Impact of ABLE 7-axes exoskeleton on upper limb kinematics during movements

The integration of exoskeletons in rehabilitation therapy requires understanding their impact on natural upper limb motion. This study therefore aimed to quantify the kinematic changes induced by the ABLE 7-axes exoskeleton. We hypothesize significant reductions in range of motion (ROM), movement velocity, and smoothness. To verify these hypotheses, fifteen healthy subjects were asked to perform a set of single-joint and multi-joint movements under three conditions: without exoskeleton (WE), with exoskeleton in human active mode (HA), and with exoskeleton in human passive mode (HP). Movements were captured using optoelectronic motion capture, analyzing their patterns, ROM, velocity, and smoothness. Results showed reductions of ROM between 10% and 76% across joints when using the exoskeleton, with shoulder internal/external rotation most affected (76% reduction) and a decrease of velocities by 29-80% in HA mode compared to unassisted movements. Multi-joint movements were less impacted than single-joint movements, while increased movement jerkiness was observed across all movements with the exoskeleton. These findings demonstrate that the ABLE 7-axes exoskeleton significantly impacts upper limb kinematics, particularly affecting shoulder motion, with implications for rehabilitation protocol design and exoskeleton development.