ECSS Paris 2023: OP-BM24
INTRODUCTION: Inter-muscular coordination measures how muscle groups synchronize their activation to move effectively and efficiently. A recent method has been developed to assess inter-muscular cross-frequency interactions through surface electromyogram (sEMG) (Garcia-Retortillo et al., 2023). The examination of spectral components within different frequency bands in sEMG signals can provide information about motor unit recruitment and fiber-type contributions to muscle activation. Females exhibit greater muscle endurance due to their higher proportion of intermediate and Type I fibers compared to males, who typically present a higher proportion of Type II fast fibers. However, sex-related differences in the coordination of distinct fiber types across muscles have not yet been investigated. This study aimed to compare inter-muscular coordination during an endurance squat test performed until exhaustion in males and females. METHODS: Thirty-one sport science students (eleven males and twenty females) performed a bodyweight squat test until exhaustion. The squatting pace was controlled using a metronome (3:3 tempo; 3 sec. for eccentric and concentric phases, respectively). Simultaneous recordings of EMG signals from specific leg and back muscles were obtained during the squat test. The EMG recordings were initially decomposed into ten frequency bands [F1-F10], representing the activation of distinct muscle fiber types. Subsequently, inter-muscular coordination was quantified by pairwise coupling (cross-correlation C; amplitude-amplitude coupling) between the time series for all EMG spectral power frequency bands in each leg/back muscle. RESULTS: Overall, female adults exhibited higher coupling strength for all EMG frequency bands in leg and back muscles (CMEAN= 0.59, SD= 0.10) compared to male adults (CMEAN= 0.48, SD= 0.13; p < 0.05). Notably, these differences were more pronounced for intermediate [F4-F7] and high [F8-F10] EMG frequency bands, associated with the activation of type-II fast fibers (CMEAN= 0.48, SD=0.15 in males; CMEAN= 0.60, SD=0.12 in females), compared to the lowest frequency [F1-F3] EMG bands (CMEAN = 0.62, SD= 0.12 in males; CMEAN = 0.65, SD=0.11 in females). CONCLUSION: The uncovered higher degree of inter-muscular coordination in young female adults suggests greater neuromuscular efficiency during muscle endurance tasks, leading to a greater tolerance to fatigue. The increase in coordination among type-II fast fibers across muscles may serve as a compensatory mechanism to offset the reduced proportion of type-II fibers in females. This dynamic network approach to inter-muscular coordination has the potential to improve the understanding of sex-related differences during exercise. REFERENCES: 1. Garcia-Retortillo, S., Romero-Gómez, C., & Ivanov, P. C. (2023). Network of muscle fibers activation facilitates inter-muscular coordination, adapts to fatigue and reflects muscle function. Communications Biology, 891(6). https://doi.org/10.1038/s42003-023-05204-3
Read CV Óscar AbenzaECSS Paris 2023: OP-BM24
INTRODUCTION: Many athletes, such as those involved in weight category sports, opt to reduce their body mass temporarily by limiting fluid intake before competing with the goal of improving their performance. However, the negative consequences of decreased hydration levels on endurance performance have been widely acknowledged. Still, there is limited understanding regarding the impact of sub-optimal hydration on strength- and power-related function. In particular, it is unclear whether acute hypohydration - in the absence of fatigue and/ or hyperthermia - influences muscle mechanical properties and neuromuscular control – therefore, performance benefits may be achievable in strength- and/ or power- based activities, without the concomitant decrements commonly observed in endurance events. We aimed to investigate the impact of passively-induced hypohydration, via fluid restriction, on muscle stiffness and contraction speed, and on strength and power performance. METHODS: Twenty healthy active participants (12 male, 8 female) were assessed in a randomized cross-over design (EUH = euhydrated and HYPO = hypohydrated conditions). Participants underwent fluid restriction (0 L consumed) during the 14-hour period prior to HYPO testing; 500 mL of water was consumed the night before and on the morning of EUH testing. Hydration status was determined by urine osmolality. Unilateral knee extensor maximal voluntary isometric contraction (MVC) and bilateral countermovement jump (CMJ) were completed to determine lower-limb strength and power, respectively. Vastus lateralis and rectus femoris contractile mechanics were assessed using tensiomyography. Neural activation was estimated from electromyogram amplitude during submaximal isometric knee extension contraction to failure. Between condition differences were explored using paired sample Student’s t-test and effect sizes were described using Cohen’s d. RESULTS: Urine osmolality was analysed to verify hydration status (HYPO = 808.5 ± 84.9 mOsm/kg vs. EUH = 251.5 ± 137.5 mOsm/kg, p < 0.001, d = 3.47), participants’ body mass decreased by 1.3 ± 0.1% in HYPO vs. EUH. Hypohydration was associated with a 4.3% reduction in strength (MVC) (p = 0.045, d = 0.51) and a 1.5% reduction in peak power (CMJ) (p < 0.001, d = 1.08). Time to submaximal contraction failure was unaffected by hydration status (p = 0.163). Neural activation was not different between conditions (p = 0.408). Knee extensor muscle contractile mechanics were unaltered between conditions (p = 0.053-0.480). CONCLUSION: Strength and power were reduced by fluid restriction-induced hypohydration, but this reduction in function was not associated with impaired muscle contractile mechanics or neural activation, nor was time to contraction failure impacted. Our findings can be used to inform athletes and practitioners regarding the negative impact of hypohydration on performance in strength- and power- related activities, this may be particularly important for competitors in weight category sports.
Read CV Lewis MacgregorECSS Paris 2023: OP-BM24
INTRODUCTION: There is a need for a comprehensive investigation of the specific neuromuscular control dysfunctions linked to chronic ankle instability (CAI), particularly of the peroneal muscles (1). METHODS: This systematic review with meta-analysis synthesised the findings related to neuromuscular characteristics of the peroneal musculature, including corticospinal excitability, strength, force sense, and electromyographic measures, in individuals aged 18-45 with CAI and compared them to their healthy counterparts (2,3). Relevant papers were retrieved from electronic databases including EBSCOhost, Ovid, Web of Science, Scopus and Cochrane Library as well as Grey literature sources. Two reviewers assessed the eligibility and methodological quality of the included studies (4,5), and the random effects model and the standard mean difference with a 95% confidence interval were used to obtain pooled estimates of the overall effect size. RESULTS: The systematic review encompassed 42 studies out of 13,670 retrieved publications. Of these, 25 were eligible for meta-analysis. The meta-analyses revealed significantly reduced evertor force accuracy at 10% (d = 0.50 [0.06, 0.94], p = 0.03; I2 = 0%, p = 0.50) and 20% of MVIC (d = 1.14 [0.64, 1.64], p < 0.00001; I2 = 0%, p = 0.57), and decreased evertor force steadiness (d = 0.43 [-0.01, 0.87], p = 0.05; I2 = 0%, p = 0.91) at 10% of MVIC in individuals with CAI compared to the control group. The pooled findings also demonstrated significantly longer peroneus longus latency (d = 1.69 [0.92, 2.46], p < 0.0001; I2 = 30%, p = 0.23) in the CAI group than the control group during single leg landing inversion perturbation test under unexpected conditions. CONCLUSION: Individuals with CAI exhibited distinct deficiencies in evertor force accuracy, steadiness, and peroneus longus latency during landing tasks, suggesting a potential association between neuromuscular dysfunction in the peroneal muscles and the underlying mechanisms of CAI pathogenesis. This underscores the importance of specifically targeting and addressing peroneal neuromuscular deficits in the rehabilitation of individuals with CAI. REFERENCES: 1) Hertel and Corbett, J Athl Train, 2019 2) Page et al., Inter J Surgery, 2021 3) Higgins et al., Coch Hand for SRs Interv, 2019 4) Downs and Black, J Epidem & Comm Health, 1998 5) Moisan et al., Gait & posture, 2017
Read CV Abdulaziz AltunECSS Paris 2023: OP-BM24