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Scientific Programme

Biomechanics & Motor control

CP-BM02 - Neuromuscular physiology

Date: 03.07.2024, Time: 16:30 - 17:30, Lecture room: Boisdale 1

Description

Chair TBA

Chair

TBA
TBA
TBA

ECSS Paris 2023: CP-BM02

Speaker A Maura Seynaeve

Speaker A

Maura Seynaeve
KU Leuven, Movement sciences
Belgium
"Impact of chronic sleep restriction on performance and neural control of sustained contractions: An EEG-EMG approach"

INTRODUCTION: In modern society insufficient sleep is increasingly prevalent, with one in three adults being chronically sleep-deprived. While the effect of this chronic sleep restriction (CSR) on cognitive functioning is well-established, the effects on motor control remain less clear. Some studies suggest a negative effect of insufficient sleep on tasks requiring higher sensorimotor control, such as balance tasks or submaximal contractions. However, we are still not able to pinpoint the exact underlying neural mechanisms behind this phenomenon. Therefore, this study aimed (i) to examine the effect of CSR on the ability to sustain submaximal plantarflexion (PF) and dorsiflexion (DF) contractions and (ii) to identify the underlying neural mechanisms using high-density electroencephalography (hdEEG) and electromyography (EMG). METHODS: Using actigraphy, we monitored the sleep pattern of healthy, young male participants for 15 consecutive nights. Motor control was evaluated after four different sleep periods: a baseline period consisting of three nights of habitual sleep (M1), a control period of four nights with normal sleep duration (M2), a period of CSR lasting four nights during which participants slept for only five hours per night (M3), and a recovery sleep period spanning three nights (M4). Motor control assessments consisted of a series of submaximal DF and PF contractions. More specifically, participants performed 6 DF and 6 PF contractions of one minute at 40% of the maximal voluntary contraction (MVC) and 1 submaximal DF and PF contraction until failure. During these contractions, brain activity was measured using hdEEG, and muscle activity of soleus, gastrocnemius, and tibialis anterior muscle using EMG. Complexity and variability of the torque and EMG signals, co-contraction ratios, time until failure, and power in different EEG bands were statistically analyzed using a repeated-measures ANOVA design. RESULTS: Data is currently being collected and analyzed. We hypothesize that participants ability to resist fatigue will be diminished after the period of CSR. Therefore, markers of fatigue will manifest earlier and to a larger extent. These fatigue markers include (i) a decrease in torque complexity based on detrended fluctuation analysis and entropy measures, (ii) an increase in torque variability, (iii) a decrease in median frequency of the EMG signal, (iv) increased muscle activity co-contraction ratios, (v) decreased time until failure and (vi) increase in EEG power bands. We anticipate that these markers will return to baseline levels following three nights of recovery sleep. CONCLUSION: A better understanding of the effect of CSR on motor control can offer important insights for clinicians, coaches, and athletes to improve performance, injury prevention programs, and overall health.

Read CV Maura Seynaeve

ECSS Paris 2023: CP-BM02

Speaker B Gael Guilhem

Speaker B

Gael Guilhem
French Institute of Sport (INSEP), Laboratory Sport, Expertise and Performance (EA 7370)
France
"Muscle activation within hamstring muscles during strengthening exercises: a systematic review"

INTRODUCTION: Hamstring muscles play a crucial role in lower limb movement with potential impact on performance, e. g. sprint running [1,2]. The distribution of electromyographic (EMG) activity within hamstrings is highly variable across individuals, influences motor performance and is affected by previous injury [3,4]. Therefore, having an exhaustive understanding of the distribution of muscle activity within hamstring muscles may be particularly useful to design individualized training programs. The aim of the present systematic review was to evaluate hamstring EMG activity during strengthening exercises. METHODS: Databases used were PubMed, Cochrane Library, and Web of Science with publication date before First January 2023. The references list from the studies included were checked. The search (PICO) strategy selected studies including healthy adults without lower extremity injury, reporting biceps femoris long heads (BFlh) and semitendinosus (ST) activation during hamstring strength exercises. No comparison was considered due to specific cross-sectional study designs. The root mean square (RMS) expressed as a percentage of maximal voluntary isometric contraction and activation ratio (BFlh/ST) were primary outcomes. Nine inclusion criteria and six exclusion criteria were checked by two distinct investigators. Hierarchical ascending classification was applied to cluster strengthening exercises according to BFlh and ST activation. RESULTS: The search strategy found 302 studies after checking for duplicates. After inclusion screening, 58 studies analysing 23 different exercises were considered. Muscle activations were highly variable across studies, ranging from 5 to 145% for BFlh and 3 to 220% for ST. Hierarchical ascending classification provided 3 different clusters. Cluster 1 exercises included exercises eliciting low activation levels (<40% MVC) preferentially oriented towards BLfh (leg raise, sit-up, leg press, lunge, squat, good morning, kettlebell swing). Cluster 2 included exercises eliciting high activation levels (>80% MVC) preferentially oriented towards BFlh (sprint, knee curl and leg curl). Custer 3 included exercises with moderate activation levels (40 to 60% MVC) oriented towards ST (sidewise jump, bridge, hip thrust, Sorenssen, Nordic hamstring, unilateral bridge, drop jump, forward jump, hip hinge, cable pulley, deadlift, glider and hip extension). CONCLUSION: A substantial amount of literature describes medial and lateral hamstring activation across various types of exercises. Significant variability in muscle activation is reported, likely due to differences in movement amplitude, exercise intensity (loading) and posture or execution variations. Independently from these factors, the present systematic review demonstrates that exercise modality can be used to modulate muscle activation in specific muscle heads. These findings can be used by coaches and practitioners to target BFlh or ST for athletic, prevention or rehabilitation purposes.

Read CV Gael Guilhem

ECSS Paris 2023: CP-BM02

Speaker C Jin Uchimaru

Speaker C

Jin Uchimaru
Sendai University, Sports Science
Japan
"Effects of electrical muscle stimulation and voluntary contraction combined with hypoxia on muscle strength and neuromuscular activity"

INTRODUCTION: Electrical muscle stimulation (EMS) also has been proved to be an alternative method or comparable therapy to traditional strength training by voluntary contractions [1]. Furthermore, both training combined with hypoxia increase muscle strength and induce hypertrophy compere to normoxia [2]. These types of training would be similar effects in skeletal muscle function [3] [4], but the fatigue process and/or muscle fibers’ activation seem to be different. Also, hypoxia would be more influence on muscle contractions, muscle fatigue and neuromuscular activations. To our knowledge, there is no research explained why the different mechanisms induce similar effects and what the specific difference is in these exercise modes. We evaluate the effects of voluntary contraction and EMS combined with hypoxia on strength and neuro-muscular activity. METHODS: Nine healthy and physically active male people participated in this study. Participants completed the four trials; 1) voluntary contraction with normoxia (N-VOL), 2) EMS with normoxia (N-EMS), 3) voluntary contraction with hypoxia (14.5% O2) (H-VOL) and 4) EMS with hypoxia (H-EMS) separated by one-week wash out period. VOL and EMS trial composed of 50 repetitions of 5 seconds tetanic contraction of the thigh. Also, the stimulation intensity with EMS was set to the maximum intensity that they could tolerate. Voluntary contraction was defined as the participants maximum effort. We measured the following measurements before and after trials: knee extent maximal isometric strength (MVC) and EMG activity of rectus femoris muscle (RF), vastus lateralis muscle (VL) and vastus medialis muscle (VM) during tetanic contraction of the thigh, and at 20%, 40%, 60%, 80% and 100%MVC. The root mean square (RMS) and integral electromyogram (iEMG) were analyzed from the EMG data. Additionally, blood lactate concentrations (BLa) were measured before and after trials. Two-way ANOVA with Tukey’s test were performed to identify any significant (P<0.05). RESULTS: MVC did not change after each trial. RMS and iEMG at maximum tetanic contraction decreased in N-EMS and increased in H-VOL and H-EMS. RMS and iEMG of VL and VM muscles at submaximal and maximal strength increased (4-10%) after the N-VOL and H-VOL trials. However, N-EMS trial decreased in RMS and iEMG of all muscles, and no change was observed in H-EMS. BLa was significantly increase after H-VOL (from 1.3 to 1.8 mmol/L), N-EMS (from 1.4 to 2.0 mmol/L) and H-EMS trials (from 1.2 to 2.1 mmol/L) (P<0.05). CONCLUSION: From these results, our main findings were as follows: 1) the decrease in EMG activity after EMS may be affected by force production and muscle fatigue with blood lactate accumulation, 2) exercise in a hypoxic environment may induce neuro-muscular activation to maintain force production, regardless of voluntary and involuntary contractions such as EMS.

Read CV Jin Uchimaru

ECSS Paris 2023: CP-BM02