LOAD DURING THE VERTICAL JUMP IN WATER: VALUES FOR PRESCRIPTION IN HYDROTHERAPY

This study aimed to analyse the vertical component of the ground reaction force (GRF) in the vertical jump in water performed by men and women at two levels of immersion. 11 men and 11 women performed three vertical jumps on a water-proof force plate at hip and chest levels of immersion. No effect of gender was observed. No difference between levels of immersion was found for peak of propulsion [1.85 and 1.89 units of body weight (BW) at the hip and chest respectively]. During the landing phase, the force peak was significantly higher at the hip level (2.62 BW) than at the chest level (2.07 BW). The force during the propulsion phase was similar between the immersions; however the vertical load on landing needs to be considered when prescribing this exercise, even in water

RELATIVE ERROR ANALYSIS DURING REPRODUCTION OF ISOMETRIC FORCE OF KNEE EXTENSORS IN YOUNG ADULTS

This study compared the force reproduction of isometric knee extension at 60°, between the target forces at 30%, 50% and 70% of the maximum voluntary isometric force (MVIF) in young adults. Twenty young males took part in the study. The trials were performed on an instrumented chair developed for the study. Feedback was given to the participants during three trials prior the beginning of data collection in each analyzed target force. Participants performed 10 trials without any feedback for the target force at 30% and 50% of the MVIF and 3 trials for the target force at 70% of MVIF. The relative error decreased as the target force increased. The differences were significant between 30% and 70% (p=0.01) and between 50% and 70% (p=0.03). The reproduction of higher forces during isometric extension of the knee will produce lower relative errors for this specific task

A DYNAMOMETRIC METHOD FOR THE EVALUATION OF HIKING IN LASER BOATS

This study aimed to develop a dynamometric method for the evaluation of hiking in Laser boats. The boat’s and sailor’s centres of mass, the hiking distance and the hiking moment were calculated from the ground reaction force, acquired by two force plates located under the boat hoof. Three sailors performed different hiking positions varying their hip and knee angles. Pearson’s coefficient was used to verify the correlation between the measures obtained through the dynamometric method and a kinematic method. A very high correlation was observed between the methods (r=0.99) and the mean error was approximately 1% for both hiking distance and moment. Thus, the new method seems to be valid and efficient since it measured the variables in a fast and precise way, facilitating the analysis and assisting sailors and coaches on decision taking

COMPARISON OF GROUND REACTION FORCES BETWEEN IN-PLACE AND FORWARD WATER RUNNING AT TWO LEVELS OF IMMERSION

This study compared GRF of in-place and forward water running at two levels of immersion. Twenty healthy subjects executed both exercises at a self selected speed at hip and chest immersion. Variables analyzed were: vertical peak (Fy), anterior peak (Fx anterior) and posterior peak (Fx posterior). Two-factor repeated measures ANOVA was used with

Simple reaction time in soccer players from differing categories and field positions

This study aimed at analyzing the visual and auditory simple reaction times in soccer players from differing categories and field positions. Participated in the study 49 male soccer players, amateurs and professionals, occupying the field positions of goalkeeper, center defender, right and left defender, half-back, midfielder, and forward. Data collection was carried out through a system composed by a switch, a mechanism of visual and auditory stimuli and appropriate acquisition software. Data were analyzed through descriptive and inferential statistics (p < .05). When comparing categories, there was no difference in visual reaction time (VRT). Professionals showed faster auditory reaction times (ART) than amateurs did. Regarding field positions, goalkeepers showed significantly faster VRT than midfielders and there was no difference in terms of ART. Main differences between players from differing categories and field positions may be due to the adoption of more complex strategies in retaining and using visual information in specific situations. ART may be less important in soccer, since this is essentially a visual game

Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis

OBJECTIVE: We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed, through a meta-analysis, the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions.METHODS: Our search was conducted from database inception to May 2020. Descriptive information was extracted from, and quality was assessed for, 45 studies. Meta-analyses and meta-regressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction.RESULTS: Procedures varied across studies with regards to muscle group tested, angular stretch amplitude, randomization of contractions, time window analyzed, and verbal command. Torque capacity in isometric (constant muscle tendon unit length and joint angle) contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions, and this effect was greater for electrically evoked muscle contractions than voluntary contractions. Residual torque enhancement differed across muscle groups for the voluntary contractions, with a significant enhancement in torque observed for the adductor pollicis, ankle dorsiflexors, ankle plantar flexors, and knee extensors, but not for the elbow and knee flexors. Meta-regressions revealed that the angular amplitude of the eccentric contraction (normalized to the respective joint's full range of motion) was not associated with the residual torque enhancement observed.CONCLUSION: There is evidence of residual torque enhancement for most, but not all, muscle groups, and residual torque enhancement is greater for electrically evoked than for voluntary contractions. Contrary to our hypothesis, and contrary to generally accepted findings on isolated muscle preparations, residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.</p

Looped Elastic Resistance during Squats: How Do Band Position and Stiffness Affect Hip Myoelectric Activity?

Looped elastic bands around the thigh are commonly used during squats and result in increased hip activation. Due to the closed kinetic chain nature of the squat exercise, one may expect that placing the elastic band on distal segments, close to the floor contact, may not result in the same increase in hip muscle activation as that achieved with a looped band around the thigh. We analyzed the effects of band position (thigh, lower leg, and forefoot) and band stiffness on the myoelectric activity of the tensor fascia latae, gluteus medius, gluteus maximus, biceps femoris, vastus medialis, and vastus lateralis during squats in 35 healthy subjects (18 men and 17 women). The greatest myoelectric activity of hip muscles was observed when the stiffest band was positioned around the forefeet with an increase in 24% for the tensor fascia latae, 83% for the gluteus medius, and 68% for the gluteus maximus compared to free (without resistance band) squatting. Contrary to previous thinking, the use of elastic bands around the forefeet during squats can elicit increased myoelectric activity of hip muscles, with a magnitude often greater than when the band is placed around the thigh segments