Abstract
Background
Most sports and leisure activities involve repetitive movements in the upper limb, which are typically linked to pain and discomfort in the neck and shoulder area. Movement variability is generally expressed by changes in movement parameters from one movement to another and is a time-dependent feature of repetitive activities. The purpose of this study was to examine the effect of repeated movement induced fatigue on biomechanical coordination and variability in athletes with and without chronic shoulder pain (CSP).
Methods
In this controlled laboratory study, 24 elite male badminton players in two groups of athletes with (N = 12) and without (N = 12) CSP were recruited. Biomechanical and Electromyographical data were recorede while the athletes asked to perform repeating reaching task (RRT). Kinematic data was recorded every 30 seconds of the minutes of the repetitive pointing task (RPT). The kinematic and electromyography data were recorded at the first 30 seconds of "Fatigue-Terminal" (FT) and the last 30 seconds of "No-Fatigue" (NF) in the repetitive pointing task (RPT). Raw data was analyzed by using MATLAB code to extract the relevant coordination and movement variability data.
Results
different fatigue conditions (non-fatigue and terminal fatigue) led to significant kinematic changes during the performance of the repetitive pointing task. The CSP group exhibited smaller variability after fatigue than before fatigue. Moreover, altered coordination between trunk movement and shoulder elevation were recorded after fatigue. In addition, the variability of the shoulder muscles in both groups was significantly differ after fatigue (P < 0.05).
Conclusions
Results of our study show that both groups can accomplish the repetitive movement task but in doing so use different movement strategies. The CSP group’s movement strategy was only focused on controlling the shoulder joint, while that of the CON group was focused both on the shoulder joint and elbow joint. This suggests that chronic pain may have found a pain–minimizing strategy to accomplish the task