The Impact of Heat Exposure on the Health and Performance of Soccer Players: A Narrative Review and Bibliometric Analysis

The impact of heat exposure on the health and performance of soccer players is a widely discussed topic. The purpose of this study is to provide a comprehensive overview of the international literature that has addressed this issue. To achieve this objective, we initially conducted a bibliometric analysis and a literature review of the main topics that emerged through bibliometric techniques. For the bibliometric analysis, we employed VOSviewer software (version 1.6.20.0) and used documents found in the Scopus database. The analysis ultimately included 133 documents published in 66 sources. Key journals and authors were identified, highlighting significant contributions to the field. Science mapping revealed collaboration networks and research focus areas such as physical health, safety, soccer performance, dehydration and hydration, physiological mechanisms and monitoring, nutrition, fluid intake, and cooling techniques. Based on the key areas highlighted in the identified clusters, which emerged from the co-occurrence analysis of the author keywords, the following three topics were developed in the literature review: (a) the physiology and health of football players; (b) performance impacts; and (c) strategies to prevent negative consequences. The review showed that high heat exposure can reduce the physical and cognitive performance of athletes and prove detrimental to their health. To mitigate the negative consequences, appropriate hydration strategies, heat acclimatization, and cooling techniques have been proposed. Our findings provide the international scientific community with comprehensive knowledge of the existing literature, laying the foundation for future research while simultaneously offering coaches and athletes the necessary theoretical knowledge to help improve safety and performance

Altered Drop Jump Landing Biomechanics Following Eccentric Exercise-Induced Muscle Damage

Limited research exists in the literature regarding the biomechanics of the jump-landing sequence in individuals that experience symptoms of muscle damage. The present study investigated the effects of knee localized muscle damage on sagittal plane landing biomechanics during drop vertical jump (DVJ). Thirteen regional level athletes performed five sets of 15 maximal eccentric voluntary contractions of the knee extensors of both legs at 60°/s. Pelvic and lower body kinematics and kinetics were measured pre- and 48 h post-eccentric exercise. The examination of muscle damage indicators included isometric torque, muscle soreness, and serum creatine kinase (CK) activity. The results revealed that all indicators changed significantly following eccentric exercise (p < 0.05). Peak knee and hip joint flexion as well as peak anterior pelvic tilt significantly increased, whereas vertical ground reaction force (GRF), internal knee extension moment, and knee joint stiffness significantly decreased during landing (p < 0.05). Therefore, the participants displayed a softer landing pattern following knee-localized eccentric exercise while being in a muscle-damaged state. This observation provides new insights on how the DVJ landing kinematics and kinetics alter to compensate the impaired function of the knee extensors following exercise-induced muscle damage (EIMD) and residual muscle soreness 48 h post-exercise

The acute effects of assisted or resisted variable resistance back squat exercise on countermovement jump performance

INTRODUCTION: Back squat warm-up activities using elastic band (EB) resistance in combination with free weight resistance (FWR) can improve subsequent countermovement jump (CMJ) performance [1], a phenomenon termed post-activation performance enhancement (PAPE). However, across the literature sub-maximal loads of 85% are commonly used, with limited research existing on the effect of lighter loads on acute performance enhancement under both FWR or EB (resisted [RES] or assisted [ASS]) conditions. The aim of the present study was to compare the effects of back squats at 50% 1-RM under two EB attachment sites (ASS and RES) and FWR alone after a task-specific comprehensive warm-up on subsequent CMJ performance. METHODS: Twenty active males (age = 24.9±3.7 y, height = 1.7±5.7 m, mass = 83.4±12.6 kg) volunteered for the study and completed three separate experimental conditions (FWR, RES, ASS) separated by 48 h following a randomised crossover design. During each condition, participants first completed initial baseline CMJ tests (BL1) followed by a task-specific comprehensive warm-up that involved 5 min of cycling, two sets of 5 bodyweight squats, 5 continuous CMJs at 70% of perceived maximum, and finally, maximal CMJs every 30 s until 3 consecutive jumps were within 3% of jump height. Baseline 2 (BL2) CMJ tests were then completed and followed by 3 back squats following either the FWR, RES or ASS protocols at 50% 1-RM with 35% of the load generated by EBs during the RES and ASS conditions. CMJs were then performed 30 s, 4 min, 8 min and 12 min later. RESULTS: Significant increases (p<0.05) in both jump height (4.6-18.8%) and peak power (5.3-10.8%) were observed across all timepoints when compared with BL1 measure in all conditions. In the ASS condition, significant increases in jump height (4.6-11.8%) and peak power (6.5-2.0%) were observed at 30 s, 4 min, 8 min, and 12 min compared to BL2. In the RES condition, significant increases in jump height (7.1-1.2%) and peak power (2.3-5.4%) were observed at 30 s, 4 min, and 8 min, and in the FWR condition, significant increases in jump height (2.2-5.7%) and peak power (1-4.6%) were observed at 30 s and 4 min. DISCUSSION: The implementation of back squats into a warm-up activity at 50% 1-RM increased jump performance when EBs were used during both the ASS and RES conditions, with the increase in jump height being greater than that observed in the FWR condition. The use of EB resistance speculatively reduces loading at the sticking point, potentially allowing for greater acceleration during the concentric phase as lower-limb joints extend at the point where more optimal muscle lengths are achieved [2].These data have important implications for warm-up design for strength and power activities. REFERENCES 1. Mina et al. (2019). Scand J Med Sci Sports. 29(3):380-392. 2. Anderson et al. (2008). J Strength Cond Res. 22(2):567-574

The effects of training with high-speed interval running on muscle performance are modulated by slope

© 2021 The Authors. Published by Wiley. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.14814/phy2.14656We examined changes in selected muscle performance parameters after 8 weeks of interval training using two opposite running inclinations. We hypothesized that the uphill training will affect endurance muscle performance outcomes, whereas the downhill training will affect power muscle performance outcomes. Fourteen physically active volunteers were randomly assigned into either the Uphill group (UG; n = 7; uphill interval running at +10% incline) or the Downhill group (DG; n = 7; downhill interval running at -10% incline) and completed 16 training sessions. Each session consisted of ten 30 s treadmill runs at 90% of maximum aerobic speed (MAS) with a work to rest ratio of 1:2. Vertical jump performance, isometric (MVC) and isokinetic torque of knee extensors and flexors, and fatigue of knee extensors were evaluated pre and post-training. Moreover, body composition (via bioimpedance) and vastus lateralis muscle architecture (via ultrasonography) were assessed pre and post-training. Relative lean tissue mass, relative fat mass, and squat jump (cm) significantly (p < .05) changed from baseline values by +4.5 ± 4.0%, -11.5 ± 9.6%, and +9.5 ± 11.7%, respectively, only in the DG. Similarly, DG improved absolute values of knee extension rate of torque development and impulse (p < .05), whereas knee flexion peak torque angle significantly decreased in both groups (p < .05). On the other hand, the UG increased the number of repetitions achieved during the fatigue protocol and total work by 21.2 ± 32.6% and 13.8 ± 21.2%, respectively (p < .05). No differences were found between groups in muscle architecture. Introducing variations in slope during HIIT could be used to induce specific improvements toward muscle endurance or power performance characteristics.Published versio

The acute effects of an intense stretch-shortening cycle fatigue protocol on the neuromechanical parameters of lower limbs in men and prepubescent boys

The study examined the differences between boys and adults after an intense stretch-shortening cycle fatigue protocol on neuromechanical parameters of the lower limb. Thirteen boys (9–11 years old) and 13 adult men (22–28 years old) were tested for maximal isometric voluntary knee extension torque and drop jump (DJ) performance from 30 cm before and immediately after a fatigue protocol, consisted of 10 × 10 maximum effort vertical jumps. Three-dimensional kinematics, kinetics and electromyographic (EMG) parameters of the lower extremities muscles were recorded during DJs before and after the fatigue test. The results indicated that reduction in maximal isometric torque and jumping performance was significantly higher in adults compared to boys. Vertical ground reaction forces, contact time and maximum knee flexion increased in a greater extend in adults than in boys. In addition, preactivation, EMG agonist activity, knee joint stiffness and stretch reflex decreased more in adults than in boys at all the examined phases of jumping tasks. It is concluded that employed fatigue protocol induced acute reduction in performance and altered motor control during jumping in both age groups. However, the differences in the level of fatigue between the 2 groups could be attributed to neuromuscular, mechanical and kinematic parameters observed between groups. © 2017 Informa UK Limited, trading as Taylor & Francis Group