Muscular Strength and Regional Lean Mass Influence Bone Mineral Health Among Young Females

Abstract

Introduction: Strength training is able to stimulate bone tissue metabolism by increasing mechanical stress on the skeletal system. However, the direct relationship is not yet well established among younger women, since it is necessary to describe which strength enhancement level is able to produce effective changes in bone integrity. Objectives: This study analyzed the influence of muscle strength on bone mineral content (BMC) and bone mineral density (BMD) among female college students. Methods: Fifteen women (24.9 ± 7.2 years) were assessed for regional and whole-body composition by dual-energy X-ray absorptiometry (DXA). The one-repetition maximum (1-RM) tests were assessed on flat bench press (BP), lat pulldown (LPD), leg curl (LC), knee extension (KE), and 45 degree leg press (45LP). Linear regression analyzed the relationships of BMC/BMD with regional composition and 1-RM test values. Measures of dispersion and error (R2 adj and SEE) were tested, defining a p-value of 0.05. Results: The mean value of whole-body BMC was 1925.6 ± 240.4 g and the BMD was 1.03 ± 0.07 g/cm2. Lean mass (LM) was related to BMC (R2 adj = 0.86, p<0.01, and SEE = 35.6 g) and BMD (R2 adj = 0.46, p<0.01, SEE = 0.13 g) in the lower limbs (LL). The 1-RM tests in BP were associated with BMC and BMD (R2 adj = 0.52, p<0.01, SEE = 21.4 g, and R2 adj = 0.68, p<0.01, SEE = 0.05 g/cm2, respectively) in the upper limbs, while the 1-RM tests in KE were related to BMC and BMD (R2 adj = 0.56, p<0.01. SEE = 62.6 g, and R2 adj = 0.58, p<0.01, SEE = 0.11 g/cm2, respectively) in the lower limbs. Conclusions: Hence, the 1-RM tests for multi-joint exercises are relevant to the regional BMC/BMD, reinforcing the need to include resistance exercises in training routines with the purpose of improving muscular strength and regional lean mass, thereby ensuring a healthy bone mineral mass. Level of Evidence II; Development of diagnostic criteria in consecutive patients (with applied reference ‘‘gold’’ standard).

Bone Health, Muscle Strength and Lean Mass: Relationships and Exercise Recommendations

“…: extensor chair and leg press 45º) were better indicators associated to BMC/BMD, both for the region engaged in the exercise (local effect, r = 0.67 to 0.78) and for others regions of the body, as well as, for whole body (remote effect, r = 0.53 to 0.85), when compared to associations evidenced for maximal strength in upper limbs (ie: bench press), with local effect only, but not negligible (r = 0.75 to 0.84). 47 In addition, the change in leg-press and knee extension muscle strength were associated to changes in femoral BMD (r = 0.37 0.46 p <0.01) for people of different ages and both sexes. 52…”

“…46 However, this regionalization of the stimulus is more evident among men than women. In the study of Guimarães et al 47 , involving young adult women, the total body LM variable showed higher associations (r ~ 0.55 to 0.93) with total and regional BMC/BMD (i.e., lower and upper limbs, hip, and thoracic and lumbar vertebrae) than the upper limb LM (r ~ 0.57 to 0.88) and lower limbs (r ~ 0.53 to 0.87). Although the effect of regional variables on body composition was not analyzed by Chaves et al 48 , the authors had already observed the potential of total body MM in determining variations in femoral colony BMD (r = 0.44) among elderly women (60-70 years), leading the authors to emphasize the benefit of musculature to postmenopausal bone tissue.…”