Submitted by: Jon YeanSub Lim, Northern State University
This study investigated the effect of creatine supplementation on the body composition, muscular strength, and power of 36 female collegiate volleyball players across 10 weeks of training . The 19- to 26-year-olds were randomly assigned, in a double-blind fashion, to either a creatine treatment group (CT) (n = 18) or placebo control group (PC) (n = 18). During an initial loading phase comprising 5 days, the CT group ingested 5 g of creatine 4 times each day; during the maintenance phase that followed, CT group members consumed 5 g of creatine once a day. The PC group followed the same administration schedule but consumed a glucose placebo. All 36 athletes participated in a conditioning program focusing on weight training and plyometric training. Measures were taken before administration of creatine began, and also at the conclusion of the study, of body weight, lean body mass, percentage of body fat, 1-repetition-maximum bench press capacity, and vertical jump (VJ) ability. For both groups, bench press and VJ results improved significantly during the study, though improvement among members of the CT group was significantly greater than among the PC group, p < 0.05. Further, the CT group had significantly greater gains in body weight and lean body mass, with no change in body fat. The findings suggest that creatine supplementation in conjunction with a good conditioning program can improve athletic performance in female collegiate volleyball players.
Effects of Creatine Supplementation on Body Composition, Strength, and Power of Female Volleyball Players
Athletes have continuously sought elixirs to enhance their performance. Their use of oral creatine supplementation for this purpose has become increasingly popular in recent years. Creatine is an amino acid compound. Of the human body’s supply of creatine, approximately 95% is in skeletal muscles and about 5% is stored in the heart, the brain, and, in males, the testes (Walker, 1979). Creatine is synthesized by the liver, kidneys, and pancreas, with additional supply obtained by consuming fish, meat, and other animal products. It is converted to phosphocreatine, which is necessary to resynthesize adenosine triphosphate (ATP). During short-term high-intensity exercise, phosphocreatine is a primary source of energy for APT resynthesis.
Numbers of prior scientific studies show creatine supplementation to significantly increase creatine concentrations in skeletal muscle, a condition that accelerates phosphocreatine resynthesis (Balsom et al., 1995; Casey et al., 1996; Greenhaff et al., 1993; Harris, Soderlund, & Hultman, 1992). As a result of creatine supplementation, increased muscle creatine enhances athletic performance during high-intensity, intermittent exercise (Haff et al., 2000; Stout et al., 1999). Creatine supplementation also delays the onset of fatigue and facilitates recovery during repeated bouts of high-intensity exercise (Greenhaff et al., 1993; Hultman et al., 1990). Supplementation with creatine also has ergogenic effects on muscular strength and power (Bosco et al., 1997). Finally, creatine supplementation significantly increases body mass, with increased fat-free mass (Earnest et al., 1995; Kreider, Ferreira, et al., 1998; Kreider, Klesges, et al., 1996; Vandenberghe et al., 1997).
Although in growing numbers of studies creatine supplementation has been found to enhance performance during high-intensity, intermittent exercise, most studies have involved short-term supplementation and have not investigated supplementation in sports-specific settings. There have been few studies, for example, of creatine supplementation among female collegiate volleyball players.
The study sample was 36 female collegiate volleyball players who had not supplemented with creatine within the 6 months preceding the data collection. The players (age = 20.6 ± 1.73 years, weight = 58.0 ± 2.2 kg, height = 176 + 8 cm) volunteered to participate in the investigation. All were currently engaged in resistance training and had 1 or more years of resistance training experience; all continued to train 3 times per week during the experimental period. Each participant completed a medical history, a lifestyle inventory, a training inventory, and an informed consent form before participating in the study. All procedures complied with human subject guidelines established by the U. S. Department of Health, Education and Welfare and the American Physiological Society. Participants were required to maintain their normal training, physical activity patterns, and dietary regimens throughout the study.
The 19- to 26-year-old athletes were randomly assigned, in a double-blind fashion, to either a creatine treatment group (CT) (n = 18) or placebo control group (PC) (n = 18) group. During an initial loading phase comprising 5 days, the CT group ingested 5 g of creatine 4 times each day; during the maintenance phase that followed, CT group members consumed 5 g of creatine once a day. The creatine supplements were measured in 5-g quantities and placed in generic capsules coded for identification. The PC group followed the same administration schedule but consumed a glucose placebo. All 36 subjects participated in a conditioning program focusing on weight training and plyometric training.
Pre- and post-experiment testing determined body weight, lean body mass, percentage of body fat, 1-repetition-maximum bench press capacity, and vertical jump (VJ) ability. The bench press test using free weight constituted a of measure muscular strength. The vertical jump test was administered to measure muscular power. Body density was determined using the hydrostatic weighing technique. Body fat percentage and fat-free mass were calculated based on the body density values.
Statistical analyses were completed using SPSS (Statistical Package for the Social Sciences) (version 9.0). A one-way analysis of variance with repeated measures was conducted to make comparisons, both between groups and over time, of the measures for bench press, vertical jump, body weight, percentage of body fat, and lean body mass. Statistical significance was accepted at an alpha level of p < 0.05. Values presented in the results are means ± SD.
Table 1 summarizes the results observed in terms of muscular strength and power measurements. Statistical analysis demonstrated that both the creatine treatment group and placebo group experienced statistically significant improvement in bench press and vertical jump after 10 weeks of training (see Figure 1). However, for both tests, the creatine treatment group improved to an extent that was, statistically speaking, more significant than the improvement shown by the control group (p < 0.05).
2 Groups’ Pre- and Post-Experiment Measurements, Bench Press/Strength and Vertical Jump/Power
||Placebo Group (n = 18)
||Creatine Group (n = 18)
|47.4 ± 5.8 kg>50.3 ± 5.8 kg*
||47.6 ± 5.0 kg55.2 ± 5.0 kg*…
|>49.4 ± 1.6 cm50.9 ± 1.7 cm*
||49.4 ± 2.6 cm52.3 ± 2.1 cm*…
Note. Values are means ± SD; n = number of subjects. Bench press used was 1-repetition-maximum.
*Significant improvement, p < 0.05
…Significant treatment effect compared with placebo, p < 0.05
Figure1. Results of bench press and vertical jump measurements
Pre- and post-experiment measures of the players’ body weight, percentage of body fat, and lean body mass are presented in Table 2. Statistical analysis demonstrated that the CT group’s gains in body weight and lean body mass were greater than the PC group’s, to a statistically significant degree, with no change in percentage of body fat (p < 0.05). In the PC group, no statistically significant differences were observed between the pre- and post-experiment measures of body weight, percentage of body fat, and lean body mass .
2 Groups’ Pre- and Post-Experiment Measurements, Body Composition
||Placebo Group (n = 18)
||Creatine Group (n =1 8)
|63.5 ± 3.1 kg
65.7 ± 3.0 kg*
|64.6 ± 2.9 kg
66.3 ± 2.7 kg*…
|Percentage Body Fat
|17.7 ± 1.2%
18.4 ± 1.1%
|17.5 ± 1.2%
17.4 ± 1.2%
|Lean Body Mass
|52.2 ± 2.6 kg
53.6 ± 2.4 kg*
|53.3 ± 2.3 kg
56.1 ± 2.6 kg*…
Note. Values are means ± SD; n = number of subjects.
*Significant improvement, p < 0.05
…Significant treatment effect compared with placebo, p < 0.05
The present results support the findings of previous studies suggesting that creatine supplementation, in conjunction with a good conditioning program, can significantly increase muscular strength and power, to an extent that conditioning programs alone do not match (Haff et al., 2000; Stout et al., 1999). A number of mechanisms have been offered in explanation. First, creatine supplementation increases creatine and phosphocreatine concentration in skeletal muscle, which appears to be directly related to enhancement of force development (Balsom et al., 1995; Casey et al., 1996; Greenhaff et al., 1993; Harris, Soderlund, & Hultman, 1992). Enhanced ability to meet high demand for ATP during maximal exercise may help explain the improvement in muscular strength and power.
The present study’s finding of an increase in lean body mass and body weight with creatine supplementation is consistent with other studies (Earnest et al., 1995; Haff et al., 2000; Kreider, Ferreira, et al., 1998; Kreider, Klesges, et al., 1996; Vandenberghe et al., 1997). Two potential mechanisms underlying such increase have been proposed: an increase in total body water and increased synthesis of myofibrillar protein (Bessman & Savabi, 1990).
The findings of the present study suggest that creatine supplementation in conjunction with a good conditioning program can be effective in improving athletic performance in female collegiate volleyball players. Further research, however, is needed concerning, specifically, long-term creatine supplementation and its effects.
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Jon YeanSub Lim, Department of Health and Physical Education, Northern State University.