Acute effects of a beverage containing bitter melon extract (CARELA) on postprandial glycemia among prediabetic adults.

BACKGROUND: Acute ingestion of bitter melon (BM) has been shown to suppress the postprandial glycemic response in diabetics, but its impact on glucose regulation among individuals with impaired glucose tolerance is unclear. Moreover, one's glucose tolerance level may influence the effectiveness of BM. This study aimed to examine the acute effects of a beverage containing BM extract on blood glucose regulation during an oral glucose tolerance test (OGTT) among prediabetics. METHODS: Ten prediabetic adults completed two OGTTs-glucose only (D2) and glucose+BM (D3). Responders were identified as subjects whose area under the glucose curve (AUCglu) during D3 was lower than D2. To compare the acute effects of the beverage among individuals with varying glucose tolerance levels, subjects were grouped by their glucose response pattern-Fastpeak (peak glucose (Glupeak) at 30 min postglucose (30P)) and Slowpeak (Glupeak after 30P). RESULTS: During D3, responders (n=5) experienced a 13.2% reduction in AUCglu (95% confidence interval (CI): -18.1% to -8.3%), 12.2% reduction in mean glucose (95% CI: -17.3% to -7.0%) and 10.6% reduction in Glupeak (95% CI: -17.5% to -3.7%); plasma glucose was reduced by 9.1% at 30P (95% CI: -15.6% to -2.6%), -24.0% at 60P (95% CI: -36.8% to -11.2%) and -20.0% at 90P (95% CI: -35.8% to -4.2%) during D3. No between-trial differences were noted for Fastpeak or Slowpeak. CONCLUSIONS: Acute ingestion of BM prior to the second OGTT (D3) led to a reduced postprandial glucose response in 50% of the subjects but did not affect the insulin response. Furthermore, the effectiveness of the beverage was seemingly uninfluenced by the subjects' glucose tolerance level. Although BM has shown to aid blood glucose management in diabetics, it remains uncertain why only a portion of subjects responded positively to the BM extract in the current study.

Effect of diet composition on acid-base balance in adolescents, young adults and elderly at rest and during exercise.

BACKGROUND: Diets rich in animal protein and cereal grains and deficient in vegetables and fruits may cause low-grade metabolic acidosis, which may impact exercise and health. We hypothesized that (1) a normal-protein diet with high amount of vegetables and fruits (HV) induces more alkaline acid-base balance compared with a high-protein diet with no vegetables and fruits (HP) and (2) diet composition has a greater impact on acid-base balance in the elderly (ELD). SUBJECTS/METHODS: In all, 12-15 (adolescents (ADO)), 25-35 (young adults (YAD)) and 60-75 (ELD)-year-old male and female subjects (n=88) followed a 7-day HV and a 7-day HP in a randomized order and at the end performed incremental cycle ergometer tests. We investigated the effect of diet composition and age on capillary (c-pH) and urine pH (u-pH), strong ion difference (SID), partial pressure of carbon dioxide (pCO2) and total concentration of weak acids (Atot). Linear regression analysis was used to examine the contribution of SID, pCO2 and Atot to c-pH. RESULTS: In YAD and ELD, c-pH (P⩽0.038) and u-pH (P<0.001) were higher at rest after HV compared with HP. During cycling, c-pH was higher (P⩽0.034) after HV compared with HP at submaximal workloads in YAD and at 75% of VO2max (maximal oxygen consumption) in ELD. The contribution of SID, pCO2 and Atot to c-pH varied widely. Gender effects or changes in acid-base balance of ADO were not detected. CONCLUSIONS: A high intake of vegetables and fruits increases blood and u-pH in YAD and ELD. ELD compared with younger persons may be more sensitive for the diet-induced acid-base changes.

Characterization of the work-time relationship during cross-country ski ergometry.

The purpose of this study was to examine the validity and reliability of estimated parameters of the work-time relationship during cross-country ski ergometry using the traditional multi-trial critical power (CP) test and a 3 min 'all-out' test (3MT). Fourteen recreationally active male participants (mean ± SD; age: 22.14 ± 2.85 yrs; height: 177.09 ± 6.57 cm; weight: 85.68 ± 13.56 kg) completed three testing visits. All testing was conducted using an upper-body ergometer (SkiErg, Concept2, Inc., Morrisville, VT). A graded exercise test was used to determined maximal oxygen uptake (VO2peak). Two separate 3MT sessions were used to determine oxygen uptake (VO23MT), end-test power (EP), work above end-test power (WEP) and end stroke rate (ESR). Additionally, three time trials completed in a single day at simulated distances of 300 m, 650 m and 1000 m were used to estimate CP, W' and critical stroke rate (CSR). VO2peak (3.65 ± 0.50 l · min(-1)) and VO23MT (3.59 ± 0.4 l · min(-1)) were not significantly different (p = 0.162). Intraclass correlation coefficients for EP, WEP and ESR were 0.809, 0.611 and 0.783, respectively. EP (148 ± 33 W) and CP (157 ± 49 W), were not significantly different between the testing methodologies (p = 0.290) and were highly correlated (r = 0.780). WEP (8.4 ± 3.0 kJ) and W' (8.3 ± 3.0 kJ) were similar (p = 0.947) but not related (r = 0.119), while ESR (45 ± 7 spm) and CSR (47 ± 7 spm) values were not significantly different (p = 0.238) and moderately correlated (r = 0.498). The 3MT using ski ergometry was shown to produce concurrently valid results with the traditional multi-trial CP test for CP and CSR, but not W', and elicited similar maximal oxygen uptake values when compared to a graded exercise test.

Tracking fat-free mass changes in elderly men and women using single-frequency bioimpedance and dual-energy X-ray absorptiometry: a four-compartment model comparison.

BACKGROUND/OBJECTIVES: To compare single estimations of fat-free mass (FFM) and to track FFM using single-frequency bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) compared with a four-compartment (4C) model in healthy elderly Americans. SUBJECTS/METHODS: Thirty-four men and thirty-eight women (Caucasian, ≥ 65 years) were included in the study. Subjects participated in either the control group or the exercise group. All testing and training took place during the 21-week investigation. Body composition assessments using nine BIA equations, DXA and a 4C model were performed during weeks 1, 12 and 24 of the study. RESULTS: Single estimations for DXA and BIA produced high r values (0.79-0.95) and low standard error of estimate values (1.62-3.3 kg), producing subjective ratings of 'ideal' for men and 'excellent' for women. Both DXA and two BIA equations revealed the same significance when comparing groups and times with the 4C model. Individual accuracy for tracking changes was similar among BIA equations and DXA compared with the 4C model, with a total agreement of 25% for BIA and 27% for DXA compared with the 4C model. CONCLUSIONS: The current data in combination with the reliability errors for both BIA and DXA FFM estimations suggest that individual results should be interpreted with caution if FFM changes are <5 kg. However, DXA and BIA are both valid methods that can be used interchangeably to estimate FFM at a single time point or for tracking changes in FFM in small groups (15-22) of healthy American older adults.

Acute effects of static stretching on peak torque and the hamstrings-to-quadriceps conventional and functional ratios.

Recent evidence has shown acute static stretching may decrease hamstring-to-quadriceps (H:Q) ratios. However, the effects of static stretching on the functional H:Q ratio, which uses eccentric hamstrings muscle actions, have not been investigated. This study examined the acute effects of hamstrings and quadriceps static stretching on leg extensor and flexor concentric peak torque (PT), leg flexor eccentric PT, and the conventional and functional H:Q ratios. Twenty-two women (mean ± SD age=20.6 ± 1.9 years; body mass=64.6 ± 9.1 kg; height=164.5 ± 6.4 cm) performed three maximal voluntary unilateral isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60 and 180°/s before and after a bout of hamstrings, quadriceps, and combined hamstrings and quadriceps static stretching, and a control condition. Two-way repeated measures ANOVAs (time × condition) were used to analyze the leg extension, flexion, and eccentric PT as well as the conventional and functional H:Q ratios. Results indicated that when collapsed across velocity, hamstrings-only stretching decreased the conventional ratios (P<0.05). Quadriceps-only and hamstrings and quadriceps stretching decreased the functional ratios (P<0.05). These findings suggested that stretching may adversely affect the conventional and functional H:Q ratios.

Exercise-induced oxidative stress: the effects of ß-alanine supplementation in women.

The purpose of this study was to evaluate the effects of ß-alanine supplementation on markers of oxidative stress. Twenty-four women (age: 21.7±2.1 years; VO2max: 2.6±0.3 l min(-1)) were randomly assigned, in a double-blind fashion, to a ß-alanine (BA, 2×800 mg tablets, 3× daily; CarnoSyn®; n=13) or placebo (PL, 2×800 mg maltodextrin tablets, 3× daily; n=11) group. A graded oxygen consumption test (VO2max) was performed to evaluate VO2max, time to exhaustion, ventilatory threshold and establish peak velocity (PV). A 40-min treadmill run was used to induce oxidative stress. Total antioxidant capacity, superoxide dismutase, 8-isoprostane (8ISO) and reduced glutathione were measured. Heart rate and ratings of perceived exertion were recorded during the 40 min run. Separate three- [4×2×2; acute (base vs. IP vs. 2 vs. 4 h)×chronic (pre- vs. post-)×treatment (BA vs. PL)] and two- [2×2; time (pre-supplement vs. post-supplement)×treatment (BA vs. PL)] way ANOVAs were used for analyses. There was a significant increase in VO2max (p=0.009), independent of treatment, with no significant changes in TTE (p=0.074) or VT (p=0.344). Ratings of perceived exertion values were significantly improved from pre- to post-supplementation for the BA group only at 40 min (p=0.02). The ANOVA model demonstrated no significant treatment effects on oxidative stress. The chronic effects of BA supplementation demonstrated little antioxidant potential, in women, and little influence on aerobic performance assessments.

Dentin hypersensitivity and oxalates: a systematic review.

Treatment of dentin hypersensitivity with oxalates is common, but oxalate efficacy remains unclear. Our objective was to systematically review clinical trials reporting an oxalate treatment compared with no treatment or placebo with a dentin hypersensitivity outcome. Risk-of-bias assessment and data extraction were performed independently by two reviewers. Standardized mean differences (SMD) were estimated by random-effects meta-analysis. Of 677 unique citations, 12 studies with high risk-of-bias were included. The summary SMD for 3% monohydrogen-monopotassium oxalate (n = 8 studies) was -0.71 [95% Confidence Interval: -1.48, 0.06]. Other treatments, including 30% dipotassium oxalate (n = 1), 30% dipotassium oxalate plus 3% monohydrogen monopotassium oxalate (n = 3), 6% monohydrogen monopotassium oxalate (n = 1), 6.8% ferric oxalate (n = 1), and oxalate-containing resin (n = 1), also were not statistically significantly different from placebo treatments. With the possible exception of 3% monohydrogen monopotassium oxalate, available evidence currently does not support the recommendation of dentin hypersensitivity treatment with oxalates.

Acute effects of passive stretching and vibration on the electromechanical delay and musculotendinous stiffness of the plantar flexors.

The purpose of the present study was to examine the acute effects of passives stretching versus prolonged vibration on the active and passive properties of voluntary and evoked muscle actions of the plantar flexors. Eleven healthy men performed the isometric maximal voluntary contractions (MVCs) and passive range of motion (PROM) assessments before and after 20 min of passive stretching (PS), vibration (VIB), and control (CON) conditions. In addition, percent voluntary activation was calculated from superimposed and potentiated doublets during the MVCs. Voluntary peak torque (PT) decreased by 11% and 4%, while surface electromyographic (EMG) amplitude decreased by 8% and 16% for the PS and VIB, respectively, with no changes during the CON The electromechanical delay (EMD) decreased and PROM increased following the PS, but was unchanged during the VIB and CON conditions. Musculotendinous stiffness (MTS) decreased at all joint angles following the PS, but decreased only at the furthest joint angle following the VIB. There were no changes in peak twitch torque (PTT), M-wave amplitude, and EMG amplitude during the PROM assessments for all conditions. Both PS and VIB elicited similar decreases in muscle activation, which may be the same centrally-mediated mechanism (i.e., y loop impairment). Changes in the EMD were inversely proportional to the changes in MTS, which occurred only following PS. The present findings indicated that the stretching- and vibration-induced force deficits may have resulted in part from similar centrally-mediated neural deficits, while an elongation of the series elastic component may also have affected the stretching-induced force deficit.

Acute effects of passive stretching vs vibration on the neuromuscular function of the plantar flexors.

This study examined the acute effects of passive stretching (PS) vs prolonged vibration (VIB) on voluntary peak torque (PT), percent voluntary activation (%VA), peak twitch torque (PTT), passive range of motion (PROM), musculotendinous stiffness (MTS), and surface electromyographic (EMG) and mechanomyographic (MMG) amplitude of the medial gastrocnemius (MG) and soleus (SOL) muscles during isometric maximal voluntary contractions (MVCs) of the plantar flexors. Fifteen healthy men performed the isometric MVCs and PROM assessments before and after 20 min of PS, VIB, and a control (CON) conditions. There were 10% and 5% decreases in voluntary PT, non-significant 3% and 2% decreases in %VA, 9-23% decreases in EMG amplitude of the MG and SOL after the PS and VIB, respectively, with no changes after the CON. PROM increased by 19% and MTS decreased by 38% after the PS, but neither changed after the VIB or CON conditions. Both PS and VIB elicited similar neural deficits (i.e., gamma loop impairment) that may have been responsible for the strength losses. However, mechanical factors related to PROM and MTS cannot be ruled out as contributors to the stretching-induced force deficit.

Putting to rest the myth of creatine supplementation leading to muscle cramps and dehydration.

Creatine is one of the most popular athletic supplements with sales surpassing 400 million dollars in 2004. Due to the popularity and efficacy of creatine supplementation over 200 studies have examined the effects of creatine on athletic performance. Despite the abundance of research suggesting the effectiveness and safety of creatine, a fallacy appears to exist among the general public, driven by media claims and anecdotal reports, that creatine supplementation can result in muscle cramps and dehydration. Although a number of published studies have refuted these claims, a recent position statement by the American College of Sports Medicine (ACSM) in 2000 advised individuals who are managing their weight and exercising intensely or in hot environments to avoid creatine supplementation. Recent reports now suggest that creatine may enhance performance in hot and/or humid conditions by maintaining haematocrit, aiding thermoregulation and reducing exercising heart rate and sweat rate. Creatine may also positively influence plasma volume during the onset of dehydration. Considering these new published findings, little evidence exists that creatine supplementation in the heat presents additional risk, and this should be taken into consideration as position statements and other related documents are published.

Effects of creatine supplementation on the onset of neuromuscular fatigue threshold and muscle strength in elderly men and women (64 - 86 years).

OBJECTIVES: This study examined the effects of 14 days of creatine supplementation on the physical working capacity at fatigue threshold (PWCFT), maximal isometric grip strength (GRIP), sit-to-stand (STS), and body weight (BW) in elderly men and women. DESIGN: Using a double blind cross-over design, fifteen men (n = 7) and women (n = 8) (age +/- SD = 74.5 +/- 6.4 yrs) were randomly assigned to either the creatine (CR) (20g.d-1 during week 1 decreasing to 10g.d-1 at week 2) or Placebo (PL) group. After a 4 to 6 week washout period, the subjects were assigned the other treatment. Before (pre) and after (post) the supplementation period, participants performed a discontinuous, cycle ergometry test to determine the PWCFT. In addition, subjects performed STS, GRIP, BW test prior to and post treatment. SETTING: Southeastern part of the United States. RESULTS: Significant increases in GRIP (6.7%) and PWCFT (15.6%) from pre- to post-supplementation were found for the CR (p < 0.05) treatment, but no change for the PL treatment was observed. However, no significant change (p superior 0.05) was noted for STS or BW for either treatment. CONCLUSION: These findings suggest that 14 days of CR supplementation may increase upper body grip strength and increase physical working capacity by delaying neuromuscular fatigue in the elderly men and women in this study. While more research is needed, CR supplementation may improve upper body grip strength and lower body muscle endurance which may be important for maintaining health and independent living in elderly men and women.

Inter-individual variability among the mechanomyographic and electromyographic amplitude and mean power frequency responses during isometric ramp muscle actions.

The purpose of this study was to examine the inter-individual variability in the patterns of responses for mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) of the vastus lateralis (VL) and rectusfemoris (RF) muscles during isometric ramp muscle actions of the leg extensors. Fifteen participants (mean +/- SD age = 24 +/- 4 years) performed two or three 6-s isometric ramp muscle actions with linear increases in torque from 15% to 90% of the highest maximal voluntary contraction (MVC) torque. Surface MMG and EMG signals were simultaneously recorded from the VL and RF muscles. The composite (averaged across subjects) and individual patterns of responses for the normalized MMG and EMG amplitude and MPF vs. isometric torque relationships were analyzed. The composite patterns for MMG amplitude for the VL and RF muscles were fit with cubic models, although, only 87% of the individual patterns (13 of 15 subjects) exhibited the same cubic pattern as the composite. For MMG MPF, the composite relationships were also cubic, but only 27% (4 subjects) and 40% (6 subjects) of the individuals exhibited the same patterns for the VL and RF respectively. 60% (8 subjects) of the individual EMG amplitude patterns of responses matched the same curvilinear composite patterns for the VL and RE, while only 7% (1 subject) and 27% (4 subjects) of the EMG MPF responses were similar to the composite models for the VL and RF muscles, respectively. Therefore, since the individual patterns did not always match the composite relationships (i.e., inter-individual variability), these findings suggested that the MMG and EMG amplitude and MPF vs. isometric torque relationships should be examined on a subject-by-subject and muscle-by-muscle basis during isometric ramp muscle actions.

Effects of 28 days of beta-alanine and creatine monohydrate supplementation on aerobic power, ventilatory and lactate thresholds, and time to exhaustion.

The effect of beta-alanine (beta-Ala) alone or in combination with creatine monohydrate (Cr) on aerobic exercise performance is unknown. The purpose of this study was to examine the effects of 4 weeks of beta-Ala and Cr supplementation on indices of endurance performance. Fifty-five men (24.5 +/- 5.3 yrs) participated in a double-blind, placebo-controlled study and randomly assigned to one of 4 groups; placebo (PL, n = 13), creatine (Cr, n = 12), beta-alanine (beta-Ala, n = 14), or beta-alanine plus creatine (CrBA, n = 16). Prior to and following supplementation, participants performed a graded exercise test on a cycle ergometer to determine VO(2peak), time to exhaustion (TTE), and power output, VO(2), and percent VO(2peak) associated with VT and LT. No significant group effects were found. However, within groups, a significant time effect was observed for CrBa on 5 of the 8 parameters measured. These data suggest that CrBA may potentially enhance endurance performance.

Effects of resistance training and protein plus amino acid supplementation on muscle anabolism, mass, and strength.

This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6-8 repetitions at 85-90% of the one repetition maximum. Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength, serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance.

Effects of beta-alanine supplementation on the onset of neuromuscular fatigue and ventilatory threshold in women.

This study examined the effects of 28 days of beta-alanine supplementation on the physical working capacity at fatigue threshold (PWCFT), ventilatory threshold (VT), maximal oxygen consumption (VO2-MAX), and time-to-exhaustion (TTE) in women. Twenty-two women (age+/-SD 27.4+/-6.1 yrs) participated and were randomly assigned to either the beta-alanine (CarnoSyn) or Placebo (PL) group. Before (pre) and after (post) the supplementation period, participants performed a continuous, incremental cycle ergometry test to exhaustion to determine the PWCFT, VT, VO2-MAX, and TTE. There was a 13.9, 12.6 and 2.5% increase (p<0.05) in VT, PWCFT, and TTE, respectively, for the beta-alanine group, with no changes in the PL (p>0.05). There were no changes for VO2-MAX (p>0.05) in either group. Results of this study indicate that beta-alanine supplementation delays the onset of neuromuscular fatigue (PWCFT) and the ventilatory threshold (VT) at submaximal workloads, and increase in TTE during maximal cycle ergometry performance. However, beta-alanine supplementation did not affect maximal aerobic power (VO2-MAX). In conclusion, beta-alanine supplementation appears to improve submaximal cycle ergometry performance and TTE in young women, perhaps as a result of an increased buffering capacity due to elevated muscle carnosine concentrations.

Evaluation of creatine transport using Caco-2 monolayers as an in vitro model for intestinal absorption.

Creatine is a nutraceutical that has gained popularity in both well-trained and casual athletes for its performance-enhancing or ergogenic properties. The major disadvantages of creatine monohydrate formulations are poor solubility and oral bioavailability. In the present study, creatine transport was examined using Caco-2 monolayers as an in vitro model for intestinal absorption. Confluent monolayers of Caco-2 cells (passage 25-35) were used for the permeability studies. Monolayers were placed in side-by-side diffusion chambers. (14)C-Creatine (0.1-0.5 microCi/mL) was added to either the apical or basolateral side, and the transport of the creatine across the Caco-2 monolayer was measured over a 90-min period. The apical to basolateral transport of (14)C-creatine was small, ranging from 0.2-3% of the original amount appearing on the receiver side in a 90-min period. Interestingly, the basolateral to apical permeability of radiolabeled creatine was substantially greater than that observed in the apical to basolateral direction. Studies with drug efflux transport inhibitors indicate that neither the P-glycoprotein nor multidrug resistance-associated protein is involved in the enhanced basolateral to apical transport of creatine.

Effects of resistance exercise and creatine supplementation on myasthenia gravis: a case study.

PURPOSE: The purpose of this case study was to determine the effects of 15 wk of resistance exercise and creatine (Cr) supplementation on body composition, training volume, peak strength, and complete blood chemistry in a patient with myasthenia gravis (MG). METHODS: The patient was a 26-yr-old man who was taking prednisone and azathioprine for his condition. The patient self-administered 5 g of Cr per day in addition to resistance exercise 3 times per week. Fasting blood samples were obtained and body weight (BW) and fat free mass (FFM; via hydrostatic weighing) were measured before and after training and Cr supplementation. In addition, isokinetic (Cybex II) peak strength for leg extension (LE), leg flexion (LF), and volume load (repetition x mass lifted) for the first and last resistance training session were determined. RESULTS: After Cr supplementation and training, the results demonstrated increases in BW (6.8%), FFM (4.3%), upper body volume load (37.0%), lower body volume load (15.0%), and peak strength for LE (37.0%) and LF (12.5%). Moreover, blood chemistry values remained within normal limits for the duration of the 15-wk study. CONCLUSION: These data suggest that resistance exercise plus Cr supplementation may promote gains in strength and FFM in patients with MG.

Ligand endocytosis drives receptor dissociation and activation in the Notch pathway.

Endocytosis of the ligand delta; is required for activation of the receptor Notch during Drosophila development. The Notch extracellular domain (NotchECD) dissociates from the Notch intracellular domain (NotchICD) and is trans-endocytosed into delta;-expressing cells in wild-type imaginal discs. Reduction of dynamin-mediated endocytosis in developing eye and wing imaginal discs reduces Notch dissociation and Notch signalling. Furthermore, dynamin-mediated delta endocytosis is required for Notch trans-endocytosis in Drosophila cultured cell lines. Endocytosis-defective delta proteins fail to mediate trans-endocytosis of Notch in cultured cells, and exhibit aberrant subcellular trafficking and reduced signalling capacity in Drosophila. We suggest that endocytosis into delta-expressing cells of NotchECD bound to delta plays a critical role during activation of the Notch receptor and is required to achieve processing and dissociation of the Notch protein.

Effects of exercise training and amino-acid supplementation on body composition and physical performance in untrained women.

The purpose of this study was to determine the effects of 6 wk of essential amino acid (EAA) supplementation on body composition and exercise performance in untrained women (n = 21). Subjects were randomly assigned to a placebo (cellulose) or an EAA (average daily dose of 18.3 g of EAAs in pill form) group. Each subject participated in aerobic and heavy-resistance training three times per week. Body composition was assessed via dual x-ray absorptiometry analysis. Muscular endurance was determined via treadmill time to exhaustion, and strength was assessed by the total amount of weight lifted for one set to exhaustion at an estimated 12 repetitions maximum. No changes occurred in either group for body weight, lean body mass, fat mass, or bone mineral content. Treadmill time to exhaustion (TTE) improved significantly (P < 0.05) in the EAA group (mean +/- SD; pre-TTE = 13.15 +/- 3.67 min, post-TTE = 14. 73 +/- 4.26 min), whereas the placebo group did not change significantly. The total weight lifted at the subject's maximum 12 repetitions did not significantly change in either group. In previously untrained individuals, the ingestion of EAAs combined with aerobic and heavy-resistance training for 6 wk did not have a significant effect on body composition or muscular strength; however, aerobic muscular endurance increased significantly.

Validity of near-infrared interactance for estimating relative body fat in female high school gymnasts.

The present investigation examined the validity of near-infrared interactance (NIR) estimates of relative body fat (% fat) from the Futrex-5000 (F5000), Futrex-5000A (F5000 A), and Futrex-1000 (F1000) instruments. Ninety-eight female high school gymnasts (X age+/-SD = 15.7+/-1.2 yr) participated in this investigation. Subsamples were used to cross-validate the F5000 (n = 52), F5000A (n = 46), and F1000 (n = 89) instruments. The NIR % fat estimates were validated against criterion % fat from underwater weighing (UWW) using the adult conversion constants of Brozek et al. (6) (UWWB) and the female age-specific constants of Lohman (23) (UWWL). The cross-validation statistical analysis included examination of the constant error (CE), standard error of estimate (SEE), r, and total error (TE). In addition, full-model multiple regression analyses were used to predict UWWB or UWWL from body weight (BW) and height (HT). BW and HT were correlated with % fat at R = 0.65-0.70, while the validity coefficients for the NIR instruments ranged from r = 0.40-0.78. The F5000 resulted in nonsignificant CE values (-0.3 % fat vs UWWB and 1.5 % fat vs UWWL; p > 0.008) as well as the lowest TE values (TE = 3.1 % fat vs UWWB and 4.0 % fat vs UWWL). All other NIR estimates of % fat resulted in TE values > or = 6.3 % fat. In addition, for all NIR instruments there were negative correlations for the plots of the CE versus the mean of predicted and criterion (UWWB and UWWL) % fat. Therefore, the present findings indicated that the F5000 provided more accurate estimates of % fat than the F5000A or F1000 instruments, but may underestimate the desired minimal body weight for female gymnasts at the low end of the % fat distribution.