Bernard Paquito, Université du Québec à Montréal (UQAM)

Physical activities of different intensities are all associated with better mental health. But too much physical activity seems to affect psychological well-being.

As a researcher on the issue of physical activity and mental health, I often hear people say, “The more physical activity I do, the better I feel”. This expression suggests that one must always do more physical activity to increase one’s psychological well-being. You may know people who have jobs that are very physically demanding or that train a lot and are not necessarily better off.

Likewise, others who spend several hours sitting underline that they do not feel well at the end of the day because of very little movement.

Therefore our group of researchers and students wondered whether there exists a linear relationship between the level of physical activity and psychological well-being and whether sedentary habits influenced this relationship (walking a lot, but sitting all day).

Physical activities of different intensities are all related to better mental health but too much physical activity seems to have the opposite effect

Surprise: The Curve Ends up Reversing Itself

Previous studies identified linear or inverted U-shaped relationships, but the biggest problem was using a questionnaire to measure the amount of physical activity. Considering, there is usually a significant difference between reported physical activity and that measured using a connected bracelet with an accelerometer.

We analyzed data from the [Canadian Health Measures Survey collected between 2007 and 2012], which is representative of more than 95% of Canadians.

More than 8,000 adults, who had assessed their level of mental health the week before, wore a bracelet (called an accelerometer) for 4 to 7 days. Thus, we were able to perform statistical analyzes that took into account variables such as sex, weight or tobacco consumption, influencing the link between daily physical activity and mental health.

Moderate to intense physical activity such as playing soccer or running for 1 to 50 minutes daily was gradually associated with better mental health. But beyond this time, people reported an increasingly degraded mental health.

For light physical activity (gardening or housework), it took longer than 6 hours for the positive effects to appear. Positive associations of this type of activity with mental health appear more marked when combined with moderate to high physical activity.

An inverted U relationship was identified between the number of steps per day and mental health. Thus, the relationship between the number of steps and good mental health is more and more obvious between 1 and 5000 steps, then it “stagnates” up to 16 000 and then reverses. In other words, every step, up to 5000, could count to improve one’s mental health.

Very Active and Very Sedentary = Mixed Results

Subsequently, we examined how the relationship between physical activity and mental health evolved with sedentary lifestyles. The same adult can be very active (30 minutes of walking daily, coupled with a weekly training and hockey game) and very sedentary if he or she is in an office job. Sedentary lifestyle includes activities in which we are awake, sitting or standing, and which result in very low energy expenditure.

When trying to understand how sedentary lifestyles affect the relationship, it seems that increased daily sedentary lifestyles may reduce the beneficial effects of physical activity on mental health.

The relationship between physical activity and mental health in Canadian adults is therefore not necessarily linear, contrary to what studies have shown so far.

It appears that adults could benefit from the first minutes of moderate to intense activity or from the first steps. On the other hand, the links between physical activity and good mental health seem more marked when daily sedentary lifestyles are low. Our results show that Pr Warburton’s key message “Move more and sit less for better health” could also apply to mental health.

Physical activities of different intensities are all related to better mental health but too much physical activity seems to have the opposite effect. It is important to emphasize that the study is transversal, so no temporal link can be identified. In other words, we can not know if it is because Canadians do physical activity that they report better mental health or whether it is their good mental health that makes it easier to be active on a daily basis.

Bernard Paquito, Professeur adjoint, Université du Québec à Montréal (UQAM)

This article has been translated from the original and is republished from The Conversation under a Creative Commons license. Read the original article.