The physical activity health paradox

Physical activity is one of the best things an individual can do to improve their health and using this rationale conventional thinking may suggest that having a physically demanding occupation therefore contributes positively to health. It is not unusual for people who work in industries such as the building trades to think that the physical nature of their work means that they’re physically active. However it would seem, ‘work is not a workout’ and the physical activity paradox suggests occupational physical activity doesn’t really improve health and can potentially negatively impact on health. 

How can this be? The physical activity paradox is not well understood, however some of the reasons for its existence are discussed below: 

To improve cardiorespiratory fitness requires performance of physical activity at high intensity levels (60%-80% maximal aerobic capacity) and it would seem that even the most physically active workplaces or jobsites aren’t reaching the levels required to improve cardiorespiratory fitness. 

The intensity levels that workers in manual labour occupations typically work at are around the 30%-35% of maximal aerobic capacity. If you spend extended periods of time at this level it can elevate your resting heart rate for 24 hours and an elevated resting heart rate is a risk factor for cardiovascular disease. Occasionally elevating the heart to these levels for extended periods is perfectly normal, however if this is happening daily in the workplace there is potential for problems. 

There is often insufficient recovery time between work shifts on the jobsite. In many occupations there can be a requirement to be physically active for 7-12 hours a day, 5 days a week with limited opportunities for recovery. The term used in sports medicine to describe fatigue associated with ongoing levels of physical activity without rest is overtraining and it would seem that extended periods of fatigue as a result of overtraining can increase cardiovascular disease risk.  

So what can be done? 

Paradox number two, it would seem to manage some of these factors workers in physically demanding occupations need to undertake occasional workouts that push their physiology in to more uncomfortable territory to challenge the cardiorespiratory system and improve cardiorespiratory fitness. Whilst also engaging with strategies and practices that support recovery from the demands of a physically demanding occupation. 

Warwick Maloney KM

More reading: 
Holtermann, A, Krause, N. and van der Beek, A.J. (2018). Editorial The physical activity paradox: six reasons why occupational physical activity (OPA) does not confer the cardiovascular health benefits that leisure time physical activity does. British Journal of Sports Medicine 52(3), 149-150. https://bjsm.bmj.com/content/bjsports/52/3/149.full.pdf 

Holtermann, A. and Stamatakis, E. (2019). Editorial Do all daily metabolic equivalent task units (METs) bring the same health benefits? British Journal of Sports Medicine, 53(16), 991-992. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6691932/pdf/bjsports-2017-098693.pdf 

Two feet firm

With age the likelihood of a fall occurring increases, it also becomes more likely that a fall will result in a serious injury. As Australia’s population is ageing, there is likely to be an increase in the occurrence of falls and fall related injuries. Falls are the most common cause of injury in older people and can affect their independence, activity levels, social interactions and quality of life. Treatment of fall related injuries is also of great expense to Australian health services. 

Some common risk factors for a falls occurrence include; older age, falls history, poor balance, muscle weakness, impaired vision and taking multiple medications. These risks can be managed via a multifactorial approach that may include exercise interventions, improving vision, reviewing medication and modifying living environment. 

Exercise is a particularly good intervention for preventing falls as it can address multiple risk factors and has been shown to improve muscular strength, balance, balance confidence and walking speed. An exercise program focusing on preventing falls should see the participant undertaking regularly physical activity, incorporating balance challenges totaling at least two hours a week. Good balance exercises may involve controlled body movements while standing with the feet close together (or standing on one leg), with as little arm support as possible. The exercises should be safe, but challenging and should aid in developing postural and lower limb strength. Tai chi has been proven to be an effective form of exercise to aid in the prevention of falls in healthy older people. 

If you think you are at falls risk and requiring guidance speak with your GP. 

More reading: Australia and New Zealand Falls Prevention Society, http://www.anzfallsprevention.org/ 

*Disclaimer, this is a discussion and does not represent an exercise prescription, for exercise or injury advice seek an appropriately trained health professional.