Trunk peak torque, muscle activation pattern and sudden loading compensation in adolescent athletes with back pain

OBJECTIVE: To evaluate trunk peak torque and muscle activation pattern during isokinetic and sudden trunk loading (STL) between adolescent athletes with/without back pain. METHODS: Nine adolescent athletes with back pain (BP) (m/f 2/7; 15.6 +/- 1.2 y; 177 +/- 9 cm; 67 +/- 13 kg; 22.5 +/- 9.8 h/week) and nine matched controls (m/f 2/7; 15.7 +/- 1.4 y; 177 +/- 12 cm; 65 +/- 9 kg; 16.5 +/- 8.0 h/week training) were included. Trunk strength in rotation and flexion/extension was assessed. Sudden trunk loading was measured during eccentric extension and rotation (30 degrees/s) with additional perturbation. Trunk muscle activity was measured using a 12 lead-EMG (electromyography). Main outcome measures were peak torque [Nm] and MVC normalized EMG-amplitudes (RMS [%]) for each muscle. Additionally, the mean EMG-RMS for four areas of the trunk was calculated (right/left ventral, right/left dorsal). RESULTS: Back pain showed lower trunk peak torque for all conditions in extension/flexion, but not for rotation. EMG amplitudes were increased for BP athletes with statistical significant differences for dorsal muscles in rotation and extension (p < 0.0042), not for ventral muscles in flexion. CONCLUSIONS: The evaluation of strength and muscle activity in isokinetic and sudden trunk loading presents altered trunk function in adolescent back pain athletes. Training interventions focusing on trunk strength and muscular activation pattern appears reasonable.