Context: The hip adductor and abductor muscles play vital roles as stabilizers in the lower-extremity. Their activation during soccer-specific actions is essential, but local muscular fatigue can hinder athletic performance and increase the risk of injury. Design: This study aimed to observe the variations in frontal plane hip strength in female college soccer players before and after a high-workload soccer-specific training session. Furthermore, the study sought to compare the relative changes in hip strength with the internal and external load measures obtained during that session. Methods: Twenty female college soccer players participated in a retrospective observational study. Isometric hip adductor and abductor strength were measured before and after a training session in the college spring season. Measurements were taken with a handheld dynamometer (MicroFET 2) while the players were supine. Global positioning system sensors (Catapult Vector S7), commonly worn by players during training sessions and competitive matches, were used to measure external and internal loads. Statistical analyses were performed using paired samples t test to assess hip adductor and abductor strength changes before and after the training session. Spearman rank was used to identify correlation coefficients between global positioning system data and isometric hip strength. Results: The findings revealed significant decreases in the strength of the right hip adduction (P = .012, −7% relative change), right abduction (P = .009, −7.6% relative change), and left abduction (P = .016, −4.9% relative change) after the training session. Furthermore, relative decreases in hip isometric adduction and abduction strength are related to the distance covered at high speeds. Conclusion: The results of this study highlight that hip isometric adduction and abduction strength tend to decrease after exposure to high workloads during soccer-specific training.

Herring, CH, Beyer, KS, Redd, MJ, Stout, JR, and Fukuda, DH. Utility of novel rotational load-velocity profiling methods in collegiate softball players. J Strength Cond Res 38(1): 136-145, 2024-The purpose of this study was to determine the reliability of bat swing (BS) and rotational medicine ball throw (RMBT) load-velocity profiling (LVP) methods and explore relationships with batting performance in NCAA Division I softball players. Bat velocity was tracked with a swing sensor during the BS method, whereas an inertial measurement unit (IMU) tracked forearm velocity during the BS and RMBT methods. Intraclass correlation coefficients (ICC) were used for relative reliability, and coefficient of variation (CV) was used for absolute reliability. With the exception of theoretical maximum velocity (V0) using the average of top 2 peak velocities (PVavg) during the RMBT, no LVP variables were found to be reliable during the RMBT or BS method using the IMU (ICC <= 0.7; CV >= 15%). For the BS method with the swing sensor, all bat loads and V0 had acceptable reliability using peak velocity (PV) and PVavg (ICC >0.7; CV <15%), whereas all LVP variables were highly related between the multiple-load and two-load models when using PV and PVavg (r = 0.915-0.988; p < 0.01). There were significant relationships (r = 0.603-0.671; p < 0.05) between PV using the 0.99 Kg bat load and V0, and several in-game batting statistics. Practitioners may use the BS with the swing sensor as a rotational LVP assessment, although they should be cautious of aiming to improve batting performance in collegiate softball players based on the correlations reported until further research is performed.

The purpose of this study was to estimate the workloads accumulated by collegiate female soccer players during a competitive season and to compare the workloads of starters and substitutes. Data from 19 college soccer players (height: 1.58 ± 0.06 m; body mass: 61.57 ± 6.88 kg) were extracted from global positioning system (GPS)/heart rate (HR) monitoring sensors to quantify workload throughout the 2019 competitive season. Total distance, distance covered in four speed zones, accelerations, and time spent in five HR zones were examined as accumulated values for training sessions, matches, and the entire season. Repeated-measures ANOVA and Student's t tests were used to determine the level of differences between starter and substitute workloads. Seasonal accumulated total distance (p < 0.001), sprints (≥19.00 km/h; p < 0.001), and high-speed distance (≥15.00 km/h; p = 0.005) were significantly greater for starters than substitutes. Accumulated training load (p = 0.08) and training load per minute played in matches (p = 0.08) did not differ between starters and substitutes. Substitutes had similar accumulated workload profiles during training sessions but differed in matches from starters. Coaches and practitioners should pursue strategies to monitor the differences in workload between starters and substitutes.

The purpose of this study was to evaluate the effects of environmental conditions on running performance and performance efficiency index (Effindex). Performance data recorded using Polar Team Pro sensors from eight collegiate female soccer players in nine matches were analyzed during the 2019 competitive season. Effindex and running performance, including total distance covered (TDREL) and distance covered in five speed thresholds relative to minutes played, were examined for indications of fatigue with respect to environmental conditions, including ambient temperature and relative humidity. Matches were separated into three groups based on environmental conditions: Low-Risk (n = 2 matches), Moderate-Risk (n = 3 matches), or High-Risk (n = 4 matches). Speed thresholds were grouped as follows: walking (WALKREL), jogging (JOGREL), low-speed running (LSRREL), high-speed running (HSRREL), and sprinting (SPRINTREL). A significant effect was observed for TDREL in all environmental conditions (η2 = 0.614). TDREL was significantly lower in the High-Risk (p = 0.002; 95.32 ± 12.04 m/min) and Moderate-Risk conditions (p = 0.004; 94.85 ± 9.94 m/min) when compared to Low-Risk (105.61 ± 9.95 m/min). WALKREL (p = 0.005), JOGREL (p = 0.005) LSRREL (p = 0.001), HSRREL (p = 0.035), SPRINTREL (p = 0.017), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to Moderate-Risk conditions. WALKREL (p = 0.005), HSRREL (p = 0.029), SPRINTREL (p = 0.005), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to High-Risk conditions. High-Risk environmental conditions may result in adverse performance in female collegiate soccer players.

The mechanical properties of knee flexors and extensors in 15 collegiate male soccer players following different warm-up protocols [small-sided games (SSG), dynamic (DYN), and plyometric (PLY)] were evaluated. Tensiomyography (TMG) was used to assess contraction time (Tc), delay time (Td) and maximal displacement (Dm) of the rectus femoris (RF) and biceps femoris (BF) of both legs before and after each warm-up, while countermovement jump height variables, 20 m sprint, t-test and sit-and-reach were measured following the warm-ups. TMG was analyzed using a three-way [condition × time × leg] ANOVA, while performance variables were analyzed with a repeated measures ANOVA. Main effects of time were observed for BF-Tc (p = 0.035), RF-Td (p < 0.001), and BF-Td, (p = 0.008), and a main effect of condition was seen for RF-Tc (p = 0.038). Moreover, participants’ 20 m sprint improved following SSG (p = 0.021) compared to DYN and PLY. Sit-and-reach was greater following PLY (p = 0.021). No significant interactions were noted for the measured TMG variables. Warm-up-specific improvements were demonstrated in sprint speed and flexibility following SSG and PLY, respectively. The present study revealed changes in certain TMG measures following the warm-ups that suggest enhanced response of lower leg muscles regardless of specific activities used.

The purpose of this study was to assess the maturity‐related differences in the aerobic and anaerobic adaptations to sprint interval training (SIT) among youth male athletes. Twenty‐seven youth male athletes were assessed for years from peak height velocity (PHV) and classified into prepubescent (PRE, n = 7, years from PHV = −2.21 ± 0.47 years), peripubescent (PERI, n = 10, years from PHV = 0.25 ± 0.88 years), and postpubescent (POST, n = 10, years from PHV = 2.81 ± 0.50 years) groups based on their years from estimated peak height velocity. Participants completed a ramp exercise protocol on a cycle ergometer to determine maximal aerobic power, maximal oxygen consumption (VO2peak), and fatigue thresholds. Following baseline, all participants completed a 4‐week SIT program that consisted of eight total training sessions. During each session, participants completed repeated 20‐s sprints on a cycle ergometer against a resistance of 7.5% of body mass. The number of sprints per sessions increased from four in session 1 to seven in session 7, with four sprints in session 8. Peak and mean power from sessions 1 and 8 were recorded. All participants completed a post‐testing ramp exercise protocol that mirrored baseline. Maximal aerobic power increased (p < .001) across all groups from baseline (212.61 ± 57.45 W) to post‐testing (223.24 ± 58.90 W); however, VO2peak only increased in POST (3.31 ± 0.43 to 3.54 ± 0.43 L min−1, p = .003). Similarly, GET, VT, and RCP increased in POST, with no changes in PRE or PERI. In terms of anaerobic performance, PERI and POST had significant increases in peak and mean power. POST improved aerobic and anaerobic performance following SIT, while PERI only experienced improvements in anaerobic performance. Conversely, PRE had no changes in aerobic or anaerobic performance. The adaptations to SIT appear to be influenced by the somatic maturity status.

Post-activation potentiation likely acutely improves power-based performance; however, few studies have demonstrated improved endurance performance. Forty collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and control (CON) warm-up protocols on a rowing ergometer, followed by a three-minute all-out test to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W') and stroke rate. Fifteen-second splits were also analysed. ISO consisted of 5 x 5-second static muscle actions with the ergometer handle rendered immovable with a nylon strap, while DYN consisted of 2 x 10-second all-out rowing bouts, separated by a 2-minute rest interval. The participants were divided into high and low experience groups by median experience level (3.75 years) for statistical analysis. Significant differences (DYN > CON; p < 0.05) were found for distance (+5.6 m), mean power (+5.9 W) and W' (+1561.6 J) for more experienced rowers (n = 19) and no differences for less experienced rowers (n = 18). Mean power in DYN was significantly greater than CON and ISO in the 15-30, 30-45, 45-60 and 60-75 second intervals independent of experience level. These results suggest that DYN may benefit experienced female rowers and that these strategies might benefit a greater power output over shorter distances regardless of experience.

Changes in skeletal muscle occur during the process of maturation that influence the expression of muscular strength. The isometric mid-thigh pull (IMTP) is used to measure force-time characteristics [peak force (PF) and rate of force development (RFD)], while the bioelectric properties of body tissues can be used to estimate lean body mass (LBM) and cellular health via phase angle. PURPOSE: To evaluate the contributions of segmental LBM, phase angle, and potentially relevant developmental indicators on IMTP performance in adolescents. METHODS: Twenty-three high school students (14 girls and 9 boys; age=15.4±0.8y; height=1.7±7.0m, body mass=68.9±14.9kg) underwent anthropometric measurements to determine somatic maturity and multi-frequency bioelectrical impedance analysis to determine whole body phase angle (50 kHz), overall LBM, and segmental LBM of the arms, legs, and trunk. Participants performed an IMTP with a custom-built rack and force plates to determine peak RFD, absolute PF, and PF relative to body mass. Stepwise linear regression was used to determine the relationships between IMTP performance and segmental LBM as well as specific developmental indicators (chronological age and somatic maturity). Independent sample t-tests were used to evaluate sex-based differences. Pearson correlations were also used to compare IMTP performance with overall LBM and whole body phase angle. RESULTS: Sex-based differences (p<0.05) were shown for maturity offset (female: 2.5±0.6y; male: 0.9±0.8y), whole body LBM (female: 46.0±7.2kg; male: 53.5±8.3kg), arm LBM (female: 4.65±1.1kg; male: 5.7±1.2kg), RFD (female: 1596.17N•s−1; male: 2742.41N•s−1. RFD was significantly associated with arm LBM (r2=0.239; p<0.05) while the addition of trunk LBM improved the model (r2=0.454; p<0.05). Neither chronological age nor somatic maturity were associated with any of the IMTP variables, while RFD was significantly correlated with both whole body phase angle (r=0.495) and overall LBM (r=0.476). CONCLUSION: Significant sex-based differences in the upper body musculature likely influence RFD in high school students despite girls displaying greater somatic maturity than boys. Phase angle may also play a role in the rate of muscular strength expression in adolescents.

PURPOSE To examine the reliability and the maturity-related differences of fatigue thresholds (FTs) among youth males. METHODS Twenty-nine youth males (11-17 y) completed 2 ramp exercise tests on a cycle ergometer. Systemic FTs were calculated from gas exchange and ventilation variables. Localized FTs were calculated from electromyography and near-infrared spectroscopy of the vastus lateralis. All FTs were determined using the maximal distance method and expressed relative to maximal oxygen consumption. All participants were grouped according to the number of years from peak height velocity into PRE- (< -1.5 y), PERI- (-1.5 to +1.5 y) and POST- (> +1.5 y) peak height velocity. Reliability was assessed with intraclass correlation coefficients, and differences between groups were assessed with analysis of variance and Cohen's d coefficients. RESULTS Analysis of variance revealed significant group differences with PRE having significantly greater systemic pulmonary FTs than POST, while localized muscular FTs were significantly greater in PRE when compared with PERI and POST. All FTs exhibited excellent reliability (intraclass correlation coefficient > .75) in all maturity groups. CONCLUSION Maturity status appears to influence the onset of FTs among youth male athletes, with FTs occurring later in younger athletes. Furthermore, all FTs were reliable measures regardless of maturity.

Tensiomyography (TMG) has been shown to be a non-invasive technique to assess the contractile properties of skeletal muscle which may have application in assessing the effectiveness of warm-up procedures prior to training and athletic competition. PURPOSE: The purpose of this study was to evaluate the effects of three different warm-up protocols on TMG variables and sprint performance in collegiate male soccer athletes. METHODS: Fifteen collegiate male soccer athletes (age = 20.1±1.3y, height = 176.6±6.9cm, body mass = 78.2±7.8kg, body fat percentage = 12.9±3.6) participated in the study. The three testing days consisted of: pre- and post-TMG assessments; warm-up protocol [dynamic (DYN); plyometrics (PLY); and passing patterns (SOC)]; and two 20-m sprints. Pre- and post-TMG assessments were completed for the biceps femoris (BF) and rectus femoris (RF) of both legs for all participants. The DYN warm-up protocol consisted of a six-minute jog followed by nine minutes of dynamic stretching. The PLY warm-up protocol consisted of a six-minute jog followed by nine minutes of plyometric exercises. The PAS consisted of a five-minute jog followed by a passing pattern drill typically used in advanced soccer athletes termed the “Rondo.” Repeated measures ANOVAs (condition x leg x time) were used to evaluate muscle displacement (Dm) and contraction time (Tc) in the BF and RF. A repeated measures ANOVA was used to evaluate the fastest of the two 20-m sprint times between conditions. RESULTS: Results showed no significant interactions for Dm (BF: 2.851 to 3.508mm; RF: 6.793 to 8.253mm) or Tc (BF: 20.04 to 24.00ms; RF: 26.87 to 29.36ms); however, a main effect for time (p=0.035) was found for BF Tc with a significant decrease from pre- (22.24±9.09ms) to post-warmup (20.47±5.01ms). Significant differences (p<0.05) between conditions for 20-m sprint performance were also noted (DYN: 2.76±0.27 s; PLY: 2.64±0.13s; SOC: 2.62±0.15s). CONCLUSION: In collegiate male athletes, the warm-up protocols did not appear to have differential effects on specific TMG variables, while differences in sprint performance were seen. The warm-up procedures decreased Tc as evaluated by TMG; however, further research is needed to examine the influence of this change on performance.

Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 ± 3.0 y, 90.0 ± 13.8 kg, 174.9 ± 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscle's length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3-5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d ∙ wk-1) of training (POST). Although three-way (muscle [RF, VL] x region [30, 50, 70%] x time [PRE, POST]) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 ± 0.69 cm2, p < 0.001) over the RF (0.59 ± 0.20 cm2, p = 0.011), while significant decreases in average FL were noted for the RF (-1.03 ± 0.30 cm, p = 0.004) but not the VL (-0.05 ± 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.

With the recent inclusion of surfing in the 2020 Olympic Games in Japan, there will be a number of surfing athletes vying for one of the twenty total available spots for their respective gender. The purpose was to evaluate relative age effects (RAEs) in surfing with consideration for specific developmental constraints. Elite competitive male surfers (n = 1590) were examined by birth month and subcategorized by competitive level, age groups, and geographical regions. The observed quarterly distribution was not significantly different (using χ2; p>0.05) from expected for the overall group or any of the subcategories. However, an odds ratio of 1.85 (90% confidence interval: 1.08-3.14) was calculated for being born in the first semester of the year compared to being born in the second semester between top 34 athletes and the rest of the field. Despite consideration for individual, environmental, and task constraints in this study, the sport of surfing does not appear to have any observable RAEs at the professional level. Thus, surfing appears to be one of the few sporting activities included in the Olympic Programme with limited RAEs.

Fatigue thresholds (FTs) can be determined via systemic pulmonary measurements such as oxygen consumption (VO2), carbon dioxide production (VCO2), and ventilation (VE) or through localized muscular measurements such as neuromuscular activation and oxygenation. Systemic and localized FT measures are non‐invasive techniques, which make them ideal tests for adolescents. During puberty, a gradual shift occurs in the metabolic response to exercise from predominantly aerobic metabolism to a balance between aerobic and anaerobic metabolic systems. However, limited research has examined the maturity related differences in systemic and localized FTs amongst adolescent male athletes.PURPOSETo examine the maturity related differences in systemic pulmonary and localized neuromuscular and oxygenation FTs amongst adolescent male athletes.METHODSTwenty‐six adolescent male athletes (age 11–17 yrs) volunteered with verbal assent and written parental consent to complete two incremental ramp exercise tests on a cycle ergometer separated by at least 48 hours. Three systemic FTs, gas exchange threshold (GET), ventilatory threshold (VT), and respiratory compensation point (RCP) were calculated from VCO2 and VE. Three localized FTs, neuromuscular fatigue threshold (NFT), deoxyhemoglobin breakpoint (HHbBP), and oxygenation breakpoint (OxBP) were calculated from electromyography and near infrared spectroscopy signals from the right vastus lateralis. Data from the second test were plotted versus VO2 and 30‐second moving averages were calculated. All FTs were determined using the maximal distance method and expressed relative to VO2max. All participants were separated according to the number of years from peak height velocity (PHV), an estimation of somatic maturity status, into PRE‐ (<−1yr), PERI‐ (between −1 to +1yr) and POST‐ (>+1yr) PHV groups. Differences between maturational groups were assessed with magnitude based inferences.RESULTSGroup means and differences between groups are presented in Table 1. All systemic and localized FTs occurred at Very Likely or Likely greater relative intensities in PRE compared to POST. Only systemic FTs occurred at Very Likely or Likely greater relative intensities in PERI compared to POST, with Unclear differences for all localized FTs. When comparing PRE and PERI, only HHbBP and OxBP occurred at Likely greater relative intensities in PRE, with Unclear differences for all other FTs.CONCLUSIONSSystemic FTs occurred at lower relative intensities in POST when compared to PRE and PERI; while localized FTs were not different between PERI and POST. Furthermore, systemic FTs and NFT did not occur at different relative intensities in PRE and PERI; however, HHbBP and OxBP occurred at greater relative intensities in PRE. Therefore, maturity related differences in FTs do exist amongst adolescent males, which may represent the change in the metabolic response to exercise that occurs with maturation. The disparity in the maturity related differences between systemic and localized FTs may indicate that maturation affects the muscular response to exercise prior to affecting the pulmonary response. Mean ± SD in fatigue thresholds (%VO2max) for each maturational group. Fatigue Threshold PRE PERI POST Systemic Pulmonary GET 60.86 ± 5.43* 61.25 ± 5.33* 52.92 ± 5.73 VT 68.64 ± 1.59* 68.05 ± 2.96# 63.70 ± 5.86 RCP 82.33 ± 4.96* 82.66 ± 4.12* 76.11 ± 6.34 Localized Muscular NFT 80.26 ± 4.20# 77.20 ± 5.68 74.61 ± 8.14 HHbBP 80.02 ± 6.83#$ 72.89 ± 10.50 74.68 ± 7.97 OxBP 64.07 ± 10.55#$ 55.54 ± 8.75 55.51 ± 10.73 Very Likely greater than POST; Likely greater than POST; Likely greater than PERI

Several studies in adult men and women have demonstrated excellent reliability and sensitivity when measuring neuromuscular fatigue threshold (NFT) during an incremental cycle ergometer test. Recently, the ability to estimate NFT in young boys (11.1+1.1yrs) was demonstrated, which may provide a new noninvasive method to examine training interventions as well as the effect of maturation on changes in motor unit recruitment strategies. However, to date, no one has examined the reliability of estimating NFT in boys. PURPOSE: To determine the reliability of estimating the onset of neuromuscular fatigue in boys across maturity status. METHODS: Twenty-four boys (age 11 to 17yrs) volunteered with parental consent to complete two graded exercise test (GXT) on a cycle ergometer separated by at least 48 hours. The NFT was estimated during the GXT by way of the maximal distance method using electromyographic amplitude values from the right vastus lateralis vs power output (W). All participants were separated according to their number of years from peak height velocity (PHV), an estimation of somatic maturity status, into PRE- (-1yr), PERI- (between -1 to +1yr) and POST- (+1yr) PHV groups. Test-retest reliability was calculated for PRE-, PERI-, POST-PHV as well as the combined group. Intraclass correlation coefficient (ICC2,1), standard error of the measurement (SEM) and minimum detectable change (MDC) were calculated using a custom written Excel spreadsheet. RESULTS: Table 1 summarizes the results. Every group independently and combined demonstrated excellent reliability (ICC>0.75) CONCLUSIONS: The current results described in Table 1 are similar to other studies that have reported ICC (0.85 to 0.95), SEM (6W to 14.6W) and MDC (17W to 34W) in adult men. The estimation of NFT, therefore, is reliable in boys regardless of maturity status.Table 1: Summary of the reliability data

Apoptosis, or programmed cell death, is an essential physiological process regulating cellular development and is often associated with advanced stages of inflammation and disease. However, limited research has focused on skeletal muscle apoptosis as result of exercise induced muscular trauma. PURPOSE: To observe the effects of an acute lower-body resistance exercise protocol and subsequent recovery on intramuscular apoptotic signaling. METHODS: Twenty-eight untrained males (22.3 ± 3.2 y, 1.7 ± 0.1 m, 81.1 ± 15.5 kg) were assigned to either a control (CON; n=11) or exercise group (EX; n=17) and completed a lower-body resistance exercise protocol consisting of the back squat, leg press, and leg extension exercise. Skeletal muscle microbiopsies were obtained from the vastus lateralis pre-exercise (PRE), 1-hour (1HR), 5-hour (5HR), and 48-hours (48HR) post-resistance exercise. Multiplex signaling assay kits (EMD Millipore, Billerica, MA, USA) were used to quantify the total protein (Caspase-3,-8,-9) or phosphorylation status of proteins (JNK, FADD, p53, BAD, Bcl-2) specific to apoptotic signaling pathways using MAGPIX® (Luminex, Austin, TX, USA). Mann Whitney U analysis was used to determine the effects of the exercise bout on intramuscular signaling. Additionally, change scores were analyzed by magnitude based inferences to determine a mechanistic interpretation. RESULTS: Mann-Whitney U analysis revealed that resistance exercise increased JNK phosphorylation at 1H (p=0.001) and 5H (p=0.022), and FADD phosphorylation at 1H (p=0.029). No other differences observed between groups. Magnitude based inferences revealed a “Likely” increase in total Caspase 3 from PRE-5H and from PRE-48H. JNK phosphorylation was “Most Likely” increased from PRE-1H and PRE-5H and FADD was “Likely” increased from PRE-1H. BAD was “Very Likely” increased from PRE-5H and Bcl-2 was “Most Likely” increased from PRE-1H and “Likely” increased” from PRE-5H. CONCLUSION: These data show that apoptotic signaling is upregulated in response to a typical resistance exercise protocol, providing additional insight into the physiological mechanisms involved in skeletal muscle remodeling following resistance exercise.

Relative age effects (RAEs) have been studied as a potential factor associated with player selection bias in numerous sports. However, little research has examined the role of RAEs among National Football League (NFL) draftees. The purpose of the current study was to determine the existence of RAEs in NFL draftees from the last 10 NFL drafts. Draftee birth dates were collected and divided into calendar and scholastic quarters (SQ1-SQ4). To determine the presence of RAEs in specific subsets, NFL draftees were grouped according to round drafted, position, level of conference play, and age at the time of the draft. Significant chi(2) tests (p <= 0.05) comparing observed birth-date distributions vs. the expected birth-date distribution from the general population were followed up by calculating the standardized residual for each quarter (z. > +/-.0 indicating significance). Overall, no RAEs were seen when birth-date distribution was assessed using calendar quarters (p = 0.47), but more draftees were born in SQ2 (December-February) than expected (p, 0.01; z = + 2.2). Significantly more draftees were born in SQ2 than expected for middle-round draftees (p = 0.01; z = + 2.4), skill positions (p = 0.03; z = + 2.3), Power Five college draftees (p, 0.01; z = + 2.6), and early draftees (p, 0.01; z = + 3.1). However, reverse RAEs were seen among late draftees, with fewer draftees being born in SQ2 (z = 23.6) and more being born in SQ4 (June-August; z = + 2.6) than expected. In contrast to previous research, the current study observed significant RAEs in NFL draftees from the last 10 years. This player selection bias should be considered when evaluating long-term athlete development models in American football.

Objective: Insulin-like growth factor -I (IGF-I) is a metabolic and anabolic biomarker that has been proposed to reflect physiological adaptations resulting from multistressor environments. The bioactivity of IGF-I is regulated by seven different insulin-like growth factor binding proteins (IGFBPs) which act not only as carriers of IGF-1, but also function as a modulator of IGF-1 availability and activity. Supplementing with beta-hydroxy-beta-methylbutyrate (HMB) has been shown to enhance physiological outcomes associated with intense training, and has been reported to augment the IGF-1 response. The purpose of this study was to examine the effect of 23 days of HMB supplementation on circulating levels of IGF-I and IGFBPs in combat soldiers during highly intense military training.Methods: Thirteen male soldiers from an elite infantry unit volunteered to participate in this double-blind, parallel design study. Soldiers were provided 3 g.day(-1) of either HMB (n = 6) or placebo (PL; n = 7). During the study soldiers performed advanced military training with periods of restricted sleep and severe environmental stressors. Blood samples were obtained prior to (PRE) and approximately 18 h following the final supplement consumption (POST).Results: No significant differences were observed for circulating IGF-1 concentrations between HMB and PL (p = 0.568). In addition, no differences were seen between the groups for IGFBP-1 (p = 1.000), IGFBP-2 (p = 0.855), IGFBP-3 (p = 0.520), IGFBP-4 (p = 0.103), IGFBP-5 (p = 0.886), or IGFBP-6 (p = 0.775). A significant difference was noted between HMB (169.9 +/- 23.0 ng.m1(-1)) and PL (2072 +/- 28.0 ng.m1(-1)) for IGFBP-7 at POST (p = 0.042).Conclusions: Although the results of this study do nbt support the influence of HMB supplementation on circulating concentrations of IGF-1 or IGFBPs1-6 during high intensity military training, it does present initial evidence that it may lower circulating IGFBP-7 concentrations. This may provide some indication of a reduced stress response, but further investigation on the physiological role of IGFBP-7 and military training is needed. (C) 2016 Elsevier Ltd. All rights reserved.