Neuromuscular and Perceptual Responses to Sub-Maximal Eccentric Cycling

ObjectiveEccentric (ECC) cycle-ergometers have recently become commercially-available, offering a novel method for rehabilitation training. Many studies have reported that ECC cycling enables the development of higher levels of muscular force at lower cardiorespiratory and metabolic loads, leading to greater force enhancements after a training period. However, fewer studies have focused on the specific perceptual and neuromuscular changes. As the two latter aspects are of major interest in clinical settings, this review aimed to present an overview of the current literature centered on the neuromuscular and perceptual responses to submaximal ECC cycling in comparison to concentric (CON) cycling.DesignNarrative review of the literature.ResultsAt a given mechanical workload, muscle activation is lower in ECC than in CON while the characteristics of the musculo-articular system (i.e., muscle-tendon unit, fascicle, and tendinous tissue length) are quite similar. At a given heart rate or oxygen consumption, ECC cycling training results in greater muscular hypertrophy and strength gains than CON cycling. On the contrary, CON cycling training seems to enhance more markers of muscle aerobic metabolism than ECC cycling performed at the same heart rate intensity. Data concerning perceptual responses, and neuromuscular mechanisms leading to a lower muscle activation (i.e., neural commands from cortex to muscular system) at a given mechanical workload are scarce.ConclusionEven though ECC cycling appears to be a very useful tool for rehabilitation purposes the perceptual and neural commands from cortex to muscular system during exercise need to be further studied

V̇ o 2peak is of great interest for clinical purposes

International audienc

Effects of Electrical Stimulation Pattern On Quadriceps Force Production and Fatigue

International audienceIntroduction: Mixed stimulation programs (MIX) that switch from constant frequency trains (CFT) to variable frequency trains have been proposed to offset the rapid fatigue induced by CFT during electrical stimulation. However, this has never been confirmed with long stimulation patterns, such as those used to evoke functional contractions. The purpose of this study was to test the hypothesis that MIX programs were less fatiguing than CFTs in strength training-like conditions (6-s contractions, 30-min). Methods: Thirteen healthy subjects underwent 2 sessions corresponding to MIX and CFT programs. Measurements included maximal voluntary isometric torque and torque evoked by each contraction. Results: There were greater decreases of voluntary and evoked torque (P<0.05) after CFT than MIX, and mean torque was 13 +/- 1% higher during the MIX session (P<0.05). Conclusions: These findings confirm that combining train types might be a useful strategy to offset rapid fatigue during electrical stimulation sessions with long-duration contractions. Muscle Nerve49: 760-763, 201

Kinematics and electromyographic activity of horse riders during various cross-country jumps in equestrian

International audienceThe objective of this study was to identify the key biomechanical patterns (functional muscles and kinematics) of amateur horse riders during various cross-country jumps in equestrian. Eleven riders first performed a control condition that corresponded to jumps over three different obstacles (log wall, brush and tree trunk) before jumping over the same three obstacles in a cross-country course. 3D Kinematics and electromyographic (EMG) activity was synchronously collected which included seven muscles of the riders back, lower and upper limbs. Maximum voluntary isometric strength of knee extensors was also measured before and immediately after the race to investigate potential fatigue. Our results showed similar EMG activity for the different obstacles. Whereas some kinematics alterations were observed between obstacles. Moreover, back movements alterations were recorded between the jumps of the cross-country as compared to the control condition. Finally, muscle strength was not altered after the race. In conclusion, our study indicates that upper and lower body muscles contributed to the realisation of various jumps during a cross-country and that the different configurations of the obstacles did not induced specific muscular and kinematic responses

In response to the article published by Fukaya et al., entitled: “Relationships between the center of pressure and the movements of the ankle and knee joints during the stance phase in patients with severe medial knee osteoarthritis”

Lettre à l'éditeur ("Knee", vol.24, no.2

Kinematics of obstacle clearance in the rat.

International audienceAlthough the rat has become the favourite animal model in preclinical research on locomotion, studies designed to assess the strategy used by rats to avoid obstacle are lacking. Using an optoelectronic 3D motion analysis system, we therefore, compared the step pattern, timing and length variables of locomotor cycles, trajectories and joint angles of limbs when rats step between and over obstacles (3 cm-high) fixed on a treadmill belt (25 cm/s). Motion in all four limbs of adult animals with an initial age of 11 weeks was serially recorded for a period of 10 weeks. The results showed that obstacle clearance is associated with the reorganization of the basic step pattern resulting in increased stride length of all limbs, increased duration of the swing phase of the hindlimbs only, and the appearance of two quadrupedal stance phases. They also revealed that the elevation of limbs above the obstacle not only involves flexion but also displacement of the corresponding girdles. Remarkably, the trajectory of the trailing forelimb to get over the obstacle is almost a mirror image of the trajectory of the leading forelimb. Lastly, all of the parameters measured remained stable over the observation period during which body weight gain reached 100g (one third of the initial body weight). In conclusion, our study may provide a basis for future studies aimed at understanding the neural pathways involved in pathologies associated with deficit/recovery of challenged locomotion in rats

Gait-dependent integration of neck muscle afferent input

We investigated the integration of neck muscle afferents during walking and running. Subjects walked or ran straight ahead, with or without an additional mass (20% of body weight). They performed all trials without vibration and with continuous vibration (80 Hz) applied to the lateral aspect of the neck. Vibration systematically caused body deviation toward the side opposite to the stimulation. The amplitude of vibration-induced body deviations was dramatically larger for walking (21.6 +/- 4.6 degrees ) than for running (8.0 +/- 2.5 degrees ). The additional mass marginally straightened body trajectory (average 5.6%), indicating that the gait-dependent effect of neck vibration cannot solely be attributed to differences in body inertia between walking and running. We concluded that neck muscle afferences are selectively gated according to the gait performe

Quantitative assessment of stereotyped and challenged locomotion after lesion of the striatum: a 3D kinematic study in rats.

BACKGROUND: Although the striatum is in position to regulate motor function, the role of the structure in locomotor behaviour is poorly understood. Therefore, a detailed analysis of locomotion- and obstacle avoidance-related parameters was performed after unilateral lesion of the striatum in rats. METHODS AND RESULTS: Using the three dimensional motion capture technology, kinematics of walking and clearing obstacles, head and body orientation were analyzed before and up to 60 days after the lesion. Recordings were performed in treadmill running rats with or without obstacles attached to the treadmill belt. The lesion, which was induced by the direct injection of the mitochondrial toxin malonate into the left caudoputamen resulted in the complete destruction of the dorsal striatum. During the first three days following the lesion, rats were unable to run on the treadmill. Thereafter, rats showed normal looking locomotion, yet the contralesional limbs exhibited changes in length and timing parameters, and were overflexed. Moreover, the head of lesioned rats was orientated towards the side of the lesion, and their postural vertical shifted towards the contralesional side. During obstructed running, the contralesional limbs when they were leading the crossing manoeuvre stepped on the obstacle rather than to overcome obstacle without touching it, yet more frequently with the forelimb than the hindlimb. Unsuccessful crossings appeared to be due to a paw placement farther away from the front of the obstacles, and not to an inappropriate limb elevation. Importantly, deficit in locomotor behaviour did not regress over the time. CONCLUSION: Our results argue that the striatum of one hemisphere controls kinematics of contralateral limbs during stereotyped locomotion and plays a prominent role in the selection of the right motor program so that these limbs successfully cross over obstacle