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Whey Protein and Leucine Supplementation 39 Journal of Exercise Physiologyonline (JEPonline) Volume 12 Number 5 October 2009 Managing Editor Tommy Boone, PhD, MPH Editor-in-Chief Jon K. Linderman, PhD Review Board Todd Astorino, PhD Julien Baker, PhD Tommy Boone, PhD Larry Birnbaum, PhD Eric Goulet, PhD Robert Gotshall, PhD M. Knight-Maloney, PhD Len Kravitz, PhD James Laskin, PhD Derek Marks, PhD Cristine Mermier, PhD Chantal Vella, PhD Ben Zhou, PhD Official Research Journal of the American Society of Exercise Physiologists (ASEP) ISSN 1097-975 Nutrition and Exercise The Effects of Whey Protein and Leucine Supplementation on Strength, Muscular Endurance, and Body Composition During Resistance Training MICHELLE MIELKE 1, TERRY J. HOUSH2, MOH H. MALEK3, TRAVIS W. BECK 4, RICHARD J. SCHMIDT2, GLEN O. JOHNSON2, and DONA J. HOUSH5 1 University of the Pacific, Stockton, California, USA 2University of NebraskaLincoln, Lincoln, USA3 School of Medicine University of California, San Diego La Jolla, USA 4 University of Oklahoma, Norman, USA 5 University of Nebraska Medical Center, Lincoln, USA ABSTRACT Mielke M, Housh TJ, Malek MH, Beck TW, Schmidt RJ, Johnson GO, Housh DJ. The Effects of Whey Protein and Leucine Supplementation on Strength, Muscular Endurance, and Body Composition During Resistance Training. JEPonline 2009;12(5):39-50. The purpose of this study was to compare the effects of: 1) two sets of resistance training without supplementation; 2) one set of resistance training with whey protein plus leucine supplementation; and 3) one set of resistance training with a carbohydrate placebo on body weight (BW), strength, muscular endurance, and body composition. Untrained adult males (N=39, ageSD = 22.72.8 years) were randomly assigned to a nonsupplement (NON-SUP; n=13), protein (PRO; n=13), or a carbohydrate (CHO; n=13) group and performed leg extensions and bench press (NON-SUP = 2 sets, no supplement; PRO = 1 set, protein supplement; CHO = 1 set, carbohydrate) 3 x week at 80% of 1-RM for 8 weeks. Mixed factorial ANOVAs indicated only significant (p<0.05) main effects for time for leg extension 1RM (pre = 82.5±22.4kg; post = 99.2±23.2kg), leg extension endurance (pre = 12±4 reps; post = 19±7reps), bench press 1RM (pre = 64.7±17.8kg; post = 77±20.4kg), and bench press endurance (pre = 7±2 reps; post = 13±4reps). These findings indicated that two sets of resistance training without supplementation, one set of resistance training plus whey protein and leucine supplementation, and one set of resistance training plus a carbohydrate supplement, resulted in similar strength, endurance, and body composition responses. Key Words: Carbohydrate, Strength, Fat-free Weight. Whey Protein and Leucine Supplementation 40 INTRODUCTION Resistance training has been shown to increase strength (1,2), muscular endurance (3,4), body weight (2) and hypertrophy (5,6), as well as result in favorable changes in body composition including decreases in percent body fat (%fat) and fat weight (FW), and increases in fat-free weight (FFW) (2, 7). Furthermore, the magnitude of the increases in strength and hypertrophy are related to the volume of the resistance training program (8,9). For example, recent studies have shown that an increase in the volume of resistance training from one set to two or more sets results in the recruitment of additional motor units and, therefore, greater neuromuscular adaptations, strength gains, and hypertrophy (8-11). This is especially true as the length of the training period increases (8,9). Recreational and competitive athletes often use a protein supplement plus resistance training to increase strength, muscular endurance, and hypertrophy. Resistance training alone stimulates muscle protein metabolism, which can lead to muscle growth and strength increases (5, 6, 12). To stimulate muscle protein synthesis, however, amino acid availability is important, especially in the first few hours after exercise (13). Protein supplementation increases muscle protein synthesis without a corresponding increase in protein breakdown, which results in a net positive protein balance, thus allowing for maximal recovery, hypertrophy, and strength gains (13). “Fast” proteins, such as whey, are characterized by the rapid appearance of their amino acid constituents in the blood and have been shown to elicit strength gains and improve muscle protein balance (12). Recent studies using whey protein supplements have demonstrated improvements in muscle hypertrophy and strength (1, 3, 12) following resistance exercise. Whey protein is a valuable source of the branched chain amino acids (BCAA) including leucine, isoleucine, and valine. Of the BCAA’s, leucine has been shown to provide the greatest stimulation of muscle protein synthesis, and prevention of muscle protein degradation (14). A recent study (1) demonstrated that 20 g whey protein plus 6.2 g leucine in conjunction with 8 weeks of unilateral (nondominant limb) leg extension resistance training elicited greater strength gains (30%) when compared to a carbohydrate placebo (22%). Although some studies have demonstrated a slight ergogenic effect from carbohydrate ingestion, most studies of protein and/or amino acid supplementation have utilized a carbohydrate placebo (1,2,15). Therefore, the purpose of this study was to compare the effects of: 1) two sets of resistance training without supplementation; 2) one set of resistance training with whey protein plus leucine supplementation; and 3) one set of resistance training with a carbohydrate placebo on body weight (BW), strength, muscular endurance, and body composition. Based on previous studies (1,2,15), it was hypothesized that: 1) there would be no difference in training induced changes in BW, strength, muscular endurance, and body composition between the group that performed two sets of resistance training without supplementation and the group that performed one set of resistance training with whey protein plus leucine supplementation; and 2) the training-induced changes in BW, strength, muscular endurance, and body composition in the group that performed two sets of resistance training without supplementation and the group that performed one set of resistance training with whey protein plus leucine supplementation would be greater than those of the group that performed one set of resistance training with a carbohydrate supplement. METHODS Subjects Thirty nine adult males (age range: 19 to 28 yrs) volunteered for this study. All subjects were untrained in resistance/power exercise. Untrained was defined as not having participated in a resistance training program for at least 90 days preceding the start of the investigation. This information was elicited via the Health History Questionnaire in which subjects were asked to provide Whey Protein and Leucine Supplementation 41 details of any type of training they currently participated in. Exclusion criteria included: 1) consumption of a medication (thyroid, hyperlipidemic, hypoglycemic, anti-hypertensive, or androgenic medications) or nutritional supplement (such as creatine, protein drinks, amino acids, or vitaminblends) that would interfere with the results of the study; 2) participation in a resistance training program for at least 90 days preceding the start of the investigation; 3) a history of medical or surgical events that would significantly affect the study outcome including cardiovascular disease, gastrointestinal problems, metabolic, renal, hepatic, neurological or active musculoskeletal disorders; and 4) participation in another clinical trial or ingestion of an investigational product within thirty days prior to screening. The subjects were randomly assigned to 1 of 3 groups: 1) a non-supplement (NON-SUP) group (n=13, age = 22.8 2.6 yr, body weight = 80.4 15.9 kg, and height = 178.7 7.1 cm); 2) a whey protein plus leucine supplement (PRO) group (n=13, age = 23.8 2.8 yr, body weight = 79.6 18.1 kg, and height = 178.3 7.3 cm); and 3) a carbohydrate supplement (CHO) group (n=13, age = 21.5 2.5 yr, body weight = 72.4 11.6 kg, and height = 175.5 6.0 cm). All procedures were approved by the University Institutional Review Board for Human Subjects and all subjects completed a health history questionnaire and signed a written informed consent prior to any testing. Procedures This study used a randomized and double-blind design. There were no dietary restrictions during the course of this study, and subjects were encouraged to continue with their normal dietary habits. The design allowed for examination of the effects of adding either a whey protein plus leucine or a carbohydrate supplement to an existing diet. This is similar to the way the product would likely be used by consumers. The whey protein plus leucine and carbohydrate supplements were isocaloric to control for differences in added energy intake. All subjects participated in a resistance training program that consisted of dynamic constant external resistance (DCER) bilateral leg extension and bench press exercises performed 3 times per week for 8 weeks. Each training session was supervised by one of the investigators. In addition, although this resistance training program was the primary mode of exercise for most of the subjects, they were not restricted from performing cardiovascular exercise during the study. The subjects were, however, instructed that they should not be involved in any other weight training program outside of the study. Pre- and post-testing was conducted the week prior to and the week following the 8-week training period, respectively. Supplement Protocol The PRO group received 20.0 g of whey protein and 6.2 g of leucine in 8 oz of water, the CHO group received 20 g of isocaloric (to control for differences in added energy intake) maltodextrin in 8 oz of water. The subjects ingested the PRO or CHO 30 minutes prior to and immediately after each resistance training session. On non-training days, the PRO and CHO groups ingested 1 dose of the protein or carbohydrate supplement in the morning and once again in the evening. The NON-SUP group did not receive any supplement. The subjects were encouraged to continue with their normal dietary habits with the addition of the protein or carbohydrate supplement as this would be similar to the way the product would likely be used by consumers. The subjects were asked to complete a preand post-test 3-day food log (two weekdays and one weekend day) to ensure that there were no significant changes in macronutrient or total caloric intake. Testing For the determination of body composition, the subjects were instructed to avoid exercise for at least 12 hours prior to testing, and each subject indicated that he was normally hydrated and in a postabsorptive state (at least 4 hours) upon arrival at the laboratory. Body weight (BW) was determined to the nearest 0.11kg using a state certified physician’s scale. Body density was assessed from underwater weighing (UWW) with correction for residual lung volume (RV). RV was measured on Whey Protein and Leucine Supplementation 42 land with the subject seated in the position similar to that assumed for UWW, using the oxygen dilution method of Wilmore (16). The scores (within 0.1L) from 2 or 3 trials were averaged and used as the representative RV. Underwater weight was measured in a submersion tank in which a nylon swing seat was suspended from a 10-kg Salter scale (REGO Designs & Patents, model #230). The average of the 2 or 3 highest weights from 6 to 10 trials was used as the representative underwater weight. Percent body fat (%fat) was calculated using the formula of Brozek et al. (17), with fat weight (FW) and fat-free weight (FFW) derived mathematically. Previous test-retest reliability data for UWW from our laboratory indicated that for 16 young men measured 24-72 hours apart, the ICC was R = 0.98 with an SEM of 0.9% fat. The DCER leg extension and bench press strength were tested by determining each subject’s 1 repetition maximum (1RM) using a Body-Solid plate-loaded leg extension machine (Model CEC340; Forest Park, IL) and a standard free-weight bench (Body Power, Williamsburg, VA) with an Olympic bar, respectively. For leg extension testing, each subject sat with his torso against the backrest and was instructed to hold tightly to the handles at the sides of the device. The backrest was adjusted to align the anatomical axes of the knees with the mechanical axis of the machine. Shin pads, attached to the machine’s lever arm, were placed against the subject’s legs. The shin pads were a fixed distance from the axis of rotation of the lever arm and thus not adjustable. Positioning, however, was consistent for each subject across all tests. For bench press testing, the subjects received a lift-off from a spotter, then lowered the bar to his chest, paused briefly, and then pressed the bar to full extension of the forearms. The 1RM was determined by applying progressively heavier loads until the subject could not complete a repetition through the full range of motion (full extension of the legs and forearms). If needed, additional trials were performed with lighter loads until the 1RM was determined within 2.27 kg. The 1RM was usually determined within five trials with two minutes of rest between each trial. For the leg extension and bench press endurance testing, subjects performed as many repetitions as possible of full extension of the legs and forearms at 80% of their 1RM. At post-testing, the same procedures for leg extension and bench press testing were performed. Leg extension and bench press endurance tests were performed at 80% of the pre-test 1RM. Previous test-retest reliability data for strength testing from our laboratory indicated that for 20 young men measured 8 weeks apart, the ICC was R = 0.99 and R = 0.98 for bench press and leg extension, respectively. Training The subjects performed leg extension and bench press training 3 times a week for 8 weeks starting at 80% of their 1RM. Each training session for bench press and leg extensions was preceded by 2 warm-up sets. Each warm-up set consisted of 6 repetitions at 50% of the target training weight. The PRO and CHO groups performed one set of 6-8 repetitions and the NON-SUP group performed two sets of 6-8 repetitions. Two minutes of rest were allowed between sets, and when the subject was able to complete 8 repetitions, the training load was increased by 2.27 kg for the next training session. Statistical Analyses Body weight, %FAT, FW, FFW, 1-RM leg extension (L-1RM), leg extension endurance (L-END), 1RM bench press (B-1RM), and bench press endurance (B-END) were analyzed with separate 3 [Group: PRO, CHO, and NON-SUP] x 2 [Time: Week 0 and 8] mixed factorial ANOVAs to determine if there were significant changes in body composition and muscle strength and endurance. The total caloric (kilocalories) and macronutrient (grams of protein, carbohydrate, and fat) intake were similarly analyzed. Group was used as a “between subjects” factor and time was used as a “within subjects” factor. An alpha level of p<0.05 was selected for all statistical comparisons. The analyses were conducted using the Statistical Package for the Social Sciences software (v.13.0, SPSS Inc., Chicago, IL). Based on the results of a previous study (1), an a priori power analysis indicated that a Whey Protein and Leucine Supplementation 43 sample size of 39 subjects resulted in a statistical power value of 0.90 or greater for increases in L1RM and B-1RM strength. Post-hoc power analyses for identifying group differences indicated that for the effect sizes found in the present study for B-1RM, B-END, L-1RM, and L-END, the power values equaled 0.87, 0.72, 0.99, and 0.99, respectively. RESULTS Body Composition The results indicated that there were no significant (p > 0.05) training-induced changes in BW, %FAT, FW, or FFW for the NON-SUP, PRO, or CHO groups (Table 1). Muscle Strength and Endurance The two-way mixed factorial ANOVAs resulted in no significant (p > 0.05) group x time interactions or main effects for group, Table 1: Body weight, body composition, and dietary values (M ± SD), n = 39. but significant (p<0.05) main effects for time for Group Pre Post L-1RM (pre = 82.5 ± 22.4 kg; post = 99.2 ± PRO (n = 13) 79.6 ± 18.1 80.2 ± 18.4 23.2 kg), L-END (pre = Body weight (kg) CHO (n = 13) 72.4 ± 11.5 72.5 ± 11.9 12 ± 4 repetitions; post NON-SUP (n = 13) 80.4 ± 15.9 80.3 ± 15.8 = 19 ± 7 repetitions), BPRO 20.6 ± 7.3 21.4 ± 5.6 1RM (pre = 64.7 ± 17.8 kg; post = 77 ± 20.4 kg), Percent fat CHO 19.2 ± 8.5 19.9 ± 8.5 and B-END (pre = 7 ± 2 NON-SUP 21.3 ± 8.5 20.8 ± 8.3 repetitions; post = 13 ± PRO 62.3 ± 6.7 62.6 ± 12.4 4 repetitions) (Figures 1 Fat free mass (kg) CHO 58.0 ± 10.6 57.7 ± 7.7 and 2). Table 2 shows the mean (± SD) values NON-SUP 62.5 ± 8.3 62.8 ± 8.5 for strength and PRO 17.3 ± 8.7 17.7 ± 8.6 endurance for the PRO, Fat mass (kg) CHO 14.4 ± 8.5 14.9 ± 7.1 CHO, and NON-SUP NON-SUP 17.9 ± 11.1 17.5 ± 10.4 groups. Total calories (kcal) Protein (g) Carbohydrate (g) Fat (g) PRO 2632.3 ± 1260.4 1987.6 ± 678.3 CHO 2494.5 ± 699.6 2156.2 ± 581.9 NON-SUP 2009.0 ± 847.2 1889.1 ± 743.0 PRO 107.9 ± 32.2 84.5 ± 21.4 CHO 93.4 ± 18.4 83.5 ± 22.4 NON-SUP 110.6 ± 27.0 85.5 ± 31.8 PRO 107.9 ± 32.2 84.5 ± 21.4 CHO 93.4 ± 18.4 83.5 ± 22.4 NON-SUP 110.6 ± 27.0 85.5 ± 31.8 PRO 95.1 ± 28.4 76.0 ± 18.6 CHO 77.5 ± 26.6 63.8 ± 17.9 NON-SUP 82.5 ± 23.4 65.4 ± 17.0 There were also no significant (p > 0.05) group x time interactions, main effects for group, or main effects for time for the macronutrients (i.e., grams of protein, carbohydrate, and fat) or total kilocalories consumed (Table 1). DISCUSSION In the current study, There were no significant (p>0.05) changes from pre- to post-training for any strength and group. PRO = supplement group; CHO = carbohydrate group; NON-SUP = non- 1RM endurance increased supplement group. similarly (Table 1), over Whey Protein and Leucine Supplementation 44 eight weeks of resistance training for all three groups (NON-SUP, PRO, and CHO). Overall L-1RM, LEND, B-1RM, and B-END increased by 20.2%, 58.3%, 14.9%, and 71.4%, respectively. These improvements, however, were not accompanied by changes in BW, %FAT, FW, or FFW for any of the groups (Table 1). Strength The magnitude of the strength gains made by the PRO and CHO groups were similar to those of the NON-SUP group inspite of the differences in the volume of Table 2: Strength and endurance values for bench press and leg training (1 set for the PRO and extension (M ± SD), n = 39. CHO groups versus 2 sets for Group Pre Post the NON-SUP group). The ergogenic effects of the PRO (n = 13) 70.1 ± 22.6 80.1 ± 24.0* increased energy intake and/or CHO (n = 13) 64.7 ± 17.8 73.4 ± 18.6* the specific nutrients in the B-1RM (kg) NON-SUP (n = 13) 68.6 ± 18.4 77.5 ± 19.4* protein and carbohydrate PRO 7±2 14 ± 5* supplement may have compensated for the increased CHO 6±2 13 ± 4* B-END (reps) volume of training by the NONNON-SUP 7±1 13 ± 3* SUP group. Therefore, the PRO 80.8 ± 23.8 99.1 ± 22.5* current findings indicate that 1 CHO 78.9 ± 16.9 94.6 ± 20.2* set of resistance training, in L-1RM (kg) conjunction with either whey NON-SUP 87.9 ± 26.3 103.8 ± 27.2* protein and leucine or PRO 12 ± 3 20 ± 7* carbohydrate intake resulted in CHO 11 ± 3 17 ± 5* the same strength gains as 2 L-END (reps) NON-SUP 12 ± 6 18 ± 7* sets of resistance training without supplementation. There were no significant (p>0.05) changes between groups. *Posttraining values were significantly greater (p<0.05) than pre-training. Whey protein and/or leucine PRO = supplement group; CHO = carbohydrate group; NON-SUP = supplementation, as well as non-supplement group. carbohydrate ingestion, have previously been shown to increase net muscle protein balance following resistance exercise (6, 18). The increase observed following carbohydrate ingestion, however, was considered modest when compared to the “maximal” effect following the ingestion of amino acids (18, 19). In the present study, the effect of carbohydrate ingestion on muscular strength was equivalent to the effect of whey protein and leucine supplementation. Previous studies have examined the effects of whey protein and/or leucine supplementation separately or in combination with carbohydrate on muscular strength with inconsistent results (1,2,4,7,15,20). The variability in factors such as the quantity and ingredients of the supplements, the timing of ingestion, as well as the volume and intensity of training, and/or the initial training status of the subjects may explain some of the inconsistencies in results obtained in these studies (1,2,4,7,15,20). For example, Coburn et al. (1) randomly assigned adult male subjects to a supplement (20 g whey protein, 6.2 g leucine), carbohydrate placebo (26.2 g maltodextrin), or control group for 8 weeks of unilateral (nondominant limb) leg extension resistance training. Even though the supplement contained similar quantities of whey protein and leucine as the current study, the protein supplemented subjects demonstrated a 30% increase in strength in the trained limb which was significantly higher than the strength increase (22%) achieved by the carbohydrate placebo group. No strength changes were observed in the control group. Similarly, Willoughby et al. (2) compared the Whey Protein and Leucine Supplementation 45 effects of a 10 week resistance training program combined with 20 g protein (14 g whey and casein protein, 6 g free (essential and non-essential) amino acids) or 20 g dextrose placebo ingested 1hr before and after exercise on muscular strength in untrained males. 120 LOAD (kg) 100 80 60 40 L-1RM 20 B-1RM 0 PRE POST Figure 1. Mean changes in leg extension (L-1RM) and bench press (B-1RM) strength from pre- to post-testing averaged across groups (SUP, PLA, and CON). The mean strength values reflect the significant (p<0.05) main effect for time (averaged across groups) because there was no significant group (SUP, PLA, and CON) x time (pre- and post-testing) interaction or main effect for group for the mixed factorial ANOVA. The results demonstrated that even though both groups demonstrated significant strength increases over time, the protein supplemented group showed greater improvements in bench and leg press strength when compared to the placebo group (bench press (supplement vs. placebo) = 53% vs. 23%; leg press (supplement vs. placebo) = 38% vs. 22%). Cribb et al. (15) examined the effects of whey protein (1.3 g∙kg-1∙d-1) and creatine monohydrate [0.3 g∙kg1∙d-1 (1 week loading phase) and 0.1 g∙kg-1∙d-1 (maintenance phase – weeks 2-11)] separately and in combination vs. carbohydrate only (1.3 g∙kg-1∙d-1) on strength increases following 11 weeks of resistance training in trained males. The groups supplementing with whey protein only or in combination with creatine exhibited greater strength increases than the carbohydrate group. Supplementation with whey protein and/or leucine and/or carbohydrate has not always resulted in differences in strength increases when combined with resistance training (4, 7, 20). For example, Kerksick et al. (20) randomly assigned 36 trained males to one of three supplement groups: whey plus casein (40 g∙d -1 of whey and 8 g∙d-1 of casein protein), whey, branched chain amino acids, and L-glutamine (40 g∙ day-1 of whey, 3 g∙day-1 branched chain amino acids, and 5 g∙d-1 L-glutamine), or a carbohydrate placebo (48 g∙d -1). Even though the quantity and ingredients of the supplement differed to that of the current study, the authors found that after 10 weeks of resistance training, significant but similar increases in muscular strength (bench and leg press 1 RM) were observed in all groups. Similarly, Chromiak et al. (4) compared the effects of 10 weeks of resistance training with a postexercise supplement (13 g whey protein, amino acids including 0.53 g of leucine, creatine, and carbohydrate) or an isocaloric carbohydrate placebo (92 g of maltodextrin) in 33 trained male subjects. Although, there were overall increases in 1 RM bench and leg press strength, there was no significant difference between the supplement and placebo group. The similar strength gains between the whey protein plus leucine and the carbohydrate groups observed in the current study may be explained by the added caloric intake (7). For example, Rankin et al. (7) found that 10 weeks of training along with either low fat chocolate milk (5 kcals∙kg-1 body weight, 0.92 g∙kg-1 carbohydrate, 0.21 g∙kg-1 protein, 0.06 g∙kg-1 fat, and natural vitamins and minerals) or a carbohydrate-electrolyte Whey Protein and Leucine Supplementation 46 drink (5 kcals∙kg-1 body weight, 1.25g∙kg-1 carbohydrate and electrolytes) elicited similar and significant increases in 1RM strength in 19 untrained men. A moderate anabolic effect (decreased protein breakdown) (21) of the carbohydrate supplement resulting in increased elevations in blood glucose, a higher glycogen synthesis rate, as well as favorable hormonal responses (i.e. increased insulin levels and decreased cortisol levels) (22) as a result of carbohydrate ingestion may also explain the similar strength gains between the protein supplement and placebo groups in the current study. # OF REPITITIONS Muscular endurance In the current study, muscular endurance was assessed by having subjects perform as many repetitions as possible at 80% of their pre-test 1RM for the bench press and leg extension. Even though the 8 weeks of training 20 did not include an endurance 18 component L-END and B-END 16 increased by 58.3% and 71.4%, respectively. The increased 14 volume of training performed by 12 the non-supplement group (2 10 sets) may have compensated 8 for the reduced volume of training (1 set) by the protein 6 and carbohydrate supplement L-END 4 groups. Therefore, the current B-END 2 findings indicate that 1 set of 0 resistance training, in conjunction with whey protein PRE POST and leucine or carbohydrate intake resulted in the same Figure 2. Mean changes in leg extension (L-END) and bench press improvement in muscular (B-END) muscular endurance from pre- to post-testing averaged endurance as 2 sets of across groups (SUP, PLA, and CON). The mean muscular resistance training without endurance values reflect the significant (p<0.05) main effect for time (averaged across groups) because there was no significant supplementation. group (SUP, PLA, and CON) x time (pre- and post-testing) interaction or main effect for group for the mixed factorial ANOVA. Few studies have examined the effects of supplementation and training on muscular endurance. Beck et al. (3) randomly assigned 51 untrained males to either a supplement group (containing 5 g creatine, 26.2 g protein, and 2.2 g leucine) or placebo group (containing 39 g carbohydrate (glucose and fructose)). After 8 weeks of resistance training, bench press and leg extension muscular endurance (assessed in the same manner as the current study) significantly increased in both groups. Chromiak et al. (4) recorded the number of repetitions completed at 85% of 1RM for bench press and leg press. The pre-test and post-test comparisons for relative muscular endurance were reported as the estimated external work [repetitions completed x resistance (kg)] performed by 33 trained male subjects. After 10 weeks of resistance training with a postexercise supplement (13 g whey protein, amino acids including 0.53 g of leucine, creatine, and carbohydrate) or an isocaloric carbohydrate placebo (92 g of maltodextrin), muscular endurance on the leg press increased significantly by 53.8%. Bench press endurance increased non-significantly by 14.4%. Kerksick et al. (20) also determined muscular endurance in 36 trained subjects by recording the number of repetitions completed at 80% of their bench press and leg press 1RM. Relative muscular endurance using bench press and leg press volume [repetitions completed x resistance Whey Protein and Leucine Supplementation 47 (kg)] was estimated at pre-testing and post-testing after 10 weeks of training and supplementation with whey plus casein (40 g∙d-1 of whey and 8 g∙d-1 of casein protein), whey, branched chain amino acids, and L-glutamine (40 g∙ day-1 of whey, 3 g∙day-1 branched chain amino acids, and 5 g∙d-1 Lglutamine), or a carbohydrate placebo (48 g∙d-1). The results indicated that only leg press lifting volume increased significantly by 15.6% across groups. The reason for the lack of an increase in bench press volume in previous studies (4,20) is unknown. In both studies, the volume of training was greater than in the current study as well as the study by Beck et al. (3). For example, Chromiak et al. (4) used resistance exercises for the major muscle groups of the body. The subjects trained 2 d∙wk-1 with the leg press, squats, leg curls, calf raises, leg extensions and abdominal crunches and 2 d∙wk-1 with the bench press, shoulder press, lateral pulldown, seated row, triceps pushdown, and biceps curl. Kerksick et al. (20) also trained subjects 2 d∙wk -1 with the leg press, leg extensions, deadlift, lunges, lying leg curls, heel raises, and abdominal crunches and 2 d∙wk-1 with the bench press, chest flies, lateral pulldown, seated row, shoulder press, shoulder shrugs, bicep curls, and triceps pushdown. In contrast, the subjects in the current investigation and that of Beck et al. (3) trained 3 d∙wk-1 with bench press and leg extension exercises only. Another difference that could potentially explain the differences in muscular endurance is the training status of the subject. Chromiak et al. (4) and Kerksick et al. (20) used trained male subjects, whereas in the present study and that of Beck et al. (3) untrained male subjects were used. Chromiak et al. (4) also attributed the improvement in muscular endurance for the leg press to the corresponding increase in muscular strength. Future research is needed to determine the effects of protein and amino acid supplementation, training status, and volume of training on muscular endurance. Body Composition In the current study, the increased volume of training associated with two sets of resistance training (without supplementation) as well as 8 weeks of single set training (with whey protein plus leucine or carbohydrate supplementation) had no effects on body composition. The results of previous research of protein and amino acid supplementation, and resistance training on body composition have also resulted in conflicting findings (1,2,7,23). The findings of the present investigation were similar to those of Coburn et al. (1) who found no combined effect of a whey protein and leucine supplement or a carbohydrate placebo plus unilateral resistance training for 8 weeks on BW, %FAT, FW, or FFW in untrained males. Similarly, Antonio et al. (23) found no change in BW, FW, or FFW in untrained females who were assigned to an essential amino acid (EAA) group or a placebo group plus 6 weeks of resistance and aerobic training. Conversely, Willoughby et al. (2) reported significant time (Posttest>Pre-test) and group (Protein >Placebo) effects for the increases in total body mass, fat-free mass, and thigh mass in untrained males for both a protein supplemented group [14 g whey and casein protein, 6 g free (essential and non-essential) amino acids], and a carbohydrate placebo (20 g dextrose) group after 10 weeks of resistance training. Rankin et al. (7) also found that mean %FAT decreased by 8% and fat-free soft tissue (FFST) mass increased by 1.2±0.3 kg after 10 weeks of training combined with either low fat chocolate milk or a carbohydrate-electrolyte drink in 19 untrained men. In addition, the milk supplemented group tended to show a greater increase in FFST than the carbohydrate group (milk vs. carbohydrate: 1.6±0.4 kg vs. 0.8±0.5 kg). Discrepancies in the results of the various studies (2,3,7,23) may have resulted from differences in supplementation protocol (ingredients and timing), energy content of the various supplements, and/or variations in the training regimens (volume and length of training period). Whey Protein and Leucine Supplementation 48 CONCLUSIONS In summary, the findings of the current study indicated that an increased volume of training (two sets without supplementation or placebo) or 8 weeks of single set leg extension and bench press resistance training (with whey protein and leucine supplementation or a carbohydrate placebo) had no effect on body composition. Increases in strength and endurance occurred across the 8 weeks, but no differential effects were observed as a result of the supplement or placebo plus single set training or the increased volume of training. Carbohydrate ingestion has previously been shown to modestly increase net muscle protein balance following resistance exercise as compared to the “maximal” (18)(p 678) effect following the ingestion of amino acids (18,19). In the present study, the effects of carbohydrate ingestion were equivalent to the effects of whey protein plus leucine supplementation. In addition, the effect of either the whey protein plus leucine or carbohydrate supplementation with one set of training equaled the effects of the increased volume of training associated with two sets of resistance exercise without supplementation. ACKNOWLEDGEMENTS This study was supported by General Nutrition Corporation (GNC). Address for correspondence: Mielke M, Ph.D., Department of Sport Sciences, University of the Pacific, Stockton, California 95211, USA. Phone: (209) 946-2209, Fax: (209) 946-3225, e-mail: [email protected]. REFERENCES 1. Coburn JW, Housh DJ, Housh TJ, Malek MH, Beck TW, Cramer JT et al. Effects of leucine and whey protein supplementation during eight weeks of unilateral resistance training. J Strength Cond Res 2006;20(2):284-91. 2. Willoughby DS, Stout JR, and Wilborn CD. Effects of resistance training and protein plus amino acid supplementation on muscle anabolism, mass, and strength. Amino Acids 2007;32(4):467-77. 3. Beck TW, Housh TJ, Johnson GO, Coburn JW, Malek MH, and Cramer JT. Effects of a drink containing creatine, amino acids, and protein combined with ten weeks of resistance training on body composition, strength, and anaerobic performance. J Strength Cond Res 2007;21(1):100-4. 4. Chromiak JA, Smedley B, Carpenter W, Brown R, Koh YS, Lamberth JG et al. Effect of a 10week strength training program and recovery drink on body composition, muscular strength and endurance, and anaerobic power and capacity. Nutrition 2004;20(5):420-7. 5. Borsheim E, Tipton KD, Wolf SE, Wolfe RR. Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab 2002;283(4):E648-657. 6. Tipton KD, Ferrando AA, Phillips SM, Doyle D, Wolfe RR. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol 1999;276(4 Pt 1):E628-34. Whey Protein and Leucine Supplementation 49 7. Rankin JW, Goldman LP, Puglisi MJ, Nickols-Richardson SM, Earthman CP, Gwazdauskas FC. Effect of post-exercise supplement consumption on adaptations to resistance training. J Am Coll Nutr 2004;23(4):322-30. 8. Kelly SB, Brown LE, Coburn JW, Zinder SM, Gardner LM, Nguyen D. The effect of single versus multiple setson strength. J Strength Cond Res 2007;21(4):1003-6. 9. Wolfe BL, LeMura LM, and Cole PJ. Quantitative analysis of single- vs. multiple-set programs in resistance training. J Strength Cond Res 2004;18(1):35-47. 10. Rhea MR, Alvar BA, Ball SD, Burkett LN. Three sets of weight training superior to 1 set with equal intensity for eliciting strength. J Strength Cond Res 2002;16(4):525-9. 11. Galvao DA and Taaffe DR. Single- vs. multiple-set resistance training: recent developments in the controversy. J Strength Cond Res 2004;18(3):660-7. 12. Tipton KD, Elliott TA, Cree MG, Wolf SE, Sanford AP, Wolfe RR. Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Med Sci Sports Exerc 2004;36(12):2073-81. 13. Tipton KD and Wolfe RR. Exercise-induced changes in protein metabolism. Acta Physiol Scand 1998;162(3):377-87. 14. Mero A. Leucine supplementation and intensive training. Sports Med 1999;27(6):347-58. 15. Cribb PJ, Williams AD, Stathis CG, Carey MF, Hayes A. Effects of whey isolate, creatine, and resistance training on muscle hypertrophy. Med Sci Sports Exerc 2007;39(2):298-307. 16. Wilmore JH. A simplified method for determination of residual lung volumes. J Appl Physiol 1969;27(1)96-100. Brozek J, Grande F, Anderson JT, Keys A. Densitometric Analysis Of Body Composition: Revision Of Some Quantitative Assumptions. Ann N Y Acad Sci 1963;110:113-40. 17. 18. Borsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, Wolfe RR. Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise. J Appl Physiol 2004;96(2):674-8. 19. Miller SL, Tipton KD, Chinkes DL, Wolf SE, Wolfe RR. Independent and combined effects of amino acids and glucose after resistance exercise. Med Sci Sports Exerc 2003;35(3):449-55. 20. Kerksick CM, Rasmussen CJ, Lancaster SL, Magu B, Smith P, Melton C, et al. The effects of protein and amino acid supplementation on performance and training adaptations during ten weeks of resistance training. J Strength Cond Res 2006;20(3):643-53. 21. Roy BD, Tarnopolsky MA, MacDougall JD, Fowles J, Yarasheski KE. Effect of glucose supplement timing on protein metabolism after resistance training. J Appl Physiol 1997;82(6):1882-8. 22. Haff GG, Lahmkuhl MJ, McCoy LB, Stone MH. Carbohydrate supplementation and resistance training. J Strength Cond Res 2003;17(1):187-96. Whey Protein and Leucine Supplementation 23. 50 Antonio J, Sanders MS, Ehler LA, Uelmen J, Raether JB, Stout JR. Effects of exercise training and amino-acid supplementation on body composition and physical performance in untrained women. Nutrition 2000;16(11-12):1043-6. Disclaimer The opinions expressed in JEPonline are those of the authors and are not attributable to JEPonline, the editorial staff or ASEP.