LOCALIZED FAT-FREE MASS DOES NOT INFLUENCE MUSCLE STRENGTH IN OBESE AND NON-OBESE BOYS

Moraes Junior, Frederico Bento de; Lopes, Wendell Arthur; Silva, Larissa Rosa da; Araújo, Cristiane Tavares; Jesus, Incare Correa de; Coutinho, Priscila Rizental; Radominski, Rosana Bento; Leite, Neiva

doi:10.1590/1517-869220182405156640

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Revista Brasileira de Medicina do Esporte

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Original Article, Physiology • Rev Bras Med Esporte 24 (5) • Sep-Oct 2018 • https://doi.org/10.1590/1517-869220182405156640 copy

LOCALIZED FAT-FREE MASS DOES NOT INFLUENCE MUSCLE STRENGTH IN OBESE AND NON-OBESE BOYS

MASSA LIVRE DE GORDURA LOCALIZADA NÃO INFLUENCIA FORÇA MUSCULAR EM RAPAZES OBESOS E NÃO OBESOS

MASA LIBRE DE GRASA LOCALIZADA NO INFLUENCIA LA FUERZA MUSCULAR EN JÓVENES OBESOSY NO OBESOS

Authorship SCIMAGO INSTITUTIONS RANKINGS

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.

Keywords:
Adolescent; Obesity; Muscle strength

Variables	Obese	Overweight	Normal Weight	F	p
	(n=14)	(n=14)	(n=11)
Age (years)	14.2±0.89	14.4±1.28	14.1±0.98	0.207	0.81
Tanner (IV/V)	7/7	7/7	6/5	^# # comparisons among proportions using the chi-squared test. 0.65	0.96
BM (kg)	87.8±17.2	79.8±13.1^b b Overweight vs. Normal Weight ^ p<0.01	58.7±5.86^c c Obese vs. Normal Weight ^* ***** p<0.001	15.07	<0.0001
Height (m)	1.69±0.07	1.73±0.06	1.72±0.06	1.15	0.32
BMI (kg/m²)	30.2±4.35^a a Obese vs. Overweight ^ p<0.01	26.2±2.71^b b Overweight vs. Normal Weight ^* ***** p<0.001	19.8±1.60^c c Obese vs. Normal Weight ^* ***** p<0.001	32.70	<0.0001
BMD	2.83±0.44	2.89±0.50^b b Overweight vs. Normal Weight ^* * p<0.05	2.45±0.33	3.48	0.04
FM (%)	38.4±4.42^a a Obese vs. Overweight ^ p<0.01	30.4±6.12^b b Overweight vs. Normal Weight ^* ***** p<0.001	15.2±4.70^c c Obese vs. Normal Weight ^* ***** p<0.001	63.26	<0.0001
FM (kg)	33.9±10.2^a a Obese vs. Overweight ^ p<0.01	24.7±8.40^b b Overweight vs. Normal Weight ^* ***** p<0.001	9.01±3.48^c c Obese vs. Normal Weight ^* ***** p<0.001	28.72	<0.0001
FFM (%)	58.2±4.15^a a Obese vs. Overweight ^ p<0.01	65.8±5.98^b b Overweight vs. Normal Weight ^* ***** p<0.001	80.6±4.79^c c Obese vs. Normal Weight ^* ***** p<0.001	61.15	<0.0001
FFM (kg)	50.4±7.95	51.4±5.77	47.0±3.72	1.66	0.20
TM Torso (kg)	40.7±10.1	36.0±6.40^b b Overweight vs. Normal Weight ^ p<0.01	25.7±2.47^c c Obese vs. Normal Weight ^* ***** p<0.001	13.25	<0.0001
TM Leg (kg)	32.4±6.37	29.6±5.71^b b Overweight vs. Normal Weight ^ p<0.01	21.5±2.15^c c Obese vs. Normal Weight ^* ***** p<0.001	13.95	<0.0001
TM Arm (kg)	9.10±1.44	8.53±1.60^b b Overweight vs. Normal Weight ^ p<0.01	6.54±0.80^c c Obese vs. Normal Weight ^* ***** p<0.001	11.57	<0.0001
FFM Torso (kg)	23.0±4.20	23.2±2.62	21.1±1.74	1.63	0.20
FFM Leg (kg)	18.1±2.87	18.6±2.24	16.4±1.47	2.82	0.07
FFM Arm (kg)	5.70±0.98	6.05±1.05	5.59±0.65	0.86	0.49

Variables	Obese	Overweight	Normal Weight	P
	(n=14)	(n=14)	(n=11)
Absolute Bench Press (kg)	41.5±9.00	45.1±9.78	41.6±11.0	0.54
Absolute Leg Press (kg)	204.4±55.5	199.2±51.0	192.7±40.2	0.84
Absolute Bicep Curl (kg)	22.2±4.62	24.8±9.78	23.6±5.18	0.43
LL Bench Press	50.5±10.1	53.7±10.9	48.1±11.5	0.44
LL Leg Press	236±59.3	228.9±54.6	214.2±40.3	0.57
LL Bicep Curl	31.31±5.62	33.3±7.29	30.1±5.73	0.43

Variables	Obese	Overweight	Normal Weight	P
	(n=14)	(n=14)	(n=11)
LL Bench Press / BM	0.58±0.07	0.68±0.12^b b Overweight vs. Normal Weight ^ p<0.05	0.82±0.17^c c Obese vs. Normal Weight ^* ***** p<0.001.	<0.001
LL Leg Press / BM	2.73±56	2.88±43^b b Overweight vs. Normal Weight ^ p<0.05	3.67±64^c c Obese vs. Normal Weight ^* ***** p<0.001.	<0.001
LL Bicep Curl / BM	0.36±0.05	0.42±0.07^b b Overweight vs. Normal Weight ^ p<0.05	0.51±0.09^c c Obese vs. Normal Weight ^* ***** p<0.001.	<0.001
LL Bench Press / FFM (kg)	0.99±0.08	1.02±0.12	1.02±0.21	0.89
LL Leg Press /FFM (kg)	4.68±0.85	4.39±0.62	4.55±0.72	0.58
LL Bicep Curl / FFM (kg)	0.62±0.11	0.63±0.08	0.64±0.06	0.83
LL Bench Press /FFM torso	2.19±0.25	2.30±0.32	2.27±0.48	0.71
LL Leg Press /FFM leg	13.0±2.46	12.1±1.75	13.0±2.23	0.48
LL Bicep Curl /FFM arm	5.49±0.42	5.48±0.38	5.33±0.62	0.68

	LL Bench Press	LL Bicep Curl	BMI	%FM	FFM
LL Leg Press	.878^ p<0.01; NS=not significant.	.865^ p<0.01; NS=not significant.	.511^ p<0.01; NS=not significant.	.196	.759^ p<0.01; NS=not significant.
LL Bench Press		.929^ p<0.01; NS=not significant.	.425^ p<0.01; NS=not significant.	.109	.745^ p<0.01; NS=not significant.
LL Bicep Curl			.380^* * p<0.05	.085	.722^ p<0.01; NS=not significant.
BMI				.890^ p<0.01; NS=not significant.	.583^ p<0.01; NS=not significant.
%FM					.302

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[1] Correspondence: Rua Leonardo Javorski, 100. Bloco 01, Apto. 12. Fazendinha, Curitiba, Paraná, Brazil. 81.330-480. freddjr@hotmail.com