ECSS Paris 2023: OP-BM13
INTRODUCTION: Blood flow restriction (BFR) applied during exercise can reduce pain sensitivity (1) and increase corticospinal excitability (2) more than free-flow exercise, but it is unclear if BFR at rest (i.e., Ischaemic preconditioning [IPC]) can also reduce pain perception and alter neurophysiological responses during active contractions. Therefore, the aim of this study was to compare pain, neuromuscular and corticospinal responses to lower-limb ischaemic preconditioning with a sham protocol and control. METHODS: In a within-subjects design, thirteen healthy participants took part in three experimental visits after a familiarisation session of procedures. During experimental visits, participants underwent baseline measures of pressure pain threshold (PPT), maximum voluntary isometric force combined with peripheral nerve stimulation to determine voluntary activation using the interpolated twitch technique, and transcranial magnetic stimulation during submaximal isometric contractions to determine excitability and inhibition of the corticospinal pathway to the right quadricep. Subsequently, in a randomised order, participants received either unilateral IPC on the right leg (3 × 5 minutes occlusion at 105% limb occlusion pressure), a SHAM (3 × 1 minute occlusion at 105% limb occlusion pressure) or CONTROL (no occlusion). Baseline measures were then repeated at 10 minutes post-intervention. Pain perception was then assessed in response to a hypertonic saline injection into the vastus lateralis muscle. RESULTS: Results revealed that the right (occluded) leg PPT was 9% greater after IPC compared to SHAM (P = 0.027) and 15% greater compared to CONTROL (P < 0.001). PPTs were also 5% greater in the contralateral leg for IPC compared to SHAM (P = 0.011). Maximum voluntary force, voluntary activation and resting twitch force was not different between conditions (all P ≥ 0.133). Similarly, measures of corticospinal excitability and inhibition also revealed no significant differences between conditions (all P ≥ 0.240). Hypertonic saline evoked pain revealed a lower sensory component in IPC compared to SHAM (P = 0.006), but not CONTROL (P = 0.229), with no difference in reporting of intensity or duration between conditions (P ≥ 0.082). CONCLUSION: In conclusion, IPC may be an effective method to reduce pain sensitivity in local and remote sites but does not subsequently enhance neuromuscular function or alter neurophysiological measures of excitability or inhibition during low intensity contractions. Therefore, the mechanisms which IPC may improve exercise performance could be related to perceptual alterations, rather than neurophysiological changes (3). References: (1) Hughes & Patterson. (2020). Journal of Applied Physiology, 128(4), 914-924. (2) Brandner et al. (2015). Frontiers in human neuroscience, 9, 652. (3) O’Brien & Jacobs. (2022). Frontiers in Physiology, 13, 2508.
Read CV Ryan NorburyECSS Paris 2023: OP-BM13
INTRODUCTION: Dynamic stretching is recommended during warm-up routines (Opplert and Babault, 2018). Mechanisms remained unclear and are partly related to a warm-up effect (Vieira et al., 2021). One can question whether increasing the intensity of dynamic stretching could exacerbate any warm-up effect. The present study aimed to explore the effects of various loading conditions during active dynamic stretching on hamstring muscle strength and range of motion. METHODS: 12 physically active volunteers (3 women and 9 men) were included in this cross-over randomized study. Experimental sessions included a standardized comprehensive warm-up followed by 1 of the 3 experimental conditions: 1. unloaded dynamic stretch, 2. loaded dynamic stretch, and 3. control (no stretch). Dynamic stretching was 5 series of 15 repetitions at 1 Hz without or with an extra-load during the concentric phase (i.e., 20 or 40 N.m for women and men, respectively). Tests were performed before all sessions (Pre), after warm-up (Post-Warm), and after the experimental conditions (Post-Stretch). Tests included maximal voluntary isometric contractions of the hamstrings combined with the electromyographic activity (EMG) of biceps femoris (BF) and semitendinosus (ST) muscles and a passive maximal range of motion (ROM) test until maximal discomfort. Tests and experimental conditions were conducted on the right hamstrings on an isokinetic dynamometer. Two-way analysis of variances was used to compare conditions (unloaded vs. loaded stretch vs. control) and time (Pre vs. Post-Warm vs. Post-Stretch) effects. RESULTS: No significant condition x time interactions were obtained for the maximal torque (p=.456). A very slight increase in maximal torque was observed Post-Warm but did not reach the level of significance (p=.129). No interaction was observed for BF and ST EMG (p=.676 and p=.587, respectively). A significant time effect was obtained for ST EMG (p=.01) with lower values Post-Warm and Post-Stretch compared to Pre. No significant interaction was observed for the ROM (p=.134). A significant time effect revealed maximal ROM was significantly increased Post-Warm as compared to Pre (p=.001) and increased further Post-Stretch (p=.001). CONCLUSION: Active dynamic stretching whether performed unloaded or with an extra-load did not alter the force production capacity. Regardless of the extra-load, dynamic stretching increased the maximal ROM. Interestingly, dynamic stretch is not mandatory for ROM increases as it was already increased after the comprehensive warm-up. Thus, performing dynamic stretching within a warm-up routine remained questioned. REFERENCES: (1) Opplert J, Babault N. Sport Med, 2018, 48:299–325. (2) Vieira D, Opplert J, Babault N. Eur J Appl Physiol, 2021, 121,957-967.
Read CV Marion HitierECSS Paris 2023: OP-BM13
INTRODUCTION: Dynamic stretching (DS) is a widely recognized warm-up practice that induces acute muscle performance adaptations, potentially due to acute neural and/or mechanical changes [1]. However, the magnitude of the acute muscle performance improvements may vary according to DS variables, such as movement velocity [2]. Despite that, the effect of DS movement velocity mechanical contractile properties adaptations remains unclear. Therefore, this study aimed to investigate the effects of DS movement velocity on muscle contractile properties. METHODS: Fourteen healthy participants (11 men and 3 women) performed four experimental sessions in random order: 1) Control Session; 2) DS at slow velocity (50 beeps per minute - bpm; SLOWDS); 3) DS at moderate velocity (70 bpm; MODDS); 4) DS at fast velocity (90 bpm; FASTDS). The protocols were conducted on the plantar flexors of the right ankle, with participants lying laterally on the isokinetic machine. Each protocol consisted of 4 sets of 10 repetitions, with a 30-second rest interval between sets. The muscle contractile properties were assessed by Peak Twitch Torque (PTT) from tibial nerve stimulation for triceps surae contraction before (PRE), immediately after (POST), 7 (P07), and 14 (P14) minutes after each protocol. RESULTS: The mean and standard deviations of the PTT (N.m) in the PRE, POST, P07, and P14 were respectively: 1) 13.34 ± 3.45, 13.53 ± 3.59, 14.07 ± 3.95, and 13.94 ± 3.74 for the Control Session; 2) 13.05 ± 4.17, 15.70 ± 4.02, 14.53 ± 4.08, and 14.17 ± 3.85 for SLOWDS; 3) 13.24 ± 4.03, 16.01 ± 5.09, 14.73 ± 4.72, and 13.94 ± 4.48 for MODDS; 4) 13.71 ± 4.37, 16.19 ± 4.64, 14.75 ± 4.91, and 14.34 ± 4.56 for FASTDS. The Repeated Measures ANOVA reported no significant main effect for condition (p = 0.414) but a significant main effect for time (p = 0.001), and time x condition interaction (p = 0.002). Indeed, the improvements in PTT were greater in DS sessions than control session, as the post-hoc analyses reported that there was no significant effect in the PTT between the time points in the Control session (p > 0.05). However, as compared to the PRE, post-hoc analyses showed that PTT was greater in the POST and P07 after SLOWDS (p = 0.001 and 0.047, respectively) and MODDS (p = 0.001 and 0.045, respectively), and just in the POST after FASTDS (p = 0.001). CONCLUSION: Our study provided evidence that DS improves muscle contractile properties independently of movement velocity. Therefore, we suggested that DS could be performed without any preferred velocity during warm-up routines to induce beneficial contractile performance effects. REFERENCES: 1. Opplert J, Babault N. Sports Medicine. 2018;48:299–325. 2. Pamboris GM, Noorkoiv M, Baltzopoulos V, Gokalp H, Marzilger R, Mohagheghi AA. PLoS One. 2018;13:e0196724.
Read CV Denis VieiraECSS Paris 2023: OP-BM13