Motor fatigability during repetitive handgrip contractions in children with spina bifida: dynamometric and electromyographic evaluation

The objective was to compare handgrip pressure, fatigability, and muscle activation between typically developing children and those with spina bifida (SB). Sixty-eight typically developing children and 20 children with SB, aged 8 to 14 years old, performed a maximal handgrip test (three 5-sec repetitions, 20-sec intervals) and a handgrip fatigue test (with repetitions until reaching the maximum perceived effort score), using a bulb dynamometer. Simultaneously, surface electromyography of the finger flexor and extensor muscles was recorded. The values from both tests were compared within and between groups using multiple linear regression models. Children with SB presented lower handgrip pressure and similar fatigability compared to typically developing children, without differences between groups for muscle activation, time-to-fatigue and perceived effort. Children with SB were weaker, but they did not show increased fatigability during repeated handgrip contractions compared to controls. There is a mechanism that preserves handgrip force during fatigue testing in SB.