Effects of oral creatine supplementation on muscular strength and body composition.

PURPOSE: The purpose of this investigation was to examine the effects of 6 wk of oral creatine supplementation during a periodized program of arm flexor strength training on arm flexor IRM, upper arm muscle area, and body composition. METHODS: Twenty-three male volunteers with at least 1 yr of weight training experience were assigned in a double blind fashion to two groups (Cr, N = 10; Placebo, N = 13) with no significant mean pretest one repetition maximum (IRM) differences in arm flexor strength. Cr ingested 5 g of creatine monohydrate in a flavored, sucrose drink four times per day for 5 d. After 5 d, supplementation was reduced to 2 g x d(-1). Placebo ingested a flavored, sucrose drink. Both drinks were 500 mL and made with 32 g of sucrose. IRM strength of the arm flexors, body composition, and anthropometric upper arm muscle area (UAMA) were measured before and after a 6-wk resistance training program. Subjects trained twice per week with training loads that began at 6RM and progressed to 2RM. RESULTS: IRM for Cr increased (P < 0.01) from (mean +/- SD) 42.8 +/- 17.7 kg to 54.7 +/- 14.1 kg, while IRM for Placebo increased (P < 0.01) from 42.5 +/- 15.9 kg to 49.3 +/- 15.7 kg. At post-test IRM was significantly (P < 0.01) greater for Cr than for Placebo. Body mass for Cr increased (P < 0.01) from 86.7 +/- 14.7 kg to 88.7 +/- 13.8 kg. Fat-free mass for Cr increased (P < 0.01) from 71.2 +/- 10.0 kg to 72.8 +/- 10.1 kg. No changes in body mass or fat-free mass were found for Placebo. There were no changes in fat mass and percent body fat for either group. UAMA increased (P < 0.01) 7.9 cm2 for Cr and did not change for Placebo. CONCLUSION: Creatine supplementation during arm flexor strength training lead to greater increases in arm flexor muscular strength, upper arm muscle area, and fat-free mass than strength training alone.

Perception of effort during high-intensity exercise at low, moderate and high wet bulb globe temperatures.

The purpose of this study was to determine the effect of low, moderate and high wet bulb globe temperatures (Twbg) on cardiovascular variables and ratings of perceived exertion (RPE) during moderately prolonged, high-intensity exercise. Six subjects [four men and two women; mean (SD) age, 22.0 (1.2) years; maximum oxygen consumption (VO2peak), 51.0 (8.4) ml.kg-1.min-1] completed 30 min of exercise (80% VO2peak) on a cycle ergometer at low [14.7 (2.1) degrees C], moderate [21.0 (1.5) degrees C], and high [27.4 (2.3) degrees C] Twbg. Two additional subjects completed 20 min of exercise in the high temperature condition, but completed 30 min in the moderate and low Twbg. Heart rate (fc), blood pressure, blood lactate (La), mean skin temperature (Tsk), VO2, and RPE were measured at 10, 20 and 30 min. Results showed that fc, rate pressure product, RPE, pulmonary ventilation and ventilatory equivalent for oxygen increased (P < 0.05) across time for all conditions, while P(a) decreased across time. Tsk and fc were significantly greater across time in the high condition [35.9 (0.65) degrees C; 176 (12.6) beats.min-1] compared to the moderate [34.6 (1.5) degrees C; 170 (17.2) beats.min-1] and the low condition [31.7 (1.5) degrees C; 164 (17.1) beats.min-1]. However, there were no differences throughout exercise in RPE [high, 16.2 (2.0); moderate, 16.4 (2.2); low, 16.3 (1.9)] and VO2 across the conditions. These data suggest that RPE is closely related to metabolic intensity but is not a valid indicator of cardiovascular strain during exercise in high Twbg conditions.

Reliability and within subject variability of VE, VO2, heart rate and blood pressure during submaximum cycle ergometry.

To assess the reliability and within subject variability of steady-rate ventilation (VE), oxygen uptake (VO2), heart rate, systolic and diastolic blood pressure, 4 subjects exercised for 10 minutes at 3 work rates on a bicycle ergometer: 50 W, 125 W and 55% of maximum work rate (55% max). Each testing session included two work rates and only 2 testing sessions were scheduled per week. The order of the work rates was counterbalanced. In 8 to 10 weeks, 3 of the subjects completed 20 trials at 50 W while the fourth subject completed 11 trials, and all the subjects completed 10 trials at 125 W and 55% max. The within subject variability (S2w) was expressed as a percent of the mean steady-rate response. VO2 ranged from 21.2% to 27.5% of VO2max at 50 W, from 37.7% to 49.7% at 125 W and from 42.9% to 63.7% at 55% max. The S2w averaged 6.8% for VE, 4.3% for VO2, 3.2% for heart rate, 7.3% for systolic blood pressure and 10.5% for diastolic blood pressure. Reliability coefficients were calculated for the steady-rate scores by dividing the between subject variation by the total variation. The reliability was similar for VE, VO2 and heart rate and ranged from r = 0.69 to r = 0.97. Systolic and diastolic blood pressure reliabilities were lower and ranged from r = 0.27 and r = 0.80. In summary, the steady-rate ventilation, oxygen uptake and heart rate responses were reliable and consistent. The reliability of blood pressure was low. It is possible that this low reliability may result from variability in stroke volume or total peripheral resistance.

Accuracy of RPE from graded exercise to establish exercise training intensity.

The purpose of this investigation was to examine the accuracy of an exercise intensity prescription based upon perceptual responses obtained during a graded exercise test. Fifteen physically active men completed a graded exercise test (GXT) on a motor driven treadmill. Heart rate (HR), oxygen uptake (VO2), and RPE were measured each minute. An RPE intensity prescription was calculated as 75% of heart rate reserve from the GXT heart rate and RPE data. A minimum of 48 h later the subjects completed 10 min of exercise (EXT) on a level treadmill at the prescribed RPE. The subjects set the treadmill speed to elicit an exercise intensity equal to the prescribed perception of effort. There were significant mean differences (P < 0.05) in heart rate between the GXT (161.8 +/- 1.3) and EXT (154.9 +/- 4.5). However, by minute 6 the subjects were within four beats.min-1 of the target heart rate. There were no significant differences (P > 0.05) between GXT and EXT for VO2 (36.1 +/- 5.2, 33.1 +/- 6.4) and VE (64.1 +/- 10.8, 58.4 +/- 13.5) respectively. The present investigation demonstrates that a subject's perceptual response to a GXT can be used to accurately prescribe exercise intensity during level treadmill running. The intensity selected was within a typical range used for exercise prescription. The advantage of RPE as a method of exercise prescription is that an individual does not need to stop during exercise and measure a heart rate, but can make pace adjustments while exercising based solely upon the perception of effort.

Reduced short-term thermic effects of a meal in obese adolescent girls.

Post-meal energy expenditure (TEM) was compared for 14 healthy obese (body fat = 45.3%, body mass index, BMI = 35.9 kg m-2) and 9 healthy nonobese (body fat = 20.7%, BMI = 17.8 kg m-2) adolescent girls. The test meal for both groups was a standard 3348.8-kJ, 0.473-1 chocolate milkshake of 15% protein (casein), 40% fat (polyunsaturated/saturated ratio = 0.05; 75 mg cholesterol) and 45% carbohydrate (lactose and sucrose). Glucose, insulin and resting energy expenditure (RMR) were measured at rest prior to meal consumption and 20, 40, 60, 90, and 120 min after the meal. Cumulative net TEM was calculated as the integrated area under the TEM curve with RMR as baseline. Reliability was assessed by retesting 4 subjects, and a placebo effect was tested by administering a flavored energy-free drink. Results indicated high reliability and no placebo effect. The meal resulted in a greater rise in insulin and glucose for the obese compared to the nonobese subjects (P < or = 0.05), and a significant TEM for both groups (P < or = 0.05). The cumulative TEM (W kg-1) was 61.9% greater for the nonobese (P < 0.01) when expressed relative to body mass, and 33.2% greater for the nonobese (P < or = 0.01) when expressed relative to the fat-free body mass. Expressed relative to the meal, the TEM was 25.5% less for the obese (P < 0.01). The data support an energy conservation hypothesis for obese female adolescents.

Gender dimorphism in size, shape and body composition of child-onset obese and nonobese adolescents.

Gender dimorphism (percent GD) for stature (S), body size, body mass (BM) distribution and body composition for obese and nonobese male and female adolescents (mean age 12.7 years, range 10.5-14.5) was compared for 22 girths, 13 bony widths, five skin + fat folds (SF), fat mass (FM), fat free mass (FFM), body density (Db), and calculated variables (BMI, BSA, unit-size mass, waist:hip ratio (WHR), and FFM/S). BM distribution was computed with the ponderal mass equivalent somatogram. There was significant (P less than or equal to 0.05) percent GD for FM, FFM, Db, for the nonobese, but not obese. Only the neck, forearm and wrist girths revealed small but significant (P less than or equal to 0.05) percent GD for the obese. There was no girth percent GD for the nonobese. The elbow, wrist and ankle diameters revealed significant (P less than or equal to 0.05) percent GD for the obese; there was no significant percent GD for the nonobese for the same bony widths. Only the subscapula and iliac SF revealed significant (P less than or equal to 0.05) percent GD for the obese. For nonobese, percent GD was significant (P less than or equal to 0.05) for the triceps, subscapula and thigh SF, Comparisons between obese and nonobese indicated significant (P less than or equal to 0.05) differences between obese and nonobese males and females for FM, FFM, all girths and SF, but not S. Surprisingly, the obese and nonobese had nearly identical trunk diameters; the sum of biacromion, chest, biilac, and bitrochanter diameters were different by only 4.6 percent (n.s.) for the obese and nonobese males, and 1.3 percent (n.s.) for the obese and nonobese females. Thus, a large central frame-size cannot be used to justify the acquisition or maintenance of a larger than average BM for the obese. The ponderal equivalent analyses revealed that the obese's abdomen was the size of a person projected to have a BM in excess of 100 kg. The use of surface anthropometry in the study of adolescent obesity was supported.

Physiological responses to nine different exercise:rest protocols.

This study determined the metabolic responses to different exercise:rest protocols during circuit exercise using hydraulic resistance. In experiment 1, nine subjects underwent nine different 27 min exercise circuits. There were three variations of three exercise:rest protocols (2:1, 1:1, 1:2). The VO2 for the nine circuits averaged (mean +/- SEM) 1.94 +/- 0.03 l.min-1 (43% of treadmill VO2max), with the largest difference between the protocols being 13%. Heart rate averaged 152.2 +/- 3.1 beats.min-1, with the largest difference between the protocols being 8%. Increasing the exercise duration per minute or the number of exercise bouts per minute had minimal effects on the mean VO2 and heart rate response to hydraulic resistive exercise. In experiment 2, nine subjects underwent three different 9 min exercise circuits using exercise:rest protocols of 2:1, 1:1, and 1:2 while work and VO2 were simultaneously measured. Surprisingly, increases in work were not necessarily accompanied by corresponding increases in VO2.

Basal metabolism of obese adolescents: inconsistent diet and exercise effects.

Effects of 20 wk of diet-plus-behavior (DB) therapy or exercise-plus-diet-plus-behavior (EDB) therapy on changes in basal energy expenditure (BEE) were studied in 36 obese male and female adolescents. BEE was assessed by open-circuit spirometry and body composition by hydrostatic weighing. Dietary restriction was based on the dietary-exchange program. Behavioral treatment included record-keeping, stimulus-control, and reinforcement techniques. EDB therapy included 50 min/d, 3 d/wk of aerobics. A time-by-group (2 X 3) repeated-measures ANOVA was used to analyze pre-to-postintervention differences between groups (DB, EDB, and control). Results revealed small but statistically significant (p less than 0.05) differences in body composition between the two experimental groups and control subjects. There were no differences in body composition between the DB and EDB groups, although all control subjects gained body mass (p less than 0.05). There was no group-by-time interaction for BEE. Moderate correlations of r = less than or equal to 0.61 were obtained between change in BEE and change in body composition for the subjects in the experimental groups.

Coronary risk incidence of obese adolescents: reduction by exercise plus diet intervention.

The incidence of coronary heart disease risk factors and the effects of 20 weeks of diet and exercise were studied in 36 obese adolescents. Values for the following risk factors were determined: serum triglyceride level, high-density lipoprotein-cholesterol level, total cholesterol level, systolic and diastolic BP, maximum work capacity, obesity, and presence of coronary heart disease in the family history. Of the subjects, 97% had four or more risk factors. Two subjects possessed all eight risk factors. The adolescents were randomly assigned to either a control, diet therapy and behavior change, or exercise, diet therapy, and behavior change group. From pre- to posttreatment, a 14.8% and 41.4% reduction in multiple risk was noted for the latter two groups, respectively. No significant difference between the control group and the diet and behavior change group was found. In contrast, the exercise-diet-behavior change group reduced multiple risk (P less than .01) more than either of the other groups. It was concluded that obese adolescents are at high risk for the development of coronary heart disease and that exercise in addition to moderate dietary restriction can result in the reduction of multiple coronary heart disease risk.

Resistance weight training during caloric restriction enhances lean body weight maintenance.

To assess the individual and combined effects of weight loss and weight training on body weight and body composition, 40 obese women were randomly assigned to one of four groups for an 8 wk weight-loss study. These groups were control (C); diet without exercise (DO); diet plus weight training (DPE); and weight training without diet (EO). Body weight decreased for DO (-4.47 kg) and DPE (-3.89 kg) compared with C (-0.38 kg) and EO (0.45 kg). Lean body weight (LBW) increased for EO (1.07 kg) compared with DO (-0.91 kg) and C (-0.31 kg) and for DPE (0.43 kg) compared with DO. Upper-arm muscle areas (determined by radiograph) increased for DPE (11.2 cm2) and EO (10.4 cm2) compared with C (2.7 cm2) and DO (2.1 cm2). It was concluded that weight training results in comparable gains in muscle area and strength for DPE and EO. Adding weight training exercise to a caloric restriction program results in maintenance of LBW compared with DO.

Oxygen uptake and energy output during walking of obese male and female adolescents.

Oxygen uptake and steady-rate energy output of 7 obese male and 13 obese female adolescents (greater than 178% ideal body weight) walking at four different speeds (1.167, 1.5667, 1.7833, and 2.125 m/s) were studied. Body composition was measured by hydrostatic weighing, and steady-rate energy output by open circuit spirometry. Energy output was expressed as kJ/min (kcal/min) and indexed to body mass and fat-free mass. A 2-by-4 ANOVA (sex by speed) revealed significant differences in the energy output between the speed conditions. There was no significant difference between the sexes. A nonlinear increase in calorie output with increasing speed indicated a decreasing efficiency with increasing speed of walking. Possible reasons include biomechanical factors such as increased upper-body forward lean needed to maintain balance at faster speeds of movement, increased energy output due to increased inertia, extra energy output needed to accelerate the limbs and torso, and increased body fat.

Metabolic responses during hydraulic resistance exercise.

Thirteen college-age men under-went a treadmill (TM)-graded VO2max exercise test on 1 d and a 24.5-min hydraulic resistive exercise circuit on a following day. Seven exercises were performed in the following order: leg extension, bent-over row, bicep curl, squat, upright row, bench press, and behind-neck press. Each exercise was performed three times with the following work-to-rest timing: 30 s exercise, 30 s rest; 30 s exercise; 30 s rest; and 30 s exercise, 60 s rest (to allow for machine switch-over to the next exercise). Thus, each exercise took a total of 120 s, of which work was for 90 s and rest 120 s. During the circuit, heart rate averaged 153.8 b X min-1 (81.2% of TM max) and VO2 averaged 1.93 l X min-1 (41.4% of TM max). Oxygen uptake for the individual exercises ranged from 1.52 l X min-1 (32.6% of TM max) for the behind-neck-press exercise to 2.43 l X min-1 (52.1% of TM max) for the squat exercise. Heart rate ranged from 135.9 b X min-1 (71.8% of TM max) for the leg extension exercise to 163.4 b X min-1 (86.3% of TM max) for the squat exercise. Hydraulic circuit resistance exercise results in an average caloric expenditure of 40.8 kJ X min-1 (9.75 kcal X min-1).

Fat patterning of adolescents.

Fat patterning of 110 adolescent males and 80 adolescent females was determined by principal components analysis of five skinfolds (triceps, subscaplular, iliac, abdominal and thigh). Densiometrically determined body fatness was employed to create two groups: obese (greater than 30% fat) and non-obese (less than 30% fat). Three fat patterning components emerged: trunk-extremity, upper-lower trunk and medial-lateral abdomen. The first two components accounted for 80% of the variance in fat distribution. The obese males and females demonstrate increased trunk fat patterning compared to the non-obese. Furthermore, obese males deposit increased trunk fat in the lower trunk while obese females deposit fat in the upper trunk.

Relationship of fat patterning to coronary artery disease risk in obese adolescents.

Fatness and fat patterning of 27 male and 33 female obese adolescents were identified by principal-components analysis of five skinfolds (triceps, subscapular, iliac, abdominal, and thigh). Correlations were computed between the component scores, based on the eigen vectors, and anthropometric and physiological variables. Overall fatness, component I, was highly correlated with all anthropometric and body composition variables. Also, component I significantly correlated with fasting insulin and VO2 max for both sexes and with basal metabolism and HDL-cholesterol for females and males, respectively. Extremity fat patterning, component II, was poorly correlated with all the anthropometric and physiological variables except diastolic blood pressure for the females. Upper-lower body fat patterning, component III, was correlated with the fewest physiological variables.