The aims of this study were to describe age- and sex-related differences in total body skeletal muscle (TB-SM) mass and to determine the variance explained by physical activity (PA). This cross-sectional study included 401 males and 402 females, aged 60–79 years. TB-SM was determined by dual-energy x-ray absorptiometry (DXA) and PA by Baecke questionnaire. Statistical analysis included t test, ANOVAs, Pearson correlations, and multiple regression analysis. TB-SM mass was higher in the youngest age group when compared with the oldest in males and females. Males had greater TB-SM values than females. PA made a significant and positive contribution to the variation in TB-SM, β = 0.071; p = .016. Sex, height, fat mass, and PA explained 77% of the variance in TB-SM. The oldest cohorts and females had lower TB-SM than the younger cohorts and males. This study suggests that PA exerts a significant role in the explanation of TB-SM.
Élvio R. Gouveia, Bruna R. Gouveia, José A. Maia, Cameron. J. Blimkie and Duarte L. Freitas
Jennifer M. Dent, Cameron J.R. Blimkie, Colin E. Webber, Angus B. McMillan and Rhona M. Hanning
Absolute total body (TB) and regional spine (RS) bone mineral content (BMC) measured by dual photon absorptiometry were lower (p < .05) in Turner syndrome (TS) girls compared to a cohort of younger (by 2 years) but taller and heavier prepubertal girls. Maximal voluntary strength (MVC) of the elbow flexors, knee extensors, and plantar flexors were also consistently and, in most cases, significantly lower in TS girls. Differences between groups in absolute bone mineral and muscle strength disappeared, however, when normalized for skeletal cross-sectional area (areal density) and for the product of muscle cross-sectional area and estimated moment arm, respectively. Maximal voluntary strength and body mass correlated moderately strongly with the bone mineral measures, but only body mass contributed significantly to the variance in total body and regional spine bone mineral measures. Bone mineral and muscle strength appear appropriate for body size and for skeletal and muscle morphology in young TS girls.
Peter N. Wiebe, Cameron J.R. Blimkie, Nathalie Farpour-Lambert, Julie Briody, Helen Woodhead, Chris Cowell and Robert Howman-Giles
The correlates and determinants of total body (TB), femoral neck (FN), greater trochanter (GT) and leg areal bone mineral density (aBMD), and FN volumetric (vol) BMD were investigated in 42 healthy 6–10-year-old girls. Predictor variables included age, height, weight, lean tissue mass (LTM), fat mass, percent body fat, physical activity level, calcium intake, isokinetic knee flexion and extension strength and endocrine (E2) status. Bone density and body composition were determined by dual energy-x-ray absorptiometry (DEXA), and pubertal status was self-determined. LTM, weight, age, knee extensor strength and fat mass were significantly correlated (Pearson correlation coefficients; 0.36 £ r ‡ 0.62) with TBaBMD. These same variables with the addition of height and knee flexor strength were significantly correlated (0.33 £ r ‡ 0.77) with leg aBMD. Only LTM correlated significantly with FNaBMD and none of the independent variables correlated with FNvolBMD or GTaBMD. Only LTM entered as a significant predictor in multiple linear regression analysis (R 2 = 46.7%) for TBaBMD. In conclusion, estradiol status, dietary calcium intake and physical activity level appeared not to be important predictors of BMD in this population, whereas LTM was consistently correlated with most BMD measures and was the single significant determinant of TBaBMD in this study.
Élvio R. Gouveia, José A. Maia, Gaston P. Beunen, Cameron J. Blimkie, Ercília M. Fena and Duarte L. Freitas
The purposes of this study were to generate functional-fitness norms for Portuguese older adults, to determine age and sex differences, and to analyze the physical activity–associated variation in functional fitness. The sample was composed of 802 older adults, 401 men and 401 women, age 60–79 yr. Functional fitness was assessed using the Senior Fitness Test. Physical activity level was estimated via the Baecke questionnaire. The P50 values decreased from 60 to 64 to 75 to 79 yr of age. A significant main effect for age group was found in all functional-fitness tests. Men scored significantly better than women in the chair stand, 8-ft up-and-go, and 6-min walk. Women scored significantly better than men in chair sit-and-reach and back scratch. Active participants scored better in functional-fitness tests than their average and nonactive peers. This study showed a decline in functional fitness with age, better performance of men, and increased proficiency in active participants.
Peter N. Wiebe, Cameron J. R. Blimkie, Nathalie Farpour-Lambert, Julie Briody, Damian Marsh, Allan Kemp, Chris Cowell and Robert Howman-Giles
Few studies have explored osteogenic potential of prepubertal populations. We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 prepubertal girls (6 to 10 yrs) randomly assigned to control (C), low-drop (LD) or high-drop (HD) exercise groups. The latter two groups performed single-leg drop-landings (3 sessions/wk−1 and 50 landings/session−1) from 14cm(LD) and 28cm(HD) using the nondominant leg. Osteogenic responses were assessed using Dual Energy X-ray Absorptiometry (DXA). Single-leg peak ground-reaction impact forces (PGRIF) in a subsample ranged from 2.5 to 4.4 × body-weight (BW). No differences (p > .05) were observed among groups at baseline for age, stature, lean tissue mass (LTM), leisure time physical activity, or average daily calcium intake. After adjusting for covariates of body mass, fat mass and LTM, no differences were found in bone mineral measures or site-specific bone mineral density (BMD) at the hip and lower leg among exercise or control groups. Combining data from both exercise groups failed to produce differences in bone properties when compared with the control group. No changes were apparent for between-leg differences from baseline to posttraining. In contrast to some reports, our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low-moderate peak ground-reaction impact forces are not osteogenic in the developing prepubertal female skeleton.