Muscle strength and body composition: associations with bone density in older subjects.

This study investigated the relationship between isokinetic muscle strength and bone density (SPA and DPA) in men and women aged 45-77 yr. Regression models were adjusted for age, weight, smoking status, and calcium supplementation. Elbow extensors (but not flexors) peak torque was correlated with radial density in men (partial r = 0.26, P < 0.05) and women (partial r = 0.24, P < 0.05). Knee flexor (but not extensor) peak torque in women was significantly correlated with spine density (partial r = 0.28, P < 0.05), and muscle mass was significantly correlated with Ward's triangle density (partial r = 0.35, P < 0.05). No associations between knee flexor or extensor muscle strength and spine or femur bone density were observed in men. Fat-free mass (FFM, hydrodensitometry) was associated with all bone density sites in males and females (partial r = 0.30-0.55; P < 0.05). These results demonstrate that 1) significant associations observed between elbow extensor strength and radial bone density in men and women may reflect loading along the longitudinal axis of the radius associated with elbow extensor activity; and 2) significant associations exist between knee flexor muscle strength and lumbar density in women only. Additionally, the associations between FFM and bone density do not necessarily reflect associations between isokinetic muscle strength and bone density.

Diet, menopause, and serum cholesterol levels in women: the Framingham Study.

Cross-sectional relationships between diet and total serum cholesterol levels were studied in a sample of 428 women from the Framingham Heart Study Cohort, aged 37 to 70 years, from 1957 to 1960. Multiple linear regression was used to control for total calorie intake, systolic blood pressure, physical activity, Metropolitan relative weight, glucose intolerance, and cigarette smoking. There was little evidence for a relationship between total serum cholesterol and dietary fat intake; whereas a marginally significant direct association was found with total fat in postmenopausal women, total and plant fat and cholesterol were inversely associated, and only cholesterol was significant in premenopausal women. A consistent inverse association was observed between total serum cholesterol levels and intake of protein, particularly from plant sources, and a weak inverse association was found with complex carbohydrate intake. Serum cholesterol in women may be influenced by a number of dietary factors and appears to differ according to menopausal status.

A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women.

The isokinetic strength of the elbow and knee extensors and flexors was measured in 200 healthy 45- to 78-yr-old men and women to examine the relationship between muscle strength, age, and body composition. Peak torque was measured at 60 and 240 degrees/s in the knee and at 60 and 180 degrees/s in the elbow by use of a Cybex II isokinetic dynamometer. Fat-free mass (FFM) was estimated by hydrostatic weighing in all subjects, and muscle mass (MM) was determined in 141 subjects from urinary creatinine excretion. FFM and MM were significantly lower (P less than 0.001) in the oldest group. Strength of all muscle groups at both testing speeds was significantly (P less than 0.006) lower (range 15.5-26.7%) in the 65- to 78- than in the 45- to 54-yr-old men and women. When strength was adjusted for FFM or MM, the age-related differences were not significant in all muscle groups except the knee extensors tested at 240 degrees/s. Absolute strength of the women ranged from 42.2 to 62.8% that of men. When strength was expressed per kilogram of MM, these gender differences were smaller and/or not present. These data suggest that MM is a major determinant of the age- and gender-related differences in skeletal muscle strength. Furthermore, this finding is, to a large extent, independent of muscle location (upper vs. lower extremities) and function (extension vs. flexion).