During short-duration, high-intensity exercises, the. Long-Term Effects of Creatine Monohydrate on Strength and Power

Journal of Strength and Conditioning Research, 1999, 13(3), 187 192 1999 National Strength & Conditioning Association Long-Term Effects of Creatine Monohydrate on Strength and Power DAVID R. PEARSON, DEREK G. HAMBY, WADE RUSSEL, AND TOM HARRIS The Human Performance Laboratory, Ball State University, Muncie, Indiana 47306. ABSTRACT The use of creatine monohydrate supplementation by athletes to increase strength and lean body mass has great anecdotal support. There has also been great interest in the use of lower doses of creatine monohydrate for extended periods during heavy resistance training. The purpose of this investigation was to document the long-term effects of creatine monohydrate supplementation on resistance-trained athletes. Sixteen collegiate football players were randomly separated into creatine monohydrate and placebo groups. Supplementation in capsule form consisted of 5 g/d of creatine monohydrate or placebo (no loading phase) throughout a 10-week supervised resistance training program. Pretesting and posttesting consisted of the following: weight; body fat estimation; 1 repetition maximum bench press, squat, and power clean; and Cybex testing. Results revealed the creatine monohydrate group was able to significantly increase measures of strength and power and increase body mass without a change in percent body fat, whereas the placebo group showed no significant changes. The results indicate that 10 weeks of creatine monohydrate supplementation while participating in a resistance training program significantly increases strength and power indices compared with placebo supplementation. These data also indicate that lower doses of creatine monohydrate may be ingested (5 g/d), without a short-term, large-dose loading phase (20 g/d), for an extended period to achieve significant performance enhancement. Key Words: resistance training, supplementation, weight training Reference Data: Pearson, D.R., D.G. Hamby, W. Russel, and T. Harris. Long-term effects of creatine monohydrate on strength and power. J. Strength Cond. Res. 13(3):187 192. 1999. Introduction During short-duration, high-intensity exercises, the energy responsible for the resynthesis of adenosine triphosphate is primarily met by the phosphocreatine and anaerobic glycolysis energy systems. The depletion of the phosphocreatine energy system occurs at an extremely high rate (10 seconds) (25). The exhaustion of this short-term energy source is believed to be a limiting factor in the maintenance of muscle force production (4, 29, 30). Creatine, via the creatine kinase reaction, is known to have a significant role in the maintenance of the phosphocreatine energy system. Creatine is a nitrogenous organic compound that is synthesized to a small extent (2%) in the liver, pancreas, and kidneys from the amino acids arginine, methionine, and glycine. However, for most individuals, most creatine obtained by the body is acquired through exogenous food sources such as fish and meat (4, 30). The exhaustion of the phosphocreatine energy system and the correlated increase in fatigue due to the decreased synthesis of adenosine triphosphate brought about the notion that creatine monohydrate supplementation may be a means of increasing phosphocreatine and creatine stores, thus reducing fatigue and increasing performance. Several short-term studies have shown that oral ingestion of creatine monohydrate can increase both intramuscular creatine and phosphocreatine concentrations, while also causing an increase in body weight (8, 14, 16, 19). In many studies, the increases in phosphocreatine were accompanied by enhanced physical performance (3, 5, 10, 12, 15, 17, 26). There has been considerable research done with regard to the short-term effects of creatine supplementation on physical performance and body weight. However, there has been limited investigation into the effects of longer-term supplementation of creatine monohydrate on body weight, power, and strength indices as a result of a resistance training program. It has been well established that resistance training alone can cause significant gains in strength and power (1, 2, 6, 7, 9, 11). It is hypothesized that individuals ingesting creatine monohydrate while participating in a resistance training program should be able to increase strength and power indices to a greater extent than those that are not ingesting creatine monohydrate. This hypothesis is based on previous investiga- 187

188 Pearson, Hamby, Russel, and Harris tions that show that creatine monohydrate supplementation can increase intramuscular creatine and phosphocreatine levels (8, 14, 16, 19). This increase in creatine and phosphocreatine would allow individuals to train at higher intensities for longer periods before experiencing fatigue. Training at a higher intensity would produce greater overload effect, which in turn would increase strength and power to a greater extent than training without creatine monohydrate supplementation. Therefore, the purpose of this investigation was to examine the long-term effects of creatine monohydrate supplementation during a resistance training program on body weight and strength and power indices following the program. Furthermore, there has been considerable interest raised regarding the effects lower doses of creatine monohydrate, without a loading phase, may have during a prolonged training program. Methods Table 1. Summer football resistance training program for hypertrophy phase weeks 1 3.* Exercise Set 1 Monday and Thursday Squats Bench press Lateral pull-down Leg extension Dumbbell incline Cable rows Leg curls Shoulder press Curls Tricep pushdowns Calves 60% 12 Tuesday and Friday Front squats High pulls Overhead squats Snatch pulls Push press *RM repetition maximum. Set 2 65% 12 Set 3 70% 12 Sixteen collegiate football players (mean age, 20.7 years; mean body mass, 101.8 kg; mean percent body fat, 14.4%), on approval of Ball State University s head football coach and the university NCAA compliance officer, were recruited for this investigation. The investigation was approved by the institutional review board committee of the university, and subjects were fully informed of the purpose and risks of participating in this investigation. One week before the start of both the resistance training program and the ingestion of capsules containing either creatine monohydrate or a placebo, subjects underwent preliminary testing. Preliminary testing consisted of the following: weight; body fat estimation; 1 repetition maximum bench press, squat, and power clean; maximal Cybex power test at 4.19 radians per second; and Cybex peak torque test at 1.05 radians per second. Individual preliminary testing was done during a period of 3 days to ensure maximal effort. A double-blind research design was used in this investigation. Subjects were randomly divided into 2 groups of 8. One group ingested 5 g of creatine monohydrate in capsule form (11 capsules) 7 days per week throughout a 10-week training program. The control group of subjects ingested an equal number of placebo capsules. This supplementation protocol was developed based on a pilot study from our laboratory that indicated that the loading phase of 20 g of creatine monohydrate for 5 days may not be necessary to bring about a significant change in postsupplement performance parameters. The results from this study support the pilot work. Subjects were instructed to report to the athletic weight room between the hours of 1 6 PM every Monday, Tuesday, Thursday, and Friday. On arrival, subjects consumed 6 capsules with water. Following ingestion of capsules, subjects began a supervised resistance training program. After completion of the day s training, subjects consumed the remainder of their capsules. For subjects to maintain their daily ingestion regimen of creatine monohydrate and placebo, participants were given capsules every Friday to consume over the weekend. The training program consisted of a 10-week resistance training routine split into 3 microcycles (Tables 1 3). The training program consisted of the training routine implemented yearly by the Ball State University football program as their off-season training program and was under the direct supervision of the strength and conditioning coach. During the week following the tenth week of the resistance training program, subjects underwent posttesting. Posttesting consisted of the same tests as preliminary testing. As in the pretests, individual testing was completed during a 3-day period to ensure maximal effort. The data were initially analyzed using paired t- tests and using Dunn s test (Bonferroni s) to control for the level expansion. Further analysis was performed with the analysis of covariance using the posttest scores as dependent measures and the pretest scores as covariates. An level of p 0.05 was used for all significance testing. Power tests were calculated on all variables and determined to be 0.87, ensuring that the sample size was large enough.

Table 2. Summer football resistance training program for strength phase weeks 4 7.* Strength and Power Effects of Creatine Monhydrate 189 Exercise Set 1 Set 2 Set 3 Set 4 Monday and Thursday Hang cleans Bench press Dumbbell incline Dumbbell shoulder press Upright row Dips Tricep pushdowns Neck Tuesday and Friday Snatch Push press Squats Stiff-leg deadlift Lateral pull down Cable row Curls Calves 77% 4 77% 4 77% 4 80% 4 80% 4 80% 4 75% 8 82.5% 4 82.5% 4 82.5% 4 78% 8 85% 4 85% 4 85% 4 81% 8 *RM repetition maximum. Dips were done without weight. Table 3. Summer football resistance training program for power phase weeks 8 10.* Exercise Set 1 Set 2 Set 3 Set 4 Monday and Thursday Hang cleans Bench press Dumbbell shoulder press Dips Neck Tuesday and Friday Snatch Squats Stiff-leg deadlift Lateral pull down 83% 2 78% 4 83% 2 75% 4 75% 3 86% 2 85% 3 86% 2 85% 3 82.5% 3 75% 10 85% 3 87.5% 3 *RM repetition maximum. Dips were done without weight. Results Table 4 presents the mean ( SD) premeasurements and postmeasurements for body composition, body mass, and strength and power indices. The data show that the creatine monohydrate supplement group was able to significantly increase measures of strength (bench and squat) and power (power clean) and increase body mass as a result of creatine monohydrate supplementation and resistance training. There were no significant changes in the same measures of strength and power in the placebo group. Statistical analysis of Cybex data found no significant changes in either the creatine monohydrate or placebo group. After the 10-week training program both 7-site and 4-site measurements of percent body fat were not significantly changed in either the creatine monohydrate or placebo group. However, a significant increase in body mass in the creatine monohydrate group did occur. Since there was no change in percent body fat, the gains in body mass are presumed to reflect positive alterations in lean body mass.

190 Pearson, Hamby, Russel, and Harris Table 4. Measurements taken before and after the study (mean SD). Measure Before After Body weight (kg) 7-site body fat (%) 4-site body fat (%) Bench press (kg) Squats (kg) Power clean (kg) Cybex 1.05 radians per second PT extension (Nm) Cybex 1.05 radians per second PT flexion (Nm) 106.25 15.61 97.78 25 15.37 5.51 13.52 10.09 15.76 6.52 13.85 10.09 149.12 12.64 130.24 26.73 241 12.64 221.88 67.95 123.32 21.65 111.58 15.42 324.92 52.15 295.21 48.46 196.78 35.12 174.34 21.11 107.67 14.22* 96.62 22.18 16.24 6.02 13.86 8.73 16.68 6.58 13.58 8.33 154.22 12.54* 128.63 22.09 268.59 56.18* 232.47 73.43 130.97 20.57* 109.32 29.32 332.90 46.86 308.40 45.06 205.10 37.40 186.54 28.75 * Change is significantly different at the p 0.05 level. Discussion Prior research by Earnest and colleagues (12) investigated the effect of creatine monohydrate supplementation on muscular power and strength in resistancetrained subjects. Results revealed a significant increase in 1 repetition maximum bench press of 6%, following 28 days of supplementation (20 g/d). Results from the present study demonstrated a statistically significant increase not only in bench and squat maximal lifts but also in maximal power clean lifts by the creatine monohydrate group. Kraemer et al. have shown the development of power to be an important determinant of success in football performance (23). Contrary to what would be expected with resistance training alone, the placebo group showed no statistically significant improvements in any measures. Moreover, the placebo group tended to show a trend toward a decrease in maximal lifting in bench press and power cleans. It is possible that the training duration was insufficient to elicit a response in this nonsupplemented group (18). Earnest et al. (12) have also shown that creatine monohydrate supplementation during resistance training induces an increase in body mass. The results of the present investigation concur with this, since a significant increase in mean body mass was observed in the creatine monohydrate group. However, it is noteworthy that the study by Earnest et al. was using a 20- g/d dose of creatine monohydrate, whereas the present study was using only 5 g/d. Since there was no statistically significant change between pre percent body fat and post percent body fat measures in the present study, the increase in body mass is presumed to reflect an increase in lean body mass. The contribution of body water to this change could not be directly assessed in this study but would appear to be secondary to protein accretion with training. It would have been expected that body mass would have increased in the placebo group after participation in the 10-week resistance training program (31). However, the results of this study revealed no significant change in body mass in the placebo group. This may potentially have been due to the already highly trained state of the subjects (18). Our results indicate that resistance training did not significantly increase isokinetic peak torque values at 1.05 rad/s within the creatine monohydrate or placebo groups as a result of a 10-week resistance training program. This indicates that dynamic strength increases are not accurately assessed by isokinetic evaluation and may be a test-specific problem. These findings are supported by Fry and colleagues (13), who examined resistance training of 23 men for 10 weeks. The results of Fry et al. revealed that although 10 repetition maximum strength values increased significantly, isokinetic torque values (30, 60, 75, and 90 per second) did not significantly increase. Performance measures were tightly linked to the specificity of training principle, which states that adaptations are specific to the characteristics of the training demands imposed. The most critical finding of the present study is that subjects ingesting creatine monohydrate and involved in heavy resistance training were able to increase strength and power measures over a similar group involved in heavy resistance training but ingesting a placebo. Two possible mechanisms by which creatine monohydrate supplementation may increase strength and power are as follows: increased creatine

Strength and Power Effects of Creatine Monhydrate 191 and phosphocreatine levels due to supplementation provide an additive metabolic effect (3, 5, 10, 12, 15, 17, 26) and creatine may be one of several chemical stimuli that couple muscular activity to increased protein synthesis (20 22). However, the exact mechanism by which creatine monohydrate improves physical performance remains speculative. The failure of the placebo group to increase any strength and power measures following 10 weeks of resistance training workouts was unclear. However, several factors may have contributed to this. Although both groups performed the same high volume of training, Hoffman et al. (18) suggest that workouts at too high a volume may result in overtraining and thus the lack of strength improvements. Also, anecdotal information gathered during this investigation from both groups revealed that most subjects were employed in heavy manual labor during morning hours before daily training. Many of the subjects in both groups also reported a decrease in their caloric intake during the training period, primarily due to lack of time to eat during the day. Stone et al. (27) state that combining stresses from training, job, and personal life can promote overtraining. Stone and colleagues also suggest that diets that are carbohydrate deficient are a strong contributor to overtraining. This is supported by recent research by Tesch et al. (28), which shows that significant depletion takes place in type II muscle fibers with a short-term bout of resistance exercise. Although this study has no direct evidence that the athletes in either group were overtrained, further investigation is warranted regarding the benefits of creatine supplementation in preventing overtraining in athletes who may have a combined set of stresses to deal with in off-season programs. 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