By Christian Jarrett

It’s well-known that physical exercise is beneficial not just to physical health but also our mental health. Yet whereas most countries have detailed, evidence-backed guidelines on the type and intensity of exercise required for various physical health benefits, such guidelines do not yet exist for exercise and mood. This is partly due to a lack of necessary evidence. However, a new systematic review in The Journal of Psychology Interdisciplinary and Applied brings us usefully up-to-date on the current findings in this area, collating evidence from 38 relevant studies that examined the associations between exercise intensity, duration and modality and any effects on mood.

Before dipping into some of the key take-aways, an important distinction made in the review is between aerobic exercise and anaerobic. The former involves such things as walking, jogging and cycling and means exercising in such a way that your body is able to use oxygen to burn fat for energy. In contrast, anaerobic exercise – such as lifting heavy weights or sprinting – is of such vigorous intensity that your body does not have time to use oxygen to create energy and so instead it breaks down glucose in your blood or muscles.

Beginning first with the influence of exercise intensity on the mood benefits of aerobic exercise, the researchers, led by John Chan at Shenzhen University, found contradictory results from 19 relevant studies. Some favoured higher intensity, others low, while seven studies found that intensity made no difference to mood benefits.

In relation to the intensity of anaerobic exercise, however, the results were far clearer – the optimum for improving mood is moderate intensity, perhaps because low intensity is too dull while high intensity is too unpleasant.

Next, Chan’s team considered exercise duration. The main finding here was that 10 minutes often appears sufficient to achieve gains in mood (although one study found that 30 minutes was required to achieve feelings of increased vigour). Overall, there was little evidence that going beyond 30 minutes leads to any further gains in mood, which is good to know for anyone who struggles to find much time for exercise in their daily schedule.

Finally, the researchers considered studies that have compared the mood benefits of aerobic and anaerobic exercise (they noted that mindfulness-based physical exercise, such as Yoga and Thai-Chi, have also shown promise for boosting mood, but that there is too little evidence to draw any firm conclusions). The picture here was that the beneficial mood effects of aerobic exercise are less consistent than is found with anaerobic exercise, and anaerobic exercise appears especially to be more beneficial for beating stress and anxiety (the researchers suggested this may be because with many forms of anaerobic exercise, such as weight training, it is easier to see your progress, leading to more immediate, rewarding feelings of mastery; also anaerobic exercise is associated with increases in BDNF – brain-derived neurotrophic factor – which may help foster beneficial structural and functional changes in the brain).

These headline results from several decades of research come with some hefty caveats. The studies were mostly lab based, used different ways of measuring intensity, and they recruited extremely varied volunteers. You can easily imagine how study findings could differ a lot depending on people’s past experience with exercise, their age and health, and even their personality and interests.

This makes it difficult to extrapolate from the findings to our own lives. However, when reflecting on the optimum type of exercise for your own mood, the common sense message is probably to take into consideration your own fitness level and preferences, to find that sweet spot, such that the exercise is enough of a challenge without being unpleasant.

Perhaps the most important lesson from this review, though, is that we clearly need much more research into how different types and intensities of exercise affect our mood in real life, and how this varies according to our own characteristics. The sophistication and ubiquity of modern fitness trackers should open up exciting new opportunities for psychology research that can address these questions.

—Therapeutic Benefits of Physical Activity for Mood: A Systematic Review on the Effects of Exercise Intensity, Duration, and Modality

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Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest