty resistance-trained individuals, 11 men {21.0 ± 2.2 years; 77.7 ± 8.7 kg; 1 repetition maximum (1RM/body mass [BM]): 0.30 ± 0.04} and 9 women (22.0 ± 3.5 years; 66.1 ± 9.1 kg; 1RM/BM: 0.30 ± 0.04), all subjects (21.5 ± 2.8 years; 72.5 ± 10.5 kg; 1RM/BM: 0.30 ± 0.04), participated in 3 testing sessions. The second and third sessions were performed using a counterbalanced and randomized design in which subjects exercised with (WS) or without (NS) KSs and performed 6 sets of leg press exercise at 80% of 1RM until failure with a 3-minute rest between sets. Number of repetitions, blood lactate (BL), heart rate (HR), rating of perceived exertion (RPE), and peak and average power were recorded after each set. Surface electromyography (EMG) of the right and left vastus lateralis muscles was also recorded to compare muscle activity between conditions. Significance was set at p ≤ 0.05, and values are presented as mean ± SD. No significant differences were observed in the total number of repetitions for all sets (p = 0.3; WS 75.3 ± 33.7, NS 79.8 ± 34.3) and the number of repetitions per set between conditions (p ≤ 0.05) or between men and women. Similarly, no significance differences (p ≤ 0.05) were observed for BL, HR, RPE, or EMG per set between conditions or between men and women. These results suggest that wearing compressive neoprene KSs has no effect on improving performance and associated variables during high-load, high-volume lower-body resistance training.

Anabolic-Androgenic Steroid Use in Sports, Health, and Society.

This consensus statement is an update of the 1987 American College of Sports Medicine (ACSM) position stand on the use of anabolic-androgenic steroids (AAS). Substantial data have been collected since the previous position stand, and AAS use patterns have changed significantly. The ACSM acknowledges that lawful and ethical therapeutic use of AAS is now an accepted mainstream treatment for several clinical disorders; however, there is increased recognition that AAS are commonly used illicitly to enhance performance and appearance in several segments of the population, including competitive athletes. The illicit use of AAS by competitive athletes is contrary to the rules and ethics of many sport governing bodies. Thus, the ACSM deplores the illicit use of AAS for athletic and recreational purposes. This consensus statement provides a brief history of AAS use, an update on the science of how we now understand AAS to be working metabolically/biochemically, potential side effects, the prevalence of use among athletes, and the use of AAS in clinical scenarios.

Hormonal stress responses of growth hormone and insulin-like growth factor-I in highly resistance trained women and men.

The purpose of this study was to examine the responses of growth hormone (GH) and insulin-like growth factor-I (IGFI) to intense heavy resistance exercise in highly trained men and women to determine what sex-dependent responses may exist. Subjects were highly resistance trained men (N = 8, Mean ± SD; age, yrs., 21 ± 1, height, cm, 175.3 ± 6.7, body mass, kg, 87.0 ± 18.5, % body fat, 15.2 ± 5.4, squat X body mass, 2.1 ± 0.4; and women (N = 7; Mean ± SD, age, yrs. 24 ± 5, height, cm 164.6 ± 6.7, body mass, kg 76.4 ± 8.8, % body fat, 26.9 ± 5.3, squat X body mass, 1.7 ± 0.6). An acute resistance exercise test protocol (ARET) consisted of 6 sets of 10 repetitions at 80% of the 1 RM with 2 min rest between sets was used as the stressor. Blood samples were obtained pre-exercise, after 3 sets, and then immediately after exercise (IP), 5, 15, 30, and 70 min post-exercise for determination of blood lactate (HLa), and plasma glucose, insulin, cortisol, and GH. Determination of plasma concentrations of IGFI, IGF binding proteins 1, 2, and 3 along with molecular weight isoform factions were determined at pre, IP and 70 min. GH significantly (P ≤ 0.05) increased at all time points with resting concentrations significantly higher in women. Significant increases were observed for HLa, glucose, insulin, and cortisol with exercise and into recovery with no sex-dependent observations. Women showed IGF-I values that were higher than men at all times points with both seeing exercise increases. IGFBP-1 and 2 showed increase with exercise with no sex-dependent differences. IGFBP-3 concentrations were higher in women at all-time points with no exercise induced changes. Both women and men saw an exercise induced increase with significantly higher values in GH in only the mid-range (30-60 kD) isoform.  Only women saw an exercise induced increase with significantly higher values for IGF fractions only in the mid-range (30-60 kD) isoform, which were significantly greater than the men at the IP and 70 min post-exercise time points. In conclusion, the salient findings of this investigation were that in highly resistance trained men and women, sexual dimorphisms exist but appear different from our prior work in untrained men and women and appear to support a sexual dimorphism related to compensatory aspects in women for anabolic mediating mechanisms in cellular interactions.

Physical Activity Patterns Among Individuals Before and Soon After Bariatric Surgery.

PURPOSE: Post-operative changes in moderate-to-vigorous physical activity (MVPA) may contribute to improved weight loss and long-term weight maintenance of individuals after bariatric surgery. Patients experience minimal changes in MVPA > 6 months after surgery, but no studies have investigated early changes in physical activity after surgery. This study aims to assess MVPA changes during the rapid weight loss phase through self-reporting and objective measures. METHODS: Physical activity patterns were assessed as minutes per day spent doing MVPA. A walking cadence of ≥ 100 steps per minute defined MVPA. Individuals completing gastric bypass (N = 7) and sleeve gastrectomy (N = 17) procedures (21 females, 3 males, age 42.2 ± 12.6 years, body mass 121.8 ± 24.8 kg, BMI 44.0 ± 6.5) completed office visits at 12 ± 6 days pre- and 35 ± 10 days post-operative. Each wore an ActiGraph GT3X tri-axial accelerometer at the hip for 7 days before and again for 7 days 30.6 ± 10 days after surgery. Assessments also included a subjective question about their anticipated and perceived post-operative MVPA (scale of - 3 to 3 with 3 being much more physically active and - 3 being much less). RESULTS: Participants did not change their minutes per day of MVPA significantly (pre-operative 1.5 ± 2.1; post-operative 2.6 ± 5.6, NS). Participants predicted their post-operative physical activity level would increase (2.8 ± 0.4). The self-reported activity level on the same scale after surgery was significantly less than predicted (1.9 ± 1.0, p < 0.05) but still suggested that participants thought they were more physically active. CONCLUSION: Consistent with reports > 6 months after surgery, MVPA did not increase in the early post-operative period, despite patient expectations. The early post-operative period may be a time for behavioral intervention.

Racial/Ethnic Disparities in US Adolescents' Dietary Quality and Its Modification by Weight-Related Factors and Physical Activity.

There are well-known disparities in the prevalence of obesity across racial-ethnic groups, although the behavioral and psychological factors driving these disparities are less well understood. Therefore, the objectives of this study were: (1) to examine differences in dietary quality by race/ethnicity and weight-related variables [body mass index (BMI), weight loss attempt, and weight dissatisfaction] and physical activity (PA) using the Health Eating Index-2015 (HEI-2015); and (2) to investigate the interactions and independent associations of race/ethnicity, weight-related variables and PA on dietary quality. Data for adolescents aged 12-19 years (n = 3373) were abstracted from the 2007-2014 National Health and Nutrition and Examination Survey and analyzed using multiple PROC SURVEYREG, adjusting for demographics and accounting for complex sampling. Analyses determined that Hispanic males had better overall HEI-2015 scores than non-Hispanic whites (48.4 ± 0.5 vs. 45.7 ± 0.6, p = 0.003) or blacks (48.4 ± 0.5 vs. 45.5 ± 0.5, p < 0.001). Hispanic females also had better dietary quality than non-Hispanic whites (50.2 ± 0.4 vs. 47.5 ± 0.5, p < 0.001) and blacks (50.2 ± 0.4 vs. 47.1 ± 0.5, p < 0.001). Meeting the PA recommendation modified racial/ethnic differences in dietary quality for females (p = 0.011) and this was primarily driven by the associations among non-Hispanic white females (ΔR2 = 2.6%, p = 0.0004). The study identified racial/ethnic and gender differences among adolescents in factors that may promote obesity. Results may be useful for obesity prevention efforts designed to reduce health disparities in adolescents.

Cold-water immersion blunts and delays increases in circulating testosterone and cytokines post-resistance exercise.

INTRODUCTION: Cold-water immersion (CWI) is often used to promote recovery by reducing exercise-induced muscle damage, soreness, and inflammation. However, recent reports have cautioned that CWI may attenuate the adaptive response to resistance training. PURPOSE: To determine the effect of post resistance-exercise CWI on circulating free testosterone (T) and cytokine (IL-6 and TNF-α) response. METHODS: Using a randomized and counterbalanced repeated-measures design, 11 resistance-trained men completed two workouts (6 sets of 10 repetitions of back squats at 80% of maximum load) a week apart after which they took part in either 15 min of CWI (15 °C) or passive recovery. T, IL-6, and TNFα were measured in blood samples taken before (PRE) and 5 (5POST), 15 (15POST), 30 (30POST), and 60 (60POST) min post-exercise and compared between treatments and over time. RESULTS: For T, a significant interaction effect of condition over time (p = 0.030) as well as greater relative concentrations of T in CON (Δ9.2%) than CWI (Δ-0.5%, p = 0.049) at 30POST were observed. In addition, at 60POST, T dropped below PRE values in CWI (Δ-10.4%, p = 0.028) but not in CON (Δ-1.6%, p = 0.850). A suppressed cytokine response was observed after CWI in IL-6 at 30POST (CWI: Δ4.9%, CON: Δ47.5%, p = 0.041) and TNFα at 15POST (CWI: Δ5.3%, CON: Δ17.0%, p = 0.022). CONCLUSIONS: CWI blunted the T and cytokine response after a bout of resistance exercise. These results indicate that CWI results in an altered anabolic response and may help to explain the previous observation of attenuated hypertrophy when CWI is used after resistance exercise.

Effects of Different Athletic Playing Surfaces on Jump Height, Force, and Power.

Hatfield, DL, Murphy, KM, Nicoll, JX, Sullivan, WM, and Henderson, J. Effects of different athletic playing surfaces on jump height, force, and power. J Strength Cond Res 33(4): 965-973, 2019-Artificial turfs (ATs) have become more commonplace. Some aspects of performance such as speed seem to be better on ATs, but there are few published studies on the effects of playing surfaces on performance. Furthermore, there is no research that compares performance on ATs, hard surfaces (HSs), and different composite natural surfaces. Forty-three subjects, 21 men (age: 20 ± 1.82 years; height: 177.53 ± 5.87 cm; body mass: 78.44 ± 11.59 kg; and body fat: 11.17 ± 4.45%) and 22 women (age: 25 ± 1.32 years; height: 161.37 ± 6.47 cm; body mass: 60.94 ± 10.24 kg; and body fat: 27.16 ± 7.08%) performed a single countermovement jump (SCMJ), repeated CMJs (RCMJs), and single depth jump (SDJ) on 4 different playing surfaces (peat soil composition turf [NT1], sandy loam composition turf [NT2], 1 AT, and 1 HS. Repeated-measures analysis of variance with Bonferroni post hoc was used to calculate differences in performance across playing surfaces. Statistical significance was set at p ≤ 0.05. Force and jump height were not different across different surfaces. Men had significantly higher force, power, and jump height on all surfaces. Only SCMJ power was lower on NT1 compared with all other surfaces. The difference in power between surfaces was not reproduced when RCMJ and SDJ were performed, and may be due to the increased reactiveness of the stretch-shortening cycle during those jumps. Because of marginal differences between athletic performance and playing surface type, future research comparing playing surface type and other aspects of athletic success such as rate of injury should be considered.

National Scouting Combine Scores as Performance Predictors in the National Football League.

Vincent, LM, Blissmer, BJ, and Hatfield, DL. National Scouting Combine scores as performance predictors in the National Football League. J Strength Cond Res 33(1): 104-111, 2019-The National Football League (NFL) hosts an annual scouting combine to evaluate the approximately 300 elite college football players who are most likely to be selected in the upcoming NFL draft. Given the public interest, player obligations, coaching staff commitments, and business aspects of the combine, several questions have arose in recent years concerning the applicability of combine scores to eventual draft NFL performance. The primary purpose of this study is to investigate the relationship between specified National Scouting Combine (NSC) scores and measures of performance by player position. A secondary aim was to determine whether correlated variables could predict player performance at the quarterback (QB), running back (RB), wide receiver (WR), defensive end (DE), defensive tackle (DT), and linebacker (LB) positions. Subjects in this study were combine participants between the years 2005-2010 who subsequently played in the NFL. The positional groups investigated were QBs (N = 44), RBs (N = 82), WRs (N = 116), LBs (N = 139), DEs (N = 59), and DTs (N = 72). Combine raw scores for 40-yd dash time, countermovement vertical jump (CMVJ) height, standing long jump (SLJ) distance, and pro-agility time were recorded. Measures of horizontal and vertical power were calculated for the 40-yd dash and CMVJ. Combine scores and on-field positional statistics for the first 4 years for QBs and 3 years of all other players' careers were analyzed to investigate relationships. Significant correlations were shown between at least one combine measure and on-field success at every position. Hierarchal regression showed combine measures could predict between 4% and 62% of the variance for individual on-field variables. Quarterback rushing yards were significantly correlated with 40T, CMVJ, vertical jump power (VJP), vertical jump relative power (VJRP), and horizontal power (HP), and those factors accounted for 62.2% of the total variance. Horizontal power and VJP were predictive of QB rushing attempts (r = 0.370). At RB, 40T and SLJ combined were predictive of total rushing yards (r = 0.200), rushing attempts (r = 0.195), and yards per game (r = 0.197). Power variables were predictive of total tackles for DEs' 40HP (r = 0.096) and VJP (r = 0.018), accounting for a total of 21% of the variance. The current study suggests that combine tests are modest predictors of future performance. Should the NFL change the current NSC testing battery, the addition of horizontal and vertical power measurements, as well as position-specific skill tests are recommended.

Thyroid hormones and commonly cited symptoms of overtraining in collegiate female endurance runners.

PURPOSE: Overtraining syndrome (OTS) is reported in endurance sports. Thyroid hormones (TH) regulate metabolism, mood, and energy production, and may play a role in OTS of endurance athletes. The purpose of this study was to investigate relationships in TH and symptoms of OTS in track and field endurance runners (ER). METHODS: Sixteen female track and field middle distance (MD; n = 9; age: 20.2 ± 1.5 years; ht: 167.86 ± 5.04 cm; body-mass: 57.97 ± 5.05 kg; VO2MAX: 53.62 ± 6.04 ml/kg/min) and long distance (LD; n = 7; age: 20.5 ± 1.5 years; ht: 162.48 ± 6.11 cm; body-mass: 56.15 ± 5.99 kg; VO2MAX: 61.94 ± 3.29 ml/kg/min) ER participated in this descriptive study (15-weeks). Thyroid-stimulating hormone (TSH), triiodothyronine (T 3), and thyroxine (T 4), were collected at pre-(PRE) and post-season (POST). A fatigue scale was administered weekly, and percent change (PΔ) in race time (season best vs. championship performance) was calculated. Wilcoxon-sign ranked tests and Spearman's rho correlations were used to determine changes and relationships between TH and performance. RESULTS: TSH, T 3 and T 4 did not change from PRE to POST. The percent change (PΔ) in T 3 from PRE to POST was correlated with running performance at the end of the season (ρ = - 0.70, p = 0.036). Fatigue at week 12 correlated with running performance at the end of the season (ρ = - 0.74, p = 0.004). CONCLUSION: TH may be valuable in assessing the overall training state of ER. TH concentrations change too slowly to be a frequent marker of monitoring OTS, but are related to markers of decreased performance. Monitoring dietary intake, and fatigue may be predictive markers to assess OTS and training status of female ER.

The effects of different exercise training modalities on plasma proenkephalin Peptide F in women.

Due to the important interactions of proenkephalin fragments (e.g., proenkephalin [107-140] Peptide F) to enhance activation of immune cells and potentially combat pain associated with exercise-induced muscle tissue damage, we examined the differential plasma responses of Peptide F to different exercise training programs. Participants were tested pre-training (T1), and after 8 weeks (T2) of training. Fifty-nine healthy women were matched and then randomly assigned to one of four groups: heavy resistance strength training (STR, n=18), high intensity endurance training (END, n=14), combined strength and endurance training (CMB, n=17), or control (CON, n=10). Blood was collected using a cannula inserted into a superficial vein in the antecubital fossa with samples collected at rest and immediately after an acute bout of 6 X 10 RM in a squat resistance exercise before training and after training. Prior to any training, no significant differences were observed for any of the groups before or after acute exercise. With training, significant (P≤0.95) elevations were observed with acute exercise in each of the exercise training groups and this effect was significantly greater in the CMB group. These data indicate that in untrained women exercise training will not change resting of plasma Peptide F concentrations unless both forms of exercise are performed but will result in significant increases in the immediate post-exercise responses. Such findings appear to indicate adrenal medullary adaptations opioid production significantly altered with exercise training.

Effects of Circadian Rhythm on Power, Force, and Hormonal Response in Young Men.

Circadian rhythms (CRs) persist in many physiological systems related to performance. The effects of circadian patterns on dynamic muscular power are minimal and conflicting. Furthermore, no study to date has investigated the effect of CR on bench press throws (BPTs) despite its popularity as a modality to increase muscular power. The purpose of this study was to examine the effects of circadian variations on muscular power output and hormonal changes in men. College aged men (n = 7, age: 23.6 ± 1.3 years, height: 179.9 ± 5.4 cm, and body mass: 81.5 ± 19.7 kg.) were recruited for this repeated measures study. Testing occurred at 4 different times of day (04:00, 10:00, 16:00, and 22:00 hours). Testosterone (T) and cortisol (C) hand dynamometer strength (GS), heart rate (HR), mental readiness (MR), BPT and squat jumps (SJs), power (P), and force (F) were measured at each time point. Statistical significance was set at (p ≤ 0.05). There were no significant differences in HR, MR, and GS among all time points. There were no decrements in P or F in BPT or SJ among any time point (p ≥ 0.05). Testosterone and C decreased significantly throughout the day (p ≤ 0.05). Although P and F output differed at various percentages of 1 repetition maximum, they were not affected by circadian pattern, such that muscular performance was not impaired at any time point. Practical implications of these data indicate that high force and power exercises using BPT or SJ may be performed any time of day without detrimental decreases in acute performance.

Comparison of the Effects of Seated, Supine, and Walking Interset Rest Strategies on Work Rate.

Ouellette, KA, Brusseau, TA, Davidson, LE, Ford, CN, Hatfield, DL, Shaw, JM, and Eisenman, PA. Comparison of the effects of seated, supine, and walking interset rest strategies on work rate. J Strength Cond Res 30(12): 3396-3404, 2016-The idea that an upright posture should be maintained during the interset rest periods of training sessions is pervasive. The primary aim of this study was to determine differences in work rate associated with 3 interset rest strategies. Male and female members of the CrossFit community (male n = 5, female n = 10) were recruited to perform a strenuous training session designed to enhance work capacity that involved both cardiovascular and muscular endurance exercises. The training session was repeated on 3 separate occasions to evaluate 3 interset rest strategies, which included lying supine on the floor, sitting on a flat bench, and walking on a treadmill (0.67 m·s). Work rate was calculated for each training session by summing session joules of work and dividing by the time to complete the training session (joules of work per second). Data were also collected during the interset rest periods (heart rate [HR], respiratory rate [RR], and volume of oxygen consumed) and were used to explain why one rest strategy may positively impact work rate compared with another. Statistical analyses revealed significant differences (p ≤ 0.05) between the passive and active rest strategies, with the passive strategies allowing for improved work rate (supine = 62.77 ± 7.32, seated = 63.66 ± 8.37, and walking = 60.61 ± 6.42 average joules of work per second). Results also suggest that the passive strategies resulted in superior HR, RR, and oxygen consumption recovery. In conclusion, work rate and physiological recovery were enhanced when supine and seated interset rest strategies were used compared with walking interset rest.

Long-term athletic development, part 2: barriers to success and potential solutions.

The first installment of this two-part commentary reviewed existing models of long-term athletic development. However, irrespective of the model that is adopted by practitioners, existing structures within competitive youth sports in addition to the prevalence of physical inactivity in a growing number of modern-day youth may serve as potential barriers to the success of any developmental pathway. The second part of this commentary will initially highlight common issues that are likely to impede the success of long-term athletic development programs and then propose solutions that will address the negative impact of such issues.

Developmental differences between boys and girls result in sex-specific physical fitness changes from fourth to fifth grade.

To better understand how developmental differences impact performance on a broad selection of common physical fitness measures, we examined changes in boys and girls from fourth to fifth grade. Subjects included 273 boys (age, 9.5 ± 0.6 years; height, 139.86 ± 7.52 cm; mass, 38.00 ± 9.55 kg) and 295 girls (age, 9.6 ± 0.5 years; height, 139.30 ± 7.19 cm; weight, 37.44 ± 9.35 kg). We compared anthropometrics, cardiorespiratory and local muscular endurance, flexibility, power, and strength. A mixed-method analysis of variance was used to compare boys and girls at the 2 time points. Pearson correlation coefficients were used to examine relationships between anthropometric and fitness measurements. Significance was set at p ≤ 0.05. Weight increased significantly (>10%) in both sexes, and girls became significantly taller than boys after growing 4.9% by fifth grade (vs. 3.5%). Both groups improved cardiorespiratory endurance and power, although boys performed better than girls at both time points. Boys were stronger in fourth grade, but girls improved more, leading to similar fifth-grade values. Girls were more flexible in fourth grade, but their significant decreases (∼32.4%) coupled with large improvements in boys (∼105%) resulted in similar fifth-grade scores. Body mass index (BMI) was positively correlated with run time regardless of grade or sex. Power was negatively correlated with BMI and run time in fourth grade. In conclusion, sex-specific differences in physical fitness are apparent before pubescence. Furthermore, this selection of measures reveals sexually dimorphic changes, which likely reflect the onset of puberty in girls. Coaches and teachers should account these developmental differences and their effects on anthropometrics and fitness in boys and girls.

Long-term athletic development- part 1: a pathway for all youth.

The concept of developing talent and athleticism in youth is the goal of many coaches and sports systems. Consequently, an increasing number of sporting organizations have adopted long-term athletic development models in an attempt to provide a structured approach to the training of youth. It is clear that maximizing sporting talent is an important goal of long-term athletic development models. However, ensuring that youth of all ages and abilities are provided with a strategic plan for the development of their health and physical fitness is also important to maximize physical activity participation rates, reduce the risk of sport- and activity-related injury, and to ensure long-term health and well-being. Critical reviews of independent models of long-term athletic development are already present within the literature; however, to the best of our knowledge, a comprehensive examination and review of the most prominent models does not exist. Additionally, considerations of modern day issues that may impact on the success of any long-term athletic development model are lacking, as are proposed solutions to address such issues. Therefore, within this 2-part commentary, Part 1 provides a critical review of existing models of practice for long-term athletic development and introduces a composite youth development model that includes the integration of talent, psychosocial and physical development across maturation. Part 2 identifies limiting factors that may restrict the success of such models and offers potential solutions.

Influence of HMB supplementation and resistance training on cytokine responses to resistance exercise.

PURPOSE: The purpose of this study was to determine the effects of a multinutritional supplement including amino acids, ß-hydroxy-ß-methylbutyrate (HMB), and carbohydrates on cytokine responses to resistance exercise and training. METHODS: Seventeen healthy, college-aged men were randomly assigned to a Muscle Armor™ (MA; Abbott Nutrition, Columbus, OH) or placebo supplement group and 12 weeks of resistance training. An acute resistance exercise protocol was administered at 0, 6, and 12 weeks of training. Venous blood samples at pre-, immediately post-, and 30-minutes postexercise were analyzed via bead multiplex immunoassay for 17 cytokines. RESULTS: After 12 weeks of training, the MA group exhibited decreased interferon-gamma (IFN-γ) and interleukin (IL)-10. IL-1ß differed by group at various times. Granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, IL-7, IL-8, IL-12p70, IL-13, IL-17, monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1 beta (MIP-1ß) changed over the 12-week training period but did not differ by group. CONCLUSIONS: Twelve weeks of resistance training alters the cytokine response to acute resistance exercise, and supplementation with HMB and amino acids appears to further augment this result.

Epinephrine preworkout elevation may offset early morning melatonin concentrations to maintain maximal muscular force and power in track athletes.

The optimal time of day for training has become an important question for many strength and conditioning specialists, and this study was designed to add some insights into this complex question. The primary purpose of this investigation was to examine physical performance within the temporal context of the relationship between physical performance, epinephrine, and melatonin concentrations in the early morning (0530 hours) and late (1500 hours) afternoon in elite collegiate male track and field athletes (jumpers and sprinters). Subjects had a mean (±SD) age, height, and body mass of 20.4 (±1.6) years, 185.8 (±9.4) cm, and 77.9 (±8.5) kg, respectively. Blood was obtained before each AM and PM testing session. Mean plasma melatonin concentrations were 34.9 ± 22.7 pg·ml and 4.8 ± 3.3 pg·ml for the AM vs. PM trials, respectively, demonstrating a significant (p ≤ 0.05) difference between time points. Mean resting plasma epinephrine concentrations for AM (171.7 ± 33.7 pmol·L) and PM (127.6 ± 47.8 pmol·L) also differed significantly between trails at the different times. In addition, significant differences were observed with respect to foot quickness in the AM (5.14 ± 1.06 seconds) and PM (4.39 ± 0.76 seconds). Mean peak power output for vertical jump power was 5,407.1 ± 1,272.9 W, 5,384.6 ± 888.3 W for AM vs. PM trials, respectively, which were not significantly different. The results of this investigation indicate that time of day did not negatively impact whole body physical performance in trained track athletes but did impact the quality of quickness. Thus in the morning, whole body power performances may be enhanced through adrenergic arousal when melatonin is elevated. However, this was not the case for movements requiring quickness and accuracy of movement. To compensate for the "sleepiness" associated with high concentrations of melatonin, being secreted from the pineal gland representing a continued "sleepiness" effect on the body, early morning practices may require greater adrenergic arousal to potentially offset melatonin's effects. The results of this study raise important questions on the use of early morning practices for more complex tasks that require high reaction speeds, even under conditions of adrenergic arousal.

The effects of myofascial release with foam rolling on performance.

In the last decade, self-myofascial release has become an increasingly common modality to supplement traditional methods of massage, so a masseuse is not necessary. However, there are limited clinical data demonstrating the efficacy or mechanism of this treatment on athletic performance. The purpose of this study was to determine whether the use of myofascial rollers before athletic tests can enhance performance. Twenty-six (13 men and 13 women) healthy college-aged individuals (21.56 ± 2.04 years, 23.97 ± 3.98 body mass index, 20.57 ± 12.21 percent body fat) were recruited. The study design was a randomized crossover design in which subject performed a series of planking exercises or foam rolling exercises and then performed a series of athletic performance tests (vertical jump height and power, isometric force, and agility). Fatigue, soreness, and exertion were also measured. A 2 × 2 (trial × gender) analysis of variance with repeated measures and appropriate post hoc was used to analyze the data. There were no significant differences between foam rolling and planking for all 4 of the athletic tests. However, there was a significant difference between genders on all the athletic tests (p ≤ 0.001). As expected, there were significant increases from pre to post exercise during both trials for fatigue, soreness, and exertion (p ≤ 0.01). Postexercise fatigue after foam rolling was significantly less than after the subjects performed planking (p ≤ 0.05). The reduced feeling of fatigue may allow participants to extend acute workout time and volume, which can lead to chronic performance enhancements. However, foam rolling had no effect on performance.