The present study examines age-related changes in skeletal muscle size and function after 12 yr. Twelve healthy sedentary men were studied in 1985-86 (T1) and nine (initial mean age 65.4 +/- 4.2 yr) were reevaluated in 1997-98 (T2). Isokinetic muscle strength of the knee and elbow extensors and flexors showed losses (P < 0.05) ranging from 20 to 30% at slow and fast angular velocities. Computerized tomography (n = 7) showed reductions (P < 0.05) in the cross-sectional area (CSA) of the thigh (12.5%), all thigh muscles (14.7%), quadriceps femoris muscle (16.1%), and flexor muscles (14. 9%). Analysis of covariance showed that strength at T1 and changes in CSA were independent predictors of strength at T2. Muscle biopsies taken from vastus lateralis muscles (n = 6) showed a reduction in percentage of type I fibers (T1 = 60% vs. T2 = 42%) with no change in mean area in either fiber type. The capillary-to-fiber ratio was significantly lower at T2 (1.39 vs. 1. 08; P = 0.043). Our observations suggest that a quantitative loss in muscle CSA is a major contributor to the decrease in muscle strength seen with advancing age and, together with muscle strength at T1, accounts for 90% of the variability in strength at T2.

OBJECTIVE -To determine the efficacy of high-intensity progressive resistance training (PRT) on glycemic control in older adults with type 2 diabetes.RESEARCH DESIGN AND METHODS -We performed a 16-week randomized controlled trial in 62 Latino older adults (40 women and 22 men; mean Ϯ SE age 66 Ϯ 8 years) with type 2 diabetes randomly assigned to supervised PRT or a control group. Glycemic control, metabolic syndrome abnormalities, body composition, and muscle glycogen stores were determined before and after the intervention.RESULTS -Sixteen weeks of PRT (three times per week) resulted in reduced plasma glycosylated hemoglobin levels (from 8.7 Ϯ 0.3 to 7.6 Ϯ 0.2%), increased muscle glycogen stores (from 60.3 Ϯ 3.9 to 79.1 Ϯ 5.0 mmol glucose/kg muscle), and reduced the dose of prescribed diabetes medication in 72% of exercisers compared with the control group, P ϭ 0.004 -0.05. Control subjects showed no change in glycosylated hemoglobin, a reduction in muscle glycogen (from 61.4 Ϯ 7.7 to 47.2 Ϯ 6.7 mmol glucose/kg muscle), and a 42% increase in diabetes medications. PRT subjects versus control subjects also increased lean mass (ϩ1.2 Ϯ 0.2 vs. Ϫ0.1 Ϯ 0.1 kg), reduced systolic blood pressure (-9.7 Ϯ 1.6 vs. ϩ7.7 Ϯ 1.9 mmHg), and decreased trunk fat mass (Ϫ0.7 Ϯ 0.1 vs. ϩ0.8 Ϯ 0.1 kg; P ϭ 0.01-0.05).CONCLUSIONS -PRT as an adjunct to standard of care is feasible and effective in improving glycemic control and some of the abnormalities associated with the metabolic syndrome among high-risk older adults with type 2 diabetes.

The longitudinal changes in isokinetic strength of knee and elbow extensors and flexors, muscle mass, physical activity, and health were examined in 120 subjects initially 46 to 78 years old. Sixty-eight women and 52 men were reexamined after 9.7 +/- 1.1 years. The rates of decline in isokinetic strength averaged 14% per decade for knee extensors and 16% per decade for knee flexors in men and women. Women demonstrated slower rates of decline in elbow extensors and flexors (2% per decade) than men (12% per decade). Older subjects demonstrated a greater rate of decline in strength. In men, longitudinal rates of decline of leg muscle strength were approximately 60% greater than estimates from a cross-sectional analysis in the same population. The change in leg strength was directly related to the change in muscle mass in both men and women, and it was inversely related to the change in medication use in men. Physical activity declined yet was not directly associated with strength changes. Although muscle mass changes influenced the magnitude of the strength changes over time, strength declines in spite of muscle mass maintenance or even gain emphasize the need to explore the contribution of other cellular, neural, or metabolic mediators of strength changes.