Post-Activation Performance Enhancement of Punch Force and Neuromuscular Performance in Amateur Boxing: Toward a More Individualized and "Real-World" Approach.

ABSTRACT: Finlay, MJ, Greig, M, Bridge, CA, and Page, RM. Post-activation performance enhancement of punch force and neuromuscular performance in amateur boxing: Toward a more individualized and "real-world" approach. J Strength Cond Res 38(6): 1063-1071, 2024-Previous research on post-activation performance enhancement has been applied in several sporting settings, although this is lacking in a boxing setting. This study explored the effectiveness of 2 upper-body conditioning activities in improving punch-specific performance during an amateur boxing-simulated bout. On 3 separate occasions, 10 male senior elite amateur boxers performed the following conditioning activities before a boxing-specific simulation protocol: isometric (ISO) punch, elastic resistance (ER) punch, and a control trial. Boxers performed maximal punches against a vertically mounted force plate, and countermovement jumps (CMJ) at baseline, before round 1, after each round, and 4 minutes after the simulation. Both conditioning activities, but not the control trial, produced small worthwhile increases (effect size ≥ 0.20; equal to or greater than the smallest worthwhile change) in punch force, although worthwhile increases in rate of force development were limited to the cross during the ISO trial. No group-based improvements in CMJ performance were observed. Individual analysis revealed that 6 boxers improved punch-specific performance to the greatest extent in the ISO trial; in contrast, only 1 boxer did so in the ER trial. Three boxers exhibited similar performance increases across trials. In conclusion, both conditioning activities may be applied to an amateur boxer's warm-up to acutely enhance punch-specific performance. The ISO conditioning activity seems most effective; however, the interindividual variability suggests a need for protocols to be individualized to each athlete. The conditioning activities in the present study may be applied to sparring, competitive bouts, or to other combat sports.

Different types of mechanical vibration application on EMG response and strength performance

Abstract Aim: The present study aimed to compare the strength performance and the neuromuscular activity during one maximum repetition test (1RM), and the maximum voluntary isometric contractions (MVIC) performed with whole-body vibration (WBV), local vibration (LV), and no vibration (NV). Methods: The sample consisted of 15 males, experienced in strength training for at least 6 months, which performed all strength tests in the barbell curl exercise across randomized trials on the following conditions: NV, WBV, and LV. During all tests, the normalized root means square values of the electromyographic signals (EMGRMS) of the biceps brachii and brachioradialis were recorded and compared between the conditions. The one-way ANOVAs with repeated measures were used to compare the results of 1RM and MVIC tests and the normalized EMGRMS between the conditions. When necessary, a post hoc Scott-Knott test was used to identify the differences reported in the ANOVAs. The significance level adopted was α < 0.05. Results: The EMGRMS response of the biceps brachii and brachioradialis muscles during the 1RM and MVIC tests presented significantly higher values at LV compared to WBV, and NV (p < 0.001). The 1RM tests, and the MVIC results were similar between conditions (p = 0.9803; p = 0.061, respectively). Conclusion: These results indicate that the application of MV was not sufficient to increase strength performance.

A realização de supersérie em uma sessão completa de treinamento impacta no volume e percepção subjetiva de esforço de praticantes de musculação / La realización de una superserie en una sesión completa de entrenamiento influye en el volumen y percepción subjetiva de esfuerzo de practicantes de musculación / Performing a superset in a complete training session impact on volume and rate of perceived exertion of resistance training practitioners

Objetivo: Comparar os protocolos tradicional e supersérie, com intervalo de recuperação equiparado, quanto ao volume total de treinamento (número de repetições x peso), número total de repetições por exercício e percepção subjetiva de esforço em uma sessão de treinamento.Método: Dezesseis homens treinados realizaram de forma randomizada os protocolos. No protocolo tradicional foram executadas três séries com intervalos de dois minutos entre séries e três minutos entre exercícios. No protocolo supersérie, 30 segundos após o término de cada série, o voluntário realizava o outro exercício. Depois de finalizado o segundo exercício da supersérie, o voluntário aguardava o término do intervalo (dois minutos) para reiniciar o primeiro exercício da supersérie.Resultados: Verificou-se maior volume total de treinamento no protocolo tradicional em comparação ao supersérie (p = 0.003). Adicionalmente, no protocolo tradicional os voluntários realizaram maior número de repetições (p < 0.05) em cinco dos oito exercícios. Com relação à percepção subjetiva de esforço, os participantes relataram maiores valores de esforço no protocolo supersérie quando comparado ao protocolo tradicional (p = 0.017).Conclusão: Foi observada redução no volume total de treinamento com a utilização do protocolo supersérie, comparado ao protocolo tradicional, em uma sessão de treinamento na musculação. Adicionalmente, houve uma maior percepção subjetiva de esforço dos sujeitos no protocolo supersérie. Sendo assim, a aplicação do protocolo tradicional torna-se uma alternativa eficiente quando o objetivo é priorizar o volume de treinamento. (AU)

Objetivo: Comparar el protocolo tradicional y el de superserie, con pausa equiparada, en cuanto al volumen total de entrenamiento (número de repeticiones x peso), número total de repeticiones por ejercicio y percepción subjetiva de esfuerzo, en una sesión de entrenamiento.Método: Dieciséis hombres entrenados realizaron de forma aleatorizada los protocolos. En el protocolo tradicional se realizaron tres series con intervalos de dos minutos entre las series y tres minutos entre los ejercicios. En el protocolo de superserie, 30 segundos después de finalizada cada serie, el voluntario realizaba el otro ejercicio. Después de finalizado el segundo ejercicio de la superserie, el voluntario aguardaba el final del intervalo (dos minutos) para reiniciar el primer ejercicio de la superserie.Resultados: Se verificó mayor volumen total de entrenamiento en el protocolo tradicional en comparación con el protocolo superserie (p = 0.003). Adicionalmente, en el protocolo tradicional, los voluntarios realizaron mayor número de repeticiones (p < 0.05) en cinco de los ocho ejercicios de la sesión de entrenamiento. En cuanto a la percepción subjetiva de esfuerzo los participantes reportaron mayores valores de esfuerzo en el protocolo superserie comparado con el protocolo tradicional (p = 0.017).Conclusión: Se observó reducción en el volumen total de entrenamiento con la utilización del protocolo superserie, comparado al protocolo tradicional, en una sesión completa de entrenamiento de musculación. Adicionalmente, hubo una mayor percepción subjetiva de esfuerzo de los sujetos en el protocolo superserie. Por lo tanto, la aplicación del protocolo tradicional se convierte en una alternativa eficiente cuando el objetivo es priorizar el volumen de entrenamiento. (AU)

Objective: To compare the traditional protocol and supersets, with equal rest interval, on volume load (number of repetitions x load), total number of repetitions per exercise, and rating of perceived exertion in a training session.Method: Sixteen resistance trained men randomly performed the protocols. In traditional protocol, three sets were performed with rest intervals of two minutes between sets and three minutes between exercises. In the superset protocol, 30 seconds after the end of each set, the subject performed the other exercise. After completing the second exercise of the superset, the volunteer waited for the end of the rest intervals (two minutes) to restart the first exercise of the superset.Results: There was a higher total training volume in traditional protocol compared to superset protocol (p = 0.003). Additionally, in traditional protocol, the volunteers performed a greater number of repetitions (p < 0.05) in five of the eight exercises of the training session. Regarding the median rating of perceived exertion of the training session, it was verified that the participants reported higher effort values in the superset protocol when compared to the traditional protocol (p = 0.017).Conclusion: A reduction in the total volume of training was observed with the use of the superset protocol alternated by body segment, compared to the traditional protocol, in a complete resistance training session. Additionally, there was a higher rating of perceived exertion of the subjects in the superset protocol. Thus, the application of the traditional protocol becomes an efficient alternative when the goal is to prioritize the training volume. (AU)

Efficacy of aqua-based plyometric exercises in the rehabilitation of patients with juvenile dermatomyositis: A randomized crossover pilot study.

BACKGROUND: Patients with juvenile dermatomyositis (JDM) experience muscle weakness, tiredness, and loss of energy, which restrict their abilities in performance of their daily living activities. OBJECTIVE: To explore the effect of aquatic-based plyometric (Aqua-PLYO) exercises on muscle strength, fatigue, and functional ability in patients with JDM. METHODS: This was a randomized, single-blind, crossover pilot study that included 16 patients with JDM (age 13.44 ± 2.85 years). They were assigned randomly to receive either the Aqua-PLYO exercises (n = 8) or the standard outpatient care (SoC ; n = 8) first. After a 1-month washout, the treatment was reversed. Lower limb muscle strength, fatigue perception, functional ability, and disease activity were evaluated before and after each treatment period. RESULTS: Irrespective of the treatment order, the Aqua-PLYO treatment yielded greater improvement in muscle strength (hip flexors and abductors [P < 0.001] or knee flexors [P < 0.001] and extensors [P = 0.0008]), fatigue perception (P < 0.001), functional ability (P = 0.009), and disease activity (P = 0.0001) than the SoC treatment. By using the shortest confidence intervals (100[1-2α]%) of the difference, the average bioequivalence of the Aqua-PLYO and SoC has not been established at P = 0.05, because the upper and lower confidence bounds of all outcomes were not between the acceptance limits. No period or carryover effects were detected in all outcomes. CONCLUSION: The Aqua-PLYO exercise protocol as implemented in this study is safe, feasible, and well-tolerated in patients with JDM and seemingly useful to help increase muscle strength, reduce fatigue, and enhance functional ability in such a patient population.

Waveform analysis of shank loaded wearable resistance during sprint running acceleration.

Lower-limb wearable resistance (WR) provides a specific and targeted overload to the musculature involved in sprint running, however, it is unknown if greater impact forces occur with the additional limb mass. This study compared the contact times and ground reaction force waveforms between sprint running with no load and 2% body mass (BM) shank-positioned WR over 30 m. Fifteen male university-level sprint specialists completed two maximum effort sprints with each condition in a randomized order. Sprint running with shank WR resulted in trivial changes to contact times at 5 m, 10 m, and 20 m (effect size [ES] = <0.20, p > 0.05) and a small, significant increase to contact time at 30 m by 1.94% (ES = 0.25, p = 0.03). Significant differences in ground reaction force between unloaded and shank loaded sprint running were limited to the anterior-posterior direction and occurred between 20% and 30% of ground contact at 10 m, 20 m, and 30 m. Shank WR did not result in greater magnitudes of horizontal or vertical forces during the initial impact portion of ground contact. Practitioners can prescribe shank WR training with loads ≤2% BM without concern for increased risk of injurious impact forces.

Effects of Chair-Based, Low-Load Elastic Band Resistance Training on Functional Fitness and Metabolic Biomarkers in Older Women.

Strength training can improve myriad health parameters in elderly cohorts. Although potentially more appropriate for the elderly, low-load resistance training protocols have been less investigated. We aimed to examine the effects of 12 weeks of chair-based, low-load resistance training with elastic band (EBT) on functional fitness and metabolic biomarkers in older women. One hundred sixty-eight women were allocated randomly to an elastic band resistance training (EBT, n = 86, 75.7 ± 8.9 years, 71.3 ± 12.2 kg) or a control group (CON, n = 82, 74.5 ± 8.2years, 70.6 ± 12.0 kg). RT protocol consisted of periodized chair-based, low-load whole-body resistance exercises (2 sets, 12-15 repetitions, 40-60% of one repetition maximum-1RM) using an elastic band, twice weekly for 12 weeks. The resistance training program was generally designed to maintain internal load over time, provided with increasing intensity using various elastic bands (Thera-Band). Functional fitness (30-s Chair Stand,30-s Arm Curl, 2-min Step Test, Chair Sit-and-Reach, Back Scratch, 8-Foot Up-and-Go, Handgrip Strength) and metabolic markers (Fasting blood glucose, triglycerides, total cholesterol, high (HDL) and low (LDL) density lipoprotein) were measured before and after the training period. To detect pre/post intervention changes and between group- differences 2x2 repeated measures ANOVA was applied. Significant improvements over time for all fitness variables for EBT comparing to CON were obtained (F = 12.78, p < 0.05 for 30-s Chair Stand; F = 14.04, p < 0.05 for 30-s Arm Curl; F = 5.18, p < 0.05 for 2-min Step Test; F = 10.90, p < 0.05 for Chair Sit-and-Reach; F = 16.57, p < 0.05 for Back Scratch; F = 11.79, p < 0.05 for 8-foot Up-and-Go; and F = 29.25, p < 0.05 for Handgrip Strength). In addition, significant improvements over time for all but one (triglycerides) biomarkers for EBT comparing to CON were obtained (F = 7.30, p < 0.05 for blood sugar levels; F = 13.36, p < 0.05 for total cholesterol; F = 8.61, p < 0.05 for HDL; and F = 11.53, p < 0.05 for LDL). Furthermore, the participants' adherence to training sessions of over 90% was reported. In conclusion, 12 weeks of EBT is safe and beneficial for improving health-related fitness and metabolic biomarkers in older women and seems to be viable model to ensure a high training adherence rate.

Changes to horizontal force-velocity and impulse measures during sprint running acceleration with thigh and shank wearable resistance.

This study determined the effects of two wearable resistance (WR) placements (i.e. thigh and shank) on horizontal force-velocity and impulse measures during sprint running acceleration. Eleven male athletes performed 50 m sprints either unloaded or with WR of 2% body mass attached to the thigh or shank. In-ground force platforms were used to measure ground reaction forces and determine dependent variables of interest. The main findings were: 1) increases in sprint times and reductions in maximum velocity were trivial to small when using thigh WR (0.00-1.93%) and small to moderate with shank WR (1.56-3.33%); 2) athletes maintained or significantly increased horizontal force-velocity mechanical variables with WR (effect size = 0.32-1.23), except for theoretical maximal velocity with thigh WR, and peak power, theoretical maximal velocity and maximal ratio of force with shank WR; 3) greater increases to braking and vertical impulses were observed with shank WR (2.72-26.3% compared to unloaded) than with thigh WR (2.17-12.1% compared to unloaded) when considering the entire acceleration phase; and, 4) no clear trends were observed in many of the individual responses. These findings highlight the velocity-specific nature of this resistance training method and provide insight into what mechanical components are overloaded by lower-limb WR.

Fatigability of the external anal sphincter muscles using a novel strength training resistance exercise device.

Exercises involving pelvic floor muscles including repetitive voluntary contractions of external anal sphincter (EAS) musculature have been used to improve fecal incontinence. Muscle fatigue is a prerequisite for successful strength training. However, muscle fatigue induced by these exercises has not been systematically studied. We aimed to assess the fatigability of EAS muscles during various exercise methods. Twelve nulliparous (21 ± 2.7 yr) women were studied. We evaluated fatigue during 40 repetitive 3-s contractions and 30-s long squeeze contractions both with and without an intra-anal compressible resistant load. The sequence of exercises was randomized. This load was provided by the continence muscles Resistance Exerciser Device. Anal canal pressures were recorded by high-resolution manometry. Exercise against a resistive load showed significant decrease in anal contractile integral (CI) and maximum squeeze pressure during repetitive short squeeze contractions compared with exercise without a load. Linear regression analysis showed a significant negative correlation between anal CI and successive contraction against load, suggesting "fatigue." Similar findings were observed for maximum squeeze pressure (slope with load = -4.2, P = 0.0003, vs. without load = -0.9, P = 0.3). Long squeeze contraction against a load was also more susceptible to fatigue than without a load (P < 0.0001). In conclusion, repetitive contractions against a compressible load induce fatigue and thus have the potential to strengthen the anal sphincter contractile function than contractions without a load. Fatigue rate in long squeeze contraction exercises with a load is significantly faster than that without a load, also indicating greater effectiveness in inducing muscle fatigue.NEW & NOTEWORTHY Fecal incontinence is a distressing disorder with a mainstay of treatment being pelvic floor muscle exercises. However, none of these exercises has proven occurrence of fatigability, which is an important prerequisite for successful muscle strengthening in rehabilitative exercises. In this study, we proved that we can fatigue the external anal sphincter muscles more efficiently by providing a resistive load during anal repetitive short squeeze contractions and long squeeze contraction exercise.

Effects of Horizontal Impeding Force Gait Training on Older Adult Push-Off Intensity.

INTRODUCTION: Aging and many gait pathologies are often characterized by deficits in push-off intensity (i.e., propulsive ground reaction forces and peak ankle moment and power output) during walking. Unfortunately, conventional interventions such as progressive resistance training, designed to enhance calf muscle mechanical output, generally fail to translate strength gains to functional improvements in habitual push-off intensity. METHODS: Horizontal impeding forces applied to the body's center of mass systematically augment the mechanical output required from muscle-tendon units spanning the ankle during the push-off phase of walking, which could convey long-term benefits via training. Therefore, the purpose of this study was to investigate the preliminary efficacy of a 6-wk horizontal impeding force training paradigm on improving habitual push-off intensity in 11 healthy but not physically active older adults (age = 76 ± 4 yr, 6 females and 5 males). RESULTS: We found that older adults significantly (P < 0.05) increased measures of isometric strength by 18%, maximum walking speed by 10%, and 6-min walk test distance by 9% as a result of horizontal impeding force training. As a more clinically significant contribution of this work, we found that those subjects also increased habitual peak ankle moment and peak ankle power during push off after training by a significant 10% and 15%, respectively (P ≤ 0.036). CONCLUSIONS: We conclude that the use of horizontal impeding forces in older adults improves their maximum muscular and walking capacities while encouraging access to newfound strength gains, thereby improving habitual push-off intensity during walking.

Effects of deceleration-focused exercise strategies on shoulder range of motion and throwing velocity in baseball and softball athletes.

This study examined the effects of deceleration-focused exercises on shoulder range of motion and throwing velocity in both softball and baseball players. Volunteers included 28 Division III William Paterson University baseball and softball athletes (18 females and 10 males), who were evenly distributed across two groups both undertaking 14 sessions of either resistance band or handheld medicine ball exercises (band vs. ball group). A pre-test and post-test measured participants' best active internal/external shoulder rotation and best throwing velocity at a target 40 ft away. A two-tailed, independent t-test showed no significant differences in velocity, internal rotation or external rotation (p < 0.01) between the band and ball groups. However, the average change in velocity in the ball group was double that of the band group (1.50 ± 2.06 m/s versus 0.73 ± 2.24 m/s). For change in both internal and external rotation the band group (2.86 ± 5.27° and 3.29 ± 3.87°, respectively) was greater than the ball mean (1.93° ± 3.32° and 1.29 ± 6.52°, respectively). These findings suggest that overhead athletes aiming to increase throwing velocity can benefit from performing deceleration training with weighted balls whereas resistance bands appear to improve shoulder rotation.

Reliability of cable downswing load-velocity performance in golf swings.

The cable-pulley downswing is a movement similar to the golf downswing, and therefore may offer a valuable golf specific rotational diagnostic and training tool. However, to be of value, measurements need to be stable across testing occasions. Therefore, the aim of this study was to quantify the test-retest reliability of the cable downswing across a spectrum of load-velocities. Ten male participants (21.7 ± 3.0 years, 84.6 ± 9.8 kg, 1.80 ± 0.05 m) volunteered to participate over 3 testing sessions' separated by a minimum of 3 days. Participants performed maximal velocity cable downswings across eight loads (1.25-18.75 kg), which were incrementally increased by 2.5 kg. Vertical cable stack velocity was collected at 50 Hz via a GymAware linear position transducer. Downswing velocity across all eight loads was observed to be extremely reliable (change in mean = -5.1% to 2.9%, coefficient of variation = 1.5-6.4% and intra-class correlation = 0.70-0.98), with reliability increasing with increasing trials. In conclusion, the cable downswing is a reliable method of tracking rotational ability similar to the golf downswing. Practitioners should establish an upper load relative to the apparatus and participant. Future research should determine the utility and sensitivity of this measure.

Validation of an opto-electronic instrument for the measurement of weighted countermovement jump execution velocity.

The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) compared to a linear velocity transducer (T-Force System) considered as the gold standard. Mean velocity (MV) and peak velocity (PV) generated in the Smith machine bar placed on the shoulders in counter-movement jump exercise (CMJ) were analysed. The study was conducted with a sample of 21 men with experience in resistance training. Five measurements were analysed for CMJ exercise in concentric phase using a progressive loading increase. Three jumps were made per load with a 3-4 min recovery between loads. The analysis of the variance confirmed that there were no significant differences (p > 0.05) in the execution velocity between Velowin and T-Force with each of the loads. The reliability analysis showed, with each of the loads, high values of the intraclass correlation coefficient (ICC = 0.95-0.99) and a 'substantial' Lin´s concordance coefficient in MV (CCC ≥0.96) and between 'substantial' (CCC = 0.98) and 'almost perfect' (CCC = 0.99) in PV. These results confirm the reliability and validity of the Velowin device is reliable for measuring the execution velocity in loaded CMJ exercise.

Recruitment of Shoulder Complex and Torso Stabilizer Muscles With Rowing Exercises Using a Suspension Strap Training System.

BACKGROUND: Suspension training systems, which use body weight resistance under unstable conditions, may be effective for muscle strengthening in persons with scapular dyskinesis or subacromial impingement syndrome. HYPOTHESIS: Greater arm, scapular, and trunk muscle recruitment will occur during horizontal abduction row exercises. STUDY DESIGN: Descriptive laboratory study. LEVEL OF EVIDENCE: Level 5. METHODS: Surface electromyography data were collected from 28 participants (14 men, 14 women). A total of 13 right-sided muscles were studied at a sampling frequency of 1000 Hz. Maximal voluntary isometric contractions (MVICs) were established. Participants completed 3 repetitions per exercise in random order. We compared muscle recruitment during 3 rowing exercises: low row, high row, and horizontal abduction row. Data were compared with repeated-measures analyses of variance and post hoc Bonferroni corrections. RESULTS: For high row and horizontal abduction row conditions, the upper, middle, and lower trapezius and posterior deltoid demonstrated >60% MVIC magnitudes of recruitment, and the upper erector spinae demonstrated 40% to 60% MVIC magnitudes of recruitment, respectively. In contrast, in the low row exercise, 40% to 60% MVIC magnitudes of recruitment were observed only in the middle trapezius, latissimus dorsi, and posterior deltoid. CONCLUSION: With the suspension system, high row and horizontal abduction row exercises promote muscle strengthening (>50% MVIC) in the upper, middle, and lower fibers of the trapezius, posterior deltoid, and upper erector spinae. CLINICAL RELEVANCE: Rowing exercises performed with suspension straps may be recommended for muscle strengthening in patients with scapular dyskinesis and subacromial impingement syndrome as well as for healthy persons in need of enhanced scapular muscle performance.

Load effects of thigh wearable resistance on angular and linear kinematics and kinetics during non-motorised treadmill sprint-running.

The aim of this study was to investigate the load effects of thigh attached wearable resistance (WR) on linear and angular kinematics and linear kinetics during sprint-running. Fourteen recreational active subjects performed a series of maximal sprints with and without WR of 1%, 2%, and 3% body mass (BM) in a randomised order. Sprints were performed on a non-motorised treadmill that collected velocity, and linear step kinematics and kinetics. Angular kinematics of the thigh were collected from an inertial measurement unit attached to the left thigh. Trivial decreases were found in peak velocity with all WR loads (-0.9 to -.2.4%, effect size [ES] 0.09-0.17, p > .05). The WR conditions resulted in significantly decreased average step frequency (-2.0% to -3.0%, ES = 0.35-0.44, p < .05) with loads of ≥2% BM, whereas average step length was statistically unchanged (1.9-2.8%, ES = 0.20-0.33). Average angular displacement was significantly decreased (-7.0% to -10.3%, ES = 0.88-1.10, p = 0.00-0.03) with loads of ≥2% BM. Average angular flexion velocity (-10.2%, ES = 1.07, p = .02) and extension velocity (-12.0%, ES = 0.85, p = .01) were significantly decreased with 3% BM. Trivial to small ES changes (p > .05) were found in the linear kinetic measures of interest. Thigh WR provides a sprint-specific rotational form of resistance resulting in greater changes to angular kinematics than linear properties of sprint-running. For practitioners who wish to target thigh angular kinematics and step frequency without decreasing step length, thigh WR of ≥2% BM offers a sprint-specific resistance training tool.

Wearable resistance sprint running is superior to training with no load for retaining performance in pre-season training for rugby athletes.

This study determined the effects of a six-week lower-limb wearable resistance training (WRT) intervention on sprint running time, velocity, and horizontal force-velocity mechanical variables. Twenty-two collegiate/semi-professional rugby athletes completed pre- and post-intervention testing of three maximal effort 30 m sprints. A radar device was used to measure sprint running velocity from which horizontal force-velocity mechanical profiling variables were calculated. All athletes completed two dedicated sprint training sessions a week for six-weeks during pre-season. The intervention (wearable resistance, WR) group completed the sessions with 1% body mass load attached to the left and right shanks (i.e. 0.50% body mass load on each limb), whilst the control group completed the same sessions unloaded. For the control group, all variables were found to detrain significantly (p ≤ 0.05) over the training period with large detraining effects (ES > 0.80) for theoretical maximal horizontal force, slope of the force-velocity profile, maximal ratio of force, index of force application, 5 and 10 m times. For the WR group, there were no significant changes to any recorded variables (all p > 0.05) and all effects of training were trivial or small (ES < 0.50). After adjustment for baseline differences, significant between group differences were found for all variables (large effects, ES > 0.80) except theoretical maximal velocity, 30 m time, and maximal velocity. The addition of light wearable resistance to sprint training during a six-week pre-season block enables the maintenance of sprint performance and mechanical output qualities that otherwise would detrain due to inadequate training frequencies.

Acute kinematics and kinetics changes to wearable resistance during change of direction among soccer players.

This study determined the acute changes in kinematics and kinetics when an additional load equivalent to 5% body mass was attached to the torso during change of direction (COD). In this within-subject repeated measures study, 14 male soccer players (age: 18.29 ± 0.32 years) volunteered to participate. Subjects performed COD under two conditions in randomized order: (1) no WR, and (2) with WR. No significant differences between the loaded and unloaded conditions in actual COD angle, approach speed, braking time, propulsive time, contact time, COD completion time (all p > 0.05, ES = 0.05-0.11), and all measured kinematic parameters (all p > 0.05, ES = 0-0.18). Nonetheless, ankle plantar/dorsi flexion ROM had possibly small increase in the loaded condition (ES = 0.24). Kinetics analysis has shown that the loaded condition was likely to have small increase in relative peak vertical propulsive ground reaction force (GRF, p = 0.11, ES = 0.41), and possible small increases in relative peak braking GRF (vertical: p = 0.21, ES = 0.42; total: p = 0.22, ES = 0.38), relative peak total propulsive GRF (p = 0.24, ES = 0.26), and relative braking impulse (horizontal, vertical, and total; p = 0.27-0.41, ES = 0.26-0.28). WR did not significantly change the acute movement techniques, meanwhile induced small increases in important kinetic stimuli for potential adaptation in COD.

Concentric and eccentric inertia-velocity and inertia-power relationships in the flywheel squat.

The aim of this study was to evaluate the effects of varying flywheel inertia on velocity and power during flywheel squats. Fifteen healthy physically active males performed 6 maximal effort flywheel half-squats at each of 0.029, 0.061, 0.089 and 0.121 kg·m2, with velocity recorded via 3D motion capture and power recorded via inbuilt transducer. Peak concentric velocity (χ2 = 37.9; p < 0.001), peak eccentric velocity (χ2 = 24.9; p < 0.001), mean concentric velocity (F(3) = 52.7; p < 0.001) and mean eccentric velocity (χ2 = 16.8; p < 0.001) all tended to decrease with increases in flywheel inertia, whereas the ratio of peak eccentric to peak concentric power (F(3) = 4.26; p = 0.010) tended to increase. Flywheel inertia had no significant effect on peak concentric or eccentric power, or the ratio of eccentric to concentric peak or mean velocities. The best fit subject-specific inertia-velocity relationships were reported for peak concentric velocity (median linear R2 = 0.95, median logarithmic R2 = 0.97). The results suggest that velocity, rather than power, should be used to prescribe and monitor flywheel squat exercise intensities, and that individualized linear relationships between inertia and peak concentric velocity can be used for this purpose.

Approaches to determining occlusion pressure for blood flow restricted exercise training: Systematic review.

Low-intensity exercise with blood flow restriction (BFR) is an increasingly common method of improving muscular strength and hypertrophy, and improving aerobic fitness, in clinical and athletic populations. The aim of this systematic review was to describe common approaches to determining occlusion pressures for BFR exercise. A comprehensive literature search yielded 1389 results, of which 129 were included. Studies were predominantly randomised control trials (86.7%) with modest sample sizes (average number of 11.4 ± 6.2 participants per BFR group/s) of young adults (average age of 34.6 ± 17.9). Five different approaches for determining occlusion pressure were identified: arbitrary pressures (56.6%), percentage of limb occlusion pressure (25.6%), brachial systolic blood pressure (10.9%), perceived tightness (3.9%) and other (3%). From 2016 to 2018, the number of published papers using a percentage of limb occlusion pressure increased yearly, paralleling a decrease use of arbitrary pressures. Of the studies included in this review, the most common approach to determining occlusion pressure was using a non-individualised, arbitrary pressure. Given the safety concerns associated with arbitrary pressures, continual dissemination regarding the optimal applications of BFR for safety and efficacy is required.

Effects of an elastic resistance band exercise program on kinetics and muscle activities during walking in young adults with genu valgus: A double-blinded randomized controlled trial.

BACKGROUND: This double-blinded randomized-controlled-trial aimed to identify the effects of an elastic band resistance training on walking kinetics and muscle activities in young adults with genu valgus. METHODS: Forty-two male young adults aged 22.5(2.7) years with genu valgus were randomly allocated to two experimental groups. The intervention group (n = 21) conducted a 14-weeks elastic band resistance training. The control group was passive during the intervention period and received the same treatment after the post-tests. Pre and post training, ground reaction forces and lower limb muscle activities were recorded during walking. FINDINGS: Results revealed significant group-by-time interactions for peak medial ground reaction force and time-to-peak for posterior ground reaction force in favor of the intervention group (p < 0.012; d = 0.83-3.76). Resistance training with elastic bands resulted in significantly larger peak medial ground reaction force (p < 0.001; d = 1.45) and longer time-to-peak for posterior ground reaction force (p < 0.001; d = 1.85). Finding showed significant group-by-time interactions for peak positive free moment amplitudes in favor of the intervention group (p < 0.001; d = 1.18-2.02). Resistance training resulted in a lower peak positive free moment amplitude (p = 0.001; d = 1.46). With regards to muscle activities, the analysis revealed significant group-by-time interactions for rectus femoris and gluteus medius activities during the push-off phase in favor of the intervention group (p < 0.038; d = 0.68-0.89). Resistance training induced higher rectus femoris (p = 0.038; d = 0.84) and gluteus medius (p = 0.007; d = 0.54) activities. INTERPRETATION: This study proved the effectiveness of resistance training using elastic bands on kinetics and muscle activities during walking in male adults with genu valgus disorder. Given that this training regime is low cost, effective, and easy-to-administer, we suggest that it should be implemented as a rehabilitative or preventive means for young adults with genu valgus.

Ocular trauma secondary to exercise resistance bands during the COVID-19 pandemic.

OBJECTIVE: To characterize injuries caused by exercise resistance bands. METHOD: Single-site retrospective case series of patients presenting to the Bascom Palmer Eye Institute emergency room with ocular injuries secondary to exercise resistance bands from March through September 2020. RESULTS: Eleven patients (9 males, 2 females, 14 eyes) were reviewed. Eight patients had a unilateral injury (3 right eyes, 5 left eyes) while 3 had bilateral injuries. Iritis was the most common presentation, seen in all 11 patients, followed by hyphema (9 patients, 82%), and vitreous hemorrhage (4 patients, 36%). Among affected eyes, the mean presenting visual acuity was approximately 20/100, improving to 20/40 on the last follow up (p = 0.06). However, 4 eyes (33%) had vision ≤20/60 at last follow up. CONCLUSIONS: Exercise resistance bands can cause a wide spectrum of ocular injuries, some leading to long-term vision loss. As such, we recommend that patients strongly consider using eye protection goggles or glasses while using resistance bands for exercise.