Relationship between natural muscle oscillation frequency and lower limb muscle performance during instrumented sit-to-stand and stand-to-sit movements on a novel device in sedentary subjects.

BACKGROUND: Despite the significance of muscle oscillation frequency, previous research has not established a correlation with muscle performance due to the challenges of applying resistance without altering natural motion during functional tests. RESEARCH QUESTION: What is the correlation between muscle oscillation frequency and lower limb muscle strength, power, and work during an instrumented sit-to-stand and stand-to- sit (iSTS-TS) task among sedentary subjects? METHODS: In a cross-sectional study, the oscillation frequency of the gastrocnemius medialis (GM), biceps femoralis (BF), and vastus medialis (VM) muscles in both the dominant (D) and non-dominant (ND) legs was assessed with a handheld myotonometer in 34 sedentary individuals before performing the iSTS-TS task. RESULTS: In the isokinetic mode, no significant correlations were found. In the isotonic mode, the BF muscle oscillation frequency in the D and ND legs exhibited significant positive correlations with peak force, peak power, and work during sitting down, as well as peak power and work during standing up. Positive correlations were observed in both legs between the GM oscillation frequency and sitting down peak force and work. Additionally, significant positive correlation was found with standing up work in the D leg. Muscle oscillation frequency of the VM exhibited a positive correlation with sitting down peak force in the ND leg. SIGNIFICANCE: Due to a greater number of correlations found, it is advisable to use the isotonic mode when assessing muscle oscillation frequency in relation to muscle performance during functional iSTS-TS tasks in sedentary subjects.

Effects of different lower limb strengthening protocols on muscle activity, strength and power in sedentary and physically inactive subjects: a systematic review / Efectos de diferentes protocolos de fortalecimiento de miembro inferior sobre la fuerza, potencia y actividad muscular en sujetos sedentarios y físicamente inactivos: una revisión sistemática

The purpose of this systematic review was: a) to determine the quality of evidence from studies assessing the effects of different lower limb strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects; and b) to determine the effectiveness of lower extremity strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed using keywords associated with strength training, lower limb, sedentary, and physical inactivity. Four databases were used: Medline via PubMed, Web of Science, Scopus and SPORTDiscus. Methodological quality was assessed using the PEDro scale. A total of 164 articles were retrieved, six included in this review. Four studies were classified as fair methodological quality, and two were considered of good methodological quality. Due to the heterogeneity in methodological aspects and the limited number of articles including the variables under study, it was not possible to establish a measure of effectiveness of lower limb strengthening protocols on muscle activity, strength, or power. In conclusion, strength training in the lower limb seems to improve the levels of strength, power, and muscular activity in sedentary subjects. However, due to the limited number of articles, methodological variability, and training methods used, it is necessary to conduct new studies that control these variables.(AU)

El propósito de esta revisión sistemática fue: a) determinar la calidad de la evidencia de los estudios que evaluaron los efectos de diferentesprotocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza y la potencia muscular en sujetos sedentarios y/o físicamenteinactivos; y b) determinar la efectividad de los protocolos de fortalecimiento sobre la actividad, fuerza y potencia muscular de miembros infe-riores en sujetos sedentarios y/o físicamente inactivos. Se siguieron los criterios PRISMA (Preferred Reporting Items for Systematic Review andMeta-Analyse) utilizando palabras clave asociadas con el entrenamiento de fuerza, extremidades inferiores, sedentarismo e inactividad física. Serevisaron cuatro bases de datos: Medline vía PubMed, Web of Science, Scopus y SPORTDiscus. La calidad metodológica se evaluó mediante laescala PEDro. Se recuperaron 164 artículos en total, seis incluidos en esta revisión. Cuatro estudios se clasificaron como de calidad metodológicaregular y dos se consideraron de buena calidad metodológica.Debido a la heterogeneidad en los aspectos metodológicos y al escaso número de artículos que incluyeron las variables en estudio, no fue posibleestablecer una medida de efectividad de los protocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza o la potenciamuscular. En conclusión, el entrenamiento de fuerza en el miembro inferior parece mejorar los niveles de fuerza, potencia y actividad muscular ensujetos sedentarios. No obstante, debido al número limitado de artículos, la variabilidad metodológica y los métodos de entrenamiento utilizados,es necesario realizar nuevos estudios que controlen estas variables.(AU)

Effects of different lower limb strengthening protocols on muscle activity, strength and power in sedentary and physically inactive subjects: a systematic review.

Introduction: The purpose of this systematic review was: a) to determine the quality of evidence from studies assessing the effects of different lower limb strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects; and b) to determine the effectiveness of lower extremity strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed using keywords associated with strength training, lower limb, sedentary, and physical inactivity. Four databases were used: Medline via PubMed, Web of Science, Scopus and SPORTDiscus. Methodological quality was assessed using the PEDro scale. A total of 164 articles were retrieved, six included in this review. Four studies were classified as fair methodological quality, and two were considered of good methodological quality. Due to the heterogeneity in methodological aspects and the limited number of articles including the variables under study, it was not possible to establish a measure of effectiveness of lower limb strengthening protocols on muscle activity, strength, or power. In conclusion, strength training in the lower limb seems to improve the levels of strength, power, and muscular activity in sedentary subjects. However, due to the limited number of articles, methodological variability, and training methods used, it is necessary to conduct new studies that control these variables.

Introducción: El propósito de esta revisión sistemática fue: a) determinar la calidad de la evidencia de los estudios que evaluaron los efectos de diferentes protocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza y la potencia muscular en sujetos sedentarios y/o físicamente inactivos; y b) determinar la efectividad de los protocolos de fortalecimiento sobre la actividad, fuerza y potencia muscular de miembros inferiores en sujetos sedentarios y/o físicamente inactivos. Se siguieron los criterios PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyse) utilizando palabras clave asociadas con el entrenamiento de fuerza, extremidades inferiores, sedentarismo e inactividad física. Se revisaron cuatro bases de datos: Medline vía PubMed, Web of Science, Scopus y SPORTDiscus. La calidad metodológica se evaluó mediante la escala PEDro. Se recuperaron 164 artículos en total, seis incluidos en esta revisión. Cuatro estudios se clasificaron como de calidad metodológica regular y dos se consideraron de buena calidad metodológica. Debido a la heterogeneidad en los aspectos metodológicos y al escaso número de artículos que incluyeron las variables en estudio, no fue posible establecer una medida de efectividad de los protocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza o la potencia muscular. En conclusión, el entrenamiento de fuerza en el miembro inferior parece mejorar los niveles de fuerza, potencia y actividad muscular en sujetos sedentarios. No obstante, debido al número limitado de artículos, la variabilidad metodológica y los métodos de entrenamiento utilizados, es necesario realizar nuevos estudios que controlen estas variables.

Test-Retest Reliability of 3 Specific Strength Tests in Professional Handball Players.

CONTEXT: Current devices to assess strength performance in handball may not be sufficiently sports-specific and reliable methods. Functional electromechanical dynamometry is a new technology that allows the development of accurate strength tests in athletes. PURPOSE: To determine the absolute and relative reliability and to compare the reliability of the right and left side, and mean and peak force of 3 specific strength tests in handball players with a functional electromechanical dynamometer: unilateral pullover, standing lift, and step forward. METHODS: Fourteen male handball players of the first Spanish division (28.79 [4.81] y; 10.38 [4.63] y of professional experience) performed a repeated-measurement design. Three testing sessions were performed (one per week). The first measurement consisted of 4 isometric tests (right and left unilateral pullover, and right and left standing lift) to obtain isometric peak force, and in the second and third sessions, 6 incremental tests until failure (right and left unilateral pullover, and right and left standing lift, right and left step forward) were performed. RESULTS: The tests provided high reliability or acceptable reliability for mean and peak strength of unilateral pullover, standing lift and step forward (intraclass correlation coefficient = .83-.97; coefficient of variation = 3.90-11.57). Effect side was negligible in any of the parameters, except for a small effect side in the left peak force for unilateral pullover and a small effect side on the left side for a step forward. Significant differences in reliability (coefficient of variation ratio > 1.15) were found between the right and left sides and peak and mean force in all exercises except peak force in unilateral pullover and step forward. CONCLUSION: These results confirm that the tests could be applied to assess physical performance in handball at the same time as regular gym training. Moreover, this is an excellent opportunity to individualize the player's weekly load.

Core training and performance: a systematic review with meta-analysis.

The purposes were to synthesize as much scientific evidence as possible to determine the effect of core training on balance, throwing/hitting velocity or distance, and jumping in healthy subjects, identify the possible differences between isolated and combined core training on performance and study training and sample variables related to performance. PRISMA guidelines were followed, and a systematic search was performed in the Scopus, Web of Science, Sports Discuss, and PubMed databases with no date restrictions until November 2022. The studies were considered for this meta-analysis following PICO; a) randomized control trials and randomized allocation studies with healthy subjects and > 12 years old b)isolated or combined core training programs with a minimum of 4 weeks in length; c) athletic performance outcomes for balance, throw/hit, and jump variables should be measured; d) sufficient data to calculate effect sizes. The Cochrane Collaboration Risk of Bias Tool and the Grading of Recommendations Assessment, Development, and Evaluation approach were used for assessing methodological quality. A total of 3223 studies were identified, 22 studies were included in the systematic review and 21 for the meta-analysis. We observed that core training improved balance outcomes (ES = 1.17; p < 0.0001), throwing/hitting velocity (ES = 0.30; p = 0.14), throwing/hitting distance (ES = 3.42; p = 0.03), vertical jumping (ES = 0.69; p = 0.0003), and horizontal jump (ES = 0.84; p = 0.01). Our findings indicate that core training improved different variables of performance such as balance, throw/hit, and vertical and horizontal jump.

Analysis of grip specificity on force production in grapplers and its effect on bilateral deficit grip specificity and bilateral deficit in force production among grapplers.

The use of strength training is important for athletes in combat sports such as judo and jiu-jitsu. Specificity is key when prescribing strength training programs for athletes, considering maximal strength, muscular power and strength-endurance. Grappling combat sports require grip control, which is necessary to execute throwing techniques and groundwork. The aim of this study was to verify the bilateral strength deficit in general and in grappling combat sport-specific action in the control group and grapplers. A sample of 73 subjects, divided into 2 groups, was used: the Student Group (15 females and 16 males) and the Grappler Group (29 males and 13 females). The male and female participants attended four laboratory sessions over a 48-hour interval, the first two to familiarize themselves with the Electromechanical Functional Dynamometer (EMFD), and the last two to collect maximal isometric strength data, using a standard grip and a judo/jiujitsu specific grip. Significant differences in mean and peak forces (p < 0.001) were found, with high performance combat sport athletes having greater maximal isometric strength compared to students both bilaterally and unilaterally (p < 0.001). All comparisons also indicated higher values for males compared to females (p < 0.001). The results suggest that specific training in combat sports as well as sex differences play a significant role in maximal isometric strength performance. The type of grip used affects the application of force in the upper limb isometric strength tests, finding a main effect of grip type (p < 0.001), with the standard grip obtaining higher levels. However, the dominance between hands remains constant. More research is needed on specific judogi/jiu-jitsu-gi grips and their impact on maximal isometric strength with the EMFD.

Strength Assessment of Trunk Rotator Muscles: A Multicenter Reliability Study.

BACKGROUND: Trunk rotator strength plays an important role in sports performance and health. A reliable method to assess these muscles with functional electromechanical dynamometer has not been described. Therefore, the objectives of this paper were (I) to explore the reliability of different strength variables collected in isokinetic and isometric conditions during two trunk rotator exercises, and (II) to determine the relationship of isometric and dynamic strength variables collected in the same exercise. METHODS: A repeated measures design was performed to evaluate the reliability of the horizontal cable woodchop (HCW) and low cable woodchop (LCW) exercises. Reliability was assessed using t-tests of paired samples for the effect size, the standard error of measurement, the coefficient of variation (CV) and the intraclass correlation coefficient (ICC). The Pearson's (r) correlation coefficient was used to explore the association between isometric and isokinetic tests. RESULTS: HCW exercise is more reliable than LCW exercise in assessing trunk rotator muscles. The strength manifestation that should be used is the average strength, and the most reliable evaluation was the HCW at 0.40 m·s-1 concentric (ICC = 0.89; CV = 10.21%) and eccentric (ICC = 0.85; CV = 9.33%) contraction and the dynamic condition that most correlated with the isometric was LWC at 0.50 m·s-1 (r = 0.83; p < 0.01). CONCLUSION: HCW is a reliable exercise to measure trunk rotator muscles.

Asociación entre la Arquitectura Muscular y el Índice de Calidad Muscular en Adultos Sedentarios / Association Between Muscle Architecture and Muscle Quality Index in Sedentary Adults

La evaluación de la calidad y la arquitectura muscular son importantes para comprender y cuantificar los cambios musculares asociados con el envejecimiento y el estilo de vida sedentario, además nos facilita información de la capacidad del músculo para generar fuerza, potencia o funcionalidad. los objetivos del estudio fueron (I) determinar la asociación entre los parámetros de la arquitectura muscular y el índice de calidad muscular (MQI) y (II) determinar la asociación entre los parámetros de la arquitectura muscular y la potencia media relativa del sit to stand test (STS). Únicamente el grosor muscular (MT) mostró una asociación moderada con el MQI (r = 0,545). En contraste, tanto la longitud del fascículo (FL) como el ángulo de penación (PA) exhibieron asociaciones "muy bajas", las cuales no resultaron significativas con el MQI. Al examinar la relación de los parámetros de la arquitectura muscular con la potencia media relativa de STS, MT presentó una asociación "moderada" (r = 0,444). Sin embargo, tanto FL como PA mostraron asociaciones "muy bajas" y "bajas", respectivamente, con la potencia media relativa al STS. En conclusión, estos hallazgos refuerzan la idea de que MT puede ser un indicador relevante de la calidad muscular y la capacidad de generar potencia en la prueba de STS. Específicamente, se observó que un aumento en MT estaba asociado con una mejora en MQI y la potencia media relativa de STS.

SUMMARY: Assessment of muscle quality and architecture is important for understanding and quantifying muscle changes associated with aging and a sedentary lifestyle and provides information on the muscle's ability to generate strength, power, or function. The aims of the study were (I) to determine the association between muscle architecture parameters and muscle quality index (MQI) and (II) to determine the association between muscle architecture parameters and mean relative power in the sit-to-stand test (STS). Only muscle thickness (MT) showed a moderate association with MQI (r = 0.545). In contrast, both fascicle length (FL) and penile angle (PA) exhibited "very low" associations, which were not significant with the MQI. When examining the relationship between muscle architecture parameters and mean relative STS power, MT presented a "moderate" association (r = 0.444). However, both LF and PA showed "very low" and "low" associations, respectively, with a mean power relative to STS. In conclusion, these findings reinforce the idea that MT may be a relevant indicator of muscle quality and ability to generate power in the STS test. Specifically, an increase in MT was associated with an improvement in MQI and mean power relative to STS.

Effect of sit-to-stand-based training on muscle quality in sedentary adults: a randomized controlled trial.

The aim of this study was to compare the effects of sit-to-stand (STS) training programs with 5 vs. 10 repetitions on muscle architecture and muscle function in sedentary adults. Sixty participants were randomly assigned into three groups: five-repetition STS (5STS), 10-repetition STS (10STS), or a control group (CG). Participants performed three sets of five or 10 repetitions of the STS exercise three times per week for 8 weeks. Before and after 8 weeks, all groups performed ultrasound measures to evaluate muscle thickness (MT), pennation angle (PA), and fascicle length (FL), and the five-repetition STS test to estimate the relative STS power and muscle quality index (MQI). After 8 weeks, both experimental groups improved MQI (40-45%), relative STS power (29-38%), and MT (8-9%) (all p < 0.001; no differences between the 5STS vs. 10STS groups). These improvements in both groups resulted in differences regarding the CG, which did not present any change. In addition, only the 5STS group improved PA (15%; p = 0.008) without differences to the 10STS and CG.This suggests that STS training is time-effective and low-cost for improving muscle function and generating adaptations in muscle architecture.

The Role of the Specific Strength Test in Handball Performance: Exploring Differences across Competitive Levels and Age Groups.

The aim of this study was to determine if specific physical tests are sufficiently discriminant to differentiate players of similar anthropometric characteristics, but of different playing levels. Physical tests were conducted analyzing specific strength, throwing velocity, and running speed tests. Thirty-six male junior handball players (n = 36; age 19.7 ± 1.8 years; 185.6 ± 6.9 cm; 83.1 ± 10.3 kg; 10.6 ± 3.2 years of experience) from two different levels of competition participated in the study: NT = 18 were world top-level elite players, belonging to the Spanish junior men's national team (National Team = NT) and A = 18 players of the same age and anthropometric conditions, who were selected from Spanish third league men's teams (Amateur = A). The results showed significant differences (p < 0.05) between the two groups in all physical tests, except for two-step-test velocity and shoulder internal rotation. We conclude that a battery combining the Specific Performance Test and the Force Development Standing Test is useful in identifying talent and differentiating between elite and sub-elite players. The current findings suggest that running speed tests and throwing tests are essential in selecting players, regardless of age, sex, or type of competition. The results shed light on the factors that differentiate players of different levels and can help coaches in selecting players.

Influence of probe position in the measurement of muscle thickness and its association with lean mass: an ultrasound study / Influencia de la posición de la sonda en la medición del grosor muscular y su asociación con la masa magra: un estudio ecográfico

SUMMARY: Skeletal muscles play a fundamental role in people's lives and their evaluation provides significant information on health. Different tools have been used to evaluate muscle mass, and the evaluation of muscle thickness (MT) using ultrasound has been included as an alternative, which can be performed with the probe in different positions; however, these could present differences. The objectives of this study were to determine whether there are differences in the measurement of MT in the vastus lateralis (VL) muscle using the probe in the longitudinal or transverse position, and to determine its association with the lean mass of the lower limbs. The results indicated no significant differences between MT measurements with the probe in the longitudinal and transverse positions (p =0.084). However, when associating these measurements with lower limb lean mass, it was found that transverse measurements had a strong association (r =0.547; p < 0.001), while longitudinal measurements had a moderate association (r =0.351; p =0.007). This suggests that measurements with the probe positioned transversely to measure the MT would be the best option. Therefore, it could be useful as an indicator of lower limb lean mass in the absence of tools, such as bioelectrical bioimpedance or magnetic nuclear resonance.

El músculo esquelético cumple un rol fundamental en la vida de las personas, y su evaluación entrega mucha información de la salud. Se han utilizado diferentes herramientas para evaluar la masa muscular, y el último tiempo se ha incluido la evaluación del grosor muscular (MT) a través de la ecografía como una alternativa para estimarla, las cuales se pueden realizar con la sonda en distintas posiciones, sin embargo, estas podrían presentar diferencias. Los objetivos del estudio fueron determinar si existen diferencias en la medición de MT en el músculo vasto lateral (VL) utilizando la sonda en posición longitudinal o transversal y determinar su asociación con la masa magra de los miembros inferiores. Los resultados indican que no existen diferencias significativas entre las mediciones de MT con la sonda en posición longitudinal y transversal (valor p: 0.084). Sin embargo, al asociar estas mediciones con la masa magra de los miembros inferiores, se encontró que las mediciones transversales poseen una asociación fuerte (r: 0.547; valor p < 0.001), mientras que las mediciones longitudinales presentan una asociación moderada (r: 0.351; valor p: 0.007). Esto sugiere que las mediciones con la sonda posicionada transversal para medir MT serían la mejor opción. Por lo tanto, podría ser de utilidad como un indicador de masa magra de los miembros inferiores en caso de no contar con herramientas como la bioimpedancia bioeléctrica o resonancia nuclear magnética.

Dynamometric Strength Profile of Hip Muscles in Youth Soccer Players.

BACKGROUND: Soccer is the most widely practiced sport in the world, demanding high-speed activities such as jumps, sprints and changes of direction. Therefore, having optimal levels of muscle strength improves performance and reduces the injury rate. OBJECTIVES: The objectives of our study were (i) to determine the dynamometric profile of hip muscle strength in young soccer players by position, evaluated at different isokinetic speeds, (ii) to describe the conventional and functional unilateral muscle strength ratios, (iii) to analyze the bilateral balance. METHODS: Thirty-seven male soccer players (age 17.02 ± 0.92 years) participated in the study. Strength assessment was performed with a functional electromechanical dynamometer, and concentric and eccentric strength of abductors, adductors, extensors and hip flexors were measured bilaterally at 0.5 m/s and 1 m/s. RESULTS: For eccentric right hip abduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.013) and stronger than forwards (p = 0.140). For eccentric right hip adduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.005) and stronger than forwards (p = 0.253), as for eccentric right hip adduction at 1 m/s, defenders are significantly stronger than midfielders (p = 0.014) and stronger than forwards (p = 0.084). There is a significant effect for the conventional strength ratio of left abduction/adduction at 1 m/s. The conventional strength ratio of forwards is significantly higher than that of defenders (p = 0.045) and higher than that of midfielders (p = 0.152). CONCLUSIONS: Concentric and eccentric hip strength values differ according to playing position.

Impact of Starting Knee Flexion Angle on Muscle Activity and Performance during Plyometrics without Jumping.

Most of the existing research has focused on jump plyometrics, where landing reaction forces must be dissipated among lower limb articulations. In contrast, the investigation of resisted plyometrics without jumping, devoid of such landing forces, remains relatively limited. This study aimed to (i) investigate the impact of resisted plyometrics without jumping at two knee flexion angles (60 and 90 degrees) on vastus muscle activity relative to limb dominance and (ii) assess strength, power, and work during the concentric-eccentric phases of these exercises. Thirty-one healthy participants underwent quantification of lower limb muscle amplitude, strength, power, and work during resisted plyometrics without jumping from both 60° and 90° knee flexion positions. After anthropometric evaluations, participants used a dynamometer with a load equal to 80% of body weight while wireless surface electromyography electrodes recorded data. Statistical analyses utilized paired t-tests or nonparametric equivalents and set significance at p ≤ 0.05. Results showed significantly higher muscle activity in the vastus medialis (VM) (dominant: 47.4%, p = 0.0008, rs = 0.90; nondominant: 54.8%, p = 0.047, rs = 0.88) and vastus lateralis (VL) (dominant: 46.9%, p = 0.0004, rs = 0.86; nondominant: 48.1%, p = 0.021, rs = 0.67) muscles when exercises started at 90° knee flexion, regardless of limb dominance. Substantial intermuscle differences occurred at both 60° (50.4%, p = 0.003, rs = 0.56) and 90° (54.8%, p = 0.005, rs = 0.62) knee flexion, favoring VM in the nondominant leg. Concentric and eccentric strength, power, and work metrics significantly increased when initiating exercises from a 90° position. In conclusion, commencing resisted plyometrics without jumping at a 90° knee flexion position increases VM and VL muscle activity, regardless of limb dominance. Furthermore, it enhances strength, power, and work, emphasizing the importance of knee flexion position customization for optimizing muscle engagement and functional performance.

Exploration of the Shoulder Internal Rotation's Influence on Throwing Velocity in Handball Players: A Pilot Study.

The main objective of this study was to test the relationship between shoulder internal rotation strength and standing throwing velocity. A repeated measures cross-sectional study was conducted with 20 professional handball players (mean ± SD; age: 19.28 ± 2.55 years, weight: 81.52 ± 9.66 kg, height: 185 ± 6 cm, BMI: 23.74 ± 1.69). The participants were instructed to perform eight standing throws from the 7 m line of the handball court at maximum velocity to calculate the mean and maximum throwing velocity. An incremental test was performed to calculate the repetition maximum (1-RM) of internal rotation shoulder strength. A Pearson's correlation analysis with a 95% confidence interval (95% CI) was performed to determine whether correlations existed between dominant arm internal rotation strength characteristics and maximum and mean ball-throwing velocity. There is no correlation between the internal rotation strength of the throwing shoulder and the velocity of the ball in the standing handball throw.

Effects of post-tetanic potentiation induced by whole-body electrostimulation and post-activation potentiation on maximum isometric strength.

It is currently unknown the most effective potentiation protocol to increase maximum strength. Hence, we investigated the separated and combined effects of post-tetanic potentiation (PTP) induced by whole-body electrostimulation (WB-EMS) and post-activation potentiation (PAP) induced by voluntary maximum isometric contractions on maximum isometric strength. Ten trained males were randomly evaluated on four occasions. In session A, maximum isometric strength (split squat) was measured in minutes 1, 4, and 8. In session B, the measurements were taken in minutes 2, 6, and 10. In session C, a WB-EMS protocol was applied to elicit PTP and the measurements were performed in minutes 1, 4, and 8. In session D, the same WB-EMS protocol was applied and the measurements were taken in minutes 2, 6, and 10. No significant differences in maximum isometric strength were observed between: (i) the control and WB-EMS in minutes 1 vs. 1 and 2 vs. 2; (ii) the control and PAP in minutes 1 vs. 4, 1 vs. 8, 2 vs. 6, and 2 vs. 10; and (iii) the PAP and WB-EMS plus PAP in minutes 4 vs. 4, 8 vs. 8, 6 vs. 6, and 10 vs. 10. In contrast, the WB-EMS plus PAP revealed a significant increase of 54% (~450 N) compared to the WB-EMS in minutes 4 and 8 compared to the minute 1 (p < 0.001), but not between minutes 2 vs. 6 and 2 vs. 10. The present results showed that PTP induced by WB-EMS in isolation or combined with PAP induced by voluntary maximum isometric contractions did not produce a significant increase in maximum isometric strength compared to the control and PAP alone, respectively.

Effect of Antioxidant Supplementation on Markers of Oxidative Stress and Muscle Damage after Strength Exercise: A Systematic Review.

BACKGROUND: The purpose of this systematic review was to determine the effect of antioxidant consumption on markers of oxidative stress and muscle damage after performing a muscle strength exercise. METHODS: The Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed. Four databases were used: Scopus, PubMed, WOS and SportDiscus. Methodological quality was assessed using the PEDro scale. RESULTS: A total of 1709 articles were retrieved and following duplicate removal and application of exclusion criteria seven articles were reviewed. Supplementation with pomegranate juice alleviates oxidative stress, taurine reduces muscle damage, melatonin protects the skeletal muscles, blueberries decrease oxidation and oats mitigate muscle damage. CONCLUSIONS: Acute administration of antioxidants immediately before or during an exercise session can have beneficial effects, such as delay of fatigue and a reduction in the recovery period. Administration of antioxidant susbtances may reduce muscle damage and oxidative stress markers.

A new reliable device to assess trunk extensors strength.

PURPOSE: This study aimed to examine the reliability of trunk extensor strength assessment with a functional electromechanical dynamometer (FEMD). METHODS: Thirty-one men performed strength assessment at different velocities (V) (V1 = 0.15 m⋅s-1 , V2 = 0.30 m⋅s-1,V3 = 0.45 m⋅s-1) and range of movement (R) (R1 = 25% cm; R2 = 50% cm), and isometric contraction at 90°. Reliability was obtained through the intraclass correlation coefficient (ICC), typical error (TE), and coefficient of variation (CV). RESULTS: The absolute reliability provided stable repeatability of the average eccentric strength in the V1R1 condition (CV = 9.52%) and the maximum eccentric strength in V1R1 (CV = 9.63%) and V2R2 (CV = 9.66%). The relative reliability of the trunk extensor's average strength was good (ICC = 0.77-0.83) for concentric and good (ICC = 0.78-0.85) and moderate (ICC = 0.67-0.74) for eccentric contraction. Also, good (ICC = 0.77-0.81) and moderate (ICC = 0.55-0.74) reliability of the maximum strength were obtained for concentric and eccentric contraction. The most reliable manifestation to evaluate the concentric (CV = 11.33%) and eccentric (CV = 9.52%) strength was the average strength in the V1R1 condition and the maximum strength (CV = 10.29%) to isometric assessment. The average concentric strength in the V2R2 condition (r = 0.69) and the maximum eccentric strength in the V1R1 condition (r = 0.65) were the best related to the maximum isometric strength. CONCLUSIONS: FEMD is a highly reliable device to evaluate trunk extensors strength.

Reliability of Isokinetic Hip Flexor and Extensor Strength Measurements in Healthy Subjects and Athletes: A Systematic Review and Meta-Analysis.

BACKGROUND: The objective of this systematic review and meta-analysis was to examine the reliability of isokinetic measurements of hip strength in flexion and extension in healthy subjects and athletes. METHODS: The databases used were Web of Science, SCOPUS, Medline and PubMed. R was used for all statistical analyses. RESULTS: Hip flexion shows moderate reliability in the supine position (ICC = 0.72; 95% CI: 0.46-0.99) and good reliability in the standing position (ICC = 0.79; 95% CI: 0.54-1.04). Hip extension shows excellent reliability in the supine position (ICC = 0.90; 95% CI: 0.85-0.96) and moderate reliability in the standing position (ICC = 0.72; 95% CI: 0.48-0.96). Flexion of 120°/s and 180°/s showed excellent reliability (ICC = 0.93; 95% CI: 0.85-1.00), (ICC = 0.96; 95% CI: 0.92-1.01). The 60°/s and 120°/s extension showed good reliability (ICC = 0.90; 95% CI: 0.82-0.98), (ICC = 0.87; 95% CI: 0.75-0.99). The 180°/s extension presented excellent reliability (ICC = 0.93; 95% CI: 0.82-1.03). CONCLUSIONS: The standing position shows good reliability for hip flexion and the supine position shows excellent reliability for hip extension, both movements have excellent reliability at velocities between 120°/s to 180°/s.

Test-retest reliability of a functional electromechanical dynamometer on swing eccentric hamstring exercise measures in soccer players.

BACKGROUND: The use of a functional electromechanical dynamometer (FEMD) has been proposed as a valid and effective tool to evaluate specific movement patterns. The aim of this study was to determine the reliability of FEMD on swing eccentric hamstring exercise (SEHE) measures in soccer players. METHODS: Nineteen federated male soccer players (20.74 ± 4.04 years) performed the SEHE at three different isokinetic velocities (20-40-60 cm/s). These evaluations were conducted in four sessions, two for familiarization and two for registration. The average and maximum load (N) of the three isokinetic velocities was calculated from the values obtained from the FEMD (Dynasystem®, Bangalore). RESULTS: The main results of this research showed that the reliability was high for the average load in the condition of 40 cm/s, presenting the highest ICC value (0.94). For maximum load, reliability was high in the condition of 20 cm/s. The manifestation of the most reliable load was the maximum load (ICC = 0.91-0.87). CONCLUSIONS: FEMD (Dynasystem®, Bangalore) is a reliable device to evaluate the eccentric strength of the hamstring muscles in soccer players.

Effects of Pre-Activation with Variable Intra-Repetition Resistance on Throwing Velocity in Female Handball Players: a Methodological Proposal.

The purpose of this study was to investigate the acute effect of pre-activation with Variable Intra-Repetition Resistance and isometry on the overhead throwing velocity in handball players. Fourteen female handball players took part in the study (age: 21.2 ± 2.7 years, experience: 10.9 ± 3.5 years). For Post-Activation Potentiation, two pre-activation methods were used: (I) Variable Intra-Repetition Resistance: 1 x 5 maximum repetitions at an initial velocity of 0.6 m·s-1 and a final velocity of 0.9 m·s-1; (II) Isometry: 1 x 5 s of maximum voluntary isometric contraction. Both methods were "standing unilateral bench presses" with the dominant arm, using a functional electromechanical dynamometer. The variable analysed was the mean of the three overhead throws. Ball velocity was measured with a radar (Stalker ATS). The statistical analysis was performed using ANOVA with repeated measures. No significant differences were found for either method (variable resistance intra-repetition: p = 0.194, isometry: p = 0.596). Regarding the individual responses, the analysis showed that 86% of the sample increased throwing velocity with the variable resistance intra-repetition method, while 93% of the sample increased throwing velocity with the isometric method. Both the variable intra-repetition resistance and isometric methods show improvements in ball velocity in female handball players. However, the authors recommend checking individual responses, since the results obtained were influenced by the short rest interval between the pre-activation and the experimental sets.