|Aerobic Exercise and Strength Training for Older Women: Is there an Optimal Starting Dose?
Len Kravitz, Ph.D.
Hunter, G.R., Bickel, C.S., Fisher, G., Neumeier, W.H., & McCarthy, J.P. (2013). Combined aerobic and strength training and energy expenditure in older women. Medicine & Science in Sports & Exercise, 45(7), 1386-1393.
In the Physical Activity Guidelines for Americans (2008), older adults (&Mac179;65 yrs) who are fit and have no limiting chronic conditions are encouraged to do at least 150 minutes a week of moderate-intensity aerobic exercise, or 75 minutes a week of vigorous-intensity aerobic physical activity, or an comparable combination of both. The guidelines also recommend muscle-strengthening activities that are moderate or high intensity and involve all major muscle groups on two or more days a week. However, a key topic of concern for personal trainers is what is the optimal dose of combined cardiovascular exercise and resistance training when initiating an exercise program for this special population. Utilizing a very comprehensive research design, Hunter and colleagues (2013) investigated this question in a large sample population of older women.
Overview of the Study
This study investigated the effect of the following three combinations of aerobic exercise and resistance training programs:
1. One day/week of aerobic exercise and one day/week of resistance training (One/One) which were on non-consecutive days
2. Two days/week of aerobic exercise and two days/week of resistance training (Two/Two)
3. Three days/week of aerobic exercise and three days/week of resistance training (Three/Three).
The researchers examined the effect each training regime would have on muscular strength, cardiovascular fitness, total daily energy expenditure (TEE), activity-related energy expenditure (AEE), non-exercise activity related energy expenditure or thermogenenesis (NEAT), subjective feelings of fatigue/depression/vigor, and proinflammatory cytokines. Cytokines are regulators of the body's responses to infection, inflammation and trauma. Some cytokines act to make the disease worse (proinflammatory), whereas others serve to reduce inflammation and promote healing (anti-inflammatory).
To better control all workout conditions, the aerobic exercise and resistance training sessions in this 16-week study were conducted in a research facility, thus eliminating potential interferences (i.e, people talking, music, noises etc.). All training sessions were supervised by exercise physiologists. Prior to each workout the subjects completed a standardized 3-4 minute treadmill or cycle ergometer warm-up followed by 3-4 minutes of stretching.
Subjects in the Study
Seventy-two women (60-74 yrs) who had no metabolic disorders (i.e., a condition that affects a persons metabolism) volunteered for the study. Subjects were non-smokers and classified as sedentary, which Hunter et al (2013) defined as exercising less then once per week for the past year.
This study incorporated a progressively overloading aerobic training stimulus, similar to how many skillful personal trainers would gradually overload a client's aerobic exercise over a period of time. The researchers were very careful in steadily increasing the exercise stimulus by manipulating changes in duration and intensity. Subjects did the following aerobic training program (Table 1), evenly divided on two modes of exercise, treadmill and cycle ergometer. Researchers determined subjects actual maximum heart rates (MHR) utilizing a graded exercise test.
Table 1. Aerobic Training Program
Week 1 Twenty minutes of aerobic exercise per session at 67% of maximum heart rate (MHR)
Weeks 2-5 Duration increased 5 minutes each week and intensity remained at 67% MHR; by week 5 the subjects were completing 40 minutes of aerobic exercise each session
Week 6 Duration was lowered to 30 minutes and intensity was increased to 71% MHR
Week 7 Duration increased to 40 minutes per session and intensity remained at 71% MHR
Week 8 Duration was lowered to 30 minutes and intensity was increased to 75% MHR
Week 9 Duration was increased to 40 minutes and intensity remained at 75% MHR
Week 10 Duration was lowered to 30 minutes and intensity was increased to 80% MHR
Week 11 Duration was increased to 40 minutes and intensity remained at 80% MHR
Weeks 12-16 Duration remained at 40 minutes and intensity remained at 80% MHR
The ten resistance training exercises in this study included squats, leg extension, leg press, leg curl, elbow flexion, lateral pull-down, bench press, military press, lower back extension, and bent leg sit-ups. Initially, the subjects completed two sessions of light loads to familiarize the subjects with the exercises. On the third session the subjects completed a 1-repetition maximum (1-RM) on all exercises, except the back extension and bent leg sit-ups (no weight was used for these two exercises) using standardized 1-RM testing procedures commonly followed in research. This same standardized 1-RM testing was completed every 5th week to ensure the subjects training sessions were at the appropriate percentage of their actual 1-RM.
For the training, subjects completed 2 sets of 10 repetitions with ~1.5 to 2 minutes of rest between sets. Following a periodized progressive overload with intensity, the subjects initially trained at 60% 1-RM with gradual increases each week until reaching 80% 1-RM with all exercises (except back extension and bent leg sit-ups, which the subjects completed with their own body weight). Subjects continued with this training program throughout the 16 weeks of the study.
Results/Discussion and Findings
A physician supervised maximal aerobic capacity test was performed before and after the 16 weeks of the study. All groups significantly increased their aerobic capacity over pre to post-testing, but three was no statistical difference observed between the One/One, Two/Two and Three/Three groups.
Body fat and lean body mass were assessed with dual-energy x-ray absorptiometry. This body composition technique determines bone body mass, lean body mass, and fat body mass. All groups significantly lost weight (~3 lbs), reduced body fat (-.05% to -1.9%) and gained muscle (+0.4 to 0.7 kg), but no statistical difference was observed between the One/One, Two/Two and Three/Three groups.
Leg press and bench press strength increased significantly, but no statistical difference was observed between the One/One, Two/Two and Three/Three groups.
Total Daily Energy Expenditure (TEE), Non-Exercise Activity Thermogenenesis (NEAT) and Activity-Related Energy Expenditure (AEE)
Interestingly, the Two/Two group improved significantly in TEE, NEAT, and AEE, where as the One/One and Three/Three groups did not. In fact, towards the end of the study the Three/Three group started decreasing in NEAT.
Subjective Feelings of Fatigue/Depression/Vigor, and Proinflammatory Cytokines
Although measures of fatigue, depression, vigor and proinflammatory cytokines showed positive changes during the 16 weeks, no statistical significance was attained between groups.
Take Home Messages From The Study
One of the fastest growing markets for personal trainers is seniors. New insights into initiating training programs for older females can be ascertained from this study (as well as some interesting observations from the researchers in Figure 1). In this sedentary group of women (60-74 years), the researchers clearly showed that during the first 16 weeks of an exercise program, resistance and aerobic training conducted once a week on non-consecutive days was as successful at improving muscular strength, body composition, and cardiovascular fitness as training more frequently. The researchers commented that subjects in the Three/Three group complained that the six-day/week commitment of exercise was excessive, suggesting long-term adherence of this protocol could be difficult. However, the Two/Two group was the only group to also show significant increases in TEE, NEAT and AEE, thus indicating this type of protocol may be optimally suited for a population of older sedentary women beginning a training program. Future research needs to determine the initial frequencies of combined aerobic and resistance training with males.
Special Observations by authors:
1.The ability to perform daily tasks reaches a peak at 30 years and declines thereafter.
2.Lower levels of physical activity are associated with lower maximum oxygen uptake: thus the need to do cardiovascular training.
3.Resistance training too frequently (&Mac179;3 times/wk) or too intensity (>80% 1-RM) may result in more fatigue and less adaptation in older women.
4.The decline in the ability to perform daily tasks is a result of reduced physical activity, a reduction in strength, and aging.
5.Improvements in muscular strength lead to increased ease in stair climbing, walking, carrying loads and rising from a chair.
U.S. Department of Health and Human Services (2008). Office of Disease Prevention and Health Promotion. 2008 Physical Activity Guidelines for Americans. www.health.gov/PAGuidelines/pdf/paguide.pdf
Accessed July 24, 2013