Article Page
Vigorous Versus Moderate-Intensity Exercise
Len Kravitz, Ph.D.

Study Reviewed:
Swain, D.P. and Franklin, B.A. (2006). Comparison of cardioprotective benefits of vigorous versus moderate intensity aerobic exercise. American Journal of Cardiology, 97: 141-147.

Much emphasis in exercise design now includes attempts at involving students and clients in structured exercise programs as well as spontaneous physical activity, which includes standing, walking and fidgeting (see Kravitz, L. (2006). A NEAT “new” strategy for weight control. IDEA Fitness Journal, 3(4), 24-25). A current escalating controversy in the fitness industry is whether there are greater health-related benefits to performing more vigorous exercise versus moderate intensity exercise. In other words, once clients start getting active and fit, should the personal trainer and fitness professional encourage the client to attain even higher levels of fitness? This article will initially describe the up-to-date health benefits of physical activity and then bring to light the results of a recent review article on the cardioprotective benefits of vigorous versus moderate intensity aerobic exercise.

The health benefits of physical activity: Current proof
The research on the positive health benefits of physical activity attained a meaningful point in fitness/health history with the evidence presented by Paffenbarger and colleagues in the 1970’s, and from their follow-up analyses of a large population of subjects, primarily men. Similar follow-up health-benefit studies by other researchers have assessed the relative risk of death from any cause to include both women and men. A recent review by Warburton, Nicol and Bredin (2006) examines the data of the benefits of regular physical activity, which is partially summarized below.

With both men and women, there is a 20%-35% relative risk reduction to all causes of death, including cardiovascular disease, for those who do the most physical activity (Warburton, Nicol & Bredin, 2006). An increase in energy expenditure to about 1000 kilocalories of physical activity a week (this is equivalent to walking one hour on five days of the week) is associated with a mortality benefit of about 20%. From a different perspective, Warburton and colleagues note that physically inactive middle-aged women (who engage in less then 60 minutes of exercise per week) are at a 52% increase to all causes of mortality. The scientists further state that persons who are fit, yet have one or more risk factors to cardiovascular disease (such as hypertension, chronic obstructive pulmonary disease, diabetes, smoking, elevated BMI, and high cholesterol levels) are also at a lower risk of premature death then their sedentary counterparts. In addition, it appears that there is a graded INDIRECT (or inverse) effect for those engaging in more (e.g. accumulating more time/week) physical activity and their associated risk reduction of death from all causes of mortality. Thus, to summarize Warburton et al., there is indisputable evidence of the positive effectiveness of regular physical activity in the primary and secondary prevention of chronic diseases such as diabetes, hypertension, obesity, cardiovascular disease, some forms of cancer, depression and osteoporosis. And, there clearly appears to be a linear association with increased physical activity and improved health status.

So, which is better for cardioprotective benefits: Vigorous or moderate intensity aerobic exercise.
To answer this difficult question on vigorous versus moderate intensity aerobic exercise, Swain and Franklin (2006) reviewed epidemiologic studies (studies that report incidence or prevalence data) that assessed the benefits of physical activity as well as clinical investigations (studies that test and analyze results) that actually trained subjects at different intensities. They note that they included only studies where energy expenditure was controlled for in the research design. This was important because vigorous exercise elicits a greater energy expenditure then moderate exercise, and thus controlling for energy expenditure allows for the optimal way to assess the effects of aerobic exercise intensity. Also, in reviewing all the studies Swain and Franklin report that identifying specific training levels for vigorous versus moderate intensity was somewhat imprecise due to the fact that studies reported intensities in some of the following ways: %VO2max (vigorous= &Mac179;60% of VO2max; moderate= < 60% VO2max), METS (vigorous= &Mac179;6 METS; moderate= <6 METS), walking/running speeds (various), and heart rate reserve (HHR) (vigorous= &Mac179;60% HRR; moderate= <60% HRR).

Regardless of the variation of methods used to report exercise intensities, a consistent pattern appeared with the findings. All of the epidemiology studies that controlled for energy expenditure found greater cardioprotective benefits from the higher aerobic exercise intensities as compared to the moderate aerobic exercise intensities. As a matter of fact, no epidemiological study reported a greater cardioprotective benefit from moderate intensity versus vigorous aerobic exercise. The clinical studies showed very similar results. When energy expenditure was controlled for in the study, the vigorous exercise intensity was more beneficial in altering one or more risk factors to coronary heart disease. Specifically, in relation to the coronary heart disease, the #1 cause of mortality in America, aerobic exercise of a more vigorous type resulted in lower incidence.

Why do the higher aerobic exercise intensities elicit the great cardioprotective results?
The known biological and psychological mechanisms of regular physical activity are numerous and summarized in Table 1. Regular physical exercise has been shown to play a critical role in the prevention and management of numerous chronic diseases including hypertension, diabetes, osteoporosis, obesity, cancer and depression (Warburton, Nicol & Bredin, 2006). However, Swain and Franklin (2006) state that the reason vigorous aerobic exercise provides greater cardioprotective benefits than moderate intensity exercise is presently unknown. However, it is well documented that vigorous exercise results in improved aerobic capacity. Swain and Franklin highlight that for each 1-MET increase in aerobic capacity there is a corresponding 8% to 17% reduction in cardiovascular disease and all causes of mortality. How improved aerobic capacity, and the numerous physiological factors associated with this cardiovascular function, elicits greater cardioprotective benefits needs to be scientifically explained. Swain and Franklin hypothesize that a possible mechanism could be improved autonomic nervous system function (or tone). With regular aerobic exercise the sympathetic nervous system (that part of the autonomic nervous system that speeds up bodily processes) is reduced at rest while the parasympathetic nervous system (that part of the autonomic nervous system that slows down bodily processes) is increased (meaning it slows down cell process even more) at rest. This major neurological system consequence from aerobic exercise may possibly be one of the underlying mechanisms that modulates (positively induces) many improved effects involved with coronary function; and thus be a foremost contribution to improved cardioprotective benefits. Swain and Franklin conclude their hypothesis with the fact that higher intensity aerobic exercise enhances these autonomic system tone changes.

Bottom line message for fitness professionals and personal trainers
From this recent review by Swain and Franklin (2006), it appears that program design goals for your students and clients seeking optimal health benefits should follow a clear training continuum. Initially and very importantly, get your students and clients regularly exercising and physically active. Then, progressively provide the exercise direction for them to get fit, and keep helping them attain higher levels of fitness.

Table 1. Biological and Psychological Mechanisms of Regular Physical Activity
Improved body composition
Improve weight control
Improved coronary blood flow
Improved cardiac function
Improved endothelial function
Improved high density lipoprotein (HDL) cholesterol
Improved glucose metabolism
Improved insulin sensitivity
Improved autonomic nervous system tone
Improved psychological well-being
Reduced blood pressure
Reduced systemic inflammation
Reduced blood coagulation
Reduced abdominal adiposity
Reduced triglyceride levels
Reduced low-density lipoprotein (LDL) cholesterol
Reduced stress, anxiety and depression
Warburton, D.E., Nicol, C.W., & Bredin, S.S. (2006). Health benefits of physical activity: the evidence. Canadian Medical Association Journal, 174(6), 801-809.

Additional Reference:
Warburton, D.E., Nicol, C.W., & Bredin, S.S. (2006). Health benefits of physical activity: the evidence. Canadian Medical Association Journal, 174(6), 801-809.
Top of Page | Research Interests | Vita | Articles | New Projects | Miscellaneous | UNM | Home