Influences of modes and intensities of handgrip exercise on neuromuscular fatigue in young adults with cerebral palsy

Purpose Exercise is an essential component for musculoskeletal care. However, there is no clear guideline for upper limb exercise for wheelchair users with cerebral palsy (CP). This study explored the influences of different modes and intensities of handgrip exercise on neuromuscular fatigue in adults with CP. Methods A total of 14 adults diagnosed with CP completed four handgrip exercise protocols: isometric and dynamic handgrip exercises at 15% and 30% of maximal voluntary contraction. The isometric handgrip exercises lasted 30 s, while the dynamic handgrip exercises were performed at a frequency of 1 Hz for 60 s to ensure an equivalent exercise load. Muscle fatigue was quantified using the median frequency and spectral moment ratio (SMR) from electromyography (EMG) of four forearm muscles (flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), flexor carpi ulnaris (FCU), and extensor carpi ulnaris (ECU)). Two-way analysis of variance with repeated measures (ANOVA) was used to examine the interaction and main effects of the handgrip protocols. Results All four protocols were well tolerated in this sample, and no adverse events were reported. The results demonstrated a significant interaction effect for the median frequency of the ECR muscle (F=8.861, P = 0.013*, effect size: 0.446). All SMR conditions demonstrated a significant main effect handgrip intensity ( P of FDS 0.049*, ECR 0.026*, FCU 0.016*, and ECU 0.031*). Two median frequency conditions also indicated a significant main effect of the intensity ( P of FDS 0.071, ECR 0.068, FCU 0.006*, and ECU 0.012*). Conclusions The results demonstrated a significant main effect of the intensity factor of handgrip exercise on neuromuscular fatigue in adults with CP. The findings support the use of low-cost handgrip exercise of both isometric and dynamic modes for exercise training in adults with CP.