The HEPHAISTOS study: compliance and adherence with a novel orthotic device for calf muscle unloading

The present manuscript seeks to discuss methodological aspects regarding the application of the novel unloading orthosis 'HEPHAISTOS' that has been specifically developed to study physiological effects of muscular unloading without altering the impact of gravitational loading. The 'HEPHAISTOS' has been applied in an ambulatory clinical interventional study. During gait, the 'HEPHAISTOS' significantly reduces activation and force production of calf muscles while it completely retains body mass-related force on the tibia. Eleven healthy male subjects participated in the study and followed their normal everyday lives while wearing the orthosis. Several measurement sessions have been performed to investigate the time course of structural and functional adaptations during intervention and recovery. Follow-up measurements were performed for one year after the intervention. In consideration of the experiences of a unique ambulant unloading study, organizational and methodological recommendations are discussed in this manuscript. Activity monitoring data obtained with portable accelerometers reveal unchanged gait activities and good subject compliance throughout the intervention. Moreover, electromyography (EMG) and motion data investigating gait properties on reambulation day are illustrated. These data show that during the initial steps following removal of 'HEPHAISTOS', gait was significantly asynchronous indicating an acutely altered motor control in the unloaded lower leg muscles.