A more efficient magnetic resonance imaging-based strategy for measuring quadriceps muscle volume.

PURPOSE: To determine the accuracy of several magnetic resonance imaging (MRI)-based strategies for assessment of quadriceps muscle volume (MV) and changes in MV with training. METHODS: Images were acquired along the length of both thighs from young (26 +/- 3 yr, N= 23) and older (69 +/- 3 yr, N= 24) men and women before and after strength training. The quadriceps cross-sectional area (QCSA) of each section was measured before and after training. MV was directly assessed using all of the sections (each 9-mm thick with a 1-mm gap). Alternative estimates of MV were calculated using increasingly greater intervals between sections: every 1.1 cm (MV2), 3.1 cm (MV4), 5.1 cm (MV6), 7.1 cm (MV8), 9.1 cm (MV10), and a single QCSA (L1). The 95% limits of agreement (LOA, +/- 2 SD) between each alternative measure and the criterion measure MV were determined with Bland and Altman plots. Regression was used to predict MV from L1 and to obtain the standard error of the estimate (SEE). RESULTS: Before training, the 95% LOA with MV for the alternative measures ranged from 0.7% to 6.36% of MV, and the prediction of MV from L1 yielded a SEE x 2 of 14.1% of MV. For change in the alternative measures, the 95% LOA ranged from 10.3% to 26.3% of the total change in MV, and the prediction of deltaMV from deltaL1 yielded a SEE x 2 of 60% of the change in MV. CONCLUSION: Increasingly greater intervals between axial MRI sections result in substantially reduced agreement with a criterion measure of MV. The use of one axial section results in relatively higher error and thus should be used only when large effect sizes are expected.

Regional bone mineral density after resistive training in young and older men and women.

PURPOSE: The purpose of this study was to determine the effects of 6 months of whole-body resistive training (RT) on total and regional bone mineral density (BMD) and bone mineral content (BMC) by age and gender in young and older men and women. METHODS: Younger men (n=10) and women (n=7) aged 20-29 years (25+/-1 years) and older men (n=10) and women (n=10) aged 65-74 years (69+/-1 years) participated in 6 months of progressive whole-body RT. Upper- and lower-body strength was assessed by the one repetition maximum (1RM) test, and total body fat, lean tissue mass, femoral neck BMD, Ward's triangle BMD, greater trochanter BMD, total-body BMD, and L2-L4 spine BMD were determined by dual-energy X-ray absorptiometry before and after 6 months of RT. RESULTS: Percent body fat decreased only in the young men (P<0.05). Lean tissue mass increased after training in young men and women and older men (P<0.05) but did not change significantly in older women. Upper- and lower-body 1RM strength increased in all groups (P<0.01). Overall, there was a significant increase in BMD at the femoral neck, ward's triangle and greater trochanter BMD, as well as total body BMC and leg BMC (P<0.05). Total-body BMD and L2-L4 spine BMD did not change with RT. There were no gender differences in the training response between men and women for any of the BMD regions and no age differences in the training response, except for a trend between young and older subjects for femoral neck (P<0.08). CONCLUSION: A 6-month RT program increases muscle mass and improves BMD of the femoral region in young and healthy older men and women as a group, with a trend for this to be greater in young subjects.