Practice of martial arts and bone mineral density in adolescents of both sexes

Ito, Igor Hideki; Mantovani, Alessandra Madia; Agostinete, Ricardo Ribeiro; Costa Junior, Paulo; Zanuto, Edner Fernando; Christofaro, Diego Giulliano Destro; Ribeiro, Luis Pedro; Fernandes, Rômulo Araújo

doi:10.1016/j.rppede.2015.09.003

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Revista Paulista de Pediatria

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ORIGINAL ARTICLES • Rev. paul. pediatr. 34 (2) • Apr-Jun 2016 • https://doi.org/10.1016/j.rppede.2015.09.003 copy

Practice of martial arts and bone mineral density in adolescents of both sexes

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective:

The purpose of this study was to analyze the relationship between martial arts practice (judo, karate and kung-fu) and bone mineral density in adolescents.

Methods:

The study was composed of 138 (48 martial arts practitioners and 90 non-practitioners) adolescents of both sexes, with an average age of 12.6 years. Bone mineral density was measured using Dual-Energy X-ray Absorptiometry in arms, legs, spine, trunk, pelvis and total. Weekly training load and previous time of engagement in the sport modality were reported by the coach. Partial correlation tested the association between weekly training load and bone mineral density, controlled by sex, chronological age, previous practice and somatic maturation. Analysis of covariance was used to compare bone mineral density values according to control and martial arts groups, controlled by sex, chronological age, previous practice and somatic maturation. Significant relationships between bone mineral density and muscle mass were inserted into a multivariate model and the slopes of the models were compared using the Student t test (control versus martial art).

Results:

Adolescents engaged in judo practice presented higher values of bone mineral density than the control individuals (p-value=0.042; Medium Effect size [Eta-squared=0.063]), while the relationship between quantity of weekly training and bone mineral density was significant among adolescents engaged in judo (arms [r=0.308] and legs [r=0.223]) and kung-fu (arms [r=0.248] and spine [r=0.228]).

Conclusions:

Different modalities of martial arts are related to higher bone mineral density in different body regions among adolescents.

Keywords
Martial arts; Bone mineral density; Adolescents

Variables	Control group (n=90)	Martial arts group (n=47)	p-value
	Mean (SD)	Mean (SD)
Age (years)	11.93 (0.90)	12.36 (1.01)	0.020
Weight (kg)	49.50 (11.36)	54.78 (15.52)	0.026
Stature (cm)	155.67 (7.73)	158.43 (11.31)	0.165
% body fatness	27.62 (12.43)	27.59 (12.56)	0.808
Fat free mass (kg)	32.43 (5.47)	35.35 (9.70)	0.065
Maturity offset^a a Age at peak height velocity.	-2.67 (0.72)	-2.26 (0.94)	0.012

Bone mineral density g/cm ²
Arms	0.68 (0.06)	0.76 (0.19)	0.007
Legs	1.08 (0.10)	1.18 (0.23)	0.015
Trunk	0.83 (0.07)	0.88 (0.09)	0.002
Pelvis	1.11 (0.97)	1.07 (0.13)	0.790
Spine	0.89 (0.11)	0.95 (0.12)	0.002
Whole body	1.01 (0.07)	1.04 (0.09)	0.010

Variables	Control (n=90)	Judo (n=17)	Karate (n=14)	Kung-fu (n=16)	ANCOVA
	Mean (SE)				p -value	Eta-squared	Effect size
Arms (g/cm²)	0.695 (0.01)	0.771 (0.02)^a a p-value<0.05 compared to the control group.	0.695 (0.03)	0.735 (0.03)	0.042	0.063	Medium
Legs (g/cm²)	1.105 (0.01)	1.173 (0.03)	1.139 (0.04)	1.150 (0.04)	0.264	0.031	Small
Trunk (g/cm²)	0.845 (0.01)	0.841 (0.01)	0.863 (0.02)	0.876 (0.01)	0.243	0.032	Small
Pelvis (g/cm²)	1.122 (0.08)	1.028 (0.20)	1.098 (0.24)	1.089 (0.23)	0.979	0.001	Trivial
Spine (g/cm²)	0.904 (0.01)	0.897 (0.02)	0.944 (0.02)	0.963 (0.02)	0.083	0.051	Small
Whole body (g/cm²)	1.021 (0.01)	1.009 (0.01)	1.033 (0.02)	1.049 (0.02)	0.292	0.029	Small

Bone mineral density (g/cm²)	Control (n=90)	Judo (n=17)	Karate (n=14)	Kung-fu (n=16)
	FFM (kg)	FFM (kg)	FFM (kg)	FFM (kg)
	β (β 95%CI)^a a Model adjusted by sex, age and somatic maturation. Bold indicates p-value significant and positive correlation between fat free mass and bone mineral density.	β (β 95%CI)^a a Model adjusted by sex, age and somatic maturation. Bold indicates p-value significant and positive correlation between fat free mass and bone mineral density.	β (β 95%CI)^a a Model adjusted by sex, age and somatic maturation. Bold indicates p-value significant and positive correlation between fat free mass and bone mineral density.	β (β 95%CI)^a a Model adjusted by sex, age and somatic maturation. Bold indicates p-value significant and positive correlation between fat free mass and bone mineral density.
Arms (g/cm²)	0.006 (0.004 to 0.009)	0.005 (-0.069 to 0.080)	0.010 (-0.001 to 0.020)	0.004 (-0.002 to 0.010)
Versus control	-	p-value=0.976	p-value=0.435	p-value=0.528
Legs (g/cm²)	0.013 (0.010 to 0.017)	0.010 (-0.085 to 0.105)	0.026 (0.011 to 0.042)	0.003 (-0.003 to 0.009)
Versus control	-	p-value=0.945	p-value=0.077	p-value=0.006
Trunk (g/cm²)	0.010 (0.007 to 0.012)	0.023 (0.006 to 0.040)	0.017 (0.005 to 0.028)	0.001 (-0.003 to 0.005)
Versus control	-	p-value=0.110	p-value=0.173	p-value=0.001
Pelvis (g/cm²)	0.022 (-0.026 to 0.070)	0.035 (0.007 to 0.064)	0.024 (0.007 to 0.040)	0.001 (-0.006 to 0.005)
Versus control	-	p-value=0.635	p-value=0.936	p-value=0.385
Spine (g/cm²)	0.012 (0.008 to 0.015)	0.031 (0.010 to 0.052)	0.026 (0.007 to 0.045)	-0.001 (-0.008 to 0.007)
Versus control	-	p-value=0.065	p-value=0.132	p-value=0.002
Whole body (g/cm²)	0.007 (0.005 to 0.010)	0.016 (-0.001 to 0.032)	0.017 (0.005 to 0.029)	0.002 (-0.003 to 0.008)
Versus control	-	p-value=0.206	p-value=0.053	p-value=0.027

Bone mineral density (g/cm²)	Control versus Judo(n=108)	Control versus Karate(n=104)	Control versus Kung-Fu(n=106)
	r(r95%CI)	r(r95%CI)	r(r95%CI)
Arms	0.308 (0.126 to 0.470)	0.018 (-0.175 to 0.210)	0.248 (0.060 to 0.419)
Legs	0.223 (0.036 to 0.395)	0.144 (-0.050 to 0.328)	0.185 (-0.006 to 0.363)
Trunk	0.012 (-0.177 to 0.201)	0.124 (-0.070 to 0.309)	0.171 (-0.020 to 0.350)
Pelvis	-0.018 (-0.206 to 0.172)	-0.008 (-0.200 to 0.185)	-0.013 (-0.203 to 0.178)
Spine	-0.009 (-0.198 to 0.180)	0.165 (-0.028 to 0.347)	0.228 (0.039 to 0.401)
Whole body	-0.071 (-0.257 to 0.120)	0.065 (-0.129 to 0.254)	0.149 (-0.043 to 0.330)

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[1] * Corresponding author. E-mail:hidekincubus@yahoo.com.br (I.H. Ito).