Journal List > Korean J Sports Med > v.34(2) > 1054565

Choi, Kim, Hur, and Lee: Body Fat Content Does Not Affect Body's Maximal Muscle Strength

Abstract

We investigated that the relationship between body fat content and maximal muscle strength when skeletal muscle mass was matched. Muscle mass was measured from 140 preliminary selected people, and 30 males were finally selected and divided into one of four experimental groups: low body fat (group 1, ≤11.9%), low-moderate fat (group 2, 12.0%−16.9%), moderate-high fat (group 3, 17.0%−22.9%), high fat (group 4, ≥23.0%). All subjects undertook one repetition maximum (1RM) test of abdominal and back upper body's and lower body's, and bench press, squat, and back strength dynamometer was used. Repeated oneway analysis of variance and Tukey's post-hoc test was adopted to specify mean differences among groups. Statistical significance level was set at α=0.05. 1RM of bench press was not different among groups (p>0.05) even though values from group 2 was marginally higher (15.9%) than group 1 values (p=0.091). 1RM of squat was higher in group 4 compared to group 2 and group 3 (p<0.05), and maximal back muscular strength was higher in group 1 and group 3 than group 2 (p<0.05). However, total 1RM values, sum of 1RM obtained from different exercises, did not reveal any statistical differences. No notable correlation was found between percent body fat (%BF) and maximal muscular strength. Interestingly, negative correlation of muscular strength was observed between %BF and relative (per kilogram) body mass (p<0.001), but not with between %BF and relative skeletal muscle mass. Therefore, it was concluded that maximal muscular strength is influenced not by fat mass but by skeletal muscle mass.

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Fig. 1.
Measurement procedures of maximum muscle strength.
kjsm-34-153f1.tif
Fig. 2.
Correlation between one repetition maximum (1RM) and percent body fat (%BF).
kjsm-34-153f2.tif
Fig. 3.
Correlation between one repetition maximum (1RM) and kilogram of body mass. BM, body mass; %BF, percent body fat.
kjsm-34-153f3.tif
Fig. 4.
Correlation between one repetition maximum (1RM) and kilogram of skeletal muscle mass. %BF, percent body fat.
kjsm-34-153f4.tif
Table 1.
Physical characteristics of subjects
Group (%body fat) Age (yr) Height (cm) Weight (kg) Body fat (%) BMI (kg/m2) Muscle mass (kg)
≤11.9% (n=7) 21.0±1.8 176.4±6.5 63.8±3.4 10.0±1.6 20.5±0.8 28.4±1.7
12.0%−16.9% (n=10) 21.5±1.6 172.6±5.0 65.4±4.7 14.5±1.3 21.9±0.6 27.4±1.5
17.0%−22.9% (n=7) 21.4±2.0 173.1±4.7 70.6±3.6 18.9±1.4 23.6±0.8 27.7±1.5
≥23.0% (n=6) 24.8±1.5 174.1±5.9 86.1±13.0 27.5±3.9 28.2±2.7 27.8±0.4
Total group (n=30) 22.0±2.2 173.9±5.4 70.4±10.5 17.1±6.4 23.2±3.0 27.8±1.4

Values are presented as mean±standard deviation.

Table 2.
One repetition maximum values obtained from bench press test
%Body fat Value (kg)
≤11.9% 72.9±13.8
12.0%−16.9% 84.5±13.6
17.0%−22.9% 78.6±14.6
≥23.0% 80.0±14.1

Values are presented as mean±standard deviation.

Table 3.
One repetition maximum values obtained from squat test
%Body fat Value (kg)
≤11.9% 110.0±17.3
12.0%−16.9% 107.0±15.5∗
17.0%−22.9% 101.4±13.5∗
≥23.0% 118.3±24.0

Values are presented as mean±standard deviation. ∗Significant difference from ≥23.0%.

Table 4.
One repetition maximum values obtained from back strength test
%Body fat Value (kg)
≤11.9% 120.0±8.38∗
12.0%−16.9% 111.7±8.98
17.0%−22.9% 127.9±24.67∗
≥23.0% 111.7±27.67

Values are presented as mean±standard deviation. ∗Significant difference from 12.0%−16.9%.

Table 5.
One repetition maximum values obtained from the sum of bench press, squat, and back strength test
%Body fat Value (kg)
≤11.9% 302.9±25.10
12.0%−16.9% 303.2±24.48
17.0%−22.9% 307.9±46.59
≥23.0% 310.0±59.32

Values are presented as mean±standard deviation.

Table 6.
Relationship between one RM and percent body fat
  Bench press Squat Back strength Total RM
R2 value 0.0201 0.0530 0.0154 0.0501
Regression equation Y=0.3069x+74.25 Y=0.6250x+97.98 Y=0.3567x+111.3 Y=1.289x+283.5

Values are presented as mean±standard deviation. RM, repetition maximum.

Table 7.
Relationship between one RM and kilogram of body mass
Variable Bench press Squat Back strength Total RM
R2 value 0.201 0.303 0.3292 0.501
Regression equation Y=−0.015x+1.396 Y=−0.0203x+1.904 Y=−0.0258x+2.130 Y=−0.0609x+5.430

Values are presented as mean±standard deviation. RM, repetition maximum.

Table 8.
Relationship between one RM and kilogram of skeletal muscle mass
Variable Bench press Squat Back strength Total RM
R2 value 0.019 0.065 0.018 0.063
Regression equation Y=0.0106x+2.676 Y=0.0227x+3.513 Y=0.0129x+3.976 Y=0.0462x+10.18

Values are presented as mean±standard deviation. RM, repetition maximum.

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