We compared the quantitative electromyographic activity of the elbow flexors during four exercises (forced inspiration, forced expiration, trunk flexion and attempted elbow flexion), following intercostal nerve transfer to the musculocutaneous nerve in 32 patients who had sustained root avulsion brachial plexus injuries. Quantitative electromyographic evaluation of the mean and maximum amplitude was repeated three times for each exercise. We found that mean and maximum elbow flexor activity was highest during trunk flexion, followed by attempted elbow flexion, forced inspiration and finally forced expiration. The difference between each group was significant (p < 0.001), with the exception of the difference between trunk flexion and attempted elbow flexion. Consequently, we recommend trunk flexion exercises to aid rehabilitation following intercostal nerve transfer.