The World Health Organization and many national governments issue guidelines as to how much exercise we should all do to stay healthy. Current exercise recommendations from the WHO for 18- to 64-year-olds include "at least 150 minutes of moderate-intensity aerobic physical activity throughout the week or at least 75 minutes of vigorous-intensity aerobic physical activity throughout the week or an equivalent combination of moderate- and vigorous-intensity activity." But do we understand exactly what counts as moderate or vigorous exercise? A recent study from Canadian researchers suggests that many people overrate how hard they work out or underestimate what moderate intensity exercise actually means.
The study from the Faculty of Health in York University, Toronto, was published last month in PLOS ONE. The objectives of this study were to determine whether individuals properly select light, moderate and vigorous intensity physical activity (PA) using the intensity descriptions in PA guidelines and determine if there are differences in estimation across sex, ethnicity, age and BMI classifications.
"Our study findings suggest that the majority of young and middle-aged to old adults underestimate the intensity of physical activity that is required to achieve health benefits," says Professor Jennifer Kuk, School of Kinesiology and Health Science. "This is worrisome both for personal and public health and well-being."
The 129 sedentary adult ages 18 to 64 recruited for the study, irrespective of their sex, ethnicity or BMI classifications, correctly estimated physical activities of light effort but underestimated moderate and vigorous effort, even after being given commonly used exercise intensity descriptors.
"We instructed volunteers to walk or jog on the treadmill at a speed which they felt corresponded to the 'light,' 'moderate' and 'vigorous' intensity descriptors used in the physical activity guide, yet they underestimated how hard they should be working to achieve moderate and vigorous intensity," lead researcher and graduate student Karissa Canning says.
Health Canada, as well as global physical activity guidelines using general terms to describe exercise intensity (determined by a given percentage of the maximum heart rate of an individual), recommend that adults ages 18 to 64 years should participate in two-and-a-half hours of moderate to vigorous physical activity per week for 10 minutes or longer at a stretch.
For adults to achieve a moderate intensity, their heart rates should be within the range of 64 to 76 per cent of their maximum heart rate and between 77 to 83 per cent for vigorous intensity, according to the Canadian and global physical activity guidelines.
Though there has been ample research that helped to develop the current guidelines, it is unclear whether individuals actually understand them as intended, notes Canning.
Physical activity guidelines published in Canada say that "Moderate-intensity physical activities will cause adults to sweat a little and to breathe harder." Activities suggested include brisk walking and bike riding. Vigorous-intensity physical activities will "cause adults to sweat and be 'out of breath'." Activities suggested include jogging and cross-country skiing.
The UK's National Health Service similarly says that "Moderate-intensity activity will raise your heart rate and make you breathe faster and feel warmer", and that "Vigorous-intensity aerobic activity means you're breathing hard and fast, and your heart rate has gone up quite a bit. If you're working at this level, you won't be able to say more than a few words without pausing for a breath."
All these guidelines are open to wide variation in interpretation. But the Canadian research suggests that even with those of us who try to exercise regularly, we may not be gaining as much benefit to health as we may think if our view of 'breathing more quickly' fails to measure up to the scientific measures of heart rate: unless, perhaps, we invest in one of the heart rate monitors so many companies are now trying to sell us!
CAB Abstracts and the Leisure Tourism Database give wide coverage to research on physical activity and health, available to subscribers. Among papers found on a quick search, O'Donovan et al. (2010) report on a review of UK guidelines for physical activity for health, and discuss how health professionals should encourage exercise in 'beginners' or 'conditioned individuals'. American recommendations are reported in Haskell et al. (2007). Brown et al. (2009) tracked evidence and associated recommendations and guidelines for optimal physical activity levels for health from the 1950s onwards.
Standage et al. (2008) consider the role of motivation in achieving moderate intensity exercise. Haskell et al. (2008) and Harrington et al. (2011) attempt to translate recommendations for moderate and intensive exercise into numbers of steps per day. In Australia, Jose et al. (2013) report on how young adults perceive health recommendations and what they regard as exercise intense enough to give benefits. Adherence to physical activity guidelines in older adults in the UK is examined by Jefferis et al. (2014).
Canning KL, Brown RE, Jamnik VK, Salmon A, Ardern CI, et al. (2014) Individuals Underestimate Moderate and Vigorous Intensity Physical Activity. PLoS ONE 9(5): e97927. doi:10.1371/journal.pone.0097927
Stand up, sit down, keep moving: turning circles in physical activity research? Brown, W. J.; Bauman, A. E.; Owen, N.; British Journal of Sports Medicine, 2009, 43, 2, pp 86-88 http://dx.doi.org/10.1136/bjsm.2008.055285
Step-based translation of physical activity guidelines in the Lower Mississippi Delta. Harrington, D. M.; Tudor-Locke, C.; Champagne, C. M.; Broyles, S. T.; Harsha, D. W.; Kennedy, B. M.; Johnson, W. D.; Allen, R.; Katzmarzyk, P. T.; Applied Physiology, Nutrition and Metabolism, 2011, 36, 4, pp 583-585, 11 ref. http://dx.doi.org/10.1139/h11-053
Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Haskell, W. L.; Lee IMin; Pate, R. R.; Powell, K. E.; Blair, S. N.; Franklin, B. A.; Macera, C. A.; Heath, G. W.; Thompson, P. D.; Bauman, A.; Circulation, 2007, 116, 9, pp 1081-1093 http://dx.doi.org/10.1161/CIRCULATIONAHA.107.185649
Adherence to physical activity guidelines in older adults, using objectively measured physical activity in a population-based study. Jefferis, B. J.; Sartini, C.; Lee, I. M.; Choi MinKyoung; Amuzu, A.; Gutierrez, C.; Casas, J. P.; Ash, S.; Lennnon, L. T.; Wannamethee, S. G.; Whincup, P. H.; BMC Public Health, 2014, 14, 382, pp (19 April 2014), 31 ref. doi:10.1186/1471-2458-14-382
Young adult perceptions of Australia's physical activity recommendations for adults. Jose, K. A.; Cleland, V. J.; Venn, A. J.; Hansen, E.; Health Promotion Journal of Australia, 2013, 24, 3, pp 199-205, 38 ref. doi: 10.1071/HE13041
The ABC of Physical Activity for Health: a consensus statement from the British Association of Sport and Exercise Sciences. O'Donovan, G.; Blazevich, A. J.; Boreham, C.; Cooper, A. R.; Crank, H.; Ekelund, U.; Fox, K. R.; Gately, P.; Giles-Corti, B.; Gill, J. M. R.; Hamer, M.; McDermott, I.; Murphy, M.; Mutrie, N.; Reilly, J. J.; Saxton, J. M.; Stamatakis, E.; Journal of Sports Sciences, 2010, 28, 6, pp 573-591, 156 ref. http://dx.doi.org/10.1080/02640411003671212
Does exercise motivation predict engagement in objectively assessed bouts of moderate-intensity exercise?: A self-determination theory perspective. Standage, M.; Sebire, S. J.; Loney, T.; Journal of Sport & Exercise Psychology, 2008, 30, 4, pp 337-352, 47 ref. http://www.ncbi.nlm.nih.gov/pubmed/18723896
Accelerometer steps/day translation of moderate-to-vigorous activity. Tudor-Locke, C.; Leonardi, C.; Johnson, W. D.; Katzmarzyk, P. T.; Church, T. S.; Preventive Medicine, 2011, 53, 1/2, pp 31-33, 12 ref. http://dx.doi.org/10.1016/j.ypmed.2011.01.014