The influence of the head-hips technique and transfer type on shoulder jerk

This study aimed to compare shoulder jerk magnitudes during level and floor transfers and evaluate the impact the head-hips technique on shoulder mechanics in full-time wheelchair users (WCUs). From an ergonomics perspective, elevated magnitudes in jerk are associated with overuse injuries. In other aspects of wheelchair biomechanics, such as propulsion kinematics, increased jerk at the shoulders during manual propulsion has been predictive of shoulder pain. Exploratorily, this study aimed to evaluate the influence of sex, weight, and physical activity on shoulder jerk.

Cross-sectional study. Setting: University-based laboratory in Champaign, USA. Participants: A convenient sample of full-time WCUs that could perform independent level and floor transfers were recruited for participation. Outcome Measures: Using Mann-Whitney U test, data was stratified based on transfer type and sex to determine if differences existed in shoulder jerk magnitudes across stratifications. Spearman's correlation was conducted to assess relationships between shoulder jerk, body weight, physical activity, and trunk flexion (i.e. head-hips technique).

Peak and average shoulder jerk magnitudes were significantly greater during floor transfers compared to level transfers. Trunk flexion was negatively correlated to peak shoulder jerk and weight during level transfers. Physical activity was negatively correlated to average shoulder jerk during level transfers. Females experienced reduced shoulder jerk compared to males during level transfers.

The use of head-hips technique and the higher levels of chronic physical activity may play a role in protecting the shoulders during transfer-related activities. Floor transfers may pose risks to shoulder health for WCUs that should be limited when possible. Clinicians should emphasize the importance of the head-hips technique and fitness for maintaining long-term shoulder health in WCUs.