Aerobic Exercise and Strength Training for Older Women: What is the Optimal Starting Dose?

The first question most sedentary individuals have when they consider beginning an exercise program is, “How much do I have to do to get results?”  Those who have been sedentary for long periods of time may not intrinsically enjoy physical activity, therefore may not be driven to exercise for reasons of pleasure and enjoyment.  Other reasons often cited for not exercising are a lack of time, not knowing what to do or how often to do it, and medical problems that render conventional structured exercise classes risky.  A new study sheds light on the question of exercise session frequency for older women just starting a fitness program, and my suspicion is that many will be pleased with the results. The Physical Activity Guidelines for Americans (US Department of Health and Human Services, 2008) stipulate that fit adults over the age of 65 who have no limiting chronic conditions should do at least 150 minutes a week of moderate-intensity aerobic exercise, 75 minutes a week of vigorous exercise, or a combination of the two.  The Public Health Agency of Canada (2011) recommends that all adults over 65 should ideally accumulate 2.5 hours per week of aerobic exercise, and include at least two sessions per week of strength training. Hunter et al. (2013) investigated the effect of the following three combinations of aerobic exercise and resistance/strength training for 72 previously sedentary, unfit older women aged 60-74: 1 + 1 day per week each of aerobic and resistance training; 2 + 2 days per week of each; and 3 + 3 days per week of each.  The study lasted 16 weeks. The researchers looked at how each training regimen influenced muscular strength, cardiovascular fitness, total daily energy expenditure, non exercise activity thermogenesis or NEAT (energy utilized while engaging in physical activity that was not structured exercise, for example stairs or housework), feelings of fatigue/depression/vigor, and pro-inflammatory cytokines.  Cytokines regulate the body’s responses to infection, inflammation and trauma.  Pro-inflammatory cytokines worsen a disease, while anti-inflammatory cytokines promote healing.  The results of the study were very different that what many people might expect:

  • Aerobic capacity – After 16 weeks all the groups significantly increased aerobic capacity, and no statistically significant differences were noted between the three groups.
  • Body composition – All groups significantly lost weight (on average, 3 lb), reduced body fat, and gained muscle mass.  Again, there were no statistically significant differences between the groups.
  • Muscular strength – Upper and lower body strength increased significantly, with no statistical differences between the groups.
  • Total daily energy expenditure and NEAT – Interestingly, the 2 + 2 group improved the most on these measures, whereas the 1 + 1 and 3 + 3 groups did not.  It can be surmised that exercising 6 times per week (the 3 + 3) group, resulted in fatigue that led to a decrease in other types of activities.
  • Feelings of fatigue and depression, and pro-inflammatory cytokines – These variables all improved significantly, with no differences between the groups.

In conclusion, for unfit older women just beginning to exercise, one session a week each of aerobic and strength training appears, from this study, to work just as well as a more demanding protocol.  Those for whom weight management is a goal would probably derive the most benefit from the 2 + 2 protocol because the impact of increased NEAT was an increase in energy expenditure of, on average, 300 calories per day.  Bear in mind that these results apply only to deconditioned, previously sedentary women, and to the initial 4 months of an exercise program.  More research is required to better understand the ideal amount of physical activity for this population beyond this time frame. References: Hunter, GR, et al. (2013).  Combined aerobic/strength training and energy expenditure in older women.  Medicine & Science in Sports & Exercise, 45 (7), 1386-93. Kravitz, L.  Aerobic Exercise and Strength Training for Older Women: Is There An Optimal Starting Dose? IDEA Fitness Journal, October 2013. Public Health Agency of Canada, 2011.  Physical Activity Tips for Older Adults.  http://www.phac-aspc.gc.ca/hp-ps/hl-mvs/pa-ap/08paap-eng.php. US Department of Health and Human Services, Office of Disease Prevention and Health Promotion.  2008 Physical Activity Guidelines for Americans.