Neuromuscular Fatigue Research Articles

Shoulder Tensiomyography and Isometric Strength in Swimmers Before and After a Fatiguing Protocol.

Shoulder muscles are active during front-crawl swimming to provide propulsion and stabilize the glenohumeral and scapulothoracic joints. Researchers have proposed that fatigue might contribute to altered activation of these muscles and represent a risk factor for injuries. Tensiomyography (TMG) might function as a noninvasive tool to detect changes in contractile measures of the skeletal muscles due to exercise-induced neuromuscular fatigue, though it has not yet been used in the shoulder muscles of swimmers. To assess the effects of a fatiguing swimming protocol on shoulder muscle TMG measures and isometric strength in competitive swimmers. Cross-sectional study. Swimming pool facility. A total of 14 young front-crawl competitive swimmers (11 males and 3 females; age = 21 ± 3 years [range, 17-26 years], height = 1.78 ± 0.06 m, mass = 73.1 ± 9.2 kg). Participants completed TMG and isometric strength assessments before and after 30-minute, high-intensity swim training. The TMG assessment was performed on 7 muscles of the shoulder according to front-crawl biomechanics and the applicability of the technique to obtain data, such as time to contraction and muscle-belly radial displacement. Isometric strength was assessed using a digital handheld dynamometer during shoulder flexion, extension, external rotation, and internal rotation. Fatigue induced a smaller radial displacement, mostly observable in latissimus dorsi (-1.0 mm; 95% CI = -1.7, -0.3 mm; P = .007) and pectoralis major muscles (-1.4 mm; 95% CI = -2.4, -0.4 mm; P = .007). Only shoulder extension showed an isometric strength reduction after the fatiguing protocol (-0.03 N/kg; 95% CI = -0.05, -0.01 N/kg; F1,13 = 4.936; P = .045; ηp2 = 0.275). This study provides preliminary evidence for the usefulness of TMG to detect fatigue-induced changes in contractile properties of the shoulder muscles in swimmers, in particular the latissimus dorsi and pectoralis major.

Mind over muscle? Time manipulation improves physical performance by slowing down the neuromuscular fatigue accumulation.

While physical performance has long been thought to be limited only by physiological factors, many experiments denote that psychological ones can also influence it. Specifically, the deception paradigm investigates the effect of psychological factors on performance by manipulating a psychological variable unbeknownst to the subjects. For example, during a physical exercise performed to failure, previous results revealed an improvement in performance (i.e., holding time) when the clock shown to the subjects was deceptively slowed down. However, the underlying neurophysiological changes supporting this performance improvement due to deceptive time manipulation remain unknown. Here, we addressed this issue by investigating from a neuromuscular perspective the effect of a deceptive clock manipulation on a single-joint isometric task conducted to failure in 24 healthy participants (11 females). Neuromuscular fatigue was assessed by pre- to post-exercise changes in quadriceps maximal voluntary torque (Tmax ), voluntary activation level (VAL), and potentiated twitch (TTW ). Our main results indicated a significant performance improvement when the clock was slowed down (Biased: 356 ± 118 s vs. Normal: 332 ± 112 s, p = .036) but, surprisingly, without any difference in the associated neuromuscular fatigue (p > .05 and BF < 0.3 for Tmax , VAL, and TTW between both sessions). Computational modeling showed that, when observed, the holding time improvement was explained by a neuromuscular fatigue accumulation based on subjective rather than actual time. These results support a psychological influence on neuromuscular processes and contribute significantly to the literature on the mind-body influence, by challenging our understanding of fatigue.

Myotendinous Thermoregulation in National Level Sprinters after a Unilateral Fatigue Acute Bout—A Descriptive Study

In the last decade there has been a growing interest in infrared thermography in the field of sports medicine in order to elucidate the mechanisms of thermoregulation. The aim of this study was to describe bilateral variations in skin temperature of the anterior thigh and patellar tendon in healthy athletes and to provide a model of baseline tendon and muscle thermoregulation in healthy sprinters following a unilateral isokinetic fatigue protocol. Fifteen healthy national-level sprinters (eleven men and four women), with at least 3 years of athletic training experience of 10–12 h/week and competing in national-level competitions, underwent unilateral isokinetic force testing and electrostimulation in which their body temperature was measured before, during, and after the protocol using an infrared thermographic camera. ANOVA detected a significant difference in the time × side interaction for patellar temperature changes (p ≤ 0.001) and a significant difference in the time/side interaction for quadriceps temperature changes (p ≤ 0.001). The thermal challenge produces homogeneous changes evident in quadriceps areas, but not homogeneous in tendon areas. These data show that metabolic and blood flow changes may depend on the physical and mechanical properties of each tissue. Future research could be conducted to evaluate the predictive value of neuromuscular fatigue in the patellar tendon and quadriceps after exercise in order to optimize post-exercise recovery strategies.

The Effects and Reproducibility of 10, 20, and 30% Velocity Loss Thresholds on Acute and Short-Term Fatigue and Recovery Responses.

Weakley, J, Johnston, RD, Cowley, N, Wood, T, Ramirez-Lopez, C, McMahon, E, and García-Ramos, A. The effects and reproducibility of 10, 20, and 30% velocity loss thresholds on acute and short-term fatigue and recovery responses. J Strength Cond Res 38(3): 465-473, 2024-This study aimed to establish the effects and reproducibility of implementing 10, 20, and 30% velocity loss thresholds (VLTs) during the free-weight barbell back squat on acute and short-term perceived soreness, neuromuscular fatigue, and physical performance. Using a repeated, counterbalanced, crossover design, 12 team-sport athletes completed on separate sessions 5 sets of the free-weight barbell back-squat until reaching VLTs of either 10, 20, or 30%. Outcomes were measured immediately postexercise and 24 hours after each session. To assess reproducibility, the same sessions were repeated after 4 weeks. Immediately postexercise, small differences in countermovement jump (CMJ) and 10-m sprint performance were observed between VLT conditions, whereas small to moderate differences in differential ratings of perceived exertion were reported (10% < 20% < 30%). At 24 hours, trivial differences in CMJ outcomes were found but small differences in 10-m sprint performance were detected between conditions (10% < 20% < 30%). In addition, at 24 hours, a single small difference in radial deformation using tensiomyography was found between 10 and 30% conditions, whereas large to very large differences in perceived soreness were reported between conditions (10% < 20% < 30%). Finally, the standard error of measurement of all outcome measures at 24 hours were of a similar magnitude to those reported in tightly controlled, short-term studies. Collectively, these findings demonstrate that VLTs help control the fatigue outcomes that occur as a response to resistance training and that they are reproducible. Therefore, for practitioners who wish to prescribe resistance training and be confident in the subsequent fatigue response, it is strongly advised that VLTs are implemented.

Neuromuscular Fatigue after Small-Sided Games in Wheelchair Basketball Players with and without Spinal Cord Injury

ABSTRACT Purpose: The aim was to analyze the differences between wheelchair basketball players with Spinal Cord Injury (SCI) and without Spinal Cord injury (Non-SCI) in psycho-physiological response and neuromuscular fatigue in a series of small-sided games (SSG). Methods: Thirteen high-level wheelchair basketball male players (age 28.8 ± 9.2 years, body mass 75.9 ± 11.3 kg) participated in four versus four SSG once a week for five consecutive weeks. Absolute and relative heart rate (HR) during SSG and muscular and respiratory perceived exertion (RPEmus and RPEres), tympanic temperature, and acceleration capacity were recorded at the end of each SSG. Results: No significant differences were observed between SCI and non-SCI players in relative HR variables in SSG series. However, the SCI group had a lower absolute HR (mean HR and peak HR) (p < .05 or p < .01, ES = 0.73–1.39) and higher perceived muscular load (RPEmusTL) (p < .01, ES = 0.75–0.82) during SSG. Regarding the evolution of the physiological response, no differences were observed between the four bouts in the SCI group. However, the Non-SCI group showed an increase in the absolute and relative variables of HR and RPEres and RPEmus (p < .05 or p < .01, ES = 0.45–1.06). On the contrary, only the SCI group showed a loss of acceleration capacity between the four series (p < .05, ES = 0.28–0.35). Conclusion: The results of this study show that there are differences between SCI and non-SCI wheelchair basketball players in their physiological response and acceleration capacity during SSG tasks.

Effects of Exercise-Induced Neuromuscular Fatigue on Jump Performance and Lower-Limb Asymmetries in Youth Female Team Sport Athletes.

The objective of the present study was to examine the effect of acute neuromuscular fatigue on unilateral jump performance and inter-limb asymmetries. Thirty elite youth female team sport athletes (age: U-14 to U-18) performed the Unilateral Countermovement Jump (UCJ) and the Unilateral Drop Jump (UDJ) (18-cm box) tests before and approximately 10 minutes after the 30-15 intermittent fitness test (30-15 IFT). A paired samples t-test showed significant reductions in UCJ jump height in the right leg after the 30-15 IFT (p = 0.018; d = 0.33), but not in the left leg (p = 0.459; d = 0.48). For the UDJ, significant reductions in jump height were shown in both the right (p < 0.001; d = 0.33) and left (p < 0.001; d = 0.33) legs. In addition, for the reactive strength index (UDJ), significant reductions were seen in the left leg after the 30-15 IFT (p < 0.001; d = 0.31), but not in the right leg (p = 0.948; d < 0.001). Only UCJ inter-limb jump height asymmetries increased significantly post 30-15 IFT (p = 0.033; d = 0.46). In conclusion, the current study indicates that the 30-15 IFT provides a sufficient dose of activity for inducing acute fatigue in elite youth female team sport athletes. Therefore, monitoring jump height in unilateral jump testing is recommended given the tests' sensitivity to detect significant differences in physical performance and inter-limb asymmetries under acutely fatigued conditions in healthy youth female athletes.

Effect of Neuromuscular Fatigue on the Countermovement Jump Characteristics: Basketball-Related High-Intensity Exercises.

Yoshida, N, Hornsby, WG, Sole, CJ, Sato, K, and Stone, MH. Effect of neuromuscular fatigue on the countermovement jump characteristics: basketball related high-intensity exercises. J Strength Cond Res XX(X): 000-000, 2023-The purpose of this study was to investigate basketball specific neuromuscular (NM) fatigue effect on countermovement jump (CMJ) force-time (F-T) curve characteristics. Eleven male college-level basketball athletes performed 6 CMJ trials at 3 baseline (pre) and 6 postexercise time points. The fatiguing protocol consisted of high-intensity basketball related exercises commensurate with basketball game or practice. Typical CMJ (CMJ-TYP) and phase-specific CMJ variables were derived from the F-T curve. Meaningful differences in CMJ performance were examined using effect size (ES) compared with baseline and previous postexercise time point. Baseline with 3 separated measurements demonstrated suitable CMJ variables reproducibility (CV, coefficient of variation). Most CMJ-TYP output and performance variables displayed substantial alterations immediately postexercise (0 hour) and returned to baseline at 24 hours postexercise, whereas the time and rate-related CMJ-TYP and CMJ-phase variables tended to display delayed decline peaked at 2 hours and delayed recovery to baseline at 48 hours postexercise. In conjunction with the return of the time and rate-related variables, CMJ performance displayed supercompensation at 72 hours postexercise. The results indicate altered NM functions with desired CMJ performance, such as jump height, which imply an altered movement strategy at early stage of recovery process. Full recovery may take 48-72 hours. Practitioners are, therefore, advised to monitor variables reflecting NM functions for precise manipulation of the intensity and volume of exercise to avoid prolonging the recovery from NM fatigue.

System-based Monitoring of Muscular Fatigue in Lower-Extremity Movement

Physical fatigue accounts for many injuries in the workplace, sports arena, or battlefield. The traditional approaches to monitor fatigue rely on detecting and measuring shifts in the person’s muscular surface electromyography (sEMG) signals. However, assessing neuromuscular fatigue based purely on sEMG signals fails to account for the changing muscle dynamics during long dynamic physical tasks. To combat this dilemma, a system-based methodology has been recently developed and applied to several upper-extremity tasks. In this paper, we validate the efficacy of this novel methodology on the lower extremities during a dynamic activity. Specifically, the system-based monitoring methodology was applied to a cycling endurance task. It was statistically demonstrated that the system-based methodology resulted in a more-sensitive and less noisy metric, in comparison with an EMG-based methodology. The efficacy of the methodology was further illustrated by analyzing the inter-segmental recovering and fatiguing trends, which aligned with each muscle’s expected inter-muscle synergistic relationship.

Thoracic-Worn Accelerometers Detect Fatigue-Related Changes in Vertical Stiffness During Sprinting.

Horsley, BJ, Tofari, PJ, Halson, SL, Kemp, JG, Johnston, RD, and Cormack, SJ. Thoracic-worn accelerometers detect fatigue-related changes in vertical stiffness during sprinting. J Strength Cond Res 38(2): 283-289, 2024-Thoracic-mounted accelerometers are valid and reliable for analyzing gait characteristics and may provide the opportunity to assess running-related neuromuscular fatigue (NMF) during training and competition without the need for additional tests, such as a countermovement jump (CMJ). However, their sensitivity for detecting fatigue-related changes in gait across different speeds is unclear. We, therefore, assessed the changes in accelerometer-derived gait characteristics, including vertical stiffness (K vert ), following a repeated sprint protocol (RSP). Sixteen recreationally active subjects performed single and repeated CMJs on a force plate and 40 m run throughs overground at 3-4, 5-6, and 7-8 m·s -1 pre-post a 12 × 40 m RSP. Gait characteristics (contact time, step frequency, step length, K vert , etc.) were derived from an accelerometer contained within a global navigation satellite system unit on the thoracic spine using a validated algorithm. Changes in running gait and CMJ performance were assessed using a linear mixed-effects model (95% confidence interval [95% CI]; effect size [ES]). Significance was set at p < 0.05. A significant reduction in K vert occurred at 7-8 m·s -1 following the RSP (-8.51 kN·m -1 [-13.9, -3.11]; p = 0.007; ES [95% CI] = -0.39 [-0.62, -0.15]) which coincided with a decreased jump height (-0.03 m [-0.04, -0.01]; p = 0.002; ES [95% CI] = -0.87 [-1.41, -0.30]). However, all other gait characteristics were not significantly different irrespective of speed. Thoracic-worn accelerometers can detect changes in K vert at 7-8 m·s -1 which may be useful for monitoring NMF during sprinting. However, a RSP does not result in altered gait mechanics in subsequent running at lower speeds.

Motor-Respiratory Coupling Improves Endurance Performance during Rhythmic Isometric Handgrip Exercise.

This study aimed to evaluate whether motor-respiratory coupling exists in rhythmic isometric handgrip exercises and its effect on endurance performance. In addition, the mechanism underlying observed effects was to be investigated if higher motor-respiratory coupling rate could enhance endurance performance. Eleven subjects completed three rhythmic isometric handgrip trials to task failure in a randomized manner. After one pretraining session to determine personal grip frequency, one trial was performed without respiration requirement (CON), and two trials were performed with inspiration-motor coupling (IMC) or expiration-motor coupling. Changes in maximal voluntary contraction (MVC) and EMG were used to measure neuromuscular fatigue. Force data during test were used to assess exercise intensity. Another 10 subjects completed electrical stimulation-induced finger flexion and extension during normal inspiration, normal expiration, fast inspiration, fast expiration, and breath holding. Force changes of different breathing conditions were compared. Normalized exercise time to exhaustion was significantly longer in IMC (1.27 ± 0.23) compared with expiration-motor coupling (0.82 ± 0.18) and CON (0.91 ± 0.18, P < 0.001). ΔMVC, grip frequency, force, and EMG indices were not different among conditions (all P > 0.05). Electrical stimulation-induced finger extensor force was significant higher during fast inspiration (1.11 ± 0.09) than normal respiration (1.00 ± 0.05) and fast expiration (0.94 ± 0.08, P < 0.05). IMC is an effective way to improve endurance performance of rhythmic handgrip exercise. This is likely due to a reduction in the energy consumption of motion control, as evidenced by similar peripheral fatigue in different conditions and modulation of corticospinal excitability by respiration.

Low-load blood flow restriction reduces time-to-minimum single motor unit discharge rate.

Resistance training with low loads in combination with blood flow restriction (BFR) facilitates increases in muscle size and strength comparable with high-intensity exercise. We investigated the effects of BFR on single motor unit discharge behavior throughout a sustained low-intensity isometric contraction. Ten healthy individuals attended two experimental sessions: one with, the other without, BFR. Motor unit discharge rates from the tibialis anterior (TA) were recorded with intramuscular fine-wire electrodes throughout the duration of a sustained fatigue task. Three 5-s dorsiflexion maximal voluntary contractions (MVC) were performed before and after the fatigue task. Each participant held a target force of 20% MVC until endurance limit. A significant decrease in motor unit discharge rate was observed in both the non-BFR condition (from 13.13 ± 0.87Hz to 11.95 ± 0.43Hz, P = 0.03) and the BFR condition (from 12.95 ± 0.71Hz to 10.9 ± 0.75Hz, P = 0.03). BFR resulted in significantly shorter endurance time and time-to-minimum discharge rates and greater end-stage motor unit variability. Thus, low-load BFR causes an immediate steep decline in motor unit discharge rate that is greater than during contractions performed without BFR. This shortened neuromuscular response of time-to-minimum discharge rate likely contributes to the rapid rate of neuromuscular fatigue observed during BFR.

Characterization of neuromuscular performances in adults with late-onset Pompe disease: A control case cross-sectional study

Adults with late-onset Pompe disease (aLOPD) are characterized by muscular contractile tissue deterioration. However, their neuromuscular performances are poorly known. We aimed to compare maximal muscle strength, activation, explosive strength and neuromuscular fatigue between aLOPD and controls. We studied 20 aLOPD and 20 matched controls. Isometric maximum voluntary contraction (MVC) torque was obtained for the hip, knee and ankle muscles. The voluntary activation level (VAL) during knee extensor MVC was assessed using interpolated twitch technique. Explosive strength was evaluated for knee and ankle muscles through the rate of torque development (RTD) during fast contractions. Neuromuscular fatigue was measured during a 30-second contraction of knee flexors and extensors. All muscle MVC torques were significantly lower in aLOPD than controls (p <0.05). The weakest muscles were the hip extensors followed by hip abductors and abductors. Raw value of RTD was lower in aLOPD for the majority of muscles (p <0.05). No intergroup differences were reported for normalized RTD, VAL and neuromuscular fatigue (p-values> 0.05). Our study shows that maximal strength was the only neuromuscular characteristic affected in aLOPD with a proximal-distal intensity gradient. This suggests that the surviving muscle tissue of aLOPD is as functionally efficient as that of control individuals.

The Effect of Using Marathon Shoes or Track Spikes on Neuromuscular Fatigue caused by a Long-distance Track Training Session.

This study aims to compare the effect of the Nike ZoomX Dragonfly track spikes and the Nike ZoomX VaporflyNext% 2 marathon shoes on the fatigue manifestations present over and after a long-distance track training session. Thirteen highly trained athletes completed two training sessions (i. e., 9- and 3-minute time trials with complete recovery) with the aforementioned footwear models. The pace, ground contact time, and stride length were measured over the time trials, and maximal countermovement jumps were performed previously and after the training session. The results revealed that, although there was no significant interaction in the pace distribution (p≥0.072), athletes tend to be only able to increase the pace at the last lap with the marathon shoes (5.4 meters [-3.7 to 14.5 meters]) meanwhile with the track spikes it further decreased (-3.1 meters [-9.8 to 3.6 meters]). A reduced ground contact time over the session (p=0.025) and a tendency toward increasing stride length (p=0.09) in the last time trial were observed. The significant interaction on the countermovement jump height (p=0.023; Track spikes: -5.60%; Marathon shoes: 0.61%) also indicates that footwear influences the resulted allostatic load.

The impact of a 40-min nap on neuromuscular fatigue profile and recovery following the 5-m shuttle run test.

This study aims to investigate the impact of a 40-min nap opportunity on perceived recovery, exertion, and maximal voluntary isometric contraction (MVIC) following the 5-m shuttle run test (5SRT), after 1 night of normal sleep. In a randomised, counterbalanced, cross-over design, 17 trained men (mean [SD] age 20 [3] years, height 173 [6] cm, body mass 68 [6] kg) performed a 5SRT under two conditions: a 40-min nap opportunity and no-nap condition. After both conditions, electromyography signals during a 5-s isometric knee extension were recorded before and immediately after the 5SRT. Two electrical nerve stimulations at the femoral nerve were measured during and after the MVIC. Force, voluntary activation level, M-wave amplitudes, potentiated twitch, and electromyography signals (root mean square) were measured during each MVIC. Perceived exertion was recorded after each repetition of the test and perceived recovery was determined after the end of the MVIC. Compared to the no-nap condition, the 40-min nap resulted in significant enhancements in both the highest distance (p < 0.01, Δ = +7.6%) and total distance (p < 0.01, Δ = +7.5%). Before and after exercise, values for MVIC, root mean square, M-wave amplitudes, and voluntary activation level were improved after the 40-min nap opportunity compared to no-nap condition (all p ≤ 0.01). Values for perceived exertion and recovery were improved after the 40-min nap opportunity in comparison with no-nap condition (p ≤ 0.01). A 40-min nap opportunity improved repeated high-intensity short-term maximal performance, perceived recovery, associated neuromuscular responses, and reduced perceived fatigue. Therefore, our findings suggest that central and peripheral processes are involved in the improvements of 5SRT performance after napping.

Bioactive Properties, Bioavailability Profiles, and Clinical Evidence of the Potential Benefits of Black Pepper (Piper nigrum) and Red Pepper (Capsicum annum) against Diverse Metabolic Complications.

The consumption of food-derived products, including the regular intake of pepper, is increasingly evaluated for its potential benefits in protecting against diverse metabolic complications. The current study made use of prominent electronic databases including PubMed, Google Scholar, and Scopus to retrieve clinical evidence linking the intake of black and red pepper with the amelioration of metabolic complications. The findings summarize evidence supporting the beneficial effects of black pepper (Piper nigrum L.), including its active ingredient, piperine, in improving blood lipid profiles, including reducing circulating levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides in overweight and obese individuals. The intake of piperine was also linked with enhanced antioxidant and anti-inflammatory properties by increasing serum levels of superoxide dismutase while reducing those of malonaldehyde and C-reactive protein in individuals with metabolic syndrome. Evidence summarized in the current review also indicates that red pepper (Capsicum annum), together with its active ingredient, capsaicin, could promote energy expenditure, including limiting energy intake, which is likely to contribute to reduced fat mass in overweight and obese individuals. Emerging clinical evidence also indicates that pepper may be beneficial in alleviating complications linked with other chronic conditions, including osteoarthritis, oropharyngeal dysphagia, digestion, hemodialysis, and neuromuscular fatigue. Notably, the beneficial effects of pepper or its active ingredients appear to be more pronounced when used in combination with other bioactive compounds. The current review also covers essential information on the metabolism and bioavailability profiles of both pepper species and their main active ingredients, which are all necessary to understand their potential beneficial effects against metabolic diseases.

Examining Central Fatigue Pathways under Stress: Integrating Insights from Graph Theoretical Neural Modeling and Motor Cortex Excitability

Acute cognitive stress affects neuromuscular fatigue, but the underlying mechanisms are not well understood. The aim of this study was to identify the influence of stress on central fatigue and associated functional changes in the brain. Thirty participants, balanced by sex, performed intermittent elbow flexion contractions at 30% of their maximum strength till voluntary fatigue. Endurance time, strength loss, and voluntary activation loss rate were collected. Functional hemodynamic changes in the participants’ prefrontal and motor areas of the brain were also collected and used to calculate functional integration and segregation in the PFC and M1. Results show that stress had a facilitative effect on fatigability and the fatigue related decline in the functional integration and segregation of prefrontal cortex were not observed under stress. These findings demonstrate how the imposition of dual task demands in the workplace delays the perception of neuromuscular fatigue, thereby increasing the risk of injury.

Contemporary Practices of Strength and Conditioning Coaches in High-Level Male Ice Hockey: A Survey-Based Investigation.

Galati, D, Turner, AN, Bishop, C, and Maloney, SJ. Contemporary practices of strength and conditioning coaches in high-level male ice hockey: a survey-based investigation. J Strength Cond Res 37(11): 2241-2250, 2023-The aim of this study was to provide an updated view of the common practices, ideologies, education level, and professional environment of strength and conditioning (S&C) coaches in elite male ice hockey. Nineteen S&C coaches from professional, semiprofessional, and top-tier collegiate hockey teams in North America completed an anonymous online survey. This was composed of 10 sections: (a) background information; (b) technology use, (c) testing and periodization, (d) strength and power, (e) flexibility/mobility, (f) speed, (g) plyometrics, (h) aerobic and anaerobic conditioning, (i) rehabilitation, and (j) challenges and areas of improvement. Fixed-response questions were analyzed through frequency analyses. Thematic analyses were used to identify common themes from open-response questions. Strength and conditioning coaches had an average of 8 (±6.5) years of experience when they accepted their current role. The majority held a master's degree and S&C certification. Muscular power, linear speed, and body composition were the most frequently tested qualities. Neuromuscular fatigue was the most important consideration during the season and least important consideration during the off-season. Training frequencies for all physical capacities were lower during the season compared with the off-season. All S&Cs had access to technology, with wearables, with force plates identified as the most used devices. This information may be used by S&C coaches to compare working practices with those used by their peers and inform them of the likely requirements and skill sets needed for job applications. Educational institutions may use this information to align teaching to current practice and to inform future research.

Effects of playing three matches consecutive days in U16-U19 soccer players’ vertical jump, rate of perceived exertion and wellness

Objective: The objective of this study was to analyze the effect of playing several friendly matches on consecutive days affects neuromuscular fatigue evaluated with countermovement jump (CMJ), session rate of perceived effort (sRPE) and wellness in young male soccer players. Participants: Forty-four young male soccer players from Under 16 (U16) (N= 23; age: 14.70 ± 0.48 years) and U19 (N= 19; age: 17.63 ± 0.52 years) participated in this study. Method: The evaluation of CMJ and Wellness was carried out pre-and post-match. sRPE was recorded 30 minutes after the end of each game. Effect sizes (ES) were calculated using Cohen’s and statistical significance was set at p &lt; 0.05. Results: [U16 group]: differences between CMJ values after the last match and first (p &lt; 0.001) and second (p &lt; 0.001) matches. Differences in fatigue, soreness and stress (p&lt;0.05) were observed. [U19 group]: Differences in CMJ were observed when baseline values were compared with post-match values (p &lt; 0.001) and also when the last match were compared to the first (p &lt; 0.001) and the second (p &lt; 0.001) matches. We only noticed differences between the second and third matches were observed in sleep, stress and humor variables (p &lt; 0.05). Conclusion: In this scenario of competitive tournaments in young players, it is important for fitness coaches to propose practical solutions for reducing the accumulation of fatigue, since this could influence the state of well-being and physical performance of players, and the possible increase on injuries. Key words: Soccer, Muscle Fatigue, Questionarie, Evaluation, Intensity Workload.

Reduced running performance and greater perceived exertion, but similar post-exercise neuromuscular fatigue in tropical natives subjected to a 10 km self-paced run in a hot compared to a temperate environment.

Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C (p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race (p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented TCORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.

Submaximal fatiguing eccentric contractions of knee flexors alter leg extrapersonal representation

This study assessed the immediate and prolonged effects of eccentric-induced fatigue on position sense, utilizing position-pointing tasks, which had not been previously implemented for this purpose. Fifteen healthy adults underwent a fatiguing eccentric protocol that entailed sets of unilateral submaximal contractions of knee flexor muscles until reaching a 20% decrease in maximal isometric torque production. Evaluations of knee flexor neuromuscular function as well as position-pointing tasks at 40° and 70° of knee flexion were conducted prior to the fatiguing eccentric protocol, immediately after (POST), and 24 h after (POST24) exercise termination. To assess neuromuscular fatigue etiology, electrical myostimulations were administered during and after maximal voluntary isometric contractions. At POST, the voluntary activation level and evoked potentiated doublet amplitude at 100 Hz were significantly reduced. In addition, position-pointing errors exhibited a significant increase at POST regardless of the tested angle, with participants positioning the pointer in a more extended position compared to their hidden exercised limb. At POST24, neuromuscular function and position sense parameters had reverted to their baseline levels. The findings of this experiment demonstrate that position-pointing accuracy was impaired immediately after the fatiguing eccentric protocol, manifesting in the presence of both central and peripheral fatigue. As position-pointing accuracy relies heavily on extrapersonal representation of the body at the brain level, acute changes in exercised limb's extrapersonal representation might have resulted from central fatigue-related mechanisms altering the cognitive processes responsible for converting kinesthetic signals into extrapersonal coordinates.