Background

It's now well established that regular exercise has a positive impact on your physical health. For instance, research has shown that keeping active is beneficial in preventing heart disease and improves the outcome in diabetes. But did you know that there are mental health benefits too? ¹, ² Many studies have revealed that aerobic exercise (e.g. running, walking and swimming) is better than no treatment at all for mild to moderate depression -- and in some instances -- compares well with standard treatments like cognitive therapy and antidepressants.

Meeting recommendations for exercise

There has long been a debate as to how much exercise, and what kind, you need to do to get the physical and mental benefits. Currently, the Centers for Disease Control and Prevention and the American College of Sports Medicine advise 30 minutes or so of moderate intensity physical exercise daily (e.g. brisk walking). What's interesting is that you can still get the benefits if you split your half-hour into short bouts of activity throughout the day -- a boon for those of us who are so busy it's hard to set aside the full 30 minutes in one go.

Exercise and mood

Brief, but frequent, exercisers will be encouraged by a new study from Dr Cheryl Hansen and her team at North Arizona University in the US. They looked at how long a group of women students needed to exercise before they felt an improvement in their mood. The answer was -- not long at all. Ten minutes was sufficient to feel the benefit, mainly in terms of increased energy. It fits in well with other studies suggesting that a short, brisk walk is highly effective in releasing built-up tension and refreshing the mind. ³

Scope and procedure of the study

Fourteen female college students aged between 20 and 26 years took part in this study. Mood state before and after the study was assessed using the standard Profile of Mood States Inventory (POMS), the most common instrument for assessing mood in this kind of research. The POMS test is designed to measure: tension-anxiety, depression-dejection, anger-hostility, vigor-activity, fatigue-inertia and confusion-bewilderment. The study participants also had a health and fitness assessment.

Then, once a week for four weeks, the women did one of four activities: pedaling at a moderate rate on an exercise bike for either 10, 20 or 30 minutes, or sitting quietly for 30 minutes. They did this at the same time on the same day and out of contact with other participants. Each bicycle testing period was followed by a 10-minute cool-down -- using the bike at a lower work-rate. They used a heart-rate monitor to ensure they reached 60% of their target heart rate, the generally-accepted level for getting benefits from aerobic exercise. Once they'd cooled down, they took the POMS test again.

Results

The researchers wondered whether increasing the duration of exercise would result in increasing positivity of the participant's mood. It turned out not to be the case. With 10 minutes of exercise, the benefits were apparent and there was no further increase beyond that. In other words, all it took was just 10 minutes of exercise to improve mood.

But, of course, mood has many dimensions. Exercising produced no obvious improvements in tension, depression or anger -- even though the participants experienced an overall improvement in mood. However, the women had low scores in these areas to start with.

Where there was an increase in score was with regard to an improvement in their energy levels, along with a corresponding decrease in perceived fatigue. Furthermore, there was no relationship between a participant's fitness levels and the improvement of their mood. This suggests that the psychological benefits of brief bouts of exercise are accessible to all, regardless of fitness level.

Exercise and mood: what is the connection?

What is not clear is how the mental health benefits of exercise work. There are various theories. It's possible that exercise releases «feel good» chemicals in the brain -- that is, endorphins, the body's natural painkillers. Endorphins are the reason why soldiers in battle and sportsmen and women in the field don't always feel the pain of injury till later; often they feel just the excitement and euphoria of taking part and, perhaps, winning.

There may also be psychological reasons why exercise makes you feel good -- a sense of achievement and doing something positive to enhance your health. The feel-good factor in exercise can act as a reinforcement -- a session makes you feel better so you carry on doing it. It is hard for researchers to discover the actual mechanism of the benefits of exercise. Indeed, it's likely that these result from a combination of physical and psychological factors.

Comment

While this study is somewhat limited by the small number, gender and age group of participants, it does carry an encouraging message for the rest of us. Dr Hansen points out that the research literature already suggests that a moderate level of any type of aerobic exercise may offer positive mood effects; some research finds that weight lifting may also elevate mood.

It is yet to be determined whether 10 minutes of exercise would really be sufficient to improve energy levels in older people. Dr Hansen says the next step is, indeed, to see if the present research can be duplicated in both men and women, and in all age groups.

But for now, the take home message from this study is that regular physical activity has physical and psychological benefits that can contribute to quality of life, says Dr Hansen.