Exercise eases chronic back pain while the stress hormone rises

Chronic nonspecific low back pain is one of the most common reasons people reduce activity, and exercise is routinely recommended as part of managing it. Cortisol sits in the background of that story: it is widely treated as a stress marker, and many people assume that anything which raises it must be working against recovery. This review asked two linked questions: does exercise actually reduce pain in adults with chronic low back pain, and what happens to their circulating cortisol while it does? Measuring both together is what makes the result interesting.

The authors ran a sweep of all the studies on this, looking for randomised controlled trials that evaluated the effects of physical exercise on both pain perception and serum cortisol in adults with nonspecific chronic low back pain. Four trials met their criteria. Across those trials, 85 participants were assigned to exercise groups and 84 to control groups. The reviewers then pooled the pain and cortisol outcomes to estimate the overall effect of exercise programmes against control conditions.

Exercise reduced low back pain, with a pooled effect of 1.61 points below control, though the trials disagreed with each other substantially on the size of that benefit, with inconsistency of 72%. At the same time, cortisol levels rose in the exercise groups, a pooled increase of 1.05, with even greater disagreement between studies at 86% inconsistency. The authors conclude that exercise practised for six weeks or more reduced pain levels, and note that programmes in this population progress over periods longer than four weeks, while cortisol climbed rather than fell.

The pain result fits comfortably with the broader consensus that staying active helps chronic low back pain. The cortisol result is the complication: it cuts against the casual assumption that successful recovery should show up as a calmer stress hormone. With only four trials, high disagreement between them, and no data here on why cortisol rose or whether it settled afterwards, this is a question raised rather than answered. Larger trials tracking hormones alongside symptoms over longer periods would be needed to say what the rise means.

For anyone managing a long-standing bad back, the useful part is the direction of the pain result: structured exercise sustained for six weeks or more was associated with less pain across these trials. The cortisol finding is a reminder that a single hormone number is a poor scoreboard for whether training is helping. Pain went down while cortisol went up, so a raised reading after weeks of consistent exercise is not, on this evidence, a sign that the programme is backfiring.