Globally, about two in three people will need major surgery at some point in their lives.

While preparing for a major operation, patients usually focus on the surgery itself. But recovery also places a substantial demand on the body.

Cardiorespiratory reserve is the body’s spare capacity to meet a sudden increase in demand for oxygen. Having enough is important as it helps people cope with the stress of surgery, inflammation and the effort of getting mobile again.

Using the time before surgery to improve a person’s physical fitness and readiness for recovery is called “prehabilitation”. This can include exercise, nutritional support, psychological preparation and making sure other medical conditions are under control.

Exercise such as walking is often the central component, but an important question remains: does it matter whether patients exercise under supervision, or can they achieve similar benefits at home on their own?

This research looked at studies involving adults preparing for colorectal, lung, cardiac, vascular and other major operations.

Aerobic exercise before surgery was associated with lower odds of complications. But this association was only seen in the supervised studies.

Supervised exercise was associated with about 40% lower odds of a post-operative complication. The association was stronger in analyses of high-intensity exercise, where the odds of complications were approximately halved compared with usual care.

The studies included different patient groups and combinations of exercise, nutrition and psychological support. The supervised programmes were more likely to include high-intensity exercise, while unsupervised studies were mostly lower-intensity activity.

Supervision may help in several ways. A clinician or exercise professional can assess whether exercise is safe, monitor symptoms and progressively increase the intensity.

There is also a behavioural component. Attending a supervised session creates structure and accountability. It may be easier to take challenging exercise when someone else is present to encourage.

For patients, the practical message is to ask the surgical or primary-care team whether prehabilitation is available and what type of exercise is appropriate. A programme should ideally include a clear exercise prescription, a way to monitor progress and advice about when to stop exercise.

Adapted from The Conversation: 29 September 2026.