Localized Fat-Free Mass Does Not Influence Muscle Strength in Obese and Non-Obese Boys

Abstract

Introduction: Obesity in adolescents has increased worldwide, and is generally associated with poor eating habits and physical inactivity. Objective: To compare absolute and relative muscle strength with body mass (BM), fat-free mass (FFM) and localized FFM of upper and lower limbs among obese and non-obese adolescents. Methods: BM, height and body mass index (BMI) were verified in 39 male adolescents (aged 13-17 years). Body composition was measured by dual-energy X-ray absorptiometry (DXA) and maximal strength of upper and lower limbs was estimated by a one-repetition maximum (1RM) test. Participants were divided into three groups: eutrophic (normal weight) (n=11), overweight (n=14), and obese (n=14). One-way ANOVA was used to compare the variables, followed by a Bonferroni post-hoc test for multiple comparisons. Pearson's correlation coefficient was used for relevant correlations and multiple linear regression to verify the influence of anthropometric variables, body composition and muscle strength of upper and lower limbs. Results: Obese and overweight adolescents had absolute muscle strength values similar to those of the eutrophic adolescents, which were lower when corrected by BM (p<0.001). However, muscle strength related to FFM and localized FFM were similar between groups in both upper and lower limbs. Linear regression showed that BMI explained 59% of the variation in absolute muscle strength of the lower limbs (β=0.59, p<0.05), FFM explained 84% of the variation in absolute muscle strength of the upper limbs (β=0.84, p<0.01) and 68% of the lower limbs (β=0.68; p<0.01), while localized FM was inversely associated in the lower limbs (β=−0.53, p<0.05). Conclusion: Muscle strength of lower and upper limbs, when corrected by localized FFM, does not distinguish between overweight and normal weight adolescents, indicating that obesity does not have a negative effect on generation of muscle strength in obese boys. Level of Evidence III; Case-control study.

Report Card Brazil: systematic review of muscle strength assessment in children and adolescents in Brazil

“…The references of included studies were analyzed in order to identify possible information on the theme not verified during the systematic search; however, no additional studies in relation to those previously identified were included. Thus, 13 studies [17][18][19][20][21][22][23][24][25][26][27][28][29] were included in this review (Figure 1).…”

“…Thirteen studies with cross-sectional design were part of the present review. Of this total, seven studies were carried out in the southern region of Brazil (Santa Catarina, n = 04; Paraná, n = 03) 19,[21][22][23][24]26,27 , two studies in the southeastern region (São Paulo, n = 01; Minas Gerais, n = 01) 18,29 , two studies in the northeastern region (Alagoas, n = 01; Piauí, n = 01) 25,28 and one study in the northern region (Amazonas) 17 . Additionally, one study 20 was conducted in states included in the southern and southeastern regions of Brazil (Paraná and São Paulo, respectively).…”

“…Additionally, one study 20 was conducted in states included in the southern and southeastern regions of Brazil (Paraná and São Paulo, respectively). With regard to the age group of participants, 10 studies were conducted with participants aged 10 years or older 17,[19][20][21][22][23][24]26,27,29 . Two studies were carried out with the participation of children and adolescents 18,25 , and one study was carried out exclusively with children 28 .…”

Physical fitness in preschool children in relation to later body composition at first grade in school

“…Some authors did not apply confounding variables [ 39 ], while in our study, the adjustments for potential confounding variables was similar to the previous study of Henriksson et al [ 31 ]. Importantly, to control the maturation, we expressed the handgrip strength as relative to BMI [ 27 , 28 ] and FFM [ 30 ]. In addition, differences in test methodology might have been affected the results.…”

“…Upper and lower body muscular strength were expressed as relative measures, normalizing by BMI [ 27 , 28 ] and FFM [ 29 , 30 ]. To calculate the grip-to-BMI ratio and the grip-to FFM ratio, handgrip strength value was divided by BMI and FFM, respectively.…”