Last updated May 15, 2018 at 10:10 am
A meta-analysis confirms that sometimes regular exercise does not bring about a health bonus.
The idea that regular physical exercise is good for health has been accorded a serious caveat following the confirmation of a paradox at its heart.
In a meta-analysis published in the British Journal of Sports Medicine, a team of researchers led by Pieter Coene from the VU University Medical Centre in the Netherlands finds that the benefits of physical exercise are significantly constrained by both context and gender.
When the physical exercise is done in the context of work, the researchers report, and when the workers in question are male, then it is associated with an 18 per cent increase in the risk of death from all causes.
No such association was found between physical work and women. Indeed, there was a slight improvement in mortality rates.
The study was not designed to interrogate the reasons for the gender difference, but doing so has now become a clear research target, and perhaps an urgent one.
The idea that regular physical exercise was good for health first emerged in the 1950s, after a UK study (among others) found that workers in the London public transport system who had physically demanding jobs were associated with a lower risk of mortality compared to their sedentary colleagues.
Fun v. quotidian necessity
Further studies confirmed the link between physical activities but tended to focus on exercise undertaken as leisure rather than work. Importantly, say Coene and colleagues, current guidelines recommending a minimum of 30 minutes of moderate intensity physical exercise do not distinguish between fun and quotidian necessity.
Using data from 17 studies, involving 193,696 participants, the researchers discovered that something has changed since the days when London transport workers drew a longevity benefit from their labours.
High-level workaday physical activity in men was associated with significantly higher mortality risk compared to those whose workload demanded little exertion. The distinction remained even after the researchers accounted for the health effects – positive and negative – of leisure-time activities.
What the researchers term the “health paradox” of occupational activity was first suggested in 2012, with a few subsequent case studies lending support to the idea.
However, the latest research, compiling data originally collected between 1960 and 2010, is the first confirm its existence statistically.
Coene and his team conclude that the results mean that henceforth “physical activity guidelines should differentiate between occupational and leisure time physical activity.”