Combined action observation and mental imagery versus neuromuscular electrical stimulation as novel therapeutics during short-term knee immobilization.

Limb immobilization causes rapid declines in muscle strength and mass. Given the role of the nervous system in immobilization-induced weakness, targeted interventions may be able to preserve muscle strength, but not mass, and vice versa. The purpose of this study was to assess the effects of two distinct interventions during 1 week of knee joint immobilization on muscle strength (isometric and concentric isokinetic peak torque), mass (bioimpedance spectroscopy and ultrasonography), and neuromuscular function (transcranial magnetic stimulation and interpolated twitch technique). Thirty-nine healthy, college-aged adults (21 males, 18 females) were randomized into one of four groups: immobilization only (n = 9), immobilization + action observation/mental imagery (AOMI) (n = 10), immobilization + neuromuscular electrical stimulation (NMES) (n = 12), or control group (n = 8). The AOMI group performed daily video observation and mental imagery of knee extensions. The NMES group performed twice daily stimulation of the quadriceps femoris. Based on observed effect sizes, it appears that AOMI shows promise as a means of preserving voluntary strength, which may be modulated by neural adaptations. Strength increased from PRE to POST in the AOMI group, with +7.2% (Cohen's d = 1.018) increase in concentric isokinetic peak torque at 30°/s. However, NMES did not preserve muscle mass. Though preliminary, our findings highlight the specific nature of clinical interventions and suggest that muscle strength can be independently targeted during rehabilitation. This study was prospectively registered: ClinicalTrials.gov NCT05072652.

A proposed test to determine physical working capacity at pain intensity threshold (PWCPIT).

PURPOSE: This study aimed to establish a new threshold parameter called the physical working capacity at pain intensity threshold (PWCPIT) using a pain intensity scale and mathematical methods similar to those used to develop the physical working capacity at oxygen consumption threshold (PWCVO2) and physical working capacity at heart rate threshold (PWCHRT). The study had two objectives: (i) to examine the relationship between PWCPIT and traditional PWC measures and (ii) to explore the physiological mechanisms underlying the relationship between pain perception and capacity thresholds. METHODS: Fourteen male volunteers (age 21 ± 2 years, height 176 ± 6 cm, weight 76 ± 9 kg, VO2peak 37.8 ± 7.8 ml/kg/min-1) underwent an incremental exhaustion test and four 8-min randomly ordered work bouts on different days at 70-100% peak power output (119-320 W) to establish their PWCPIT, PWCHRT and PWCVO2. One-way repeated-measures ANOVA with Bonferroni post hoc tests and a zero-order correlation matrix were used to analyze these thresholds. RESULTS: PWCPIT significantly correlated with PWCHRT (r = 0.88, P < 0.001), PWCVO2 (r = 0.84, P < 0.001), and gas exchange threshold (GET) (r = 0.7, P = 0.006). CONCLUSION: The model for estimating PWCHRT and PWCVO2 can be applied to determine the PWCPIT. By examining how PWCPIT aligns with, differs from, or complements existing PWC threshold measures, researchers may provide a more comprehensive understanding of the factors that govern endurance performance.

The impact of acute and chronic resistance training on appetite and energy intake: A scoping review examining resistance exercise and comparisons with other exercise modalities.

PURPOSE: The effects of exercise on appetite have recently been systematically evaluated with a focus on endurance training (ET). However, resistance training (RT) may induce different adaptations than ET. This scoping review aimed to examine the acute and chronic effects of isolated RT and comparisons with other exercise modalities on appetite-related variables and energy intake. RESULTS: 17 acute studies were identified, six examining isolated RT, while 11 focused on RT intensity, amount of exercise, targeted muscle groups, or comparison with ET and combined training (RT plus ET; CT). Nine chronic studies were identified. Three investigated isolated RT vs control and six manipulated the amount of RT exercise, types of RT, or comparison with ET and CT. CONCLUSIONS: Acute RT compared to control conditions appears to induce responses favoring appetite inhibition. While the amount of RT exercise may acutely play a role in the suppression of appetite, while ET seems to have more potential to suppress appetite. Chronic RT does not seem to stimulate compensatory mechanisms; however, there is not clear evidence regarding the role of RT intensity or other exercise modalities. Chronic ET and CT may be more prone to favor appetite inhibition than RT. More comprehensive evaluations including the exploration of multiple appetite-related factors are needed for future studies.

Injury Risk Analysis among Judo Athletes with Intellectual Disabilities.

The main aim of this study was to evaluate injury prevalence, incidence rate, and burden in judo athletes with intellectual disabilities (ID) who participate in international competitions. This retrospective cross-sectional study analyzed data from the past year for 182 judo athletes with ID. Data was collected using a self-reported questionnaire, adapted from previous research, that included questions about injuries impacting training or competition, injury type, mechanism, severity, diagnosis, and location on the body. The injury prevalence among judo athletes with ID occurred most often during training (68.2%) and primarily affected the lower extremities (35%). Age group and injury prevalence were significantly related (χ2=7.91; P=0.04), while gender, weight, and ability level were not. Results were closer to those previously reported for conventional judo, which is likely due to the lower practice intensity among judo athletes with ID. Injury prevalence was lower than in prior studies, but the incidence rates aligned when considering training time in judo athletes with ID. Injury burden analysis revealed that females had a lower burden than males, while older athletes experienced a higher burden than younger athletes. Most injuries occur during training, which is likely attributable to safety-focused competition rules.

Innovations in the Assessment of Skeletal Muscle Health: A Glimpse into the Future.

Skeletal muscle is the largest organ system in the human body and plays critical roles in athletic performance, mobility, and disease pathogenesis. Despite growing recognition of its importance by major health organizations, significant knowledge gaps remain regarding skeletal muscle health and its crosstalk with nearly every physiological system. Relevant public health challenges like pain, injury, obesity, and sarcopenia underscore the need to accurately assess skeletal muscle health and function. Feasible, non-invasive techniques that reliably evaluate metrics including muscle pain, dynamic structure, contractility, circulatory function, body composition, and emerging biomarkers are imperative to unraveling the complexities of skeletal muscle. Our concise review highlights innovative or overlooked approaches for comprehensively assessing skeletal muscle in vivo. We summarize recent advances in leveraging dynamic ultrasound imaging, muscle echogenicity, tensiomyography, blood flow restriction protocols, molecular techniques, body composition, and pain assessments to gain novel insight into muscle physiology from cellular to whole-body perspectives. Continued development of precise, non-invasive tools to investigate skeletal muscle are critical in informing impactful discoveries in exercise and rehabilitation science.

Comparing Device-Generated and Calculated Bioimpedance Variables in Community-Dwelling Older Adults.

Despite BIA emerging as a clinical tool for assessing older adults, it remains unclear how to calculate whole-body impedance (Z), reactance (Xc), resistance (R), and phase angle (PhA) from segmental values using modern BIA devices that place electrodes on both sides of the body. This investigation aimed to compare both the whole-body and segmental device-generated phase angle (PhADG) with the phase angle calculated using summed Z, Xc, and R from the left, right, and combined sides of the body (PhACalc) and to compare bioelectric variables between sides of the body. A sample of 103 community-dwelling older adults was assessed using a 50 kHz direct segmental multifrequency BIA device. Whole-body PhACalc values were assessed for agreement with PhADG using 2.5th and 97.5th quantile nonparametric limits of agreement and Spearman's rho. Bioelectrical values between sides of the body were compared using Wilcoxon rank and Spearman's rho. A smaller mean difference was observed between PhADG and right PhACalc (-0.004°, p = 0.26) than between PhACalc on the left (0.107°, p = 0.01) and on the combined sides (0.107°, p < 0.001). The sum of Z, R, and PhACalc was significantly different (p < 0.01) between the left (559.66 ± 99.55 Ω, 556.80 ± 99.52 Ω, 5.51 ± 1.5°, respectively) and the right sides (554.60 ± 94.52 Ω, 552.02 ± 94.23 Ω, 5.41 ± 0.8°, respectively). Bilateral BIA values do not appear to be interchangeable when determining whole-body measurements. Present data suggest that using right-sided segmental values would be the most appropriate choice for calculating whole-body bioelectrical variables.

Utility of Novel Rotational Load-Velocity Profiling Methods in Collegiate Softball Players.

ABSTRACT: 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.

Changes in Hip Isometric Strength of Female College Soccer Players After High-Workload Training Session.

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.

SIRT1 induction in the skeletal muscle of male mice partially preserves limb muscle mass but not contractile force in response to androgen deprivation.

In males, the factors that decrease limb muscle mass and strength in response to androgen deprivation are largely unknown. Sirtuin1 (SIRT1) protein levels are lower in the limb muscle of male mice subjected to androgen deprivation. The present study aimed to assess whether SIRT1 induction preserved limb muscle mass and force production in response to androgen deprivation. Physically mature male mice containing an inducible muscle-specific SIRT1 transgene were subjected to a sham or castration surgery and compared to sham and castrated male mice where the SIRT1 transgene was not induced. SIRT1 induction partially preserved whole-body lean mass, tibialis anterior (TA) mass and triceps surae muscle mass in response to castration. Further analysis of the TA muscle showed that muscle-specific SIRT1 induction partially preserved limb muscle soluble protein content and fibre cross-sectional area. Unilateral AAV9-mediated SIRT1 induction in the TA muscle showed that SIRT1 partially preserved mass by acting directly in the muscle. Despite those positive outcomes to limb muscle morphology, muscle-specific SIRT1 induction did not preserve the force generating capacity of the TA or triceps surae muscles. Interestingly, SIRT1 induction in females did not alter limb muscle mass or limb muscle strength even though females have naturally low androgen levels. SIRT1 also did not alter the androgen-mediated increase in limb muscle mass or strength in females. In all, these data suggest that decreases in SIRT1 protein in the limb muscle of males may partially contribute to the loss of limb muscle mass in response to androgen deprivation. KEY POINTS: SIRT1 induction in skeletal muscle of male mice subjected to androgen deprivation partially preserved limb muscle mass and fibre cross-sectional area. SIRT1 induction in skeletal muscle of male mice subjected to androgen deprivation did not prevent preserve limb muscle force generating capacity. SIRT1 induction in skeletal muscle of females did not alter baseline limb muscle mass, nor did it affect the androgen-mediated increase in limb muscle mass.

Development and test-retest reliability of the Combat Sports Post-Career Health Questionnaire (CSPCHQ).

The long-term impact of weight cycling on health status, eating habits, physical activity and the lifestyle of former combat sports athletes is still insufficiently explored. Therefore, a novel questionnaire in English, Portuguese, Spanish and Croatian language was constructed. To determine the reliability and the content/face validity, a total of 110 participants filled the questionnaire on two occasions. With the majority of intra-class correlation coefficient values above 0·75, the questionnaire items were shown to be very stable. Additionally, according to κ values, the questionnaire has fair test-retest reliability, with only one coefficient being labelled as poor (Q40 in ESP). All questionnaire sub-scales showed moderate to very good internal consistency when the overall sample was observed (α ranging from 0·605 to 0·802). Poor α values were found only in Godin-Shephard Leisure-Time Physical Activity Questionnaire for CRO and ESP samples. Wilcoxon's signed rank test showed significant differences only in the Mindful Eating Questionnaire sub-scale scores (overall: P = 0·002, effect size = -0·208 [moderate]; CRO: P = 0·005, effect size = 0·303 [moderate]). It can be concluded that the newly developed questionnaire had strong test-retest reliability. Further validity research in a larger sample of former combat sports athletes should be considered.

Influence of Body Composition, Load-Velocity Profiles, and Sex-Related Differences on Army Combat Fitness Test Performance.

ABSTRACT: Boffey, D, DiPrima, JA, Kendall, KL, Hill, EC, Stout, JR, and Fukuda, DH. Influence of body composition, load-velocity profiles, and sex-related differences on army combat fitness test performance. J Strength Cond Res 37(12): 2467-2476, 2023-The Army Combat Fitness Test (ACFT) became the U.S. Army's mandatory physical fitness test in April of 2022. The purpose of this study was to determine the relationship between ACFT performance and both body composition and velocity profiles and to determine sex differences for these variables. Data were collected at 2 timepoints 4 months apart, from male (n = 55) and female (n = 17) Army Reserve Officers' Training Corps (ROTC) cadets. Body composition was assessed with a bioelectrical impedance spectroscopy device, and cadets completed a hex bar deadlift load-velocity profile (LVP) and ACFT on separate days. Stepwise multiple regressions were used to explain the amount of variance in ACFT total score and individual event performance. Significance for statistical tests was defined as an alpha level of p ≤ 0.05. Muscle mass and body fat percentage accounted for 49% of shared variance of total ACFT score, and deadlift maximal power and maximal velocity accounted for 67% of shared variance of total ACFT score. The 3 repetition maximum deadlift, standing power throw, hand-release push-up, and sprint-drag-carry events favored cadets with more muscle mass, whereas the leg tuck was influenced by the body fat percentage and the 2-mile run was affected by fat mass. Sex had greater predictive capability for the 2-mile run than body composition. Men outperformed women on all individual events, with the greatest differences on standing power throw and sprint-drag-carry. It is recommended that Army ROTC cadets taking the ACFT maximize lower-body power production and increase muscle mass.

Time of Day Effects on Anaerobic Performance Using a Nonmotorized Treadmill.

ABSTRACT: Renziehausen, JM, Bergquist, AM, Park, J-H, Hill, EC, Wells, AJ, Stout, JR, and Fukuda, DH. Time of day effects on anaerobic performance using a nonmotorized treadmill. J Strength Cond Res 37(10): 2002-2007, 2023-The purpose of this study was to determine the effects of time of day on performance during a maximal effort sprinting assessment (30nmt) and determine potential differences based on chronotype and sex. Twenty-six recreationally active men (n = 12) and women (n = 14) between the ages of 18 and 35 years old (21.5 ± 2.4 years) completed the 30nmt at 9:00 am, 2:00 pm, and 7:00 pm in a randomized order over a 24-hour period. Resting heart rate and temperature assessments were taken at each visit. A dietary recall and the Morningness-Eveningness Questionnaire were used to assess kilocalories (kcals) and chronotype, respectively. Two-way (time x sex) repeated measures analyses of variance were conducted to determine differences in peak/mean power, peak/mean velocity, distance, resting heart rate, temperature, and kcals at each time point. Paired sample t tests were used to assess peak and nadir of each performance variable. A significance level was set at p < 0.05. There was a significant main effect for temperature (p < 0.001), resting heart rate (p = 0.007), and pre-exercise caloric intake (p = 0.021) throughout the day. No significant main effects for time were found for peak power (p = 0.766), mean power (p = 0.094), peak velocity (p = 0.497), mean velocity (p = 0.193), or distance (p = 0.262). There were no significant time × sex interactions for any dependent performance variables (p > 0.05). Significant differences were shown between the peak and nadir of each performance variable (p < 0.001). There were no significant differences in performance during maximal effort anaerobic assessments shown throughout the day; however, peak/nadir of performance times may be individualized and differ between morning types and intermediate types.

Acute Effects of Continuous and Intermittent Blood Flow Restriction on Sprint Interval Performance and Muscle Oxygen Responses.

ABSTRACT: Wizenberg, AM, Gonzalez-Rojas, D, Rivera, PM, Proppe, CE, Laurel, KP, Stout, JR, Fukuda, DH, Billaut, F, Keller, JL, and Hill, EC. Acute effects of continuous and intermittent blood flow restriction on sprint interval performance and muscle oxygen responses. J Strength Cond Res 37(10): e546-e554, 2023-This investigation aimed to examine the acute effects of continuous and intermittent blood flow restriction (CBFR and IBFR, respectively) during sprint interval training (SIT) on muscle oxygenation, sprint performance, and ratings of perceived exertion (RPE). Fifteen men (22.6 ± 2.4 years; 176 ± 6.3 cm; 80.0 ± 12.6 kg) completed in random order a SIT session with CBFR, IBFR (applied during rest), and no blood flow restriction (NoBFR). Each SIT session consisted of two 30-second all-out sprint tests separated by 2 minutes. Peak power (PP), total work (TW), sprint decrement score (S dec ), RPE, and muscle oxygenation were measured during each sprint. A p value ≤0.05 was considered statistically significant. PP decreased to a greater extent from sprint 1 to sprint 2 during CBFR (25.5 ± 11.9%) and IBFR (23.4 ± 9.3%) compared with NoBFR (13.4 ± 8.6%). TW was reduced similarly (17,835.6 ± 966.2 to 12,687.2 ± 675.2 J) from sprint 1 to sprint 2 for all 3 conditions, but TW was lower (collapsed across time) for CBFR (14,320.7 ± 769.1 J) than IBFR (15,548.0 ± 840.5 J) and NoBFR (15,915.4 ± 771.5 J). There were no differences in S dec (84.3 ± 1.7%, 86.1 ± 1.5%, and 87.2 ± 1.1% for CBFR, IBFR, and NoBFR, respectively) or RPE, which increased from sprint 1 (8.5 ± 0.3) to sprint 2 (9.7 ± 0.1). Collective muscle oxygenation responses increased across time and were similar among conditions, whereas increases in deoxy[heme] and total[heme] were greatest for CBFR. Applying BFR during SIT induced greater decrements in PP, and CBFR resulted in greater decrements in work across repeated sprints. The larger increases in deoxy[heme] and total[heme] for CBFR suggested it may induce greater metabolite accumulation than IBFR and NoBFR when combined with SIT.

Efficacy of Rest Redistribution During Squats: Considerations for Strength and Sex.

ABSTRACT: Boffey, D, Clark, NW, and Fukuda, DH. Efficacy of rest redistribution during squats: Considerations for strength and sex. J Strength Cond Res 35(3): 586-595, 2021-This study examined the kinematic, perceptual, and heart rate responses to rest redistribution (RR) and traditional sets (TS) during the barbell back squat for men and women possessing a wide range of strength levels. Forty-five resistance-trained subjects (30 men and 15 women) performed 40 repetitions of the barbell squat with 65% 1RM load with TS (4 × 10 repetitions, 3-minute rest) or RR (10 × 4 repetitions, 1-minute rest), in a randomized order on days separated by ≥72 hours. The significance was set at p ≤ 0.05 for all statistical analyses. The mean velocity (MV) maintenance was significantly higher for RR compared with TS (87.70 ± 4.50% vs. 84.07 ± 4.48%, respectively; p < 0.01, d = 0.35). Rating of perceived exertion (active muscles) was significantly lower for RR compared with TS (5.38 ± 1.42 vs. 6.08 ± 1.43, respectively; p = 0.02, d = -0.35). Rating of perceived exertion (overall) was also significantly lower for RR compared with TS (5.60 ± 1.40 vs. 6.48 ± 1.49, respectively; p = 0.02, d = -0.37). The relative strength ratio (relative strength ratio; squat 1RM: body mass) was significantly correlated with the difference in MV maintenance between RR and TS (r = -0.34, p = 0.02). No sex-based differences (p > 0.05) were found for any dependent variables. Rest redistribution produced significantly higher mean HR (143.25 ± 21.11 vs. 135.05 ± 20.74, p < 0.01) and minimum HR (102.77 ± 19.58 vs. 95.97 ± 22.17, p < 0.01). Subjects were better able to maintain velocity with RR compared with TS, while experiencing less perceived effort. Rest redistribution can be recommended for both men and women, but very strong individuals may not improve their velocity maintenance with RR to the same extent as less strong individuals.

Use of Tensiomyography in Evaluating Sex-Based Differences in Resistance-Trained Individuals After Plyometric and Isometric Midthigh Pull Postactivation Potentiation Protocols.

ABSTRACT: Herring, CH, Goldstein, ER, and Fukuda, DH. Use of tensiomyography in evaluating sex-based differences in resistance-trained individuals after plyometric and isometric midthigh pull postactivation potentiation protocols. J Strength Cond Res 35(6): 1527-1534, 2021-The purposes of this study were to determine if there are sex-based differences in muscular contractile properties as measured by tensiomyography (TMG) and to determine if plyometrics or the isometric midthigh pull are effective methods of eliciting postactivation potentiation (PAP). Thirty strong, resistance-trained men (n = 15) and women (n = 15) underwent 3 testing days consisting of a PAP or control protocol, and pre-TMG and post-TMG and performance testing. Contractile properties from TMG were assessed in the gastrocnemius medial head (GMH), gluteus maximus (GM), rectus femoris (RF), and biceps femoris (BF). Performance testing included countermovement jumps (CMJs) and 30-m sprints. A time × sex interaction was found for GM delay time with women primarily influencing changes (mean difference = 2.74 ms) rather than men (mean difference = 1.32 ms). Main effects for time revealed an increase in GMH velocity of contraction (+0.004 mm·ms-1) and reductions in GM contraction time (-2.85 ms), GM delay time (-2.03 ms), RF delay time (-0.65 ms), CMJs (-2.74 cm), and 30-m time (0.05 seconds). Main effects for sex revealed greater values in women for GM contraction time (+15.50 ms), GM delay time (+6.65 ms), RF delay time (+2.26 ms), BF contraction time (+8.44 ms), BF delay time (+4.07 ms), BF maximal displacement (+2.27 mm), and 30-m time (+0.67 seconds), and lower values in women for GM velocity of contraction (-0.039 mm·ms-1) and CMJs (-13.46 cm).These findings may help practitioners optimize performance through enhanced assessments for injury risk, targeting specific muscles for training, and by selecting proper CAs and rest periods when using PAP.

Relative Age Effects as Evidence of Selection Bias in Major League Baseball Draftees (2013-2018).

ABSTRACT: Herring, CH, Beyer, KS, and Fukuda, DH. Relative age effects as evidence of selection bias in major league baseball draftees (2013-2018). J Strength Cond Res 35(3): 644-651, 2021-The purpose of this study was to examine if relative age effects (RAEs) or the unequal birth-date distribution among a cohort group of individuals exist in Major League Baseball (MLB) draftees. This study comprised 7,078 men drafted in the MLB first-year player draft from 2013 to 2018. Data collected for each draftee included birth date, year drafted, academic-level classification, position, round drafted, batting side, and throwing arm. Draftee's birth dates were categorized into quarters based on the calendar year for baseball in the United States (Q1: August-October; Q2: November-January; Q3: February-April; Q4: May-July). Player birth-date distributions were compared with average expected birth-date distributions and evaluated with the χ2 goodness of fit statistic. Significant χ2 tests were followed up by calculating the standardized residual for each quarter. Differences from the expected frequencies were found for the overall group (p < 0.001) with standardized residuals for baseball athletes born in Q1 (z = +4.45) and Q3 (z = -4.15) exceeding ±2.0. Similar patterns were noted for high schoolers (Q1: z = +3.30; Q3: z = -3.28), pitchers (Q1: z = +2.78; Q3: z = -3.12), early middle rounders (Q1: z = +3.08; Q3: z = -2.67), late rounders (Q1: z = +2.70; Q3: z = -2.61), right-side hitters (Q1: z = +3.23; Q3: z = -2.26), left-handed pitchers (Q1: z = + 2.12; Q3: z = -2.59), and right-handed positional players (Q1: z = +3.12; Q3: z = -2.12). Consistent with the majority of previous research, RAEs are apparent in MLB draftees, with specific patterns of unequal distribution among subsets of athletes.

Effect of Knee Joint Angle on Regional Hamstrings Activation During Isometric Knee-Flexion Exercise.

CONTEXT: Each hamstring muscle is subdivided into several regions by multiple motor nerve branches, which implies each region has different muscle activation properties. However, little is known about the muscle activation of each region with a change in the knee joint angle. Understanding of regional activation of the hamstrings could be helpful for designing rehabilitation and training programs targeted at strengthening a specific region. OBJECTIVE: To investigate the effect of knee joint angle on the activity level of several regions within the individual hamstring muscles during isometric knee-flexion exercise with maximal effort (MVCKF). DESIGN: Within-subjects repeated measures. SETTING: University laboratory. PARTICIPANTS: Sixteen young males with previous participation in sports competition and resistance training experience. INTERVENTION: The participants performed 2 MVCKF trials at each knee joint angle of 30°, 60°, and 90°. OUTCOME MEASURES: Surface electromyography was used to measure muscle activity in the proximal, middle, and distal regions of the biceps femoris long head (BFlh), semitendinosus, and semimembranosus of hamstrings at 30°, 60°, and 90° of knee flexion during MVCKF. RESULTS: Muscle activity levels in the proximal and middle regions of the BFlh were higher at 30° and 60° of knee flexion than at 90° during MVCKF (all: P < .05). Meanwhile, the activity levels in the distal region of the BFlh were not different among all of the evaluated knee joint angles. In semitendinosus and semimembranosus, the activity levels were higher at 30° and 60° than at 90°, regardless of region (all: P < .05). CONCLUSION: These findings suggest that the effect of knee joint angle on muscle activity level differs between regions of the BFlh, whereas that is similar among regions of semitendinosus and semimembranosus during MVCKF.

Alterations in energy system contribution following upper body sprint interval training.

PURPOSE: The primary purpose of this study was to examine the influence of different work-to-rest ratios on relative energy system utilization during short-term upper-body sprint interval training (SIT) protocols. METHODS: Forty-two recreationally trained men were randomized into one of three training groups [10 s work bouts with 2 min of rest (10:2, n = 11) or 4 min of rest (10:4, n = 11), or 30 s work bouts with 4 min of rest (30:4, n = 10)] or a control group (CON, n = 10). Participants underwent six training sessions over 2 weeks with 4-6 'all-out' sprints. Participants completed an upper body Wingate test (30 s 'all-out' using 0.05 kg kg-1 of the participant's body mass) pre- and post-intervention from which oxygen consumption and blood lactate were used to estimate oxidative, glycolytic, and adenosine triphosphate-phosphocreatine (ATP-PCr) energy system provisions. An analysis of covariance was performed on all testing measurements collected at post with the associated pre-values used as covariates. RESULTS: Relative energy contribution (p = 0.026) and energy expenditure (p = 0.019) of the ATP-PCr energy system were greater in 10:4 (49.9%; 62.1 kJ) compared to CON (43.1%; 47.2 kJ) post training. No significant differences were found between groups in glycolytic or oxidative energy contribution over a 30 s upper body Wingate test. CONCLUSION: SIT protocols with smaller work-to-rest ratios may enhance ATP-PCr utilization in a 30 s upper body Wingate over a 2-week intervention.

Tracking 25 years of judo results from the World Championships and Olympic Games: Age and competitive achievement.

We quantified the peak age of judokas during the World Championships (WC) and Olympic Games (OG) according to sex, weight category and competitive achievement and determined the relationship between competition year and athlete age. A retrospective study including 12,005 athletes who took part in the last 16 WC and 6 OG. Athletes were divided by sex, weight category and competitive achievement. Overall, females were younger than males, and older athletes competed at the OG compared to the WC. A weight category effect was also observed, with lighter athletes being younger than heavier athletes (p < 0.05). A competitive achievement effect was found for females, with athletes being defeated in the eliminatory phases being younger than those advancing further in the competitions (p < 0.05). Significant associations (p < 0.05) were shown between competition year and age category for males at the WC and for females at both the WC and OG. In general, lighter athletes are younger than heavier ones (p < 0.05). No difference in age was found  between males concerning their competitive achievement in WC and OG, whereas younger females are defeated in the eliminatory phases (p < 0.05).

Dynamic post-activation potentiation protocol improves rowing performance in experienced female rowers.

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 × 5-second static muscle actions with the ergometer handle rendered immovable with a nylon strap, while DYN consisted of 2 × 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.