PURPOSE: Consumption of energy drinks by both recreational and competitive athletes, as well as the general population, has increased dramatically since the late 1980's when these drinks were first introduced to the market. The primary ingredients in most energy drinks include caffeine (CAF) in various forms, taurine (TAUR), B vitamins, and sugar. Although several studies have examined the effect of energy drinks on endurance exercise performance, less is known regarding their effect on anaerobic exercise, particularly the sugar-free (SF) versions of these products. Therefore, this study examined the effect of a popular SF energy drink that contains CAF and TAUR to a CAF only SF drink and a placebo (PL) on upper body muscular strength and endurance. METHODS: Thirteen physically active men (mean age ± SD = 21 ± 1 yr; body weight = 87.2 ± 8.8 kg; %Fat = 9.9 ± 3.0%) who had been strength training ≥ 3 times/wk for at least 6 mo, and who habitually consumed ≤ 50 mg/d of CAF were recruited for the study. The subjects visited the laboratory on 3 separate occasions separated by 1 wk and were instructed to refrain from alcohol, CAF, and upper-body resistance training 24 hr before testing and arrive in a fasted state (at least 4 hr after their last meal). Sixty minutes prior to strength testing, each subject received one of the following drinks in a double-blind, randomized order: A) 16 oz of a commercially available SF energy drink containing CAF (160 mg) and TAUR (2000 mg); B)16 oz of a SF drink containing CAF only (160 mg); or C) a SF, CAF-free PL drink. The drinks were similar in taste and appearance, served in an opaque container, and consumed as quickly as possible. In the hour before strength testing, the subjects sat quietly and studied, read, or watched TV. Prior to 1RM bench press (BP) testing, each subject completed a 5 min warm-up on a treadmill or elliptical machine followed by 10 reps at 40–60% of each subject's perceived 1RM on the BP and, after 3 min rest, they performed 3–5 reps at 60–80% of their perceived maximum. The representative 1RM was recorded as the weight of the last successfully completed lift, which typically took 3-5 attempts with 5 min rest between each attempt. After determination of the 1RM, subjects rested 5 min and then completed as many reps as possible at 70% of their 1RM to assess muscular endurance. Differences between trials for 1RM BP and the volume load (VL = reps × load at 70% 1RM) were identified using one-way repeated measures ANOVA (p<0.05). RESULTS: The results indicated that SF energy drinks containing CAF or CAF + TAUR had no effect on 1RM BP (118.6 ± 15.4 kg and 118.6 ± 15.6 kg, respectively) or VL (1187.7 ± 146.2 kg and 1184 ± 169.2 kg, respectively) compared to PL (1RM = 117.4 ± 15.5 kg; VL = 1146.0 ± 198.4 kg). CONCLUSIONS:Although the CAF content in the energy drinks used in the present study may be considered low when expressed relative to BW (1.8 mg/kg), the finding of no effect of the CAF containing energy drinks for 1RM BP are in agreement with previous studies using untrained men using intakes of approximately 4.9 mg/kg. Practical Applications: These findings suggest that SF energy drinks containing CAF with or without TAUR have no effect on 1RM BP or VL in resistance trained men.

The purpose of this study was to determine gastrointestinal (GI) permeability during prolonged treadmill running (60 min at 70 % V.O2max) with and without fluid intake (3 ml/kg body mass/10 min). Twenty runners (11 males, 9 females; age = 22 +/- 3 (SD) yrs; mean V.O2max = 55.7 +/- 5.0 ml/kg/min) completed four experiments: 1) rest, 2) running with no fluid (NF), 3) running with ingestion of a 4 % glucose solution (GLU), and 4) running with ingestion of a water placebo (PLA). To determine GI permeability, subjects also drank a solution containing 5 g sucrose (S), 5 g lactulose (L), and 2 g rhamnose (R) immediately prior to each trial. Gastroduodenal permeability was determined by urinary S excretion, while small intestinal permeability was determined by the L/R excretion ratio. Percent body mass loss (i.e., dehydration) was negligible during rest, GLU and PLA, while NF resulted in a 1.5 % loss of body mass (p < 0.05). Gastroduodenal and intestinal permeability were significantly (p < 0.008) increased in NF compared to rest. There were no other differences in GI permeability. These results indicate that fluid restriction during 1 h of steady-state running increases GI permeability above resting levels.

PURPOSE: To examine gender differences in body composition and estimated arm muscle area (AMA) as well as absolute and relative concentric, isokinetic peak torque in young swimmers. METHODS: One hundred twelve (n = 56 females; n = 56 males) age-group swimmers (age ± SD = 11.2 ± 1.8 yr.; range = 7.1 - 13.9 yrs) volunteered to perform maximal isokinetic forearm flexion and extension muscle actions (dominant arm) at 30, 180, and 300 ± s−1 on a calibrated Cybex II dynamometer to determine peak torque (PT). Percent body fat (% fat) and fat-free weight (FFW) were determined from underwater weighing using age-specific conversion constants to estimate % fat from body density. The subjects also underwent anthropometric assessment (arm circumference and triceps skinfold) to estimate AMA. RESULTS: There were no significant (p > 0.0017; Bonferroni corrected alpha) gender (F = females, M = males) differences for age (F = 10.7 ± 1.8 yr; M = 11.7 ± 1.8 yr), body weight (BW, F = 39.9 ± 13.0 kg; M = 36.4 ± 7.5 kg), FFW (F = 34.0 ± 9.5 kg; M = 33.0 ± 6.1 kg), or AMA (F = 20.6 ± 2.8 cm2; M = 19.9 ± 2.2 cm2). The females (13.5 ± 6.3% fat), however, had greater % fat than the males (8.7 ± 5.0% fat). In addition, there were no gender differences in absolute PT (range of mean differences = 1.2 - 4.1 Nm) or PT per unit of BW (0.08–0.18 Nm/kg), or AMA (0.14 - 0.28 Nm/cm2) at any velocity. CONCLUSION: The results of this study demonstrated close similarities for young female and male swimmers in forearm flexion and extension torque production capabilities and body composition characteristics. Growth-related gender differences in swimming performance in this age group may be due to factors such as metabolic considerations, body build characteristics, or biomechanical efficiency.

PURPOSE: To compare the anthropometric characteristics of high school female gymnasts to a national representative sample of adolescent females (Cycle II of the Health Examination Survey by the Department of Health and Human Services). METHODS: One hundred two high school female gymnasts (mean age ± SD = 15.75 ± 1.15 yr) volunteered for this study. The subjects were assessed for height, body weight, five circumferences (forearm, upper arm, calf, hip, and waist), and six diameters (biacromial, biiliac, bitrochanteric, elbow, knee, and wrist) using standard procedures. The national sample consisted of 526 females with an average of age of 15.75 yr. RESULTS: There were significant (p < 0.05) differences between the gymnasts and the national sample (G = gymnasts, N = national sample) for body weight (G = 54.1 ± 6.5 kg; N = 57.4 ± 0.7 kg), forearm circumference (G = 22.4 ± 1.4 cm; N = 23.4 ± 2.0 cm), upper arm circumference (G = 23.6 ± 1.9 cm; N = 26.2 ± 3.4 cm), calf circumference (G = 32.7 ± 2.0 cm; N = 34.7 ± 3.2 cm), hip circumference (G = 88.3 ± 5.7 cm; N = 93.4 ± 7.8 cm), biacromial diameter (G = 32.5 ± 3.1 cm; N = 35.4 ± 1.6 cm), biiliac diameter (G = 26.4 ± 2.2 cm; N = 25.6 ± 2.4 cm), elbow diameter (G = 6.0 ± 0.5 cm; N = 6.2 ± 0.4 cm), knee diameter (G = 9.1 ± 0.8 cm; N = 8.9 ± 0.6 cm), and wrist diameter (G = 5.1 ± 0.3 cm; N = 5.0 ± 0.3 cm). The gymnasts and the national sample were the same height and there were no mean differences (p > 0.05) for waist circumference or bitrochanteric diameter. The range of percent mean differences for the anthropometric variables was 0.3% (bitrochanteric diameter) to 9.9% (upper arm circumference). CONCLUSIONS: The results of this study demonstrated that the high school female gymnasts were similar to the national sample in height, but lighter in body weight and smaller in four of the five circumferences. The circumference differences may reflect the low levels of body fatness typically found in gymnasts. This is supported by the close agreements between the groups in height and extremity diameter measures (elbow, knee, and wrist) which suggests similarities in skeletal size.

The purpose of this study was to examine the validity of skinfold (SF), near-infrared interactance (NIR), and bioelectrical impedance (BIA) methods for estimating percent body fat (% fat) in young, male swimmers. Sixty-five male swimmers (age ± SD = 12.1 ± 2.0 yr) volunteered to have their % fat determined by underwater weighing (UWW) using age-specific conversion constants to estimate % fat from body density ( SD = 9.0 5.7 % fat), four age-specific SF equations, a Futrex - 5000A NIR instrument, and an RJL Systems BIA - 106 Spectrum analyzer. The cross-validation analyses indicated that the validity coefficients ranged from r = 0.26 - 0.62, constant error (mean difference) = −5.4 - 14.6 % fat, SEE = 4.5 - 5.5 % fat, and total error = 7.0 - 16.7 % fat. The results of this study indicated that the errors associated with the SF, NIR, and BIA estimates of % fat were too large to be of practical value. These findings suggest that new SF, NIR, and BIA equations should be developed for use with young, male swimmers. These new equations should then be cross-validated on independent samples of swimmers as well as young athletes in various sports.

Recently, Tanita® introduced a commercially available bioelectrical impedance (BIA) device that resembles a bathroom scale and measures both body weight and percent fat (% fat). The scale ranges in cost from $80 – $160 and the manufacturer claims that it is as accurate as more sophisticated body composition techniques, such as underwater weighing (UWW). Therefore, the purpose of the present study was to compare estimates of % fat obtained from the Tanita® scale (TAN) and skinfold (SF) equations (Σ 7 and Σ 3) to values obtained from UWW. Twenty-one inactive males (n = 7) and females (n = 14) (X age ± SD = 26 ± 7 yr, range = 19 - 50 yr, X % fat = 22.5 ± 7.7%, range = 11.8 - 39.7%) volunteered to participate. Body weight (BW) was measured with a calibrated Detecto scale to the mearest 0.11 kg. The SF measurements were taken at the triceps, subscapular, midaxillary, supcailiac, abdomen, chest, and thigh sites. Body density values were calculated using the generalized Σ 7 and Σ 3 SF equations of Jackson and Pollock (Br. J. Nutr. 40:497–504, 1978) and Jackson, Pollock and Ward (MSSE 12:175–182, 1980) for the males and females, respectively. The manufacturer did not supply the BIA equation included with the TAN. Validation analyses included examination of the constant error (CE), correlation (r), standard error of estimate (SEE) and total error (TE): (p < 0.017, Bonferroni corrected alpha 0.05/3 = 0.017)TableThe results indicated that TAN (TE = 5.3 % fat) and SF equations (Σ 7 TE = 4.9 % fat; Σ 3 TE = 5.4 % fat) resulted in TE values that were too large to be of practical value. The results for the SK's are in agreement with others who reported that the technique and these equations have limited applicability to overweight and obese individuals, which represented the majority of subjects in the present study (X % fat ± SD = 19.3 ± 5.0 % and 28.5 ± 6.9 % for the males and females, respectively). Based upon these findings, the TAN and SF techniques are not recommended for estimating % fat in males and females with average to moderately high body fatness.

The purpose of this investigation was to determine the effect of creatine (Cr) loading on the onset of neuromuscular fatigue by monitoring electromyographic fatigue curves from the vastus lateralis muscle using the physical working capacity at the fatigue threshold (PWCFT) test. Using a double-blind random design, 15 women athletes [mean age 19.0 +/- 2.0 (SD) yr] from the university crew team received a placebo (n = 8; 20 g glucose) or Cr (n = 7; 5 g Cr monohydrate + 20 g glucose) four times per day for 5 consecutive days. Analysis of covariance was used to analyze the data (covaried for presupplementation PWCFT values). The adjusted mean postsupplementation PWCFT value for the Cr group (mean = 186 W) was significantly (P < 0.05) higher than that of the placebo group (mean = 155 W). These findings suggest that Cr loading may delay the onset of neuromuscular fatigue.

831 The purpose of the present study was to determine the validity of near-infrared interactance (NIR) and bioelectrical impedance (BIA) instruments for estimating percent body fat (% fat) in young male swimmers. Fifty male, age-group swimmers (X age ± SD=12.5 ± 1.9 yrs) volunteered to have their% fat estimated by underwater weighing (UWW), a Futrex-5000A NIR instrument, and an RJL Systems BIA-106 Spectrum analyzer. The cross-validation procedures used to compare estimated% fat values from NIR and BIA to criterion% fat from UWW included the constant error (CE), validity coefficient(r), standard error of estimate (SEE), and total error (TE). TableTableThe findings from the present study indicated that the NIR (TE=6.1% fat), and BIA (TE=5.2% fat) instruments resulted in TE values that were too large to be of practical value. Thus, the NIR and BIA instruments used in the present study are not recommended for estimating% fat in young male swimmers.

365 The purpose of this study was to describe and compare the relationships among electromyography (EMG), mechanomyography (MMG), and peak torque (PT) during repeated maximal concentric isokinetic muscle actions. Nine adult males(age 22-26 years) volunteered to perform 50 maximal isokinetic concentric muscle actions of the leg extensors on a Cybex II. Bipolar surface EMG electrodes were placed over the vastus lateralis muscle with the piezoelectric MMG recording device placed between the EMG electrodes. Coefficient of determination (r2) was used to assess variance shared for EMG and MMG versus PT. One-way ANVOVA was used to examine the differences in percent (%) decline values between EMG, MMG and PT observed during the 50 repetitions. The r2 values for the EMG and MMG amplitudes versus PT values were 0.03 and 0.79, respectively. In addition, one-way ANOVA with Tukey Post Hoc tests indicated significant (p<0.05) differences in% decline values for EMG(-1.9±30.43%) and PT (65.5±6.03%), however% decline values for PT were not significantly (p>0.05) different from MMG (65.3±22.0). The results of this study demonstrated that MMG more accurately reflects torque output during fatiguing isokinetic contractions when compared to EMG.

828 The present study examined the validity of dual-energy x-ray absorptiometry(DXA) for assessing changes in fat-free weight (FFW) following 8 weeks of weight training by comparing the estimates to values obtained from underwater weighing (UWW). Ten, college-age ([horizontal bar over]X age = 19.0 ± 0.7 yr) football players (n=8 Caucasian; n = 2 Black) served as subjects. FFW from DXA was determined using a Hologic QDR-2000 bone densiometer. Validation analyses pre-training (PRTR) and post-training (POTR) included examination of the constant error (CE), SEE, r value and total error (TE). FFW increased significantly by 3.8 kg following the training period (73.8 to 77.6 kg; p < 0.001). FFW from DXA was not significantly different (p > 0.025) from UWW both PRTR (CE = 0.4 kg) and POTR (CE = 0.3 kg) and resulted in TE values of 2.6 and 2.9 kg, respectively. Correlation analyses indicated that the estimated changes in FFW determined by DXA were moderately correlated with actual changes from UWW (r = 0.46). When evaluating individual data, DXA correctly identified the direction of change in all 10 subjects. However, the magnitude of the change (within 1.0 kg) was only correctly identified in five of the subjects. In summary, DXA was as accurate as UWW for assessing changes in FFW. However, it should be noted that there were differences between the methods for monitoring individual changes in FFW.

The purpose of this study was to examine the effects of fluid replacement on power output (PO), rating of perceived exertion (RPE), heart rate (HR), body weight (BW), urine osmolarity (Uosm), and urine electrolyte concentrations ([UNa+], [UK+], [UCl-]) in physically active men (n = 4) and women (n = 7). The participants were asked to generate their highest possible PO during 60 minutes of cycling under 3 randomized conditions: ingestion of (a) no fluid (trial 1); (b) 1200 ml of distilled water (trial 2); and (c) 1,200 ml of Gatorade (trial 3). BW and urine volume (Vu) were measured before and after the ride to determine sweat rate [(SR = deltaBW + Vfluid intake + Vu)/time]. The results indicated that there were no significant differences between trials for PO (123-127 W), RPE (14), HR (140-142 b x min(-1)), and SR (11.9-12.4 ml x min(-1)). However, [UNa+] was significantly (p < 0.05) lower postexercise for all 3 trials, and [UCl-] was significantly reduced following trials 2 and 3. There was a significant increase (p < 0.001) in BW postexercise for trials 2 and 3 when compared with the no-fluid trial; however, the effects of water and Gatorade were similar. These results suggest that fluid replacement during 1 hour of moderately intense cycling does not enhance performance in physically active men and women who are normally hydrated.

The purpose of this study was to compare estimates of percent fat (% fat) from dual-energy x-ray absorptiometry (DEXA), bioelectrical impedance analysis(BIA) and near-infrared interactance (NIR; Futrex 5000, Futrex 1000) to values obtained from underwater weighing. Eighteen Caucasian college-age football players ([horizontal bar over]X age = 19.3 ± 1.0 yr.; [horizontal bar over]X% fat = 17.6 ± 8.1%) served as subjects. Percent fat from DEXA and BIA was determined using the Hologic QDR 2000 bone densiometer and the RJL BIA-106 Spectrum analyzer, respectively. Validation analyses included examination of the constant error (CE), r value, SEE, and total error (TE):(CE values were non-significant at an adjusted alpha level of p<0.0125)Table DEXA, which has the advantage of correcting for bone mineral content, resulted in the lowest SEE and TE values (2.0 and 2.1% fat, respectively) and, therefore, most accurately estimated% fat. The NIR-5000 (TE=3.3%fat) and NIR-1000 (TE = 3.8% fat) also provided accurate estimates of% fat and may be considered acceptable field techniques for estimating body composition in the present sample.

The purpose of this study was to examine changes in fat-free mass (FFM), 1RM bench press strength (BPS), vertical jump (VJ) and 100 yd dash time in football (FB) players following 8 weeks of supplementation with creatine monohydrate (CM), CM & glucose (GLU), or a GLU placebo (PL). Using a double blind random design, 24 NCAA Division II FB players ([horizontal bar over]xage±SD=19.9±1.6 yr) were placed into one of three supplemental conditions: 1)(PL, n=8), 35g of flavored GLU powder; 2) (GP1, n=8) 5.25g of CM and 1g GLU in a flavored powder blend; 3)(GP2, n=8) 5.25 g of CM, 33g GLU, 633 mg of sodium and potassium phosphates and 1g taurine in a flavored powder blend (Phosphagen HP™, EAS, Golden, CO.). Subjects ingested the supplements four times per day for five consecutive days and twice daily thereafter. All subjects weight trained for one hour and were involved in 30 minutes of speed drills four times per week during the supplementation period. Oneway-ANOVA's indicated that GP2 experienced a significant (p <0.05) increase in FFM (via DEXA), BPS, 100yd dash time, and VJ compared to the PL group. Mean changes for GPI in all of the variables measured were greater than the changes observed for the PL group, however, they did not reach statistical significance (p>0.05).Table We were unable to reproduce previous observations noting increases in FFM, BPS, and VJ within the group receiving CM (GP1). This may be due to the large intra-group variance among subjects. These data suggest that key nutrients taken with CM may augment its effects on FFM and performance.

Gordon, P.; Danduran, M.; Sullivan, J. J.; Visich, P.; Eckerson, J.; Goodwin, J.; Ecker, K. Author Information

Eckerson, J.; Stout, J.; Housh, T. FACSM; Johnson, G. FACSM; Gordon, P. Author Information

Belford, M.; Stout, J.; Eckerson, J.; Housh, T. FACSM; Johnson, G. FACSM Author Information