EMG activity is not elevated during exercise-related transient abdominal pain.

Skeletal muscle cramp has been proposed as the aetiology of exercise-related transient abdominal pain (ETAP). The aim of this study was to determine whether or not localised electromyographic (EMG) activity indicative of skeletal muscle cramp is elevated during ETAP. Surface EMG activity was quantified at the site of ETAP in 14 symptomatic individuals (ETAP group) while the pain was present and after the pain subsided. Additionally, measurements were taken in another 14 subjects (Comparison group) who performed the same experimental procedure but did not experience ETAP. In the ETAP group, localised EMG activity did not increase when the pain was present or decrease when the pain subsided. The level of EMG activity detected while the pain was present was indistinguishable from noise (0.20+/-0.18microV). No difference was observed between the ETAP and Comparison groups in the level of localised EMG activity (p=0.89) at any time. After the pain subsided in the ETAP group, EMG activity was recorded at the site of the pain while the subjects performed a diaphragm-dependent sniff manoeuvre (8.3+/-0.7microV) and a maximum voluntary contraction of the abdominal muscles (17.5+/-0.7microV). It was concluded that ETAP is not associated with elevated EMG activity, suggesting that the pain is not the result of muscle cramping.