The results of treatment with short-wave diathermy were compared with those achieved by short-wave diathermy combined with back extension or lumbar isometric flexion exercises in 43 patients with back pain. Subjects were relatively young and normally engaged in sporting activities. Marginally more patients improved amongst those receiving extension exercises. Significant reduction of pain and increase of spinal flexion occurred with each treatment and the periods taken to resume work or sport were similar in each group. Neither exercise regime appeared to have a major influence on recovery. Isometric flexion exercises did not seem to be more beneficial for those with a prominent lumbar lordosis.