Back extensor muscle fatigue in patients with lumbar disc herniation. Pre-operative and post-operative analysis of electromyography, endurance time and subjective factors.

We investigated back muscle fatigue and endurance in patients with lumbar disc herniation before and after surgery, and established the degree of association between perceived fatigue and objectively measured fatigue. Additionally, the relationships between muscle fatigue and endurance time on the one hand, and activity, participation, self-efficacy and health on the other, were investigated to clarify the grades of association between these factors. Forty-three consecutive patients with lumbar disc herniation were tested before surgery and 4 weeks after surgery. The protocol comprised an isometric endurance test (modified Sørensen's test) with concomitant measures of electromyography, and Borg ratings of pain and fatigue. To measure activity, participation, self-efficacy and health, the patients also filled in questionnaires. Results showed a post-operatively significant improvement in lumbar muscle fatigue expressed as a flatter L5 slope for the men. No significant improvement was found for endurance times or for Borg ratings. Endurance time correlated with questionnaire answers on physical activity, the Roland-Morris, the Oswestry, self-efficacy and some items of the SF-36 with correlation coefficients ranging from 0.52 to 0.91. The L5 slope correlated with the Roland-Morris, the Oswestry and some items of the SF-36 only in women with correlation coefficients between 0.53 and 0.77. We conclude that the effects of surgery reduced muscle fatigue for the men. There is an association between muscle fatigue and endurance with activity limitations, participation restrictions, self-efficacy and health in patients undergoing surgery for lumbar disc herniation.