ECSS Paris 2023: OP-PN01
INTRODUCTION: In sport climbing, high-load resistance training (HLRT) is traditionally used for performance enhancement, with an important part of it dedicated to improving finger specific isometric flexor digitorum (FD) muscle strength and endurance. However, specific FD training at high intensity can be traumatic, often leading to injuries in climbers. Low-load blood-flow resistance training (LLBFR) has been shown to be a promising substitute to HLRT for promoting strength and endurance while reducing mechanical stress on tissues (e.g. lower training loads). However, the physiological responses associated with LLBFR to climbing-specific exercises are poorly understood. Therefore, the aims of the study were to i) examine acute and chronic muscular responses to LLBFR during climbing specific FD training, and ii) compare these responses to HLRT. METHODS: An acute and a chronic phase were completed. The acute phase involved 15 advanced to elite climbers who conducted two bouts of three sets of FD intermittent exercise on a hangboard under two experimental conditions in a randomized order: 1) HLRT (~70% maximal voluntary contraction, MVC); 2) LLBFR (~40% MVC with a cuff pressure of 60% of the individual limb occlusion pressure). Finger flexors muscle oxygenation was measured throughout exercise by near-infrared spectroscopy; muscle fatigue was quantified as MVC decrement 1, 5 and 15 min post exercise. Perceived discomfort, effort, and finger pain were assessed at the end of each set. Moreover, 36 advanced to elite climbers participated in the chronic study phase and were randomized to 3 groups: LLBFR, HLRT and a control group (CON). Participants of the LLBFR and HLRT groups conducted the specific training session presented in the acute study phase twice a week over 5 weeks, while the CON group maintained their usual climbing routine. FD MVC, endurance and oxygenation and brachial artery blood flow during contraction were measured before and after the training protocol. RESULTS: The acute study phase demonstrated higher muscle fatigue in LLBFR than in HLRT 1 min post exercise (25±8% vs 19±7% of MVC loss, p=0.016), which recovered faster, leading to similar fatigue between the two modalities 15 min post exercise. LLBFR led to greater muscle deoxyhemoglobin values (+20±25%, d=0.9), greater upper-limb discomfort during inter-sets recoveries, and less finger pain during exercise. The chronic phase showed that LLBFR and HLRT induced similar improvements in FD MVC (+9±8%, d=1.0 and +13±11%, d=1.2, respectively), and endurance (+22±15%, d=1.7 and +24±21%, d=1.2, respectively). CONCLUSION: Climbing specific LLBFR FD training led to comparable chronic muscular adaptations to HLRT, while reducing exercise intensity and FD pain. These chronic adaptations may be due to the repetitive acute higher metabolic stress during LLBFR sessions, illustrated by the higher muscle fatigue and greater deoxygenation, despite lower mechanical stress.
Read CV Titouan PerrinECSS Paris 2023: OP-PN01
INTRODUCTION: Performance fatigability alters neuromuscular function in a task-dependent manner [1,2]. In isometric conditions, the motor-unit (MU) discharge behavior appeared to be adjusted differently when performing intermittent or sustained contractions [3]. After knee-extension isokinetic exercise at slow speed, MU discharge rate increased to overcome peripheral impairments [4]. During daily life, dynamic tasks at various speed are usually performed and it remains unclear how high-velocity contractions affect MU discharge characteristics. This study aimed to investigate the MU behavior immediately after a maximum-velocity isotonic fatiguing exercise. METHODS: Healthy young participants (n=16, 4 females) underwent a fatiguing task consisting in 80 maximal-velocity isotonic contractions (1 every 3 s) at 40% of the maximal voluntary isometric contraction (MVIC) torque [5]. Power output was quantified at the initial and final phases of the exercise. MVIC with voluntary activation (VA) and potentiated resting twitch (St) were assessed, through femoral nerve stimulation, before (PRE) and immediately after (POST) the exercise. Vastus lateralis high-density electromyography signals were recorded during isometric contractions at 25% of MVIC (10s ramp + 10s plateau) both in PRE and POST. MU spike trains were decomposed and edited. Recruitment threshold (RT) of each MU was normalized by the MVIC PRE to categorize MUs into early-recruited (0-12.5% MVIC) and late-recruited (LR; 12.5-25.0% MVIC) populations. Mean discharge rate (DR) was analyzed during recruitment (first 5 spikes) [6] and plateau phase (10s) of each MU. The coefficient of variation (CoV) of force was calculated during the plateau at target force. RESULTS: Power output started from 247±81W and it decreased by 36±18%. MVIC torque declined from 168.1±39.4Nm to 110.9±31.5Nm (p<0.001). VA and St torque decreased in POST (all p<0.04). Global EMG amplitude increased after the fatiguing task (p=0.02). During ramps, RT did not change (24.9±6.1Nm; p>0.05). Mean DR increased during recruitment phase (7.9±1.7 to 8.6±2.6pps in POST; p=0.007) but not during plateau. Notably, only the LR MUs exhibited increased DR both at recruitment (7.8±1.5 to 8.9±2.9pps; p=0.002) and plateau phases (10.0±1.6 to 10.8±2.5pps; p=0.02). CoV of force increased from 2.6±0.9% (PRE) to 3.8±2.4% (POST; p=0.03). CONCLUSION: High-velocity fatiguing task induced loss of muscle force and power due to impairments in both voluntary activation and muscle contractile proprieties. Following the maximal-velocity fatiguing task, mean motor unit recruitment discharge rate increased while only late-recruited MUs showed a higher discharge rate in the plateau phase. Thus, in fatiguing state, impaired central motor drive and excitation-contraction coupling affect motor unit behavior to maintain absolute force output References: 1. Adam & De Luca, 2005; 2. Taylor et al., 2016; 3.Valencic et al., 2024; 4. Hirono et al., 2022; 5. Sundberg et al., 2018; 6. Del Vecchio et al., 2020
Read CV Marco GattiECSS Paris 2023: OP-PN01
INTRODUCTION: Objectively determined physical and mental fatigue has detrimental effects on cognition. However, subjective perception of fatigue can vary significantly from person to person. The aim of this study was to determine an extent to which subjectively reported parameters (SRPs) of physical and mental fatigue can be used to assess cognitive performance. METHODS: 39 male and 4 female amateur cyclists (38.8±8.7 y/o, BMI: 25.2±2.8 kg/m2) who completed an ultra-endurance cycling race in under 24-hours completed cognitive function test battery (Stroop test (ST), Finger tapping test (FTT)) pre-race, post-race and ~20h in the recovery period. Additionally, following SRPs were evaluated: sleep hours, sleep quality, mental fatigue, physical fatigue, physical strength, stress levels during the previous day, effort to answer the questions in a scale from 1 to 10. Changes between the timepoints were assessed by one-way repeated measures ANOVA or Friedman test. The association between cognitive function test variables that changed significantly and SRPs was analysed using mixed model regressions. RESULTS: Significant change in all SRPs except for stress levels during the previous day was observed from pre- to post-race (p<.001). While in recovery sleep quality, mental fatigue and effort to answer the questions had returned to pre-race levels, there was a significant increase in sleep hours, physical fatigue and reduced physical strength reported. The increase in muscle pain in post-race (from 2 (1;2) to 5 (4;8) was sustained in recovery (5 (3;7), p<.001). The post-race ST average time for correct reaction of all 3 stages increased: by 22, 35 and 68 ms (p<.001), correspondingly. Stage 1 and 3 values returned to baseline in recovery, yet stage 2 showed an improvement compared to baseline (from 651 (88) to 630 (89) ms, p<.001). Performance in ST stage 2 was associated with a better sleep quality, reducing the average time for correct reactions by 10.10 ms (p<.001) for a point increase. In stage 3, average time for correct reactions was increased by stress levels during the previous day by 12.80 ms (p=.015) and decreased physical strength by 12.70 ms (p=0.006) per point. FTT showed impaired performance of the non-dominant hand in post-race; average number of taps decreased from 54.7 (6.4) to 52.0 (6.9), p<.001, average interval between taps increased from 189.0 (22.5) to 202.0 (27.1) ms, p<.001 and returned to baseline in recovery. Higher effort to answer questions was associated with a diminished performance in the FTT for non-dominant hand (p=0.028). CONCLUSION: A single SRP cannot estimate the changes in cognition, but perceived effort to answer the questions is associated with fine motor performance measured by FTT, and sleep quality, stress levels and physical strength are associated with executive functions measured by ST.
Read CV Diana LismaneECSS Paris 2023: OP-PN01