Biomedical subjects

Nicolas Babault

Publications and source records attributed to Nicolas Babault.

5 recordsLinked to original sources

PubMed2026

Effect of knee and hip joint positions on passive stiffness of the rectus femoris and vastus lateralis in healthy individuals.

Passive muscle stiffness is a key determinant of musculoskeletal function and is influenced by structural components such as titin, connective tissue, and fascia. However, the effects of joint position, muscle depth, and sex on quadriceps passive stiffness remain unclear. To investigate the passive stiffness of the rectus femoris (RF) and vastus lateralis (VL) under different joint configurations, muscle depths, and between sexes using shear wave elastography (SWE). Thirty-six healthy young adults (18 men and 18 women) participated in this randomized crossover study. Passive stiffness was assessed in four positions of knee flexion: supine with 60° (SUP60), supine with 20° (SUP20), sitting with 60° (SIT60), and sitting with 20° (SIT20). SWE measurements (m/s) were obtained from 30 regions of interest (ROIs) per muscle, categorized into superficial, intermediate, and deep levels. Data were analyzed using Generalized Estimating Equations (GEE). A significant effect of position was observed, with higher stiffness values in the SUP60 condition for both RF and VL (p < 0.001). Superficial regions consistently exhibited greater stiffness compared to intermediate and deep regions across all positions (p < 0.001). Additionally, men demonstrated significantly higher stiffness values than women (p < 0.001). Significant interactions were found between position and muscle, as well as position and depth. Quadriceps passive stiffness is influenced by joint position, muscle depth, and sex. The SUP60 position elicits the highest stiffness, while superficial muscle regions are consistently stiffer. These findings highlight the non-uniform mechanical behavior of the quadriceps and may have implications for clinical assessment, rehabilitation, and exercise prescription. Clinical trial registration: This study was registered at Clinicaltrials.gov in June 06th, 2023. Register number NCT05905406. Link to access https//clinicaltrials.gov/study/NCT05905406.

Humans↗

PubMed2003

Neuromuscular differences between endurance-trained, power-trained, and sedentary subjects.

This study tested the hypothesis that neuromuscular characteristics of plantar flexor (PF) and knee extensor (KE) muscles explain differences of both performance in vertical jump and maximal voluntary isometric contraction (MVC) between endurance-trained (END, n = 9), power-trained (POW, n = 8), and sedentary subjects (SED, n = 8). Evoked twitch characteristics of PF and KE were measured. MVC, maximal voluntary activation (%VA) of KE, and performance in vertical jump were also measured. POW have higher maximal rate of twitch force development (MRFD) than SED and END for both PF (p < 0.05) and KE (p < 0.01); %VA and MVC were higher for POW and END than SED (p < 0.01). Higher performances were measured in vertical jump for POW compared with END and SED. Significant relationships were found between the squat jump performance and MRFD for both KE and PF (R = 0.71, p < 0.0001 and R = 0.55, p < 0.01, respectively). These findings show that low MRFD on lower limbs extensors does not limit expression of MVC on subjects with high levels of activation, whereas intrinsic muscular qualities have a direct influence on performance during the vertical jump.

Adult↗

PubMed2002

Effect of quadriceps femoris muscle length on neural activation during isometric and concentric contractions.

The effect of muscle length on neural drive (here termed "neural activation") was investigated from electromyographic activities and activation levels (twitch interpolation). The neural activation was measured in nine men during isometric and concentric (30 and 120 degrees /s) knee extensions for three muscle lengths (35, 55, and 75 degrees knee flexion, i.e., shortened, intermediate, and lengthened muscles, respectively). Long (76 degrees ), medium (56 degrees ), and short (36 degrees ) ranges of motion were used to investigate the effect of the duration of concentric contraction. Neural activation was found to depend on muscle length. Reducing the duration of contraction had no effect. Neural activation was higher with short muscle length during isometric contractions and was weaker for shortened than for intermediate and lengthened muscles performing 120 degrees /s concentric contractions. Muscle length had no effect on 30 degrees /s concentric neural activation. Peripheral mechanisms and discharge properties of the motoneurons could partly explain the observed differences in the muscle length effect. We thus conclude that muscle length has a predominant effect on neural activation that would modulate the angular velocity dependency.

Adult↗

PubMed2002

EMG activity and voluntary activation during knee-extensor concentric torque generation.

This study was designed to re-examine and compare the neural drive of the knee extensors during isokinetic concentric muscular actions by means of the twitch interpolation technique (activation level, AL) and surface electromyographic (EMG) recordings (root mean square, RMS). Torque, AL and RMS amplitudes of three knee extensors and one knee flexor were measured in nine subjects during maximal and sub-maximal voluntary contractions, performed under concentric (60 degrees.s(-1) and 120 degrees.s(-1); Con60 and Con120, respectively) and isometric (Iso) conditions. Mean (SD) maximal voluntary torque was significantly lower ( P<0.01) during concentric contractions [Con60: 208.6 (26.8) Nm and Con120: 184.7 (26.4) Nm] compared with isometric contractions [327.4 (52.0) Nm]. A significantly lower AL ( P<0.05) was recorded during Con60 [80.9 (8.8)%] compared with Iso [87.9 (5.1)%] and Con120 [88.2 (6.6)%] maximal contractions. Simultaneously, a lower knee extensor average RMS amplitudes (av.RMS) was measured during Con60 maximal contractions compared with Iso and Con120 maximal contractions. The antagonist biceps femoris RMS values were not different between maximal Iso, Con60 and Con120 contractions. During sub-maximal voluntary contractions, the RMS/torque relationships were similar whatever the muscle considered (vastus lateralis, vastus medialis or rectus femoris) and the AL/av.RMS relationships did not reveal any noticeable differences between each contractile condition. The results of the present study indicate that av.RMS and AL describe similarly the neural drive during maximal and sub-maximal efforts and indicate that during maximal voluntary efforts, neural drive is dependent upon concentric angular velocity (up to 120 degrees.s(-1)). Thus, our results suggest that when applying different contractile conditions, the torque output is regulated via complex interactions between intrinsic muscular properties and the neural drive.

Adult↗

PubMed2002

Is eccentric exercise-induced torque decrease contraction type dependent?

PURPOSE: This study was designed to determine whether torque decrease following an acute eccentric exercise is contraction type dependent. METHODS: Ten active males performed an exercise session consisting of five sets of ten maximal eccentric muscle actions of the elbow flexors. Before and immediately after the exercise, maximal voluntary eccentric (-60 degrees.s-1; Ecc60), isometric (0 degrees.s-1; Iso) and concentric (60 degrees.s-1; Con60 and 240 degrees.s-1; Con240) torque were measured. In order to distinguish central from peripheral factors involved in torque decrement, activation level (twitch interpolation technique), myoelectrical activity (RMS) of biceps brachii, as well as electrically evoked M-wave and peak twitch torque (Pt) were recorded. RESULTS: The eccentric exercise induced a significant torque reduction (P < 0.01), whatever the muscular contraction type [mean (SD): -22.3 (8.1)% for Ecc60; -20.8 (11.2)% for Iso; -18.5 (6.1)% for Con60 and -12.5 (8.9)% for Con240]. Relative torque decrement was however significantly less for Con240 compared with Ecc60, Iso, and Con60 (P < 0.05). Torque decreases were associated with a reduction of both M-wave amplitude (P < 0.01) and Pt (P < 0.001), probably related to an impairment of the excitation-contraction coupling. Concurrently, activation level was reduced (P < 0.01), therefore indicating the occurrence of central fatigue, as also confirmed by RMS decreases for all the conditions (P < 0.05), except Con240. DISCUSSION: An acute eccentric exercise induced a significant voluntary maximal torque reduction during eccentric, isometric, and concentric muscle actions ascribed to both peripheral and central failure of force production capacity. It can be concluded that eccentric exercise-induced torque decrease is not contraction type dependent.

Adult↗