Aerobic Exercise and Strength Training for Older Women: Is There an Optimal Starting Dose?

Hunter, G.R., et al. 2013. Combined aerobic/strength training and energy expenditure in older women. Medicine & Science in sports & Exercise, 45 <7), 1386-93.

We have good exercise guidance for fit older adults, but the advice for seniors just starting a fitness program has been less clear.

The Physical Activity Guidelines for Americans (HHS 2008) say fit older adults (≥65 years) 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-intensity aerobic physical activity, or a comparable combination of both. The guidelines also recommend moderate- or high-intensity muscle-strengthening activities that involve all major muscle groups on 2 or more days a week.

Yet personal trainers cannot help wondering: What is the optimal dose of combined cardiovascular exercise and resistance training for older adults who are initiating an exercise program? Using a comprehensive research design, Hunter and colleagues investigated this question in a large sample population of older women.

Overview of the Study

Hunter et al. (2013) investigated the effect of the following three combinations of aerobic exercise and resistance training programs:

• 1+1: 1 day a week of aerobic exercise and 1 day a week of resistance training on nonconsecutive days.
• 2+2: 2 days a week of aerobic exercise and 2 days a week of resistance training.
• 3+3: 3 days a week of aerobic exercise and 3 days a week of resistance training.

The researchers examined how each training regime influenced the following:

• muscular strength
• cardiovascular fitness
• total daily energy expenditure (TEE)
• nonexercise activity-related energy expenditure or thermogenesis (NEAT)
• free living activity-related energy expenditure (AEE)
• subjective feelings of fatigue/depression/vigor
• proinflammatory cytokines

Cytokines regulate the body’s responses to infection, inflammation and trauma. Proinflammatory cytokines worsen a disease, while anti-inflammatory cytokines promote healing.

To better control workout conditions, researchers conducted all 16 weeks of the aerobic exercise and resistance training sessions in a research facility, thus eliminating potential interference (people talking, music, noises, etc.). All training sessions were supervised by exercise physiologists. Before each workout, the women completed a standardized 3- to 4-minute treadmill or cycle ergometer warm-up followed by 3–4 minutes of stretching.

Subjects in the Study
Seventy-two women (60–74 years old) who had no metabolic disorders (conditions that would affect their metabolism) volunteered for the trial. The women were nonsmokers and classified as sedentary, which Hunter et al. defined as exercising less than once a week in the year prior to the study.

Cardiovascular Training
This study incorporated an aerobic training stimulus that the researchers progressively overloaded, in the same way many skillful personal trainers gradually overload a client’s aerobic exercise over time. The investigators steadily increased the exercise stimulus by very carefully manipulating changes in duration and intensity. Subjects did the training program in Table 1, evenly divided between treadmills and cycle ergometers. Researchers used a graded exercise test to determine each subject’s actual maximum heart rate.

Resistance Training

Researchers used 10 resistance training exercises: squat, leg extension, leg press, leg curl, elbow flexion, lateral pull-down, bench presses, military press, low-back extension and bent-leg sit-up.

Initially, subjects completed two sessions with light loads to familiarize themselves with the exercises. In the third session, the women completed a 1-repetition maximum on all exercises except back extension and bent-leg sit-up (no weight was used for these two exercises); the study used standardized 1-RM testing procedures commonly followed in research. The standardized 1-RM testing was repeated every fifth week to ensure that subjects’ training sessions were at the appropriate percentage of their actual 1-RM.

For the training, the women completed 2 sets of 10 repetitions with approximately 1.5–2 minutes of rest between sets. Using periodized progressive overload, subjects initially trained at 60% of 1-RM and gradually increased intensity each week until they reached 80% of 1-RM for all exercises (except back extension and bent-leg sit-up, which subjects completed with their own body weight). This program continued throughout the 16 weeks of the study.

Discussion and Findings
Aerobic Capacity
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, but the study observed no statistical differences among the 1+1, 2+2 and 3+3 groups.

Body Composition
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 pounds), reduced body fat (-0.05% to -1.9%) and gained muscle (0.4–0.7 kilograms), but the study found no statistical differences among the 1+1, 2+2 and 3+3 groups.

Muscular Strength
Leg press and bench press strength increased significantly, with no statistical differences among the 1+1, 2+2 and 3+3 groups.

Total Daily Energy Expenditure, Nonexercise Activity Thermogenesis and Activity-Related Energy Expenditure
Interestingly, the 2+2 group improved significantly in TEE, NEAT and AEE, whereas the 1+1 and 3+3 groups did not. In fact, toward the end of the study NEAT began to decrease in the 3+3 group. Importantly, the increases in TEE, NEAT and AEE for the 2+2 group suggest that this combination of aerobic and resistance training offers the prospect of promising weight management improvements, as this group increased energy expenditure by almost 300 kilocalories per day.

Subjective Feelings of Fatigue/Depression/Vigor; Proinflammatory Cytokines
Although measures of fatigue, depression, vigor and proinflammatory cytokines improved during the 16 weeks, there were no statistically significant differences among the three groups.

Take-Home Messages From the Study
Seniors represent one of the fastest-growing markets for personal trainers. The study provides new insights into how to initiate training programs for older women (as well as some interesting observations from the researchers, shown in Figure 1):

• In this group of sedentary 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 nonconsecutive days could improve muscular strength, body composition and cardiovascular fitness as successfully as training more frequently could.
• Subjects in the 3+3 group complained that the 6-day-per-week exercise commitment was excessive, suggesting that long-term adherence to this protocol could be difficult.
• The 2+2 group was the only one that—in addition to improving muscular strength, body composition and cardiovascular fitness—showed significant increases in TEE, NEAT and AEE, thus indicating that this type of protocol may be optimally suited for a population of older sedentary women beginning a training program that includes weight management goals.

Future research will be needed to determine the initial frequencies of combined aerobic and resistance training appropriate for older men.