Biomedical subjects

Annabelle Couillandre

Publications and source records attributed to Annabelle Couillandre.

2 recordsLinked to original sources

PubMed2003

How does the heel-off posture modify gait initiation parameter programming?

The authors studied the adjustment of the 2 distinct known expressions of gait velocity, the velocity of the center of gravity (CG) and the velocity of the center of foot pressure (CP) at the end of the 1st step in 2 experimental situations: natural gait initiation (the control situation, CS) and heel-off gait initiation (the test situation, TS). Gait was initiated by 7 healthy participants, from an erect spontaneous posture in the CS and from a posture with heels raised in the TS, on a force platform at 3 self-selected speed conditions. Biomechanical data from the force platform were collected in both experimental situations, and the authors used a particular gait analysis based on the differential method of Y. Brenière (2003) in order to approach velocity modulation by means of step length and frequency. Results showed that CG and CP velocities were adjusted differently during heel-off gait initiation than during natural gait initiation. CP velocity, as compared with CG velocity, was overestimated in TS. Results also established the relevance of the expression of step velocity by means of step length and frequency: The central nervous system, taking into account the specific postural constraints of each experimental situation, uses a reference value and a regulating parameter to modulate step velocity. Moreover, the contributions of 1st step length and frequency to the expression of step velocity in TS and CS were different. Thus, a specific locomotor behavior corresponds to a given experimental situation that is characterized by its own initial biomechanical constraints.

Adult↗

PubMed2002

Voluntary toe-walking gait initiation: electromyographical and biomechanical aspects.

This study was carried out to investigate the biomechanical constraints of toe-walking gait initiation and the associated changes in motor program compared to the well documented heel-toe walking gait initiation. Seven healthy subjects volunteered for this study. Gait was initiated on a force platform, at three self-selected speed conditions, from an erect spontaneous posture in the control situation (CS) and from a posture with heels raised in the test situation (TS). Surface electromyographical (EMG) activities of muscles soleus (Sol) and tibialis anterior (TA) were recorded on both limbs. We analysed the consequences of the heel-off posture on EMG patterns and biomechanical activities. Whatever the speed condition, the centre of foot pressure was initially located more ahead of the ankle axis in TS than in CS, with an increased Sol and TA EMG activity. The EMG pattern which expresses the motor program governing gait initiation was modified in TS in comparison to CS and induced adaptations of the anticipatory postural adjustments (APA) that precede toe-off of the stepping limb. A lengthening of the APA duration allowed the subjects in TS to reach a gait velocity similar to the one obtained in CS at the end of the anticipatory movements and also at the end of the first step. In TS, the velocity of the centre of gravity at time of toe-off covaried, as in CS, with CG velocity at the end of the first step, still resulting from TA muscular actions during the APA but also probably from other combined muscular actions.

Adaptation, Physiological↗