Go Hard or Go Home: Do We Need More Intensity in Our Exercise?

Editor's Note: Commentary based on Lee IM, Shiroma EJ, Lobelo F, et al. Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy. Lancet 2012;380:219-29.

It is widely accepted that exercise is a potent intervention to increase the health of a population. Regular physical exercise is associated with improvements in physical and mental well-being, in addition to increased longevity.1 As a result, guidelines in many countries have made recommendations about the desirable amount of exercise for their populations. There is; however, still debate regarding the "best" form of exercise, the optimal duration of exercise, and how to account for variations in overall physical activity in comparing moderate to vigorous exercise. Many recent studies have focused on the use of high-intensity interval training, and have suggested that more vigorous exercise, albeit brief in this type of training, may offer advantages in both health and in diseases such as heart failure.2 The study, "Effect of moderate to vigorous exercise on all-cause mortality in middle-aged and older Australians", from Gebel, et al3 uses data from a long term Australian cohort study to investigate the effects of exercise intensity on total mortality, and account for the confounding effects of the overall amount of moderate to vigorous physical activity (MVPA).

The study used data from a prospective cohort study of randomly selected individuals between 45–74 years of age, enrolled between 2006 and 2009. The 204,545 participants comprised approximately 10% of the population of the state of New South Wales within this age range. Physical activity levels including the total amount of MVPA; the amount that was in the vigorous range was self-reported using well-validated tools. Examples of moderate activities, for the purposes of this study, included gentle swimming, social tennis, vigorous gardening, or work around the house. Vigorous activity was defined as activities which make you breathe hard, such as jogging, cycling aerobics, and competitive tennis. The cohort was followed for 6.52 years (1,444,927 person years), and the outcome of interest was all-cause mortality determined from the state death registry. The proportion of vigorous activity as a percentage of MVPA and its relationship to mortality were examined with participants stratified by the total MVPA being undertaken. Multivariate analyses was included to account for confounding effects of a number of variables including age, sex, education, obesity, total activity levels, and smoking.

Of the study participants, 93.9% were undertaking MVPA, with 52% including no vigorous activity (moderate activity only), 15.3% including 0–30% vigorous activity, and in 26.6%, vigorous activity accounted for greater than 30% total MVPA. There were 7,435 deaths (8.34%) during follow-up. Mortality risk was highest in those not undertaking any MVPA (8.34%). Increasing total duration of MVPA per week was a lower risk of mortality; however, within each stratum of total MVPA the mortality risk was lowest in those with >30% vigorous physical activity (Hazard Ratio (HR) 0.87), and intermediate in those with 0–30% vigorous activity (HR 0.91), when compared to those with no vigorous activity (HR 1). This finding was consistent when examined across different age groups, sexes activity levels, obese vs. non-obese, and in those with and without pre-existing cardiovascular disease.

The authors concluded that independent of the total amount of exercise performed, inclusion of some exercise within the vigorous range is protective against all-cause mortality, and should therefore be encouraged in guidelines for physical activity in middle-aged and older adults. Even after exclusion of patients who were missing variables of interest, this remains a large study of physical activity levels in middle-aged and older adults, with a reasonable length of follow-up in which the outcome variable of interest, mortality, has been collected from a state death registry and therefore should be reliable. Other factors to consider include the fact that the data is observational, and, as acknowledged by the authors, the possibility that the ability to be able to engage in vigorous activity may be a marker for reduced mortality for reasons independent of the effects of the exercise itself cannot be excluded. However, as an interventional study with mortality as an endpoint is unlikely to be performed to definitively answer this question, one must assume that the findings of lower mortality in those with more vigorous exercise as a part of their physical activity are at least in part due to the effects of vigorous exercise itself.

In the same journal edition, Arem, et al4 also examined the relationship between exercise volume and intensity in 661,137 subjects from six population-based cohorts from the United States and Europe. They found that even low levels of leisure time physical activity were associated with lower mortality when compared to those reporting no exercise, but that higher levels of moderate- to vigorous-intensity were associated with even lower risk, with the lowest risk (HR 0.61) seen in those undertaking three to five times the recommended minimum level of physical activity. While these findings are consistent with those of Gebel, Arem did not examine whether inclusion of higher volumes of vigorous exercise was associated with lower mortality.

At one end of the spectrum, there is ongoing debate about whether extreme levels of endurance exercise may be harmful5,6 and while it appears that long-term endurance training is associated with increased risk for atrial fibrillation7, with regards to the general population, the discussion centers around the most effective prescription for health and longevity, and it is clear firstly that any exercise is better than none. The work of Gebel shows that both duration and intensity of exercise are important in the reduced risk of mortality seen with regular physical activity in the general population, with mortality rates 11–13% lower in those adults who included some additional vigorous activity in their regular physical activity. It provides a rationale for recommending to our patients not only to exercise, but to exercise hard with inclusion of some vigorous activity, in order to get all the benefits that exercise has to offer in improving long term health outcomes.

References

  1. Lee IM, Shiroma EJ, Lobelo F, et al. Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy. Lancet 2012;380:219-29.
  2. Haykowsky MJ, Timmons MP, Kruger C, McNeely M, Taylor DA, Clark AM. Meta-analysis of aerobic interval training on exercise capacity and systolic function in patients with heart failure and reduced ejection fractions. Am J Cardiol 2013;111:1466-9.
  3. Gebel K, Ding D, Chey T, Stamatakis E, Brown WJ, Bauman AE. Effect of Moderate to Vigorous Physical Activity on All-Cause Mortality in Middle-aged and Older Australians. JAMA Intern Med 2015;175:970-7.
  4. Arem H, Moore SC, Patel A, et al. Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship. JAMA Intern Med 2015;175:959-67.
  5. Heidbuchel H, Prior DL, La Gerche A. Ventricular arrhythmias associated with long-term endurance sports: what is the evidence? Br J Sports Med 2012;46 Suppl 1:i44-50.
  6. O'Keefe JH, Lavie CJ. Run for your life ... at a comfortable speed and not too far. Heart 2013;99:516-9.
  7. Aizer A, Gaziano JM, Cook NR, Manson JE, Buring JE, Albert CM. Relation of vigorous exercise to risk of atrial fibrillation. Am J Cardiol 2009;103:1572-7.

Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Prevention, Sports and Exercise Cardiology, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Exercise, Smoking

Keywords: Atrial Fibrillation, Cohort Studies, Exercise, Exercise Therapy, Follow-Up Studies, Heart Failure, Jogging, Life Expectancy, Longevity, Longitudinal Studies, Middle Aged, Motor Activity, Multivariate Analysis, Obesity, Prospective Studies, Registries, Self Report, Smoking, Sports, Swimming, Tennis


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