Lauren Gulka, James Dziura and Loretta DiPietro
Little attention has been paid to the study of transient growth hormone (GH) responses to exercise in older women. We determined the effect of a single bout of exercise on GH in fit and unfit older (age 55 to 81 y; n = 19) and younger (age 18 to 25 y; n = 19) women.
Exercise consisted of five 15-min intervals of treadmill exercise at 75% VO2peak. Blood samples were taken before, during, and following exercise for determination of plasma GH and insulin concentrations.
GH responses to exercise were attenuated in older compared with younger women (P < 0.01); however, these age differences were minimized in older age by fitness level. Adjusted area under the curve for GH was 5.50 and 1.76 µg/L · 102 for fit and unfit older women (P < 0.01), and 8.46 and 8.46 µg/L · 102 for fit and unfit younger women.
Low levels of cardiorespiratory fitness in older women may require a greater relative exercise stimulus to augment meaningful GH responses.
Loretta DiPietro, Catherine W. Yeckel and James Dziura
Few studies have compared long-term moderate-intensity aerobic versus light-resistance training on serial improvements in glucose tolerance in older people.
Healthy, inactive older (74 ± 5 [SD] years) women (N = 20) were randomized into either a high-volume, moderate-intensity aerobic (ATM, n = 12) or a lower-intensity resistance training (RTL, n = 8) group. Both groups exercised under supervision 4 times per week for 45- to 60-minute sessions over 9 months. Measurements of plasma glucose, insulin, and free fatty acid (FFA) responses to an oral glucose tolerance test (OGTT) were performed at baseline and at 3, 6, and 9 months 48 hours after the last exercise session.
We observed significant improvements in 2-hour glucose concentrations at 3, 6, and 9 months among women in the RTL (152 ± 42 vs 134 ± 33 vs 134 ± 24 vs 130 ± 27 mg · dL−1; P < .05), but not the ATM (151 ± 25 vs 156 ± 37 vs 152 ± 40 vs 155 ± 39 mg · dL−1) group. These improvements were accompanied by an 18% (P < .07) decrease in basal FFA concentrations in the RTL group, whereas basal and 30-minute FFA concentrations increased (P < .05) after training in the ATM group.
These findings suggest that the net physiological benefits of exercise might have been blunted in the ATM group, owing to higher circulating levels of FFA, which might have temporarily interfered with insulin action.
James Dziura, Stanislav V. Kasl and Loretta Di Pietro
It is not clear whether physical activity can exert a protective role on diabetes risk in older people that is independent of the changes in body weight that occur with both aging and disuse. The purpose of this analysis was to determine the relation between current physical activity, 3-year change in body weight, and the subsequent risk of type 2 diabetes in an older cohort.
We studied prospectively 2,135 older (≥65 years) persons living in New Haven, CT, between 1982 and 1994. Physical activity was self-reported in 1982 and again in 1985; body weight and diabetes were self-reported annually over 12 years. Data were analyzed using multivariable Cox Proportional Hazards modeling with adjustments for age, sex, race, education, body mass index (BMI), smoking, chronic conditions, physical function, and alcohol intake.
Although an inverse graded relation was observed between level of activity and rate of diabetes, this dose–response relation did not reach statistical significance. However, older people who reported at least some activity at baseline experienced a significantly lower rate of diabetes between 1983 and 1994 compared to those reporting no activity (RR = 0.55; 95%CI = 0.35, 0.87). When 3-year changes in physical activity and body weight between 1982 and 1985 were added to the model, the relation between physical activity and reduced diabetes risk was unchanged (RR = 0.49; 95%CI = 0.24, 0.99).
Even in advanced age, physical activity exerts an important and independent role in the prevention of type 2 diabetes. Continued physician counseling on the health effects of physical activity and referrals to community-based exercise programs should be encouraged among older people.