The Effect of Crank Resistance on Arm Configuration and Muscle Activation Variances in Arm Cycling Movements

Abstract

Arm cycling on an ergometer is common in sports training and rehabilitation protocols. The hand movement is constrained along a circular path, and the user is working against a resistance, maintaining a cadence. Even if the desired hand trajectory is given, there is the flexibility to choose patterns of joint coordination and muscle activation, given the kinematic redundancy of the upper limb. With changing external load, motor noise and changing joint stiffness may affect the pose of the arm even though the endpoint trajectory is unchanged. The objective of this study was to examine how the crank resistance influences the variances of joint configuration and muscle activation. Fifteen healthy participants performed arm cranking on an arm-cycle ergometer both unimanually and bimanually with a cadence of 60 rpm against three crank resistances. Joint configuration was represented in a 3-dimensional joint space defined by inter-segmental joint angles, while muscle activation in a 4-dimensional "muscle activation space" defined by EMGs of 4 arm muscles. Joint configuration variance in the course of arm cranking was not affected by crank resistance, whereas muscle activation variance was proportional to the square of muscle activation. The shape of the variance time profiles for both joint configuration and muscle activation was not affected by crank resistance. Contrary to the prevailing assumption that an increased motor noise would affect the variance of auxiliary movements, the influence of noise doesn’t appear at the joint configuration level even when the system is redundant. Our results suggest the separation of kinematic- and force-control, via mechanisms that are compensating for dynamic nonlinearities. Arm cranking may be suitable when the aim is to perform training under different load conditions, preserving stable and secure control of joint movements and muscle activations.

Neuromechanical Differences between Pronated and Supinated Forearm Positions during Upper-Body Wingate Tests

“…The neurophysiological and biomechanical responses of arm-cycling have been of interest in recent years due to its affect on performance improvement and injury prevention (Kraaijenbrink et al, 2021). During arm-cycling, variations such as forearm position (Lockyer et al, 2021a), cycling direction (Lockyer et al, 2021a;Nippard et al, 2020), intensity (Chaytor et al, 2020;Forman et al, 2016;Mravcsik et al, 2021), and work volume (Mravcsik et al, 2021) have been shown to modulate corticospinal excitability which may impact the power output, crank-pedal force production and neuromuscular activity (Chaytor et al, 2020;Lockyer et al, 2023). To the best of our knowledge, no comparison has been performed on arm-cycling with regards to forearm position and their influence on power output, crank-pedal forces and bilateral muscle activity.…”