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.

Resistance Training using VAriable Resistance Suit (VARS) Increased Isometric and Isokinetic Muscle Strength.

While resistance training promotes muscle hypertrophy and strength, accessibility of equipment is a barrier. This study evaluated a wearable VAriable Resistance Suit (VARS) as a novel and alternative method to achieve muscle strength improvement. It was hypothesized that by providing adjustable, bi-directional and speed dependent resistance, VARS can target specific muscles to improve muscle strength via an accessible and portable device. Twelve untrained healthy male adults (22.08 ± 4.1 years old) participated in an 8-week long resistance training using VARS to strengthen four muscles (biceps brachii, triceps brachii, biceps femoris, rectus femoris) of their non-dominant arm and leg using VARS. The results showed significant improvements in the muscle strength measured by isokinetic dynamometer - 49.9±9.6% increase in isokinetic force and 30.6±7.6% increase in isometric force. Muscle size and body composition were also assessed using ultrasound imaging and bioelectrical impedance analysis, which did not show significant changes. The study demonstrates the efficacy and feasibility of VARS as a resistance training tool to achieve muscle strength improvement and its potential extension to clinical populations.

Gamified delivery of at-home rehabilitation for individuals with nonspecific low back pain: a randomized controlled trial.

PURPOSE: To measure the change in pain and disability during and after a 6-week gamified delivery of home exercise compared to a take-home packet. MATERIALS AND METHODS: A 6-week at-home exercise protocol included participants randomly allocated to a gamified delivery group or packet group. The exercise protocol included the plank, side plank, foot elevated side plank, dead bug, and bird dog completed until discontinuation. The gamified delivery group received on-demand exercise videos and weekly exercise duration leaderboards. The packet group received a take-home packet. RESULTS: Forty participants were randomized into a packet group and leaderboard group, and 30 participants completed the study. Disability was significantly lower at 6-weeks (11.29 ± 9.81%) compared to baseline (15.93 ± 11.65%) in the packet group (χ2(2) =10.89, Z= -3.163, p=.002, r=.708). Percent disability was significantly lower at 6-weeks (8.00 ± 5.91%) compared to baseline (13.01 ± 7.17%) in the gamified delivery group (χ2(2) =13.235, Z= -3.399, p= <.001, r= -0.760). Worst pain was higher at baseline (7.05 ± 1.61%) than at 6-weeks (5.75 ± 1.68%) in the packet group (χ2(2) =8.067, Z = 2.760, p=.006, r= -0.617). Worst pain was higher at baseline (6.90 ± 1.33%) than at 6-weeks (5.24 ± 2.38%) in the gamified delivery group (χ2(2) =6.250, Z= -2.810, p=.005, r= -0.628). No significant difference in the change of disability from baseline to 6 weeks was found between groups (p=.483). CONCLUSIONS: Core exercises completed until failure may improve disability and pain at 6-weeks and positively influence perceived patient improvement.Registry: Clinicaltrials.gov; Registration number: NCT05573932.

Nonspecific low back pain affects individuals on a personal, societal and economic level.Both interventions and exercises in this study influenced disability and pain, the outcome variables most important to individuals suffering from nonspecific low back pain.Targeting core musculature during at-home exercise may decrease pain and disability in the nonspecific low back pain population.

The physical and psychosocial benefits of a family judo program for parents of children with Autism Spectrum Disorder: A pilot study.

BACKGROUND: Parents of children with Autism Spectrum Disorder (ASD) tend to have high levels of stress and poor health habits. There is a lack of interventions that focus on improving health outcomes in parents of children with ASD. OBJECTIVE: To examine the physical and psychosocial effects of a family-based judo program on parents of children diagnosed with ASD. METHODS: This study utilized a pre-post single group design. Eighteen parent-child dyads participated in a 14-week judo program for families of children with ASD. Judo sessions were held once a week for 45 min. Parents wore wrist accelerometers to assess physical activity/sleep quality, and completed surveys regarding self-reported stress levels pre- and post-judo. Parents also completed open-ended questions regarding their experience in the program. Paired sample t-tests were conducted to examine changes in stress, physical activity, and sleep quality from pre-to post-program. RESULTS: Both a decrease in parental stress (47.77 vs. 41.61, p < 0.01) and an increase in minutes per day of physical activity (35.49 vs 45.94, p = 0.002) were observed from baseline to post-program. Fourteen of the 18 parents (78 %) reported at least one psychosocial benefit (e.g. increased self-confidence) or physical health benefit (e.g. increased physical activity) from participation in the program. CONCLUSIONS: A family judo program may provide health benefits, such as reducing stress levels and increasing physical activity in parents of children with ASD. Further research involving larger sample sizes is necessary to better determine the effects of judo on both parents and their children with ASD.

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.

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.

Comparing Sensitivity, Specificity, and Accuracy of Fall Risk Assessments in Community-Dwelling Older Adults.

Purpose: The US Centers for Disease Control and Prevention (CDC) has implemented the Stopping Elderly Accidents, Deaths, and Injuries (STEADI) initiative. This initiative provides an algorithm for fall risk screening. However, the algorithm has the potential to overcategorize individuals as high risk for falling upon initial screening, which may burden clinicians with the task of recategorizing individuals after follow-up testing. Therefore, this study aimed to compare the accuracy, sensitivity, and specificity of fall risk appraisal between the STEADI, Short Fall-Efficacy Scale International (FES-I), and portable balance system (BTrackS) assessments in community-dwelling older adults. Patients and Methods: This cross-sectional analysis included 122 community-dwelling older adults, comprising 94 women and 28 men. Center-of-pressure postural sway was assessed using the BTrackS, fear of falling was assessed using the Short FES-I questionnaire, and all participants completed the STEADI checklist. Each assessment categorized participants as either high or low fall risk and fall risk appraisal was compared between groups using McNemar tests. Results: The STEADI checklist (high risk: n = 62; low risk: n = 60) significantly differed in fall risk appraisal compared to the BTrackS (high risk: n = 44; low risk: n = 78; p = 0.014) and the Short FES-I (high risk: n = 42; low risk: n = 80; p = 0.002). Compared to the BTrackS, the STEADI checklist had a specificity of 62.8%, sensitivity of 70.5%, and accuracy of 65.6%. Compared to the Short FES-I, the STEADI checklist had a specificity of 67.5%, sensitivity of 81.0%, and accuracy of 72.1%. Conclusion: The STEADI checklist appears to overcategorize individuals as high fall risk more frequently than direct assessments of postural sway and fear of falling. Further research is needed to examine potential improvements in accuracy when combining the STEADI checklist with direct assessments of postural sway and/or fear of falling.

Fall risk assessments are crucial for preventative care in older adults. However, the demands of clinical practice require an accurate and time-efficient method. The U.S Centers for Disease Control and Prevention (CDC) has implemented a fall risk checklist through the Stopping Elderly Accidents, Deaths, and Injuries (STEADI) initiative. However, the STEADI checklist might cost clinicians more time than expected, as some patients initially classified as high risk for falling may not actually be at high risk. This leads to unnecessary follow-up assessments. In this study, we compared the STEADI checklist to direct measures of postural sway (balance) using the BTrackS system and fear of falling using the Short FES-I survey to determine how they differed in classifying community-dwelling older adults as high versus low fall risk. Our results show that the STEADI checklist classifies older adults as high risk more frequently than the BTrackS and Short FES-I. Considering that the follow-up assessments for a high-risk classification by the STEADI checklist include a balance test, we suggest that combining a balance test such as the BTrackS with a questionnaire or checklist may yield better screening outcomes and accurately identify high-risk individuals in a timely manner. Further research is needed to determine the effectiveness of this combination and to establish a true gold standard method for fall risk appraisal.

Associations between monitor-independent movement summary (MIMS) and fall risk appraisal combining fear of falling and physiological fall risk in community-dwelling older adults.

Introduction: Fall Risk Appraisal (FRA), a process that integrates perceived and objective fall risk measures, serves as a crucial component for understanding the incongruence between fear of falling (FOF) and physiological fall risk in older adults. Despite its importance, scant research has been undertaken to investigate how habitual physical activity (PA) levels, quantified in Monitor-Independent Movement Summary (MIMS), vary across FRA categories. MIMS is a device-independent acceleration summary metric that helps standardize data analysis across studies by accounting for discrepancies in raw data among research-grade and consumer devices. Objective: This cross-sectional study explores the associations between MIMS (volume and intensity) and FRA in a sample of older adults in the United States. Methods: We assessed FOF (Short Falls Efficacy Scale-International), physiological fall risk (balance: BTrackS Balance, leg strength: 30-s sit-to-stand test) and 7-day free-living PA (ActiGraph GT9X) in 178 community-dwelling older adults. PA volume was summarized as average daily MIMS (MIMS/day). PA intensity was calculated as peak 30-min MIMS (average of highest 30 non-consecutive MIMS minutes/day), representing a PA index of higher-intensity epochs. FRA categorized participants into following four groups: Rational (low FOF-low physiological fall risk), Irrational (high FOF-low physiological fall risk), Incongruent (low FOF-high physiological fall risk) and Congruent (high FOF-high physiological fall risk). Results: Compared to rational group, average MIMS/day and peak 30-min MIMS were, respectively, 15.8% (p = .025) and 14.0% (p = .004) lower in irrational group, and 16.6% (p = .013) and 17.5% (p < .001) lower in congruent group. No significant differences were detected between incongruent and rational groups. Multiple regression analyses showed that, after adjusting for age, gender, and BMI (reference: rational), only irrational FRA was significantly associated with lower PA volume (ß = -1,452.8 MIMS/day, p = .034); whereas irrational and congruent FRAs were significantly associated with lower "peak PA intensity" (irrational: ß = -5.40 MIMS/day, p = .007; congruent: ß = -5.43 MIMS/day, p = .004). Conclusion: These findings highlight that FOF is a significant barrier for older adults to participate in high-intensity PA, regardless of their balance and strength. Therefore, PA programs for older adults should develop tailored intervention strategies (cognitive reframing, balance and strength exercises, or both) based on an individual's FOF and physiological fall risk.

Phase Angle and Impedance Ratio as Indicators of Physical Function and Fear of Falling in Older Adult Women: Cross-Sectional Analysis.

Background: Older adults experience a significant decline in muscle integrity and function with aging. Early detection of decreased muscle quality can pave the way for interventions to mitigate the progression of age-related physical declines. Phase angle (PhA) and impedance ratio (IR) are measures of muscle integrity, which can be assessed quickly via bioelectrical impedance analysis (BIA) and may be indicative of physical function. Objective: This study aimed to characterize the relationships among handgrip strength (HGS), sit-to-stand (STS), BTrackS balance scores, fear of falling (evaluated using the Short Falls Efficacy Scale-International [Short FES-I]), and IR among community-dwelling older adult women classified as having a low or high PhA. Methods: A cross-sectional analysis was conducted with 85 older women (mean age 75.0, SD 7.2 years; mean weight 71.0, SD 15.0 kg; mean height 162.6, SD 6.1 cm). To examine the influence of PhA on performance measures, participants were divided into 2 PhA groups: high (>4.1°; n=56) and low (≤4.1°; n=29). Data were nonnormative; hence, the Mann-Whitney U test was used to evaluate between-group differences, and Kendall τ coefficients were used to determine the partial correlations. Results: The low PhA group had a significantly higher IR (mean 0.85, SD 0.03) than the high PhA group (mean 0.81, SD 0.03; r=.92; P<.001). The high PhA group had superior HGS (mean 21.4, SD 6.2 kg; P=.007; r=0.36), BTrackS balance scores (mean 26.6, SD 9.5 cm; P=.03; r=0.30), and STS scores (mean 16.0, SD 5.5; P<.001; r=0.49) than the low PhA group (mean HGS 17.6, SD 4.7 kg; mean BTrackS balance score 37.1, SD 21.1 cm; mean STS score 10.7, SD 6.2). Both PhA and IR were significantly correlated with HGS and BTrackS balance, STS, and Short FES-I scores (P<.05). However, on adjusting for the whole sample's age, only PhA was strongly correlated with HGS (τb=0.75; P=.003) and STS scores (τb=0.76; P=.002). Short FES-I scores were moderately correlated with IR (τb=0.46; P=.07) after controlling for age. No significant between-group differences were observed for height, weight, or BMI. Conclusions: PhA and IR are associated with physical function and the fear of falling in older women. However, only PhA was significantly associated with physical function (HGS and STS) independent of age. Conversely, only IR was significantly associated with the fear of falling. Diminished physical function and increased IR appear to be characteristics of older women with a PhA of ≤4.1°. These findings suggest that PhA and IR measured through BIA together may serve as a valuable tool for early identification of older women at the risk of functional decline and a heightened fear of falling.

Sex differences in muscle-quality recovery following one week of knee joint immobilization and subsequent retraining.

This manuscript represents the second phase of a clinical trial designed to examine the effects of knee joint immobilization and retraining on muscle strength and mass. In Phase 2, we examined sex differences in the recovery of multiple indices of muscle quality after a resistance training-based rehabilitation program. Following 1 week of immobilization, 27 participants (16 males, 11 females) exhibiting weakness underwent twice weekly resistance training sessions designed to re-strengthen their left knee. Unilateral retraining sessions utilizing leg press, extension, and curl exercises were conducted until participants could reproduce their pre-immobilization knee extension isometric maximal voluntary contraction (MVC) peak torque. Post-immobilization, both sexes demonstrated impaired MVC peak torque (males = -10.8%, females = -15.2%), specific torque (-9.8% vs. -13.1%), echo intensity of the vastus lateralis (+6.9% vs. +5.9%) and rectus femoris (+5.9% vs. +2.1), and extracellular water/intracellular water ratio (+7.8% vs. +9.0%). The number of retraining sessions for peak torque to return to baseline for males (median = 1, mean = 2.13) versus females (median = 2, mean = 2.91) was not significantly different, though the disparity in recovery times may be clinically relevant. Following retraining, specific torque was the only muscle-quality indicator that improved along with MVC peak torque (males = 20.1%, females = 22.4%). Our findings indicate that measures of muscle quality demonstrate divergent recovery rates following immobilization, with muscle mass lagging behind improvements in strength. Greater immobilization-induced strength loss among females suggests that sex-specific rehabilitation efforts may be justified.

Physiological Perturbations in Combat Sports: Weight Cycling and Metabolic Function-A Narrative Review.

Combat sports athletes seeking a competitive edge often engage in weight management practices to become larger than their opponents, which ultimately includes periods of gradual weight loss, rapid weight loss, and weight regain. This pattern of weight loss and regain is known as weight cycling and often includes periods of low energy availability, making combat sports athletes susceptible to metabolic dysfunction. This narrative review represents an effort to explore the metabolic perturbations associated with weight cycling and outline the short-, medium-, and long-term effects on metabolic flexibility, function, and health. The short-term effects of rapid weight loss, such as a reduced metabolic rate and alterations to insulin and leptin levels, may prelude the more pronounced metabolic disturbances that occur during weight regain, such as insulin resistance. Although definitive support is not currently available, this cycle of weight loss and regain and associated metabolic changes may contribute to metabolic syndrome or other metabolic dysfunctions over time.

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.

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.

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.

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.

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.

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.

Optimizing normalization methods of the external oblique: A cross-sectional study.

BACKGROUND: Adequate normalization methodology to establish maximum voluntary isometric contraction (MVIC) is needed to compare %MVIC values for core exercise completed until discontinuation. Clinicians can use %MVIC classifications to guide their preventative and rehabilitative exercise interventions. OBJECTIVE: The aim of this study was to compare %MVIC of the external oblique (EO) between normalization techniques of side-lying lateral trunk flexion and Roman chair lateral trunk flexion. METHODS: Twenty-two participants completed two MVIC techniques followed by one repetition of the prone bridge plank (PBP), torso elevated side plank (TESP), foot elevated side plank (FESP), dead bug and bird dog. The average %MVIC during the first 5-seconds, last 5-seconds and overall duration of exercise were included for analysis. ANOVA was used to compare normalized %MVIC from each of the 5 exercises between MVIC techniques. Alpha set a priori p= 0.05. RESULTS: The side-lying table technique yielded no %MVIC values above 100%, while the Roman chair technique produced 7 values above 100%. The largest mean difference between techniques was during the last 5-seconds of the torso elevated side plank (57.87 ± 38.51%MVIC, p< 0.001). CONCLUSION: The side-lying table technique likely provides the optimal methodology of %MVIC determination.

The Influence of Transcranial Magnetic Stimulation Interpulse Interval Duration on Knee Extensor Corticospinal Excitability.

Background/Purpose: To examine the influence of interpulse interval duration on knee extensor corticospinal excitability. Methods: Seventeen college-aged males and females participated in a single laboratory visit, during which 25 single transcranial magnetic stimulation pulses were delivered to the motor cortex with interpulse intervals of 5, 10, 15, and 20 sec. Surface electromyographic signals were detected from the dominant vastus lateralis and rectus femoris. Motor evoked potential amplitude was compared across the four conditions. Results: For the vastus lateralis, the Friedman test indicated significant differences among conditions (chi-squared [3] = 7.80, p = 0.050); however, there were no pairwise differences (p ≥ 0.094) and small effect sizes (d ≤ 0.269). For the rectus femoris, the Friedman test results showed no significant differences among conditions (chi-squared [3] = 2.44, p = 0.487). Across all muscles and conditions, low intraclass correlation coefficients and high standard errors of measurement were suggestive of poor reliability. Conclusion: Unlike resting hand muscles, interpulse interval duration has little influence on corticospinal excitability for the knee extensors during active contractions.