The Mortality Benefits of Exercise

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In our previous article, we explored the positive relationship between regular exercise and mental wellbeing. In today’s article, we will examine the relationship between exercise and mortality. Let’s begin by reviewing some key points from our previous article.

The Centers for Disease Control (“CDC”) and the World Health Organization (“WHO”) both recommend a weekly regimen of ≥2.5 hours of moderate-intensity exercise (50-70% maximal heart rate), ≥1.25 hours of vigorous-intensity exercise (70-85% maximal heart rate), or a combination thereof.1,2 We should note that the health benefits of 0.5 hours of vigorous-intensity exercise appear to be roughly equivalent to the benefits afforded by 1 hour of moderate-intensity exercise.1,2

Recall that maximal heart rate can be calculated by taking 208 – 0.7 x age (an older, unvalidated version of this equation used 220 as the base).3 As an example, a 30-year old’s maximal heart rate is calculated to be 187 beats per minute (“bpm”). This means that in our 30-year old example, a moderate-intensity activity would achieve a heart rate of 95-130 bpm while a vigorous-intensity exercise would produce a heart of 130-160 bpm.

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We concluded our previous article by stating that an ideal exercise program to maximize mental wellbeing might consist of 2-4, thirty-minute, vigorous-intensity activities per week. Today we will move beyond the effects of exercise on the mind and delve into the research on optimal exercise habits for reducing mortality, cancer, and weight.

The incidence of all-cause premature mortality is 30-40% lower in those who exercise regularly when compared to more sedentary individuals.1,4 In fact, there is a dose-response relationship between sitting time and all-cause mortality. Individuals that spend most of the day sitting have all-cause mortality rates up to 50% higher than those who spend less than half the day sitting.5 This reduced mortality may translate to as many as 3-6 additional years of life for those who regularly exercise!6,7

Not many people would say no to the prospect of adding the better half of a decade onto their life expectancy, but the $64,000 question is: how much do you have to exercise to appreciate this extension? The answer, surprisingly, is: not as much as you might think.

Evidence suggests that increasing vigorous-intensity physical activity from zero to one hour per week accounts for about 66% of the total mortality reduction associated with maximum quantities of physical activity.8 In fact, for every additional 8 minutes of vigorous-intensity exercise per day beyond the first 45 minutes of exercise per week, all-cause mortality is reduced by 4% and all-cancer mortality is reduced by 1% (note: data has been converted to vigorous-intensity equivalents from the original study, which studied moderate-intensity level exercise).7 Notably, health gains begin to plateau after the first 1-2 hours of vigorous-intensity exercise per week,7 and appear to peak after 3 hours of vigorous-intensity activity per week.9,10 This data is not included to suggest a limit to an already existing exercise program, but to give perspective and encouragement for those struggling to establish one.

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Let’s take a closer look at the role that exercise intensity level plays in reducing mortality rates. Returning to our earlier example of a target heart rate for a 30-year old individual, we defined a vigorous-intensity exercise as achieving a heart rate of 130-160 bpm. Is there any evidence that an intensity that achieves 160 bpm is superior to one that achieves 130 bpm? To answer this question, we need to review the concept of metabolic equivalents of task, or “METs.”

METs are used to compare different exercises in respect to the energy costs of the activity. For example, our resting metabolic rate while sitting still is equivalent to 1 MET. Conversely, the energy expended during sleep is equivalent to 0.9 METs, reflecting the decreased metabolic rate associated with non-REM sleep. Walking at a speed of 2.5 mph is equivalent to 3 METs while walking at 3.5 mph is equivalent to 4.3 METs. Running at a speed of 6 mph is equivalent to 9.8 METs while running at 7 mph is equivalent to 11 METs.11 We have used running as an example activity; however, METs associated with alternative physical activities can be found here.

There is some evidence to suggest that there may not be a mortality benefit of an exercise intensity beyond 10-12 METs.6,12 Thus, although we cannot definitively say whether exercises associated with higher heart rates are better than comparable “vigorous” activity of lower heart rate, we can postulate that there may not be a significant marginal utility in running at a pace faster than 7mph, or an 8.5-minute mile. Anecdotally, one of the authors tracked his heart rate running a few 8.5 minute miles and found that he averaged around 140 bpm consistent with a “vigorous-intensity” activity as defined by the CDC and WHO. The correlation between an energy expenditure of 11 METs and an average heart rate of 140 bpm is not necessarily generalizable beyond this particular author, but it serves to illustrate the correlation between the different methods of classifying exercise intensity level.

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We have addressed the duration and intensity of exercise, but what about frequency? Recent evidence suggests that frequency may not matter as long as individuals achieve the CDC and WHO duration and intensity goals. In other words, if you exercise for 1.25 hours every Saturday at a vigorous-intensity level you may achieve the same health benefits as you would if you exercised for 0.5 hours Monday through Friday at a moderate-intensity level.4

This review of the evidence is hopefully making regular exercise look more and more like an attainable goal, but what if you slack off for a week or two? Will you lose all your gains?

The short answer is probably not: evidence suggests that the beneficial physiological adaptations that accrue during regular aerobic exercise are sustained in periods of inactivity for 1-2 weeks before they begin to degrade. Moreover, strength training benefits may be maintained by as little as one episode of resistance training per week.13

What if, in addition to mortality benefits, you are trying to lose weight?

Most research suggests that the most effective weight loss strategies utilize a combination of exercise and diet rather than relying solely on either modality in isolation. Although exercise alone may be associated with modest weight loss in a dose-response fashion,14–16 diet appears to be superior when considering a single modality approach.17,18 In fact, diet alone or diet plus exercise are associated with weight loss 3-5 times that of exercise alone.19

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Exercise is often challenging initially for individuals trying to lose weight. But if you are unable to sustain activities at a vigorous-intensity level, then rest assured that most research suggests that equivalent moderate-intensity exercise is as effective in producing weight loss.20 And finally, if your weight loss plateaus for a period, that’s okay. In regards to mortality reduction it is more important to become “fit” than to lose weight; that is, as you exercise your weight may remain the same despite fat being supplanted by muscle on the scale.21

We have covered a lot of ground today so let’s try to summarize our findings. What would an optimal exercise program look like for someone hoping to maximize his or her mortality benefits?

The duration and frequency appear to be mostly at the discretion of the exerciser and his or her schedule. If the exerciser achieves the 1.25 hours of vigorous-intensity (or moderate-intensity equivalent) per week, then there does not appear to be a significant difference between stacking a lot of exercise on a single day compared to getting it done in small bursts throughout the week.

As to the intensity within the moderate to vigorous-intensity spectrum, we may be able to provide more concrete guidelines. If you are capable and enjoy vigorous-intensity exercise, then it may be more economical to cut your time in half by exercising at this level of intensity. And when you are contemplating the specific intensity level within the vigorous category it may help to consider the research suggesting that health benefits peak around 10-12 METs. If you are a runner, then this would mean that your health benefits peak at a pace of about an 8.5-minute mile (7 mph).

Obviously, the exact variety of exercise routine that you engage in will only be limited by your imagination; however, for those seeking an example routine let’s use our newfound knowledge to design an “ideal” program.

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First, let’s recall the ideal mental wellbeing exercise routine from our previous article: 2-4, thirty-minute, vigorous-intensity episodes of exercise per week. Interestingly, this regimen is very similar to an optimal mortality-reducing regimen outlined in an article by Schnohr et al., which suggested a running program that consisted of three 30-minute runs per week at a pace of 6-7 mph.12 Our literature review supports Schnohr et al.’s model routine with some important caveats. Even though doubling the duration or frequency of this routine might offer some marginal benefits, the cost to sustainability would likely offset any gains. Also, there is no evidence that a program that more than doubled this routine would confer any additional health benefits.

Thus, an ideal exercise regimen to appreciate both the maximal mental health and mortality benefits may be a program that aims for three 30-minute runs per week at a pace of 6-7 mph (9.8-11 METs) with a target heart rate 70-85% that of the age-adjusted maximal rate.

And when the unavoidable week or two pass during which your schedule prohibits regular exercise don’t throw in the proverbial towel, simply resolve to get back on the path, bike, or treadmill with the knowledge that your hard-earned fitness has not degraded in this short period of decreased activity.

References

  1. Centers for Disease Control and Prevention (CDC). Physical activity and health. CDC.gov. https://www.cdc.gov/physicalactivity/basics/pa-health/. Accessed November 12, 2016.
  2. World Health Organization. Physical Activity and Adults. WHO. http://www.who.int/dietphysicalactivity/factsheet_adults/en/. Accessed January 15, 2017.
  3. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153-156. doi:10.1016/S0735-1097(00)01054-8.
  4. O’Donovan G, Lee I, Hamer M, Stamatakis E. Association of “weekend warrior” and other leisure time physical activity patterns with risks for all-cause, cardiovascular disease, and cancer mortality. JAMA Intern Med. January 2017. doi:10.1001/jamainternmed.2016.8014.
  5. Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting Time and Mortality from All Causes, Cardiovascular Disease, and Cancer: Med Sci Sports Exerc. 2009;41(5):998-1005. doi:10.1249/MSS.0b013e3181930355.
  6. Merghani A, Malhotra A, Sharma S. The U-shaped relationship between exercise and cardiac morbidity. Trends Cardiovasc Med. 2016;26(3):232-240. doi:10.1016/j.tcm.2015.06.005.
  7. Wen CP, Wai JPM, Tsai MK, et al. Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. The Lancet. 2011;378(9798):1244-1253. doi:10.1016/S0140-6736(11)60749-6.
  8. Samitz G, Egger M, Zwahlen M. Domains of physical activity and all-cause mortality: systematic review and dose–response meta-analysis of cohort studies. Int J Epidemiol. 2011;40(5):1382-1400. doi:10.1093/ije/dyr112.
  9. Lee D, Pate RR, Lavie CJ, Sui X, Church TS, Blair SN. Leisure-Time Running Reduces All-Cause and Cardiovascular Mortality Risk. J Am Coll Cardiol. 2014;64(5):472-481. doi:10.1016/j.jacc.2014.04.058.
  10. Sattelmair J, Pertman J, Ding EL, Kohl HW, Haskell W, Lee I-M. Dose Response Between Physical Activity and Risk of Coronary Heart DiseaseClinical Perspective. Circulation. 2011;124(7):789-795. doi:10.1161/CIRCULATIONAHA.110.010710.
  11. Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: A Second Update of Codes and MET Values. Med Sci Sports Exerc. 2011;43(8):1575-1581. doi:10.1249/MSS.0b013e31821ece12.
  12. Schnohr P, O’Keefe JH, Marott JL, Lange P, Jensen GB. Dose of Jogging and Long-Term Mortality. J Am Coll Cardiol. 2015;65(5):411-419. doi:10.1016/j.jacc.2014.11.023.
  13. Garber CE, Blissmer B, Deschenes MR, et al. Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise. Med Sci Sports Exerc. 2011;43(7):1334-1359. doi:10.1249/MSS.0b013e318213fefb.
  14. Slentz CA, Duscha BD, Johnson JL, et al. Effects of the Amount of Exercise on Body Weight, Body Composition, and Measures of Central Obesity: STRRIDE—A Randomized Controlled Study. Arch Intern Med. 2004;164(1):31. doi:10.1001/archinte.164.1.31.
  15. Wood PD, Stefanick ML, Dreon DM, et al. Changes in Plasma Lipids and Lipoproteins in Overweight Men during Weight Loss through Dieting as Compared with Exercise. N Engl J Med. 1988;319(18):1173-1179. doi:10.1056/NEJM198811033191801.
  16. Ross R, Dagnone D, Jones PH, et al. Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men: A randomized, controlled trial. Ann Intern Med. 2000;133(2):92-103. doi:10.7326/0003-4819-133-2-200007180-00008.
  17. Franz MJ, VanWormer JJ, Crain AL, et al. Weight-Loss Outcomes: A Systematic Review and Meta-Analysis of Weight-Loss Clinical Trials with a Minimum 1-Year Follow-Up. J Am Diet Assoc. 2007;107(10):1755-1767. doi:10.1016/j.jada.2007.07.017.
  18. Villareal DT, Chode S, Parimi N, et al. Weight Loss, Exercise, or Both and Physical Function in Obese Older Adults. N Engl J Med. 2011;364(13):1218-1229. doi:10.1056/NEJMoa1008234.
  19. Miller WC, Koceja DM, Hamilton EJ. A meta-analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention. Int J Obes Relat Metab Disord J Int Assoc Study Obes. 1997;21(10):941-947.
  20. Jakicic JM, Marcus BH, Gallagher KI, Napolitano M, Lang W. Effect of Exercise Duration and Intensity on Weight Loss in Overweight, Sedentary Women: A Randomized Trial. JAMA. 2003;290(10):1323-1330. doi:10.1001/jama.290.10.1323.
  21. Tjønna AE, Lee SJ, Rognmo Ø, et al. Aerobic Interval Training Versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome. Circulation. 2008;118(4):346-354. doi:10.1161/CIRCULATIONAHA.108.772822.

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