Overload Injury of the Knees With Resistance-Exercise Overtraining: A Case Study

This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?vid=3&sid=cc60431c-6281-4940-bc2d-85f4c9ff2060%40sessionmgr11&hid=17&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=SPHS-67196

Effect of sprint approach velocity and distance on deceleration performance in NCAA Division I female softball athletes

Team sports require athletes to rapidly reduce whole body momentum and velocity, to efficiently change direction, or to avoid defenders. Decelerations often occur following varying approach distances and velocities. The aim of this study was to investigate the effects of different sprinting approach distances, and therefore velocities and momenta on measures of horizontal deceleration performance within female NCAA Division I softball players. Athletes performed an acceleration:deceleration assessment (ADA) over 20 yards (18.29 m) (ADA20) and 10 yards (9.14 m) (ADA10), respectively. The sample was divided into high and low performance groups for approach velocity and approach momentum, and between-group differences were studied for each test. Correlations between measures of deceleration were analysed between the ADA10 and ADA20. Results suggested that during the ADA20 trials, athletes initiated the deceleration phase at greater approach velocities (p < .001, ES = 2.71) and momenta (p < .001, ES = 2.65), generating greater reductions in velocity (p < .001, ES = 1.60) and momentum (p < .001, ES = 1.50). Within the ADA10, athletes within the high velocity group saw significantly greater reductions in velocity (p = .009, ES = 1.24). This was not observed within the ADA20. A significant negative association was found between average deceleration within the ADA10 and ADA20 (r = -0.443, p = .039). Findings suggest that horizontal decelerations are influenced by the approach distance, velocity, and momentum, which athletes are exposed to before initiating the deceleration phase. This should be accounted for when implementing training to enhance such qualities

Regionalization of Hydrologic Response in the Great Lakes Basin: Considerations of Temporal Scales of Analysis

Methods for predicting streamflow in areas with limited or nonexistent measures of hydrologic response commonly rely on regionalization techniques, where knowledge pertaining to gauged watersheds is transferred to ungauged watersheds. Hydrologic response indices have frequently been employed in contemporary regionalization research related to predictions in ungauged basins. In this study, we developed regionalization models using multiple linear regression and regression tree analysis to derive relationships between hydrologic response and watershed physical characteristics for 163 watersheds in the Great Lakes basin. These models provide an empirical means for simulating runoff in ungauged basins at a monthly time step without implementation of a rainfall-runoff model. For the dependent variable in these regression models, we used monthly runoff ratio as the indicator of hydrologic response and defined it at two temporal scales: (1) treating all monthly runoff ratios as individual observations and (2) using the mean of these monthly runoff ratios for each watershed as a representative observation. Application of the models to 62 validation watersheds throughout the Great Lakes basin indicated that model simulations were far more sensitive to the temporal characterization of hydrologic response than to the type of regression technique employed, and that models conditioned on individual monthly runoff ratios (rather than long term mean values) performed better. This finding is important in light of the increased usage of hydrologic response indices in recent regionalization studies. Models using individual observations for the dependent variable generally simulated monthly runoff with reasonable skill in the validation watersheds (median Nash-Sutcliffe efficiency = 0.53, median R2 = 0.66, median absolute value of deviation of runoff volume = 13%). These results suggest the viability of empirical 3 approaches to simulate runoff in ungauged basins. This finding is significant given the many regions of the world with sparse gaging networks and limited resources for gathering the field data required to calibrate rainfall-runoff models

Repeat sprint fatigue and altered neuromuscular performance in recreationally trained basketball players

The primary aim of the present study was to investigate how the fatigue induced through a repeat sprint protocol acutely affected different measures of neuromuscular performance. Recreationally trained basketball players (n = 25) volunteered to participate in the study, and performed three countermovement jumps (CMJ), as well as three drop jumps (DJ) prior to a fatiguing repeat sprint protocol. These procedures were repeated two minutes, and 15 minutes, following the protocol. Various force-time metrics were extracted from the jump tasks, and linear mixed models with subject ID as the random factor, and time as the fixed factor were used to investigate changes across the three time points. To account for the performance during the repeat sprint protocol, a second, two factor model was performed with time and repeat sprint ability (RSA) as the fixed factors. Study results indicated that the sample as a whole merely experienced fatigue-induced decreases in jump height from pre-repeat sprint ability protocol (pre-RSA) within the CMJ compared to two minutes post-repeat sprint ability protocol (post-RSA1) and 15 minutes post-repeat sprint ability protocol (post-RSA2), while jump height within the DJ was only significantly different from pre-RSA at post-RSA1. Further, despite the implementation of the fatiguing RSA protocol, over the course of the three time-points, participants seemed to perform the two jump tasks more efficiently, seen through significantly lower contraction times, greater eccentric (ECC) peak power, and greater ECC mean deceleration force within the CMJ following the RSA task. The two-factor model revealed that several significant time*RSA interactions were found for metrics such as ECC peak velocity and peak power in the CMJ, as well as reactive strength index in the DJ. This suggests that the level of RSA influenced changes across CMJ and DJ characteristics and should be accounted for when interpreting fatigue-induced changes in neuromuscular performance

Repeatability of Motion Health Screening Scores Acquired from a Three-Dimensional Markerless Motion Capture System

The purpose of the present study was to examine the repeatability of five algorithm-derived motion health screening scores (i.e., readiness, explosiveness, functionality, quality, and dysfunction) obtained from an innovative three-dimensional markerless motion capture system, composed of eight high-definition cameras recording at 60 fps. Thirteen females and six males performed two sets of three motion capture screenings, separated one week apart (six in total). The screenings consisted of 20 body movements performed in sequential order. Each screening within a testing session was separated by a 30 min rest interval to avoid the possible influence of fatigue. A trained research team member, facing the participant and standing outside of the camera capture range, was present to demonstrate each individual movement. The order in which motions were performed was identical across all participants. Repeated measures analysis of variance and intraclass correlation coefficients were used to examine statistically significant differences and measurement agreement across six testing sessions. The findings of the present study revealed no significant differences in algorithm-based motion health screening scores across multiple testing sessions. Moreover, excellent measurement reliability was found for readiness scores (ICC, 95% CI; 0.957, 0.914–0.980), good-to-excellent for functionality (0.905, 0.821–0.959) and explosiveness scores (0.906, 0.822–0.959), and moderate-to-excellent for dysfunction (0.829, 0.675–0.925) and quality scores (0.808, 0.635–0.915)

The Relationship between resistance exercise induced testosterone and cortisol responses and steroid receptor phosphorylation

The precise contribution of hormones to resistance training adaptations remains unclear. Recently, resistance exercise (RE) has been shown to change phosphorylation of androgen (pAR) & glucocorticoid receptors (pGR). Examining the relationships between the hormonal responses & steroid receptor phosphorylation may elucidate the role of acute hormonal responses to training adaptations. PURPOSE: The purpose of this study was to examine relationships between exercise-induced hormonal responses and pGR & pAR. METHODS: Resistance trained (RT) (n = 10; age = 21.3±1.7yrs, ht = 175.8±6.8cm, bodymass = 84.5±13.5kg) & untrained (UT) (n = 9; age = 20.8±3.1yrs, ht = 178.7±8.9cm, bodymass = 81.0±14.0kg) men completed an acute RE session of 6 sets of 10 reps, & 4 sets of 10 reps at 75% 1RM of barbell back squats, & knee extension, respectively. Muscle biopsies were obtained at rest, 10+, 30+, 60+, & 180+ minutes post-exercise & analyzed for total AR, pAR at ser81, ser213, ser515, ser650, total GR, and pGR at ser134, ser211, ser226. Testosterone & cortisol samples were obtained before, & up to 45 minutes post-exercise. Pearson correlations were performed to determine relationships between endocrine responses (area-under-curve [AUC]) & changes in total & phosphorylated AR & GR. Significance was determined at p≤0.05. RESULTS: The change in total AR at 180+ was correlated with cortisol (Pooled: r = -0.668, p = 0.002) & was strongest in RT subjects (RT: r = -0.767, p = 0.010). Cortisol was correlated with pARser81 at 60+ (r = 0.601, p = 0.006) & 180+ (r = 0.537, p = 0.018). Cortisol was correlated with the change in pARser650 at 180+ (r = 0.724, p = 0.018) in RT subjects. In UT the changes in pGRser134 & pGRser226 were correlated at 10+ (r = 0.987, p = 0.001) & 30+ (r = 0.943, p = 0.001). CONCLUSION: Cortisol responses were related to AR content, & changes in phosphorylation at sites regulating AR ligand sensitivity, & AR localization. There was a training status-specific relationship in UT subjects between pGR sites that regulate receptor localization, & GR sensitivity to cellular stress. Individualized cortisol responses are strongly related to AR activity and may explain the discrepancy in studies that solely investigated anabolic hormones & training adaptations, since these relationships also appear to be specific to different training statuses

Impact of Distance and Proficiency on Shooting Kinematics in Professional Male Basketball Players

Shooting efficiency is one of the key performance parameters related to securing the desired game outcome at various levels of basketball competition, and it is largely influenced by the biomechanical adjustments incorporated during the preparatory and release phase of the shooting motion. Thus, the purpose of the present study was twofold: (a) to examine the differences in the kinematic characteristics between free-throw, two-point, and three-point shots, and (b) to examine the differences between shooters with excellent (≥80%) and good (<80%) levels of shooting proficiency. A total of 10 professional male basketball players performed 5 free-throw (4.57 m), two-point (5.18 m), and three-point (6.75 m) shots, combining for a total of 150 shots. A high-definition camera recording at 120 fps was used to capture the shooting motion from a sagittal point of view, and video analysis software was used to analyze the kinematic variables of interest. The findings of the present study reveal that the kinematic characteristics during the preparatory phase of the shooting motion remain unchanged between free-throw and two-point shots. Three-point shots required lower elbow positioning, influenced by greater knee and hip flexion when compared to free-throw and two-point shots. The release angle was notably lower for shots attempted beyond the three-point line but remained unchanged between the free-throw and two-point shooting motions. Release height and vertical displacement were significantly greater for two- and three-point shots when compared to free-throw shots, while no difference was observed between the two- and three-point shots. In addition, no significant differences in shooting kinematics were observed between those participants with excellent and good levels of shooting proficiency

Lean Body Mass and Muscle Cross-Sectional Area Adaptations Among College Age Males With Different Strength Levels Across 11 Weeks of Block Periodized Programmed Resistance Training

The block periodization training paradigm has been shown to produce enhanced gains in strength and power. The purpose of this study is to assess resistance training induced alterations in lean body mass and cross-sectional area using a block periodization training model among individuals (n = 15) of three differing strength levels (high, moderate and low) based on one repetition maximum back squat relative to body weight. A 3 × 5 mixed-design ANOVA was used to examine within-and between-subject changes in cross-sectional area (CSA), lean body mass (LBM), lean body mass adjusted (LBMadjusted) and total body water (TBW) over an 11-week resistance training program. LBMadjusted is total body water subtracted from lean body mass. The ANOVA revealed no statistically significant between-group differences in any independent variable (p \u3e 0.05). Within-group effects showed statistically significant increases in cross-sectional area (p \u3c 0.001), lean body mass (p \u3c 0.001), lean body mass adjusted (p \u3c 0.001) and total body water (p \u3c 0.001) from baseline to post intervention: CSA: 32.7 cm2 ± 8.6; 36.3 cm2 ± 7.2, LBM: 68.0 kg ± 9.5; 70.6 kg ± 9.4, LBMadjusted: 20.4 kg ± 3.1; 21.0 kg ± 3.3 and TBW: 49.8 kg ± 6.9; 51.7 kg ± 6.9. In conclusion, the results of this study suggest subjects experienced an increase in both lean body mass and total body water, regardless of strength level, over the course of the 11-week block periodized program. Gains in lean body mass and cross-sectional area may be due to edema at the early onset of training

Relationship between Upper and Lower Body Strength and Basketball Shooting Performance

Strength is one of the key physiological performance attributes related to optimal on-court basketball performance. However, there is a lack of scientific literature studying how strength relates to shooting proficiency, as a key basketball skill capable of discriminating winning from losing game outcomes. Thus, the purpose of the present study was to examine the relationship between maximal upper and lower body strength and free-throw, two-point, and three-point shooting accuracy. Ten males and seven females performed bench press and back squat one repetition maximum (1RM) and basketball shooting testing during two laboratory visits. The shooting protocol consisted of five sets of 15 free-throw, two-point, and three-point shots performed in sequential order. Each set was separated by a 30 min rest interval to minimize the influence of fatigue. Each subject attempted 225 shots, combining for a total of 3825 shots. The average free-throw, two-point, and three-point shooting accuracy for men were 74.5 ± 11.9, 68.4 ± 9.9, and 53.3 ± 14.9%, and for women 79.2 ± 11.2, 65.5 ± 8.4, and 51.2 ± 15.3%, respectively. The average bench press and back squat 1RM for men was 88.2 ± 18.6 and 117.0 ± 21.2 kg, and for women, 40.6 ± 7.5 and 66.9 ± 9.9 kg, respectively. The findings of the present study revealed no significant relationships between maximal upper and lower body strength and basketball shooting performance for both male and female participants. Neither bench press nor back squat 1RM was a good predictor of free-throw, two-point, and three-point shooting performance

Endocrine responses and acute mTOR pathway phosphorylation to resistance exercise with leucine and whey

Leucine ingestion reportedly activates the mTOR pathway in skeletal muscle, contributing to a hypertrophy response. The purpose of the study was to compare the post-resistance exercise effects of leucine and whey protein supplementation on endocrine responses and muscle mTOR pathway phosphorylation. On visit 1, subjects (X±SD; n=20; age=27.8±2.8yrs) provided baseline blood samples for analysis of cortisol, glucose and insulin; a muscle biopsy of the vastus lateralis muscle to assess mTOR signaling pathway phosphorylation; and were tested for maximum strength on the leg press and leg extension exercises. For visits 2 and 3, subjects were randomized in a double-blind crossover design to ingest either leucine and whey protein (10g+10g; supplement) or a non-caloric placebo. During these visits, 5 sets of 10 repetitions were performed on both exercises, immediately followed by ingestion of the supplement or placebo. Blood was sampled 30 min post-, and a muscle biopsy 45 min post-exercise. Western blots quantified total and phosphorylated proteins. Insulin increased (α<.05) with supplementation with no change in glucose compared to placebo. Relative phosphorylation of AKT and rpS6 were greater with leucine and whey supplementation compared to placebo. Supplementation of leucine and whey protein immediately after heavy resistance exercise increases anabolic signaling in human skeletal muscle