The relationship between muscle strength and bone mineral content (BMC) and bone mineral density (BMD) is supposed from the assumption of the mechanical stress influence on bone tissue metabolism. However, the direct relationship is not well established in younger men, since the enhancement of force able to produce effective changes in bone health, still needs to be further studied. This study aimed to analyze the influence of muscle strength on BMC and BMD in undergraduate students. Thirty six men (24.9 ± 8.6 y/o) were evaluated for regional and whole-body composition by dual energy X-ray absorptiometry (DXA). One repetition maximum tests (1RM) were assessed on flat bench-press (BP), lat-pull down (LPD), leg-curl (LC), knee extension (KE), and leg-press 45° (LP45) exercises. Linear regression modelled the relationships of BMD and BMC to the regional body composition and 1RM values. Measurements of dispersion and error (R2adj and standard error of estimate (SEE)) were tested, setting ρ at ≤0.05. The BMD mean value for whole-body was 1.12±0.09 g/cm2 and BMC attained 2477.9 ± 379.2 g. The regional lean mass (LM) in upper-limbs (UL) (= 6.80±1.21 kg) was related to BMC and BMD for UL (R2adj = 0.74, p<0.01, SEE = 31.0 g and R2adj = 0.63, SEE = 0.08 g/cm2), and LM in lower-limbs (LL) (= 19.13±2.50 kg) related to BMC and BMD for LL (R2adj = 0.68, p<0,01, SEE = 99.3 g and R2adj = 0.50, SEE = 0.20 g/cm2). The 1RM in BP was related to BMD (R2adj = 0.51, SEE = 0.09 g/cm2), which was the strongest relationship among values of 1RM for men; but, 1RM on LPD was related to BMC (R2adj = 0.47, p<0.01, SEE = 44.6 g), and LC was related to both BMC (R2adj = 0.36, p<0.01, SEE = 142.0 g) and BMD (R2adj = 0.29, p<0.01, SEE = 0.23 g/cm2). Hence, 1RM for multi-joint exercises is relevant to BMC and BMD in young men, strengthening the relationship between force and LM, and suggesting both to parametrizes bone mineral health.

Introduction There is limited consensus regarding the recommendation of the most effective form of exercise for bone integrity, despite the fact that weight training exercise promotes an increase in muscle mass and strength as recurrent responses. However, strength variations in women do not depend on muscle mass development as they do in men, but strength enhancement has shown the potential to alter bone mineral content (BMC) for both sexes. Objective This study analyzed the potential of muscle strength, as well as that of whole-body and regional body composition, to associate femoral BMC in young women. Methods Fifteen female college students (aged 24.9 ± 7.2 years) were assessed for regional and whole-body composition using dual-energy X-ray absorptiometry (DXA). Maximum muscle strength was assessed by the one-repetition maximum (1RM) test in the following exercises: bench press (BP), lat pulldown (LP), knee flexion (KF), knee extension (KE) and 45° leg press (45LP). Linear regression analyzed BMC relationships with regional composition and 1RM values. Dispersion and error measures (R 2 aj and SEE), were tested, defining p ≤0.05. Results Among body composition variables, only total lean body mass was associated with femoral BMC values (R 2 aj = 0.37, SEE = 21.3 g). Regarding strength values, 1RM presented determination potential on femoral BMC in the CE exercise (R 2 aj = 0.46, SEE = 21.3 g). Conclusions Muscle strength aptitude in exercises for femoral regions is relevant to the femoral mineralization status, having associative potential that is similar to and independent of whole-body lean mass. Therefore, training routines to increase muscle strength in the femoral region are recommended. In addition, increasing muscle strength in different parts of the body may augment bone remodeling stimulus, since it can effectively alter total whole-body lean mass. Level of Evidence II; Development of diagnostic criteria in consecutive patients (with universally applied reference ‘‘gold’’ standard).

Although muscle strength, lean mass and bone mineral content/density (BMC/BMD) are consistently reported as major outcomes of resistance training (RT), there is still no agreement on the RT regimen that is capable of achieving this result in men and women of different ages. This study describes the effects of RT on muscle strength, lean mass and bone mineralization, highlighting the relationships between them and analyzing the effectiveness of the RT protocol. Information searches were conducted in open access online academic libraries, using the BMC/BMD indices combined with muscle strength, body composition, and resistance exercises. The results showed changes in BMC/BMD in 72% of the studies published in the last decade. Among these, 77% recommended loads ≥ 80% 1-RM, 61% involved older individuals (> 60 years) and 61% had planning protocols of between 3 and 5 months (~12-20 weeks). The results also highlight muscle strength as a promising index of variations in BMC/BMD, with a moderate to high level of association (r2>0.5), which are specific for men and women in relation to the body region with best responsiveness. Among the studies published in last decade, about 61% had protocols involving only RT, and of these, 82% observed combined changes in BMC/BMD, body composition and muscle strength. This review therefore concludes that RT is important for improving muscle strength, increasing lean mass (whole-body and regional) and preventing risk factors that could impair the mineral integrity of the bone tissue, in individuals of all ages and sexes. Level of Evidence I; Systematic review of Level I RCTs (and study results were homogenous).

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).

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