Addition of aerobic physical activity to resistance exercise for hip osteoarthritis (PHOENIX): a randomised comparative effectiveness trial.

Exercise is already a standard recommendation for hip osteoarthritis, but it has been unclear whether adding aerobic activity to strength training gives people better results than strength training on its own. The PHOENIX trial compared these two approaches directly: one group did resistance exercise plus moderate-intensity aerobic activity, the other did resistance exercise alone, with both groups following a home programme and meeting a physiotherapist nine times over three months. Both groups improved in hip pain and physical function by three months, but the group that added aerobic activity did not do any better than the resistance-only group, and the difference between them was not statistically significant. This is interesting because it suggests the strength component may be doing most of the work, though the trial only tested moderate-intensity aerobic activity, so it cannot rule out benefit from more vigorous training such as interval-style exercise.

If you have hip osteoarthritis, you have probably been told that exercise helps, but there are many ways to exercise and it is not always clear which combination works best. This trial looked at whether adding aerobic activity, like walking or cycling at a moderate pace, to a strength training programme would ease hip pain and improve daily function more than strength training by itself. People in both groups, whether they did strength exercises alone or strength exercises plus aerobic activity, saw their pain and function improve over three months.

However, adding the aerobic activity did not lead to noticeably better results than doing strength training on its own. In other words, both approaches helped similarly, and the researchers did not find evidence that combining the two was more effective. It is worth understanding that this trial specifically tested moderate-intensity aerobic activity delivered alongside physiotherapist visits over three months.

It does not tell us whether more intense aerobic exercise, like interval training, might make a difference, and the improvements seen may partly reflect the overall attention and structured care both groups received, not just the specific exercises.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This trial addresses a practical question that comes up often in managing hip osteoarthritis: when structuring an exercise programme, does layering aerobic physical activity onto resistance training add meaningful symptomatic benefit beyond resistance exercise alone? PHOENIX randomised 196 participants with symptomatic hip osteoarthritis to either resistance exercise plus moderate-intensity aerobic activity (n=97) or resistance exercise only (n=99), with both arms receiving a home programme and nine physiotherapist consultations over three months. At three months, both groups improved on hip pain severity and WOMAC function scores, but the between-group differences were small and not statistically significant (pain mean difference 0.3, 95% CI -0.3 to 0.8; function mean difference -0.9, 95% CI -3.6 to 1.8). This indicates no statistically significant advantage to adding aerobic activity in this comparative effectiveness design, though it does not establish that aerobic activity is without value, only that at the intensity and dose tested it did not outperform resistance training alone.

Related adverse events were reported in both groups (24 with combined exercise, 31 with resistance only), none serious. The main limitation for practice is that only moderate-intensity aerobic activity was tested; the authors themselves note that higher-intensity interval training remains untested, so clinicians should not read this as closing the question of whether any aerobic component adds benefit, only that this particular moderate-intensity addition did not.