Negative Association Between Bone-loading Index And Grip Strength In Circum-menarcheal Females

PURPOSE: Our team has validated an arm bone-loading index (BLI3yr), demonstrating that 3 years of circum-menarcheal bone-loading positively correlated with non-dominant arm DXA muscle mass and bone properties in 2 cohorts of post-menarcheal females. Grip strength has been shown to indicate overall health and quality of life. Thus, we aimed to determine whether BLI3yr correlates with grip strength in post-menarcheal gymnasts and non-gymnasts. METHODS: For 48 circum-menarcheal females, we used detailed physical activity records to calculate a validated 3-year non-dominant arm bone-loading index (BLI3yr) to reflect magnitude, frequency, and velocity of site-specific loading. Mann-Whitney U tested for group differences in key variables. Multiple linear regression models were run for the full cohort & subgroups to determine predictive value of arm BLI3yr on grip strength, accounting for height, BLI3yr, and non-dominant arm DXA muscle mass. RESULTS: No significant differences were detected between gymnasts (n=24) and non-gymnasts (n=24) for gynecological age, BMI, body mass, height, or non-dominant arm grip strength (p≥0.70). Gymnasts had higher BLI3yr and non-dominant arm muscle mass than non-gymnasts (p<0.001 to p=0.034). In Table 1, BLI3yr was a significant negative predictor of grip strength in the full cohort (Model 1) and non-gymnast subgroup (Model 2), but BLI3yr did not predict grip strength in gymnasts (Model 3). CONCLUSION: Our bone-loading index appears to be a negative predictor for grip strength in circum-menarcheal females, and in a subgroup of non-gymnasts, but not in gymnasts. Our findings suggest that exercises that enhance arm bone properties and muscle mass in adolescent females do not promote grip strength.NIH/NIAMS R01 AR54145