Study of mechanical characteristics of the knee extensor and flexor musculature of volleyball players     

《European Journal of Sport Science》2013,13(5):399-407

Abstract

The aim of the present study was to analyse differences in muscle response and mechanical characteristics of the vastus medialis, rectus femoris, vastus lateralis, and biceps femoris in elite volleyball players of both sexes using tensiomyography. To this end, 47 players of nine nationalities playing for teams in the men's and women's Spanish Superleagues were assessed. The sample comprised 22 women (age 24.6±4.3 years; weight 72.14±10.06 kg; height 178.40±8.50 cm) and 25 men (age 25.0±4.3 years; weight 88.76±9.07 kg; height 194.71±7.84 cm). Tensiomyography was used to assess muscular response and muscular mechanical characteristics. For this purpose, the following variables were analysed: maximum radial displacement of muscle belly and normalized response speed. The findings show, both in men and women, a higher normalized response speed score in the vastus lateralis and vastus medialis compared with the rectus femoris and biceps femoris. A marked lateral symmetry of maximum radial displacement of the muscle belly was also observed in the musculature of the lower limbs, with no statistically significant differences being detected in either men or women. There were, however, clear differences in terms of normalized response speed between male and female volleyball players: women displayed a more pronounced difference in the normalized response speed of the musculature responsible for extension (vastus medialis, rectus femoris, and vastus lateralis) and flexion (biceps femoris) of the knee joint than men. Moreover, tensiomyography proved to be a highly sensitive tool for detecting such changes.  相似文献   

Comparison of EMG activity during stable and unstable push-up protocols     

《European Journal of Sport Science》2013,13(1):42-48

Abstract

This experiment examined muscle activation measured using electromyography (EMG) during a standardized push-up performed on stable and unstable surfaces. Fifteen highly trained participants performed four push-ups: standard (hands and feet on the floor), either the hands or feet on an unstable surface (single instability), and with both hands and feet on unstable surfaces (dual instability). Unstable surfaces were created using a stability ball and an extreme balance board. EMG activity was recorded from three core stabilizers (erector spinae, rectus abdominus and internal obliques), one prime mover (triceps), and one lower body stabilizer (soleus). The EMG time series were smoothed using a 10-point moving average and root mean squares (RMS) were calculated for the entire time series. The results showed that push-ups performed with dual instability had significantly greater EMG activation compared to single instability or the stable push-up. In addition, as instability increased, there was a greater amount of muscle activation for the core stabilizers, prime movers and lower body stabilizers. The findings are consistent with the position that unstable surfaces in conjunction with standard exercises can be used to increase activation of core trunk stabilizers. This may in turn provide increased trunk strength and greater resistance to injury.  相似文献   

Does maturation influence neuromuscular performance and muscle damage after competitive match-play in youth male soccer players?     

《European Journal of Sport Science》2013,13(8):1130-1139

Abstract

Poor neuromuscular control and fatigue have been proposed as a risk factor for non-contact injuries especially around peak height velocity (PHV). This study explored the effects of competitive soccer match-play on neuromuscular performance and muscle damage in male youth soccer players. 24 youth players aged 13-16y were split into a PHV group (?0.5 to 0.5y) and post PHV group (1.0–2.5y) based on maturity off-set. Leg stiffness, reactive strength index (RSI), muscle activation, creatine kinase (CK), and muscle soreness were determined pre and post a competitive soccer match. Paired t-tests were used to explore differences pre and post competitive match play and independent sample t-tests for between groups differences for all outcome measures. There was no significant fatigue-related change in absolute and relative leg stiffness or muscle activation in both groups, except for the gastrocnemius in the post PHV group. RSI, CK and perceived muscle soreness were significantly different after soccer match-play in both groups with small to large effects observed (ES:0.41–2.82). There were no significant differences between the groups pre match-play except for absolute and relative leg stiffness (P?<?0.001; ES?=?1.16 and 0.63 respectively). No significant differences were observed in the fatigue related responses to competitive match play between groups except for perceived muscle soreness. The influence of competitive match-play on neuromuscular function and muscle damage is similar in male youth around the time of PHV and those post-PHV indicating that other factors must contribute to the heightened injury risk around PHV.  相似文献   

Can more than one incremental cycling test be performed within one day?     

《European Journal of Sport Science》2013,13(5):459-467

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Physiological and psychological responses to lead and top rope climbing for intermediate rock climbers     

《European Journal of Sport Science》2013,13(1):13-20

Abstract

Rock climbing is a popular adventure sport with an increasing research base. Early studies in the field did not make comparisons of ascents using different styles of climbing. More recently, differences in the physiological responses for an on-sight lead climb and subsequent lead climb have been reported. The purpose of the present study was to examine the effect of style of climb (lead climb or top rope climb) on the physiological and psychological responses to rock climbing. Nine intermediate climbers volunteered for, and completed, two randomly assigned climbing trials and a maximum oxygen uptake (VO_2max) test on a separate occasion. The climbers ascended the same 6a (sport grade) climb for both trials. Before climbing, heart rate, perception of anxiety (Revised Competitive State Anxiety Inventory-2), and blood lactate concentration were measured. Climb time, heart rate, VO₂, lactate concentrations, and task load (National Aeronautics and Space Administration Task Load Index) in response to each trial were also recorded. Results indicated significant differences (P<0.05) between the trials for climb time, blood lactate concentration immediately after and 15 min after climbing, and heart rate 1 min after climbing. During lead and top rope climbing, mean VO₂ and represented 44% and 42% of treadmill VO_2max and mean heart rate represented 81% and 77% of maximum heart rate, respectively. There were no significant differences in feelings of anxiety before either climb, although climbers reported the lead climb to be physically and mentally more demanding, requiring more effort and resulting in greater frustration (P<0.05) than the top rope climb. Our results indicate that the physiological and psychological responses of intermediate climbers are different for a lead climb and top rope climb.  相似文献   

Does a water-training macrocycle really create imbalances in swimmers' shoulder rotator muscles?     

《European Journal of Sport Science》2013,13(2):167-172

Abstract

The continuous execution of swimming techniques may cause muscle imbalances in shoulder rotators leading to injury. However, there is a lack of published research studies on this topic. The aim of this study was to analyze the influence of a competitive swim period on the shoulder rotator–cuff balance in young swimmers. A randomized controlled pretest–posttest design was used, with two measurements performed during the first macrocycle of the swimming season (baseline and 16 weeks). Twenty-seven young male swimmers (experimental group) and 22 male students who were not involved in swim training (control group) with the same characteristics were evaluated. Peak torque of shoulder internal and external rotators was assessed. Concentric action at 1.04 rad s^?1 (3 repetitions) and 3.14 rad s^?1 (20 repetitions) was measured using an isokinetic dynamometer (Biodex System 3). External/internal rotators strength ratios were also obtained. For both protocols, there were significant training effects on internal rotator strength and external/internal rotator ratios (p ≤ .05). This trend was the same for both shoulders. Within-group analysis showed significant changes from baseline to 16 weeks for internal rotators strength and unilateral ratios of the experimental group. Swimmers' internal rotator strength levels increased significantly. In contrast, a significant decrease of the unilateral ratios was observed. Findings suggest that a competitive swim macrocycle leads to an increase in muscular imbalances in the shoulder rotators of young competitive swimmers. Swimming coaches should consider implementing a compensatory strength-training program.  相似文献   

Whole-body vibration as a method of recovery for soccer players     

《European Journal of Sport Science》2013,13(1):2-8

Abstract

The aim of this study was to determine whether superimposed whole-body vibration could improve the recovery-related effects of a traditional cool-down in high-level soccer players. Sixteen high-level junior soccer players performed a repeated-sprint ability test, after which they performed a traditional cool-down, with (experimental group) or without (control group) superimposed whole-body vibration. Functional recovery was measured through vertical jump height and maximal voluntary isometric force in leg-extension. The repeated-sprint ability test induced increases (from 161 to 215%; P<0.05) in muscle pain measured by visual analogue scale in the control group only. Vertical jump height was recovered earlier with than without whole-body vibration (24 h after the repeated-sprint ability test; P<0.05). The results of this study demonstrate that whole-body vibration in combination with a traditional cool-down can reduce perceived muscle pain and enhance recovery after a soccer-specific exercise.  相似文献   

The nitrate-nitrite-nitric oxide pathway: Its role in human exercise physiology     

《European Journal of Sport Science》2013,13(4):309-320

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Change-of-direction,speed and jump performance in soccer players: a comparison across different age-categories     

Irineu Loturco  Ian Jeffreys  César C. Cal Abad  Ronaldo Kobal  Vinicius Zanetti  Lucas A. Pereira 《Journal of sports sciences》2020,38(11-12):1279-1285

ABSTRACT

This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players’ specialization process.  相似文献   

Running economy and effort after cycling: Effect of methodological choices     

Chantelle du Plessis  Anthony J. Blazevich  Chris Abbiss  Jodie Cochrane Wilkie 《Journal of sports sciences》2020,38(10):1105-1114

ABSTRACT

Prior exercise can negatively affect movement economy of a subsequent task. However, the impact of cycling exercise on the energy cost of subsequent running is difficult to ascertain, possibly because of the use of different methods of calculating economy. We examined the influence of a simulated cycling bout on running physiological cost (running economy, heart rate and ventilation rates) and perceptual responses (ratings of perceived exertion and effort) by comparing two running bouts, performed before and after cycling using different running economy calculation methods. Seventeen competitive male triathletes ran at race pace before and after a simulated Olympic-distance cycling bout. Running economy was calculated as V?O₂ (mL?kg^?1?min^?1), oxygen cost (EO₂, mL?kg^?1?m^?1) and aerobic energy cost (E_aer, J?kg^?1?m^?1). All measures of running economy and perceptual responses indicated significant alterations imposed by prior cycling. Despite a good level of agreement with minimal bias between calculation methods, differences (p < 0.05) were observed between E_aer and both V?O₂ and EO₂. The results confirmed that prior cycling increased physiological cost and perceptual responses in a subsequent running bout. It is recommended that E_aer be calculated as a more valid measure of running economy alongside perceptual responses to assist in the identification of individual responses in running economy following cycling.  相似文献