![]() ![]() showed that upper limb pedaling exhibited a greater diversity of muscle patterns than lower limb pedaling, with greater inter-individual variability in the synergies identified. This observation held true even when analyzing both legs 8. showed that the structure of these synergies (coefficients and vectors) was little modified by the force required, the pedaling speed or the posture of the participants. In a study based on electromyographic analysis of 11 leg muscles during pedaling, Hug et al. Each synergy is described by (1) its activation coefficient which represents the relative contribution of the synergy to the overall muscle activity during one cycle (i.e., during a pedal revolution) (2) a muscle vector that specifies the relative weight of each muscle corresponding to these activation coefficients. This type of analysis supports the hypothesis that the central nervous system (CNS) generates a reduced number of patterns, as several muscles can be activated synchronously during the same phase of a cycle. Muscle coordination during pedaling has often been described in terms of synergies to provide a simplified view of motor patterns by reducing the dimensionality of motor behaviors 4, 5, 6. Both walking and pedaling results from the rhythmic coordinated and highly reproducible muscular activities that are centrally generated and many similarities have been put forward between the muscle activity patterns of walking and pedaling 2, 3. While the risk of falling makes it essential to take gravity into account during bipedal walking, this is less true during a pedaling movement thanks to the maintenance of the body by external supports other than the pedals (saddle, handlebars, etc.) which allow stabilization. This challenging task requires moving at various speeds while reducing the energy cost of the movement as much as possible 1. Gravity is one of the main constraints that applies to terrestrial locomotion. This research has contributed to a better understanding of how the human locomotor system responds to varying gravitational conditions, shedding light on the potential mechanisms underlying astronauts’ gait changes upon returning from space missions. This implies that the types of muscle fibers recruited during exercise in modified gravity are similar to those used in normogravity. Furthermore, electromyography analysis suggest that neuromuscular discharge frequencies were not affected by gravity changes. The findings strongly suggest that the CNS dynamically manages the shift in body weight by finely tuning muscular coordination, thereby ensuring the maintenance of a stable motor output. Despite these changes, the velocity profile of pedaling remained stable across gravity conditions. The timing of synergy activation was influenced by gravity, with a delay in activation observed in microgravity compared to other conditions. Muscular activities were characterized by two synergies representing pull and push phases of pedaling. Cadence increased with higher gravity and decreased with higher resistance levels. Results indicate that pedaling cadence adjusted naturally in response to both gravity and resistance changes. The goal was to identify potential changes in muscle synergies and activation strategies under different gravitational contexts. Participants pedaled on an ergometer with varying resistances. The experiment was conducted in parabolic flights, simulating microgravity, hypergravity (1.8 g), and normogravity conditions. It explores how pedaling behaviors, kinematics, and muscle activation patterns dynamically adapts to changes in gravity and resistance levels. This study investigates the impact of gravity on lower limb muscle coordination during pedaling. ![]()
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