The aim of the present research was to determine the association between historical physical activity and baseline bone measurements in a group of 223 postmenopausal women participating in a clinical trial in Pittsburgh, Pennsylvania, from 1981 to 1986 by evaluating the effect of moderate physical activity on bone loss. Historical physical activity was assessed by a survey which divided the life span into four time periods (14-21, 22-34, 35-50, and 50+ years) and inquired about participation in leisure time physical activities for each period. From the responses, kilocalories of energy expenditure were calculated. Cortical bone density and area were measured in the radius with a computerized tomography scanner. The historical physical activity survey was administered a second time two to three months after the initial test to a 10% random sample of the women in order to determine the test-retest reliability of the instrument. Since the measurements of historical physical activity proved to be reliable, estimates of kilocalories determined for the entire population of women were correlated with bone area and density. A significant relation was found to exist between historical physical activity and dimensions of adult bone, particularly bone area. This association remained significant after adjustment for potential confounding variables and seemed to be strongest in the earlier age periods. To the authors' knowledge, this is the first report of a significant association between historical physical activity and bone.

Skeletal mass is a major determinant of susceptibility to osteoporotic fracture in menopause. At menopause, the skeletal mass is the resultant of the Peak Skeletal Mass (PSM) reached early adulthood minus the bone mass lost through the process of Adult Bone Loss (ABL). Current interventions for the maintenance of skeletal resilience in advanced age address the ABL peri- or postmenopausally. This study indicates that the effects of milk consumption in childhood and adolescence on bone density may manifest as higher bone density decades later in menopause. The assumed mechanism of the reported effect is through augmentation of the PSM, and acquisition of favorable nutritional habits which may influence the extent of ABL.

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Five methods for assessing physical activity were evaluated in a population of 255 white, postmenopausal women participating in a randomized trial on the effects of walking on bone loss. Methods were the Paffenbarger survey, a modified Paffenbarger, the large-scale integrated activity monitor (LSI), caloric intake, and the Baecke survey. Significant increase in physical activity was observed in the intervention group. Activity measures were weakly related to each other. Results of factor analyses suggest that factor I reflected voluntary leisure-time pursuits (such as walking) and factor II, activities of daily living. Participation in sports was not a significant contributor to overall activity of the women. Research on physical activity must define the particular dimension of activity measured. Several types of instruments should be used because different instruments reflect different activity patterns which, in turn, may be differentially related to disease.

This report deals with the analysis of data from a 3-year clinical trial on the effect of walking on postmenopausal bone loss. Two hundred fifty-five women, with an average age of 57 at entry, were randomized into two groups, a walking and a control group. Bone measures in the shaft of the radius were carried out with a CT scanner in search of generalized skeletal effects rather than effects localized to the bones of the leg. Although bone density losses were comparable in the two randomized groups, changes in the cross-sectional area of the radius were significantly greater in the walkers with high grip strength (greater than 25 Kg) than in the controls with comparable high grip strength which corresponded to the upper half range of the grip-strength distribution. It is concluded that the moderate activity of walking exerted systemically positive effects on the radius which, within the protocol of the study, could be substantiated only when synergized with inherent muscle strength.