International Journal of Sport Nutrition, 1992, 2, 328-334
Effects of Carbohydrate Loading and Weight-lifting on Muscle Girth Thomas W. Balon, Jeffrey F. Horowitz, and Karen M. Fitzsimmons Bodybuilders have used different carbohydrate loading regimens in conjunction with resistance exercise prior to competition in the belief that this would result in increased muscle size. To investigate this possibility, muscle girth measurements were obtained from nine weight-trained males before and after a control (standard isocaloric diet) and an experimental trial (carbohydrate loading). The latter regimen consisted of 3 days of intense weight-lifting while the subjects ingested a diet of 10% carbohydrate (CHO), 57% fat (F), and 33% protein (P), followed by 3 days of light weight-lifting and a day of rest while ingesting a diet of 80% CHO, 5% F, and 15% P. The control trial consisted of an identical weight-lifting regimen while subjects ingested an isocaloric (45 kcal/kg BWIday) diet. Body weight and girths (forearm, upper arm, chest, thigh, waist, and calf) were obtained before and after each trial in a relaxed and flexed state. The results indicated that an exercise/carbohydrate loading regimen had no significant effect on muscle girth as compared to the control trial. It is concluded that CHO loading has no additional advantage to enhancing muscle girth in bodybuilders over weight-lifting alone.
Traditionally, endurance athletes have used carbohydrate loading regimens to increase substrate stores and improve endurance performance (2, 1.5, 29). In addition, there is also evidence that inadequate glycogen stores may hamper performance in events that are shorter in duration (19). More recently, similar regimens involving resistance exercise and altered carbohydrate intake have been advocated for bodybuilders in the popular literature (1 1, 18, 33). Since a number of investigations have postulated that 2.4 to 4.0 g of water is associated with each gram of glycogen (8, 24, 26), it is believed that the carbohydrate loading might increase muscle girth for competition. The purpose of this investigation was to determine whether a carbohydrate loading/exercise regimen has a significant effect on muscle girth of weight-trained subjects.
Balon is with the Dept. of Diabetes at City of Hope Medical Center, 1500 E. Duarte Rd., Duarte, CA 91010. Horowitz is with the Dept. of Kinesiology and Health, Univ. of Texas at Austin, Austin, TX 78712. Fitzsimmons is with the Dept. of Pathology, Coll. of Medicine, Univ. of Iowa, Iowa City, IA 52242. Request reprints from Dr. Balon.
Effects of Carbohydrate Loading / 329
Methods
International Journal of Sport Nutrition 1992.2:328-334.
Subjects and Measurements
Nine young, lean males participated in the study. Their physical characteristics are presented in Table I. All had engaged in a self-motivated weight-lifting program for at least 2 years prior to this study. Before the tests, each subject was given both an oral and a written explanation of the procedures, dietary recall sheets, and exchange lists, and each one signed an informed consent form in accordance with guidelines establishedby the University of Iowa Human Subjects Committee D. All subjects participated in both a control and an experimental trial in a randomized order. On Day 1 the subjects' standing height, body weight, skinfolds, and muscle girths were measured. Skinfold fat was measured at the chest, axilla, triceps, subscapula, abdomen, umbilicus, and front thigh using a Lange skinfold caliper (Cambridge Scientific Industries, Inc., Cambridge, MD). Percent body fat was calculated using the formulas of Jackson and Pollack (12). Girth measurements were made of the upper arm, forearm, chest, thigh, and calf using a Gulick measuring tape (Country Technology Inc., Gays Mills, WI) according to standardized guidelines (4) in both a relaxed and a flexed state. The flexed-state measurement was preceded by a brief lifting bout designed to pump up the muscle in order to simulate a bodybuilder's competitive form. Skinfold and girth measurements were made by the same individual during the study to minimize intraobserver variability. Diet Protocol
On the 1st day of both the control and the experimental trials, girth measurements, skinfolds, and body weight were recorded. In addition, the 10-repetition maximum was determined for each lift. Also, all of the subjects were reinstructed on the Table 1 Characteristics of Subjects
Subject
Age (Yrs)
Height (cm)
Weight (kg)
Body mass index
Body fat Wo)
International Journal of Sport Nutrition 1992.2:328-334.
330
/ Balon, Horowitz, and Fitzsimmons
use of the dietary recall sheets and exchange lists and were given assistance in constructing a diet that would conform to the desired guidelines. On Days 2, 3, and 4 of the control trial, the subjects were kept on an isocaloric diet (45 kcalkg body weight) and followed an intense lifting protocol. On Days 5 and 6 the subjects stayed on the isocaloric diet, from which 15, 30, and 55% of the total calories were derived from protein, fat, and carbohydrate, respectively. In addition, the subjects reduced their lifting during these days. During Days 2-4 of the experimental trial, in addition to intense lifting the subjects adhered to a low carbohydrate diet. This diet of 45 kcalkg body weight derived 33% of caloric intake from protein, 57% from fat, and 10% from carbohydrates. On Days 5-7 the subjects were kept on a high carbohydrate diet consisting of 15% protein, less than 5% fat, and more than 80% carbohydrates while maintaining the same caloric intake as on Days 2-4. All dietary recall sheets were collected on the 8th day of each trial. These data were assessed for total caloric intake and percentage of substrate with exchange lists from the American Diabetes Association and the American Dietetic Association. Wrappers or containers of those foods not listed on the exchange lists were saved and recorded for necessary nutrient information. Exercise Protocol
During Days 2-4 of each trial, five sets of 10 repetitions of all lifts were attempted using the individual's predetermined 10-repetitionmaximum. The specific muscle groups recruited by the resistive exercise were divided during this period. On Day 2 of each trial, subjects performed bench presses, incline bench presses, decline bench presses, close-grip bench presses, French curls, and push-downs in order to recruit the chest and triceps. Squats, leg curls, leg extensions, calf raises, military presses, upright rows, and shoulder shrugs were performed on Day 3 in order to recruit the legs and shoulders. Exercises that recruited the arms and shoulders were executed on Day 4. These lifts included behind-the-back pulldowns, front pull-downs, seated rows, preacher curls, straight bar curls, and dumbbell curls. The severity of our exercise protocol was evident when several of the subjects were unable to complete the last repetitions of the fourth and fifth sets on the last 2 days of the depletion phase. On the next 2 Days (5 and 6), the subjects curtailed their lifting to one set of 10 repetitions at 50% of their 10-repetition maximum. The lifts performed on Day 5 included the bench press, incline press, French curl, push-downs, military press, and upright rows, whereas on Day 6 the subjects performed squats, leg curls, leg extensions, behind-the-back pull-downs, front pull-downs, seated rows, preacher curls, straight bar curls, and dumbbell curls. On Day 7 the subjects did no lifting. On Day 8, weight and muscle girths were measured in the same manner as on Day 1. The experimental design is illustrated in Table 2. It is common for bodybuilders to follow this type of program the week before competition (17). In addition, the lifting protocol utilized several exercises with a similar number of sets and repetitions that would recruit the same muscle groups as are typically used by competitive bodybuilders (5). All values listed are means standard error of the mean. An analysis of variance was used to test for differences between the two dietary regimens. A statement of significance implies a probability (P) value less than 0.05.
+
Effects of Carbohydrate Loading / 331
Table 2 Experimental Design Day
1
2-4
5-6 7
International Journal of Sport Nutrition 1992.2:328-334.
8
Control
Experimental
Girth measurements (relaxed & flexed) and body weights lsocaloric diet & intense lifting lsocaloric diet & light lifting lsocaloric diet & no lifting Same as Day 1
Girth measurements (relaxed & flexed) and body weights High protein and fat diet & intense lifting High carbohydrate diet & light lifting High carbohydrate diet & no lifting Same as Day 1
Results and Discussion Compliance to the prescribed diets in both trials was ascertained by dietary recall. Neither the actual number of calories nor the percentage of calories derived from the desired foodstuffs deviated from prescribed guidelines by more than 4%. Though the subjects were younger and percent body fat was higher than for subjects in other studies (5, 7, 16, 25, 28, 3 1) (age range, 25.0 k1.6 to 30.1 k2.7 yrs; percent body fat range = 7.2 f0.4 to 9.9 +0.6), their characteristics were typical of bodybuilding athletes. Girth measurements from the four measurement periods are listed in Table 3. There were no differences in girths or body weights between precontrol and preexperimental periods in either the relaxed or flexed state. Likewise, there was no effect of diet on muscle girth measurements or body weight in either the relaxed or flexed condition. As expected, there were significant differences @
Effects of Carbohydrate Loading and Weight-lifting on Muscle Girth Thomas W. Balon, Jeffrey F. Horowitz, and Karen M. Fitzsimmons Bodybuilders have used different carbohydrate loading regimens in conjunction with resistance exercise prior to competition in the belief that this would result in increased muscle size. To investigate this possibility, muscle girth measurements were obtained from nine weight-trained males before and after a control (standard isocaloric diet) and an experimental trial (carbohydrate loading). The latter regimen consisted of 3 days of intense weight-lifting while the subjects ingested a diet of 10% carbohydrate (CHO), 57% fat (F), and 33% protein (P), followed by 3 days of light weight-lifting and a day of rest while ingesting a diet of 80% CHO, 5% F, and 15% P. The control trial consisted of an identical weight-lifting regimen while subjects ingested an isocaloric (45 kcal/kg BWIday) diet. Body weight and girths (forearm, upper arm, chest, thigh, waist, and calf) were obtained before and after each trial in a relaxed and flexed state. The results indicated that an exercise/carbohydrate loading regimen had no significant effect on muscle girth as compared to the control trial. It is concluded that CHO loading has no additional advantage to enhancing muscle girth in bodybuilders over weight-lifting alone.
Traditionally, endurance athletes have used carbohydrate loading regimens to increase substrate stores and improve endurance performance (2, 1.5, 29). In addition, there is also evidence that inadequate glycogen stores may hamper performance in events that are shorter in duration (19). More recently, similar regimens involving resistance exercise and altered carbohydrate intake have been advocated for bodybuilders in the popular literature (1 1, 18, 33). Since a number of investigations have postulated that 2.4 to 4.0 g of water is associated with each gram of glycogen (8, 24, 26), it is believed that the carbohydrate loading might increase muscle girth for competition. The purpose of this investigation was to determine whether a carbohydrate loading/exercise regimen has a significant effect on muscle girth of weight-trained subjects.
Balon is with the Dept. of Diabetes at City of Hope Medical Center, 1500 E. Duarte Rd., Duarte, CA 91010. Horowitz is with the Dept. of Kinesiology and Health, Univ. of Texas at Austin, Austin, TX 78712. Fitzsimmons is with the Dept. of Pathology, Coll. of Medicine, Univ. of Iowa, Iowa City, IA 52242. Request reprints from Dr. Balon.
Effects of Carbohydrate Loading / 329
Methods
International Journal of Sport Nutrition 1992.2:328-334.
Subjects and Measurements
Nine young, lean males participated in the study. Their physical characteristics are presented in Table I. All had engaged in a self-motivated weight-lifting program for at least 2 years prior to this study. Before the tests, each subject was given both an oral and a written explanation of the procedures, dietary recall sheets, and exchange lists, and each one signed an informed consent form in accordance with guidelines establishedby the University of Iowa Human Subjects Committee D. All subjects participated in both a control and an experimental trial in a randomized order. On Day 1 the subjects' standing height, body weight, skinfolds, and muscle girths were measured. Skinfold fat was measured at the chest, axilla, triceps, subscapula, abdomen, umbilicus, and front thigh using a Lange skinfold caliper (Cambridge Scientific Industries, Inc., Cambridge, MD). Percent body fat was calculated using the formulas of Jackson and Pollack (12). Girth measurements were made of the upper arm, forearm, chest, thigh, and calf using a Gulick measuring tape (Country Technology Inc., Gays Mills, WI) according to standardized guidelines (4) in both a relaxed and a flexed state. The flexed-state measurement was preceded by a brief lifting bout designed to pump up the muscle in order to simulate a bodybuilder's competitive form. Skinfold and girth measurements were made by the same individual during the study to minimize intraobserver variability. Diet Protocol
On the 1st day of both the control and the experimental trials, girth measurements, skinfolds, and body weight were recorded. In addition, the 10-repetition maximum was determined for each lift. Also, all of the subjects were reinstructed on the Table 1 Characteristics of Subjects
Subject
Age (Yrs)
Height (cm)
Weight (kg)
Body mass index
Body fat Wo)
International Journal of Sport Nutrition 1992.2:328-334.
330
/ Balon, Horowitz, and Fitzsimmons
use of the dietary recall sheets and exchange lists and were given assistance in constructing a diet that would conform to the desired guidelines. On Days 2, 3, and 4 of the control trial, the subjects were kept on an isocaloric diet (45 kcalkg body weight) and followed an intense lifting protocol. On Days 5 and 6 the subjects stayed on the isocaloric diet, from which 15, 30, and 55% of the total calories were derived from protein, fat, and carbohydrate, respectively. In addition, the subjects reduced their lifting during these days. During Days 2-4 of the experimental trial, in addition to intense lifting the subjects adhered to a low carbohydrate diet. This diet of 45 kcalkg body weight derived 33% of caloric intake from protein, 57% from fat, and 10% from carbohydrates. On Days 5-7 the subjects were kept on a high carbohydrate diet consisting of 15% protein, less than 5% fat, and more than 80% carbohydrates while maintaining the same caloric intake as on Days 2-4. All dietary recall sheets were collected on the 8th day of each trial. These data were assessed for total caloric intake and percentage of substrate with exchange lists from the American Diabetes Association and the American Dietetic Association. Wrappers or containers of those foods not listed on the exchange lists were saved and recorded for necessary nutrient information. Exercise Protocol
During Days 2-4 of each trial, five sets of 10 repetitions of all lifts were attempted using the individual's predetermined 10-repetitionmaximum. The specific muscle groups recruited by the resistive exercise were divided during this period. On Day 2 of each trial, subjects performed bench presses, incline bench presses, decline bench presses, close-grip bench presses, French curls, and push-downs in order to recruit the chest and triceps. Squats, leg curls, leg extensions, calf raises, military presses, upright rows, and shoulder shrugs were performed on Day 3 in order to recruit the legs and shoulders. Exercises that recruited the arms and shoulders were executed on Day 4. These lifts included behind-the-back pulldowns, front pull-downs, seated rows, preacher curls, straight bar curls, and dumbbell curls. The severity of our exercise protocol was evident when several of the subjects were unable to complete the last repetitions of the fourth and fifth sets on the last 2 days of the depletion phase. On the next 2 Days (5 and 6), the subjects curtailed their lifting to one set of 10 repetitions at 50% of their 10-repetition maximum. The lifts performed on Day 5 included the bench press, incline press, French curl, push-downs, military press, and upright rows, whereas on Day 6 the subjects performed squats, leg curls, leg extensions, behind-the-back pull-downs, front pull-downs, seated rows, preacher curls, straight bar curls, and dumbbell curls. On Day 7 the subjects did no lifting. On Day 8, weight and muscle girths were measured in the same manner as on Day 1. The experimental design is illustrated in Table 2. It is common for bodybuilders to follow this type of program the week before competition (17). In addition, the lifting protocol utilized several exercises with a similar number of sets and repetitions that would recruit the same muscle groups as are typically used by competitive bodybuilders (5). All values listed are means standard error of the mean. An analysis of variance was used to test for differences between the two dietary regimens. A statement of significance implies a probability (P) value less than 0.05.
+
Effects of Carbohydrate Loading / 331
Table 2 Experimental Design Day
1
2-4
5-6 7
International Journal of Sport Nutrition 1992.2:328-334.
8
Control
Experimental
Girth measurements (relaxed & flexed) and body weights lsocaloric diet & intense lifting lsocaloric diet & light lifting lsocaloric diet & no lifting Same as Day 1
Girth measurements (relaxed & flexed) and body weights High protein and fat diet & intense lifting High carbohydrate diet & light lifting High carbohydrate diet & no lifting Same as Day 1
Results and Discussion Compliance to the prescribed diets in both trials was ascertained by dietary recall. Neither the actual number of calories nor the percentage of calories derived from the desired foodstuffs deviated from prescribed guidelines by more than 4%. Though the subjects were younger and percent body fat was higher than for subjects in other studies (5, 7, 16, 25, 28, 3 1) (age range, 25.0 k1.6 to 30.1 k2.7 yrs; percent body fat range = 7.2 f0.4 to 9.9 +0.6), their characteristics were typical of bodybuilding athletes. Girth measurements from the four measurement periods are listed in Table 3. There were no differences in girths or body weights between precontrol and preexperimental periods in either the relaxed or flexed state. Likewise, there was no effect of diet on muscle girth measurements or body weight in either the relaxed or flexed condition. As expected, there were significant differences @
