Effects of Circuit Resistance Training on Body Composition and Bone Status in Young Males

Submitted by Yilmaz Ucan

Dr. Ucan is the chairman of the AIBU Sports Club and is responsible for the university fitness and health center.

ABSTRACT

The purpose of this study was to determine the effects of circuit type resistance training on body composition and bone status in young males.  Twenty eight moderately active male volunteers were randomly assigned to 12 weeks of circuit resistance training (CRT) (n=15; 24.3±1.4 years) or control (C) (n=13; 24.8±2.1 years).  Total body fat (%BF), fat mass (FM), fat-free mass (FFM), bone mineral content, and bone mineral density (BMD) measurements were performed with dual-energy X-ray absorptiometry.  At the end of the 12-week training period, there was a decrease (p<.05) in the CRT group %BF (-1.63%), FM (-1.03kg), an increase in FFM (1.46kg), and no change (p>.05) in body weight or BMD.  In C, no significant (p>.05) changes were observed.  CRT bone mineral density values were significantly (p<.05) higher (.003g/cm2) after the 12 week training period versus the control group values (-.005g/cm2).

Results suggest that 12 weeks of circuit resistance training in moderately active young males had a positive effect on body composition and bone status, with no effect on body weight.  Additional studies may identify effects of circuit resistance training on body composition and bone mineral density in women and aging.

INTRODUCTION

Body composition is of great interest to coaches and athletes.  Body size influences physical performance in many sports.  Body characteristics such as height or arm length remain relatively unchanged with training.  Other components such as fat and fat-free mass respond to diet and exercise practices (20).  Body composition consists of absolute and relative amounts of muscle, bone and fat tissues, water, minerals and other components of total body mass (14).  Researchers, in general, refer to body composition in terms of fat percentage, fat mass (FM), and fat-free mass (FFM), with fat-free mass as body structures excluding fat-mass (29).

Body composition is related to maximal performance, physiological parameters and training-based adaptations.  For example, with two individuals having the same fat-free mass, a higher body fat percentage or fat mass suggests a decreased performance in weight-bearing physical activities such as jumping and running (20).  Monitoring the body composition of athletes on a regular basis provides useful information for training adjustments, where optimal body weight and composition are required for optimal performance (27).

Body structure and size are related to genetics and changes in development (29).  Body weight and body composition are directly related to energy balance.  Energy balance is influenced by expenditure from physical activity, recreational exercise, and occupational exercise (14, 16).  Studies suggest that regular exercise has a positive effect on body weight, body composition, and aging (5, 10, 14).  A variety of exercise modes benefits body composition, improves health, and enhances exercise performance.  Moderate-intensity cardiorespiratory exercise and weight training, regardless of gender, are effective for decreasing body fat percentage, fat weight, and body weight (14).  Resistance training helps build fat-free mass and bone-mineral status (22, 29), as well as promoting positive changes in body composition (6, 21, 23, 26).  Changes in biochemical, neurological and morphological components from strength training generally results in positive changes in body composition (1).  Improvements in fitness components, muscular strength and size, fat-free mass, and decreased body fat have a positive effect on athletic performance (15).

Bone-mineral status in early adulthood is a major factor in the incidence of bone fractures.  Bone-mineral status is in a constant state of change (19, 22).  Bone-mineral status is influenced by force mechanics, hormonal changes, and dietary mechanisms (9).  Individuals who are physically active show greater bone mineral density versus sedentary individuals (18).  Resistance training is beneficial for increasing bone strength, muscular strength, and bone mineral content (3, 8, 17, 18).

According to Wilmore & Costill (1994), resistance exercise increases strength, muscular endurance and flexibility.  Circuit resistance exercise may affect body composition through an increase in fat-free body mass, muscular strength, and bone-mineral status.  In this context, the aim of this study was to investigate the effects of circuit resistance trainings (CRT) on body composition and bone status in young males.

 METHODS

 Participants

Twenty-eight moderately active males volunteered to participate in this study and were randomly assigned to circuit resistance training (CRT) (n=15; 24.3±1.4 years) or a control (C) group (n=13; 24.8±2.1 years).  Physical characteristics of the subjects are presented in Table 1.  The subjects did not smoke and none participated in resistance training.  The study was performed in accordance with the Helsinki Declaration of 1975.  All subjects were informed of the purpose of the study, completed a medical history form, and signed a written consent form approved by the Düzce University, School of Medicine, Ethics Committee of Non-invasive Clinical Researches.

tables

Anthropometric Measurements

Weight and height: All measurements took place under laboratory conditions.  Participants were instructed to refrain from eating or drinking within two hours of the appointment and to empty the bladder before measurements were taken.  Body weight and height were measured by using a mechanical scale with height rod (Seca 700, Seca GmbH & Co. KG., Hamburg, Germany).  Weight graduation was 50 g, and measure rod graduation was 1 mm.  Subjects were weighed in the morning, wearing shorts and T-shirt and in bare feet.

Body composition and bone mineral status: Body composition was assessed by dual-energy X-ray absorptiometry (DXA) using the GE Lunar DPX Pro (GE Medical Systems Lunar, Europe, Belgium).  The total body scan provided values for bone mineral content, non-bone lean tissue, and fat mass (FM) in the whole body and in the arms, legs, trunk, android, and gynoid, separately.  Fat-free mass (FFM) was defined as the sum of non-bone lean tissue and bone mineral content.

Exercise program

After completing the pre-test measurements, the CRT group participated for 12 weeks at 3 days per week in resistance exercise.  All subjects were instructed not to change regular daily activities and dietary habits.  The resistance training program was a circuit training model that included the following 15 exercises: barbell curl, preacher curl, pushdown, triceps extension, back press, lateral raise, chest press, pec deck fly, lat pull down, seated row, leg press, leg extension, supine leg curl, machine hip extension, and crunch.  Each training session began with a 5–10 minute warm-up.  The resistance training sessions began with a 5-10 minute warm-up, followed by 3 sets for each exercise and 12–14 repetitions per set.  The maximum intensity was approximately 50–60% of one repetition.  Each resistance-training session lasted approximately one hour.  The control group refrained from participation in aerobic or resistance exercise during the 12-week study period.  The training protocol is presented in Table 2.

tables2

RESULTS

The major findings are changes in body composition in young male participants in a 12-week CRT program with diet not controlled.  Pre- and post-training body composition results of CRT are presented in Table 3.  After training, CRT showed a decrease in percentage BF (t=-5.07; p<.05), FM (t=-3.74; p<.05), an increase in FFM (t=5.06; p<.05), with no significant change in body weight (t=1.33; p>.05) or BMD (t=1.16; p>.05).

table3

The pre- and post-test body composition results of the control group are presented in Table 4.  The control group showed no significant change in body weight (t=-.28; p>.05), BF percentage (t=.55; p<.05), FM (t=.29; p<.05), FFM (t=-.07; p<.05), and BMD (t=-1.18; p>.05).

table4

table5

The results after the 12-week period between CRT and control are presented in Table 6.  There were significant differences between CRT and control in BF (t=-3.33; p<.05), FM (t=-2.20; p<.05), FFM (t=3.40; p<.05), and BMD (t=2.06; p<.05), with no significant differences in body weight (t=.99; p>.05).

table6

 DISCUSSION

In the present study, the effects of CRT with no dietary restriction on body composition parameters (BF percentage, FM, FFM, BMD, and body weight) were examined.  Results suggest that 12 weeks of CRT improves body composition parameters and bone status of young male subjects.

Resistance training is a common mode to increase FFM and decrease BF percentage (11, 14, 26, 29).  In CRT, significant differences were found in percentage BF, FM, and FFM in response to twelve weeks of training.  The CRT group exhibited a significant decrease in BF (-1.63%),  FM (-1.03 kg), a significant increase in FFM (1.46 kg), with no change in body weight or BMD.  In the control group, there were no significant changes in BF, FM, FFM, or BMD.

The literature supports the findings of the present study.  Shaw et al. (2009) studied the effects of resistance exercise training on abdominal fat, with no restriction on energy intake.  Twenty-five healthy male subjects (25±1 years) participated in a resistance exercise program for 16 weeks, 3 times per week.  At the end of the 16-week period, significant decreases were observed for BF, total skinfold, and body mass index (BMI).  Ferreira et al. (2010) conducted a study on 14 sedentary females (33–45 years old) using a 10-week, 3-days-per-week CRT program for body composition.  No significant changes were found in waist circumference and waist to hip ratio.  The results suggested that CRT increased FFM and decreased FM and BF percentage.  Forty-seven females and 26 males (mean 20.3 years) volunteered for a study conducted by Wilmore (1974) with resistance exercise for 10 weeks, 2 days per week.  At the end of the 10-week period, body weight did not change but relative FM decreased by 10% and 7.6% for males and females, respectively.

Results from other studies vary with respect to resistance exercise and body composition.  Brown and Wilmore (1974) conducted research in which 7 female national throwers (aged 16–23) engaged in resistance exercises for six months, three days per week.  At the end of the six-month period, all showed a considerable gain in strength, with no change in body weight or BF percentage.  In 81 healthy volunteer subjects (male=35, female=46; aged 65–85) in response to 22 weeks of resistance training at 3 days per week, Hanson et al. (2009) found an increase in FFM with no difference in BF percentage in both the males and females.  In a study by Harber et al. (2004), a circuit resistance training program of 10 exercises for 10 weeks at 3 times per week in young adult men (aged 18–35) found no differences in body weight, FFM, FM, or percentage BF.

One of the aims of the present study was to examine the effects of CRT on bone status in young males.  During adulthood, one goal of physical activity is to maintain bone mass and bone health.  In adults, bone mineral density response to exercise training is unclear (2).  In the present study, at the end of the 12-week period, there were no significant within-group differences in bone mineral density in CRT or the control group.  However, bone mineral density was significantly higher in CRT at the end of the 12-week period versus the control group.  Almstedt et al. (2011) conducted a study on recreationally active men (n = 12) and women (n = 12) aged 18–23 to reveal the effects of a 24-week resistance-training program on bone mineral density.  Results indicated that resistance training was effective in increasing BMD in the young men.  The females in the study who followed the same protocol did not receive the same benefits.  Ryan et al. (2004) investigated the effects of 6 months of progressive whole-body resistance training on body composition in younger men (n=12) and women (n=7) aged 20-29 years and older men (n=10) and women (n=10) aged 65-74 years.  Results found an increase in muscle mass and improved bone mineral density of the femoral region in both the healthy young and older men and women.

Limitations in the current study included conducting the study only on young men.  Resistance training in young women and the elderly may reveal different results.  Long-term effects of treatment beyond 12 weeks may be considered.

 CONCLUSIONS

The present study found that a 12 week resistance training program increased FFM, and decreased percentage BF and FM in young moderately-active males.  Bone mineral density values were significantly higher after training in CRT versus control, with no significant changes in body weight in CRT or control.

 APPLICATIONS IN SPORT

The evidence suggests that resistance training is an effective exercise to improve body composition and bone mineral density in untrained young males.  The findings of this study suggest that moderate-intensity circuit resistance training reduces body fat percentage and increases lean body mass and bone mineral density.  CRT is suggested to improve body composition, bone mass, and application in specific sports and health care aspects, especially for young males.

ACKNOWLEDGMENTS

None

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