Search

The purpose of the present study was to examine the oxygen uptake (Vo2), heart rate (HR), and ratings of perceived exertion (RPE [OMNI-Leg 0-10]) responses during continuous 1-hour cycle ergometer rides at the PWCVo2 (physical working capacity at the oxygen consumption threshold). Eight subjects (mean age +/- SD = 23 +/- 3.2 years) performed a maximal test to exhaustion for the determination of Vo2peak and ventilatory threshold (VT). The subjects also performed 4 randomly ordered 8-minute workbouts at different power outputs (ranging from 84 to 245 W) to determine the PWCVo2 and a continuous 1-hour cycle ergometer ride at the PWCVo2 during which Vo2, HR, and RPE data were collected every 2 minutes. The PWCVo2 (114 +/- 39 W) and VT (133 +/- 44 W) were not significantly different and occurred at 56 and 63% Vo2peak, respectively. Linear regression showed that the slope coefficients for the Vo2, HR, and RPE vs. time relationships for the continuous 1-hour workbouts were significantly greater than zero. Furthermore, a t-test about a single mean indicated that the mean slope coefficient for the HR vs. time relationship was significantly greater than 0.1 bpm x min(-1) (the rate of increase in HR that can be maintained for an 8-hour day). The results of this study indicated that PWCVo2 could be maintained for an extended period. However, the maximal power output associated with steady state Vo2, HR, and RPE responses was overestimated. The mean increase in Vo2 during the continuous 1-hour ride was 270 mL, which suggested that the PWCVo2 may demarcate the moderate from heavy exercise domains. The mean HR slope coefficient of 0.3 bpm x min(-1) indicated that the power output at the PWCVo2 could likely be maintained for greater than 2 hours. [ABSTRACT FROM AUTHOR]

The purpose of this study was to validate the Physical Working Capacity at the Heart Rate Threshold (PWC HRT) and Physical Working Capacity at the Oxygen Consumption Threshold (PWC V O2) tests by 1) using individual power vs. duration relationships to estimate the times to exhaustion (ETTE) at the PWC HRT and PWC V O2, and 2) comparing the power outputs and ETTE values of the PWC HRT and PWC V O2 with those of the ventilatory threshold (VT). Ten adults (mean age +/- SD = 23 +/- 1 years) performed an incremental test to exhaustion on a cycle ergometer for the determination of V O2 peak and VT. The subjects also performed four randomly ordered workbouts to exhaustion at different power outputs (ranging from 98 to 246 W) to determine the PWC V O2, PWC HRT, and power vs. duration relationship. Power curve analyses (y = ax b) were used to define the hyperbolic power vs. duration relationship for each subject and to determine the ETTE at the PWC V O2, PWC HRT, and VT. Two separate one-way repeated-measures analyses of variance indicated that there were significant differences among the fatigue thresholds (PWC V O2 > PWC HRT) and ETTE values (PWC HRT > PWC V O2): PWC V O2 (mean +/- SD = 147 +/- 43 W; ETTE = 21 +/- 3 minutes), PWCHRT (136 +/- 37 W; ETTE = 29 +/- 6 minutes), and VT (143 +/- 44 W; ETTE = 27 +/- 11 minutes). These findings were consistent with previous studies that indicated that the PWC HRT occurred at a lower power output than the PWC V O2. Furthermore, the PWC HRT was maintained for a mean of 29 minutes, whereas the PWC V O2 and VT were maintained for 21 and 27 minutes, respectively. These findings indicate that the ETTE values for the PWC V O2 and PWC HRT were substantially less than those suggested in previous studies. [ABSTRACT FROM AUTHOR]

The purposes of this study were to 1) compare the patterns of responses for plasma ammonia concentration ([NH3]) during moderate- vs. heavy-intensity cycle ergometry, and 2) examine the relationship between the V O2 slow component (V O 2SC) and plasma [NH3]. Thirteen healthy, untrained men (mean +/- SEM age = 24.8 +/- 0.6 years) performed a total of eight constant power output exercises (7 minutes in duration) at two different intensities (moderate, 60% gas exchange threshold [GET] = 60% of the gas exchange threshold; and heavy, Delta 50% = 50% of the difference between GET and V O2 max). Blood was collected from an antecubital vein before the exercise, during the last 3 minutes of the 6-minute warm-up, and during each minute of the 7-minute constant power output workbout. The time course of changes in plasma [NH3] and V O2 during the two constant power output exercise intensities were assessed separately using 2 (intensity) x 7 (time) repeated-measures analyses of variance. For 60% GET, there were no significant differences in the mean normalized plasma [NH3] during the 7-minute workbout. For Delta 50%, there was a significant increase in the mean normalized plasma [NH3] during the 7-minute workbout. These findings suggest a potential relationship between exercise-induced hyperammonemia and the V O 2SC during heavy-intensity exercise. [ABSTRACT FROM AUTHOR]

Abstract Background Complementary and alternative medicine (CAM) use is prevalent among HIV-infected patients to reduce the toxicity of antiretroviral therapy. Ginseng has been used for treatment of hyperglycemia and insulin resistance, a common side effect of some HIV-1 protease inhibitors (PI). However, it is unknown whether American ginseng (AG) can reverse insulin resistance induced by the PI indinavir (IDV), and whether these two agents interact pharmacologically. We evaluated potential pharmacokinetic interactions between IDV and AG, and assessed whether AG improves IDV-induced insulin resistance. Methods After baseline assessment of insulin sensitivity using the insulin clamp technique, healthy volunteers received IDV 800 mg q8 h for 3 days and then IDV and AG 1g q8h for 14 days. IDV pharmacokinetics and insulin sensitivity were assessed before and after AG co-administration. Results There was no difference in the area-under the plasma-concentration-time curve after the co-administration of AG, compared to IDV alone (n = 13). Although insulin-stimulated glucose disposal per unit of insulin (M/I) decreased by an average of 14.8 ± 5.9% after 3 days of IDV (from 0.113 ± 0.012 to 0.096 ± 0.014 mg/kgFFM/min per μU/ml of insulin, p = 0.03, n = 11), M/I remained unchanged after co-administration of IDV and AG. Conclusion IDV decreases insulin sensitivity, which is unaltered by AG co-administration. AG does not significantly affect IDV pharmacokinetics.

Music is widely used as an ergogenic aid in sport, but there is little evidence of its effectiveness during closed-loop athletic events. In order to determine the effectiveness of music as an ergogenic aid, well-trained and task-habituated cyclists performed 10-km cycle time trials either while listening to self-selected motivational music or with auditory input blocked. There were no statistically significant differences in performance time or physiological or psychological markers related to music (time-trial duration17.75 ± 2.10 vs 17.81 ± 2.06 min, mean power output 222 ± 66 vs 220 ± 65 W, peak heart rate184 ± 9 vs 183 ± 8 beats/min, peak blood lactate12.1 ± 2.6 vs 11.9 ± 2.1 mmol/L, and final rating of perceived exertion 8.4 ± 1.5 vs 8.5 ± 1.6). It is concluded that during exercise at competitive intensity, there is no meaningful effect of music on either performance or physiology.

The purpose of this study was to examine the effects of 7 days of supplementation with 20 g·d⁻¹ of creatine monohydrate (CM) on mean power (MP) and peak power (PP) from the Wingate anaerobic test (WAnT), body weight (BW), 1-repetition maximum (1RM) bilateral leg extension (LE) strength, and 1RM bench press (BP) strength. This study used a randomized, double-blind, placebo-controlled design. Twenty-two men (mean ± SD: age = 22.1 ± 2.0 years; height = 178.0 ± 5.8 cm; body weight [BW] = 77.6 ± 7.6 kg) were randomly assigned to either a supplement (SUPP; n = 10) or placebo (PLAC; n = 12) group. The SUPP group ingested 20 g·d⁻¹ of CM powder for 7 days, whereas the PLAC ingested 20 g·d⁻¹ of maltodextrin powder. Measurements for the PLAC and SUPP groups included BW, PP, and MP from two 30-second WAnTs (separated by 7 minutes), and 1RM strength for LE and BP. Testing was conducted before (PRE) and after (POST) 7 days of ingesting either the supplement or placebo. The results of this study indicated that there was a significant (p ≤ 0.05) increase from PRE to POST testing in MP for the SUPP group (5.4%) but not for the PLAC group (-0.3%). There were no between-group differences, however, for 1RM LE and 1RM BP strength. Furthermore, there were no changes in PP or BW for either group. The findings of this study indicated that loading with 20 g·d⁻¹ of CM for 7 days increased MP (5.4% increase) from the WAnT, but it had no effect on strength (1RM LE and 1RM BP), PP, or BW.

The purpose of the present investigation was to compare the electromyographic (EMG) responses and the estimated physical working capacity at the fatigue threshold (PWC(FT)) values recorded from electrode arrangements placed: (1) parallel to the muscle fiber pennation angle (MFPA), (2) parallel to the long axis of the femur, and (3) over the innervation zone (IZ) during incremental cycle ergometry. Thirteen college-aged males and females (mean age ± SD=22.4 ± 3.4 years) performed an incremental test to exhaustion on a cycle ergometer. A linear electrode array was utilized to determine the MFPA and location of the IZ of the vastus lateralis (VL). For determination of the PWC(FT) values, EMG signals were recorded from three bipolar electrode arrangements at different locations over the VL. The results of a one-way repeated measures ANOVA indicated there were no significant (p<0.05) mean differences in PWC(FT) values among the electrode arrangements (parallel to the MFPA=190 ± 36 W; parallel to the long axis of the femur=194 ± 40 W; and over the IZ=199 ± 51 W) or the EMG amplitude and MPF values at the common power outputs. There were also significant correlations (r=0.75-0.91) among the three electrode arrangements for PWC(FT) values. These findings suggested that the PWC(FT), like absolute EMG amplitude and MPF, is robust to the influence of electrode placement over the IZ as well as the orientation with respect to the MFPA during cycle ergometry., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The purposes of this study were to (a) determine if the mathematical model that has previously been used to estimate the critical power (CP) was applicable to heart rate (HR) to estimate the critical heart rate (CHR), and (b) compare the CHR to the HR values at the CP (CP(HR)), ventilatory threshold (VT(HR)), and respiratory compensation point (RCP(HR)). Fifteen women (mean age ± SD = 21.7 ± 2.1 years) performed an incremental test to exhaustion to determine VO₂peak, VT(HR), and RCP(HR). The subjects also performed 4 exhaustive workbouts at different power outputs for the determination of CP and CHR. For each power output, the total number of heart beats (HB(lim)) was calculated as the product of the average 5-second HR (bpm) and total time to exhaustion (T(lim) in minutes). The HB(lim) and total work (W(lim) in kilograms-meters) were plotted as a function of the T(lim) at each power output, and the slope coefficients of the regression lines between HB(lim) or W(lim) and T(lim) were defined as the CHR and CP, respectively. A 1-way repeated-measures analysis of variance (ANOVA) indicated that CHR (172 ± 11 bpm, 92.9 ± 2.7%HRmax) was similar to RCP(HR) (172 ± 9 bpm, 92.9 ± 2.2%HRmax) but was higher (p < 0.05) than CP(HR) (154 ± 10 bpm, 83.2 ± 4.0%HRmax) and VT(HR) (152 ± 12 bpm, 82.1 ± 4.3%HRmax). The relationship between HR and T(lim) from the CHR test can be described by the CP model. The CHR test may be a practical method for estimating RCP without the need to measure expired gas samples. Furthermore, like the RCP, the CHR test may be used to demarcate the heavy from severe exercise intensity domains, predict endurance exercise performance, and prescribe a training intensity for competitive cyclists.

The purpose of this study was to compare the body composition, body build, and anthropometric characteristics of boy and girl sprint swimmers. Two groups (boys, n = 38 and girls, n = 31) of sprint swimmers (mean age ± SD = 11.03 ± 2.29 and 10.45 ± 2.29 years, respectively) volunteered for this study. The subjects were members of local swimming clubs who competed in sprint swimming events (≤ 200 m). Gender comparisons were made for age, body weight (BW), height (HT), fat-free weight (FFW), percent body fat (%fat), endomorphic rating, mesomorphic rating, ectomorphic rating, sum of 12 diameters, sum of 11 circumferences, biacromial diameter/biiliac diameter, and FFW/HT. The results of the independent t-tests indicated that the only mean differences between the boy and girl sprint swimmers were for % fat (boys = 9.40 ± 5.35% fat; girls = 12.73 ± 6.19% fat) and endomorphic rating (boys = 2.87 ± 0.96; girls = 4.29 ± 1.22). For the current age group of sprint swimmers the only gender differences were for measures associated with body fatness, and there were no differences for body build measures associated with musculoskeletal size, muscularity, skeletal size, total body mass, or body breadth dimensions. These findings suggest that the swimming performance for girls may be improved through training programs designed to reduce body fatness.

The purpose of the present study was to compare the age-related patterns of anthropometric dimensions of female high school gymnasts to those of a national representative sample of teenage girls. One hundred and one female high school gymnasts (X ± SD age = 15.8 ± 1.1 year; height [HT] = 162.2 ± 5.7 cm; body weight [BW] = 54.1 ± 6.5 kg) volunteered as subjects in the present study. The sample was divided into 4 independent age groups: age group 14 (AG14) = 14.00 to 14.99 years (n = 26); AG15 = 15.00 to 15.99 years (n = 27); AG16 = 16.00 to 16.99 years (n = 29); and AG17 = 17.00 to 17.99 years (n = 19). Nine variables including BW; HT; body mass index (BMI); subscapular and triceps skinfolds; and waist, mid-arm, maximal calf, and mid-thigh circumferences were assessed on each subject. Independent t-tests indicated that for all age groups, the female high school gymnasts exhibited lower BW, BMI, circumferences (waist, mid-arm, maximal calf, and mid-thigh) and skinfolds (subscapular and triceps) than the national sample, except AG 17 for BW and maximal calf and mid-thigh circumferences. There were no significant differences in HT between samples for any of the age groups. Furthermore, there were no differences between the high school gymnasts and the national sample for the slope coefficients for the anthropometric dimensions vs. age relationships. These findings indicated that in females, participation in high school gymnastics does not adversely affect yearly changes in anthropometric dimensions.

Unlabelled: Theoretically, the critical torque (CT), electromyographic mean power frequency fatigue threshold (EMG MPF(FT)), and mechanomyographic mean power frequency fatigue threshold (MMG MPF(FT)) describe the maximal non-fatiguing isometric torque level., Purpose: The purposes of this study were threefold: (1) to determine if the mathematical model for estimating the EMG MPF(FT) during isometric muscle actions of the leg extensors was applicable to isometric muscle actions of the forearm flexors; (2) to determine if the mathematical model for estimating the EMG MPF(FT) from the frequency of the EMG signal was applicable to the frequency domain of the MMG signal to estimate a new fatigue threshold called the mechanomyographic mean power frequency fatigue threshold (MMG MPF(FT)); and (3) to compare the mean torque levels derived from the CT, EMG MPF(FT), and MMG MPF(FT) tests during isometric forearm flexion muscle actions., Methods: Ten adults (4 men and 6 women, mean ± SD; age = 22.0 ± 2.1 years) performed three or four continuous, fatiguing, isometric muscle actions of the forearm flexors at 30, 45, 60, and 75% of maximum voluntary isometric contraction (MVIC) to determine the time to exhaustion (T(lim)) values. The slope coefficient of the linear relationship between total isometric "work" (W(lim) in Nms=torque × T(lim)) and T(lim) was defined as the CT. Surface EMG and MMG signals were recorded from the biceps brachii muscle during each fatiguing isometric muscle action. The EMG and MMG MPF(FT) were defined as the y-intercepts of the isometric torque versus slope coefficient (EMG and MMG MPF versus time) plots., Results: There were no significant differences between fatigue thresholds (CT=26.3 ± 0.8, EMG MPF(FT)=31.4 ± 4.2, and MMG MPF(FT)=29.5 ± 7.0%MVIC), and the mean torque values (Nm) from the three fatigue thresholds were significantly intercorrelated at r = 0.94-0.96., Conclusion: The EMG MPF(FT) test may provide a non-invasive method to examine the effects of interventions on the conduction velocity and shape of the action potential waveform. In addition, the effects of interventions on the global motor unit firing rate of the unfused, activated motor units may be examined by the non-invasive methods of the MMG MPF(FT) test., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The purpose of the present investigation was to examine the effects of 28 days of polyethylene glycosylated creatine (PEG-creatine) supplementation on 1-repetition maximum bench press (1RMBP) and leg extension (1RMLE), mean power (MP), and peak power (PP) from the Wingate Anaerobic test and body weight (BW). This study used a randomized, double-blind, placebo-controlled, parallel design. Twenty-two untrained men (mean age ± SD = 22.1 ± 2.1 years) were randomly assigned to either a Creatine (n = 10) or Placebo (n = 12) group. The Creatine group ingested PEG-creatine (5 g·d), whereas the Placebo group ingested maltodextrin powder (5 g·d). All subjects performed bench press and bilateral leg extension exercises to determine their 1RM values, and 2 consecutive Wingate Anaerobic Tests (separated by 7 minutes) on a cycle ergometer to determine MP and PP before supplementation (day 0) and after 7 (day 7) and 28 (day 28) days of supplementation. The results indicated that there was a significant (p < 0.05) increase in 1RMBP between days 0 and 28 for the Creatine group but not for the Placebo group. There were no significant changes, however, in 1RMLE, MP, PP, or BW for the Creatine or Placebo group. These findings indicated that 28 days of PEG-creatine supplementation without resistance training increased upper body strength but not lower body strength or muscular power. These findings supported the use of the PEG-creatine supplement for increasing 1RMBP strength in untrained individuals.

The purposes of this study were twofold: 1) to derive the mechanomyographic mean power frequency fatigue threshold (MMG MPFFT) for submaximal cycle ergometry; and 2) to compare the power outputs associated to the MMG MPFFT to other neuromuscular and gas exchange fatigue thresholds. 9 adults (5 men and 4 women; mean+/-SD age=23.7+/-3.7 years; body weight=66.3+/-8.2 kg) performed an incremental cycle ergometry test to exhaustion while expired gas samples, electromyographic (EMG), and MMG signals were measured from the vastus lateralis muscle. The non-significant correlations (r=0.17 to 0.66; p>0.05) among the physical working capacity at the fatigue threshold (PWCFT), MMG MPFFT, and gas exchange threshold (GET) suggested that different physiological mechanisms may underlie these 3 fatigue thresholds. A significant correlation (r=0.83) for the MPFFT vs. respiratory compensation point (RCP) suggested that these fatigue thresholds may be mediated by a common physiological mechanism. In addition, the significantly lower mean values found for the PWCFT (mean+/-SD=163+/-43 W), MMG MPFFT (132+/-33 W), and GET (144+/-28 W) than MPFFT (196+/-53 W) and RCP (202+/-41 W) suggested that these gas exchange and neuromuscular fatigue thresholds may demarcate different exercise intensity domains., (Georg Thieme Verlag KG Stuttgart . New York.)

The purposes of the present study were to determine the patterns of age-related changes in 1) height (HT), body weight (BW), fat-free weight (FFW), and absolute isokinetic peak torque (PT); and 2) isokinetic PT covaried separately for HT, BW, FFW, and HT and BW combined in young wrestlers. One hundred twenty-five male wrestlers (mean age +/- SD = 14.3 +/- 2.4 yr; range = 11.1-18.2 yr) volunteered to perform concentric, isokinetic leg extension and flexion at 180 degrees xs-1 on a Cybex II dynamometer to measure PT as well as underwater weighing to determine FFW. The polynomial regression analyses indicated there were significant quadratic increases across age for HT (R = 0.62), BW (R = 0.56), and FFW (R = 0.47). For leg extension, there were significant increases across age for absolute PT (quadratic, R = 0.66), PT covaried for HT (linear, r = 0.10), PT covaried for BW (linear, r = 0.12), PT covaried for FFW (quadratic, R = 0.32), and PT covaried for HT and BW combined (quadratic, R = 0.11). For leg flexion, there were significant increases across age for absolute PT (linear, r = 0.59), PT covaried for HT (linear, r = 0.07), PT covaried for BW (linear, r = 0.08), PT covaried for FFW (quadratic, R = 0.23), and PT covaried for BW and HT combined (linear, r = 0.03). The results of this study indicated that age-related increases in leg-extension and flexion PT for the current sample of young wrestlers could not be accounted for by changes in HT, BW, FFW, or HT and BW combined. These findings suggested that neural maturation may contribute to increases in leg strength across age in young wrestlers.

The purposes of this study were threefold: (1) to compare the power output related patterns of absolute and normalized MMG amplitude and MPF responses for proximal and distal accelerometer placements on the vastus lateralis (VL) muscle during incremental cycle ergometry; (2) to examine the influence of accelerometer placements on mean absolute MMG amplitude and MPF values; and (3) to determine the effects of normalization on mean MMG amplitude and MPF values from proximal and distal accelerometer placements. Fifteen adults (10 men and 5 women; mean+/-SD age=23.9+/-3.1 years) performed incremental cycle ergometry tests to exhaustion. Two accelerometers were placed proximal and distal on the VL muscle. Paired t-tests indicated that absolute MMG amplitude values for the proximal accelerometer were greater (p<0.05) than the distal accelerometer at all power outputs. The normalized MMG amplitude also had greater values for the proximal accelerometer at all power outputs, except 50W. There were no differences, however, between proximal and distal accelerometers for absolute MMG MPF, except at 75W, and normalization eliminated this difference. Twenty-seven percent of the subjects exhibited different power output related patterns of responses between accelerometer placements for MMG amplitude and 47% exhibited different patterns for MPF. These findings indicated that normalization did not eliminate the influence of accelerometer placement on MMG amplitude and highlighted the importance of standardizing accelerometer placements to compare MMG values during cycle ergometry., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

Unlabelled: The electromyographic (EMG) mean power frequency (MPF) and amplitude versus time relationships are commonly used to characterize localized muscle fatigue., Purpose: The purpose of this study was to compare the effect of epoch length on the individual and mean slope coefficients and y-intercepts resulting from the EMG MPF and amplitude versus time relationships of the vastus medialis (VM) muscle during fatiguing isometric muscle actions at 30 and 75% of maximum voluntary isometric contraction (MVC)., Methods: Eight adults performed two continuous, isometric muscle actions of the leg extensors at 30 and 75% MVC to exhaustion. Six, 5.0 s epochs of the surface EMG signals were recorded from the VM during each minute. Epoch lengths of 0.5, 1.0, and 2.0 s were selected from the middle of each 5.0 s epoch. Linear regression was used to estimate the slope coefficient and y-intercept values for the EMG MPF and amplitude versus time relationships for each epoch length (0.5, 1.0, 2.0, and 5.0 s) and subject., Results: There were no significant differences between epoch lengths for the individual or mean slope coefficients or y-intercepts (EMG MPF and amplitude versus time relationships)., Conclusion: This study indicated that epochs of 0.5 - 5.0 s resulted in the same characterization of EMG (MPF and amplitude) versus time relationships during isometric muscle actions.

The purpose of the present study was to examine the effects of the daily administration of an arginine-based supplement for 4 weeks on the gas exchange threshold (GET) and peak oxygen uptake. The study used a double-blind, placebo-controlled design. Forty-one college-aged males (mean age +/- SD = 22.1 +/- 2.4 years) were randomized into either the PLACEBO (n = 20) or ARGININE (n = 21) group. The placebo was microcrystalline cellulose. The ARGININE group ingested 3.0 g of arginine, 300 mg of grape seed extract, and 300 mg of polyethylene glycol. All subjects performed an incremental test to exhaustion on a cycle ergometer prior to supplementation (PRE) and after 4 weeks of supplementation (POST). The GET was determined by using the V-slope method of the carbon dioxide output vs. oxygen uptake relationship. The results indicated that there were significant mean increases (PRE to POST) in GET (4.1%), as well as in carbon dioxide output (4.3%) and power output (5.4%) at the GET for the ARGININE group, but no significant changes for the PLACEBO group (2.5%, 4.3%, and 3.9%, respectively). In addition, there were no significant changes in peak oxygen uptake for the ARGININE (-1.0%) or PLACEBO (-1.5%) groups. These findings supported the use of the arginine-based supplement for increasing GET and the associated power output, but not for increasing peak oxygen uptake during cycle ergometry.

Unlabelled: Theoretically, the mechanomyographic (MMG) mean power frequency fatigue threshold (MMG MPF(FT)) describes the maximal isometric torque that can be maintained for an extended period of time with no change in the global firing rate of the unfused, activated motor units., Purpose: The purposes of this study were twofold: (1) to determine if the mathematical model for estimating the electromyographic (EMG) MPF(FT) from the frequency of the EMG signal was applicable to the frequency domain of the MMG signal to estimate a new fatigue threshold called the MMG MPF(FT); and (2) to compare the mean torque levels derived from the MMG MPF(FT) test for the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles during isometric leg extension muscle actions., Methods: Nine adults (4 men and 5 women; mean+/-S.D. age=21.6+/-1.2 years) performed three or four continuous, fatiguing, isometric muscle actions of the leg extensors at 30, 45, 60, and 75% of maximum voluntary isometric contraction (MVIC) to exhaustion. Surface MMG signals were recorded from the VL, VM, and RF muscles during each fatiguing isometric muscle action. The MMG MPF(FT) was defined as the y-intercept of the isometric torque versus slope coefficient (MMG MPF versus time) plot., Results: There were no significant differences among the MMG MPF(FT) values for the VL, VM, and RF (34.8+/-23.4, 32.1+/-16.1, and 31.6+/-15.2 Nm, respectively) muscles., Conclusion: The MMG MPF(FT) test may provide a non-invasive method to examine the effects of various interventions on the global motor unit firing rate during isometric muscle actions., (Copyright (c) 2009 Elsevier B.V. All rights reserved.)

The purposes of this study were threefold: (1) to compare the isometric torque-related patterns of absolute and normalized electromyographic (EMG) amplitude and mean power frequency (MPF) responses for electrode orientations that were parallel and perpendicular to the muscle fibers; (2) to examine the influence of electrode orientation on mean absolute EMG amplitude and MPF values; and (3) to determine the effects of normalization on mean EMG amplitude and MPF values from parallel and perpendicular electrode orientations. Ten adults (5 men and 5 women mean +/- SD age = 23.8 +/- 2.3 years) volunteered to participate in the investigation. Two sets of bipolar surface EMG electrodes (20 mm center to center) were placed parallel and perpendicular to the muscle fibers over the biceps brachii. The subjects performed a maximal voluntary isometric contraction (MVIC) test followed by randomly ordered submaximal muscle actions in 10% increments from 10 to 90% MVIC. Paired t-tests indicated that absolute EMG amplitude values for the parallel electrode orientation were greater (p < 0.05) than those for the perpendicular orientation at all isometric torque levels except 10% MVIC For normalized EMG amplitude values, however, there were no significant mean differences between electrode orientations. There were also no differences between electrode orientations for absolute or normalized EMG MPF values. In 30% of the cases, different torque-related patterns of responses were observed between the parallel and perpendicular electrode orientations for the absolute and normalized EMG amplitude and MPF values. Therefore, the results of the present study support the need for standardizing electrode orientation to compare the pattern of responses for EMG amplitude and MPF values and normalizing EMG amplitude data to compare the mean values.

The purpose of the present study was to examine the acute effects of a caffeine-containing supplement (SUPP) on 1 repetition maximum (1RM) bench press and leg extension strength, as well as time to exhaustion (TTE), during cycle ergometry at a power output that corresponded to 80% of VO2peak. The study used a double-blinded, placebo-controlled, crossover design. Twenty-one untrained men (mean +/- SD age = 23.0 +/- 2.6 yr) were randomly assigned to take either the SUPP or placebo (PLAC) first. The SUPP contained 400 mg of caffeine, 66.7 mg of capsicum extract, 10 mg of bioperine, and 40 mg of niacin, and the PLAC was microcrystalline cellulose. Sixty minutes after taking either the SUPP or PLAC, the subjects were tested for 1RM bench press and leg extension strength, as well as TTE. After 1 week of rest, the subjects ingested the opposite substance (SUPP or PLAC) and were retested for 1RM bench press and leg extension strength, as well as TTE. The results indicated that the SUPP had no effect on 1RM bench press strength, 1RM leg extension strength, or TTE at 80% VO2peak. These findings did not support the use of the caffeine-containing SUPP in the present study as an ergogenic aid in untrained individuals.

The purposes of this investigation were twofold: (1) to determine if the model used for estimating the physical working capacity at the fatigue threshold (PWC(FT)) from electromyographic (EMG) amplitude data could be applied to the frequency domain of the signal to derive a new fatigue threshold for cycle ergometry called the mean power frequency fatigue threshold (MPF(FT)), and (2) to compare the power outputs associated with the PWC(FT), MPF(FT), ventilatory threshold (VT), and respiratory compensation point (RCP). Sixteen men [mean (SD) age = 23.4 (3.2) years] performed incremental cycle ergometer rides to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. There were significant (p < 0.05) mean differences for PWC(FT) [mean (SD) = 168 (36) W] versus MPF(FT) [208 (37) W] and VT [152 (33) W] versus RCP [205 (84) W], but no mean differences for PWC(FT) versus VT or MPF(FT) versus RCP. The mean difference between PWC(FT) and MPF(FT) may be due to the effects of specific metabolites that independently influence the time and frequency domains of the EMG signal. These findings indicated that the PWC(FT) model could be applied to the frequency domain of the EMG signal to estimate MPF(FT). Furthermore, the current findings suggested that the PWC(FT) may demarcate the moderate from heavy exercise domains, while the MPF(FT) demarcates heavy from severe exercise intensities.

Unlabelled: Theoretically, critical torque (CT) is the maximal isometric torque that can be maintained without fatigue, and anaerobic work capacity (AWC) is the total "isometric work" associated with stored energy sources within the muscle., Purpose: The purpose of this study was twofold: 1) to determine whether there were differences among the estimates of CT and AWC from linear and nonlinear mathematical models and 2) to compare the estimated time to exhaustion (ETTE) values associated with the CT estimates from the linear and nonlinear mathematical models., Methods: Nine adult subjects (mean +/- SD age = 21.6 +/- 1.2 yr) performed three or four continuous, fatiguing, isometric muscle actions of the leg extensors at 30%, 45%, 60%, and 75% of maximum voluntary isometric contraction to determine the time to exhaustion (Tlim) values. Five mathematical models (two linear, two nonlinear, and one exponential) were used to estimate CT and AWC (the exponential model did not estimate AWC) from the relationships between "isometric work" or torque and Tlim. Individual torque versus Tlim curves was also generated from the fatiguing isometric muscle actions to calculate the ETTE values., Results: The exponential model resulted in greater mean CT and lower ETTE values than the other models. There were no significant differences, however, between models for AWC., Conclusion: Torque-curve analyses indicated that the mean ETTE values range from 7.26 to 16.98 min, and therefore all five CT models (23.0 to 37.0 N x m) overestimated the torque levels that could be maintained for an extended period without fatigue.

The purposes of this study were threefold: (1) to compare the power output related patterns of absolute and normalized EMG amplitude and MPF responses for electrode orientations that were approximately parallel and perpendicular to the muscle fibers of the vastus lateralis muscle (VL); (2) to examine the influence of electrode orientation on mean absolute EMG amplitude and MPF values; and (3) to determine the effects of normalization on mean EMG amplitude and MPF values from parallel and perpendicular electrode orientations. Twenty adults (10 men and 10 women mean+/-SD age=23.4+/-3.6 years) performed incremental cycle ergometry tests to exhaustion. Two sets of bipolar surface EMG electrodes were placed approximately parallel and perpendicular to the muscle fibers over the VL. Paired t-tests indicated that absolute EMG amplitude values for the parallel electrode orientation were greater (p<0.05) at 50, 75, and 100W. The normalized EMG amplitude also had greater values for the parallel electrode orientation at 75 and 100W. For absolute EMG MPF, the parallel electrode orientation had greater values for all six power outputs, but after normalization, the perpendicular electrode orientation had a greater value at 75W. Ten percent of the subjects exhibited different power output related patterns of responses between electrode orientations for EMG amplitude and 35% exhibited different patterns for MPF. These findings indicated that normalization reduced, but did not eliminate the influence of electrode orientation and highlighted the importance of standardizing electrode orientation to compare EMG values during cycle ergometry.

Unlabelled: Theoretically, the critical torque (CT) and electromyographic mean power frequency fatigue threshold (EMG MPF(FT)) describe the maximal non-fatiguing isometric torque level., Purpose: The purposes of this study were two-fold: (1) to determine if the mathematical model for estimating the EMG fatigue threshold (EMG(FT)) from the amplitude of the EMG signal was applicable to the frequency domain of the EMG signal to estimate a new fatigue threshold called the EMG MPF(FT); and (2) to compare the torque level derived from the CT test to that of the EMG MPF(FT) test for the vastus lateralis (VL) muscle during isometric muscle actions of the leg extensors., Methods: Nine adults (4 men and 5 women; mean+/-SD age=21.6+/-1.2 yr) performed three or four continuous, fatiguing, isometric muscle actions of the leg extensors at 30, 45, 60, and 75% of maximum voluntary isometric contraction (MVIC) to determine the time to exhaustion (T(lim)) values. The slope coefficient of the linear relationship between total isometric "work" (W(lim) in Nms=TorquexT(lim)) and T(lim) was defined as the CT. Surface EMG signals were recorded from the vastus lateralis (VL) muscle during each fatiguing isometric muscle action. The EMG MPF(FT) was defined as the y-intercept of the isometric torque versus slope coefficient (EMG MPF versus time) plot., Results: There were no significant differences between CT (19.7+/-5.8%MVIC) and EMG MPF(FT) (21.4+/-8.7%MVIC)., Conclusion: These findings provided indirect validation of the EMG MPF(FT) test.

Purpose: The purpose of the present study was to compare the age-related patterns of anthropometric characteristics in young wrestlers (8-13 yr) to those of a national representative sample of boys the same age., Methods: Two hundred and fifty-three young wrestlers (X age +/- SD, 11.1 +/- 1.6 yr; height (HT), 145.5 +/- 11.4 cm; body weight (BW), 40.7 +/- 10.9 kg) volunteered as subjects in the present study. The sample of young wrestlers was divided into six independent age groups: age group 8 (AG8), 8.00-8.99 yr (n = 27); AG9, 9.00-9.99 yr (n = 43); AG10, 10.00-10.99 yr (n = 50); AG11, 11.00-11.99 yr (n = 45); AG12, 12.00-12.99 yr (n = 56); and AG13, 13.00-13.99 yr (n = 32). Nine variables including BW, HT, body mass index (BMI), subscapular and triceps skinfolds, waist, midarm, maximal calf, and midthigh circumferences were assessed on each subject., Results: The results showed that there was only one (midthigh circumference) difference between the young wrestlers and the national sample for yearly changes in the anthropometric dimensions., Discussion: These findings indicated that participation in age group wrestling was not associated with age-related patterns of anthropometric characteristics that were different from those of a national representative sample of boys the same age.

Unlabelled: Theoretically, the critical force (CF) and the EMG fatigue threshold (EMGFT) tests demarcate fatiguing from nonfatiguing isometric torque levels., Purpose: The purpose of this study was twofold: 1) to determine whether the mathematical model for estimating the EMGFT during cycle ergometry was applicable to isometric leg extension muscle actions and 2) to compare the mean torque level from the CF test to those of EMGFT tests for the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles during isometric muscle actions., Methods: The slope coefficient of the linear relationship between total "isometric work" (Wlim in newton-meters per second) and time to exhaustion (Tlim in seconds) was defined as the CF. The EMGFT was defined as the y-intercept of the isometric torque versus EMG fatigue curve slope coefficient relationship., Results: There was a significant (P < 0.05) mean difference between the CF (25.9 +/- 12.1 N.m) and the EMGFT value for the RF (41.1 +/- 20.7 N.m) muscle. There were no significant differences, however, in EMGFT values among the three superficial muscles of the quadriceps femoris. In addition, the mean CF (17.6% maximum voluntary isometric contraction [MVIC]) occurred at a percentage of MVIC that is typically not affected by circulatory occlusion (20% MVIC), whereas the mean EMGFT values for the VL (25.9% MVIC), VM (22.9% MVIC), and RF (27.8% MVIC) exceeded this threshold.

The purpose of this study was to cross-validate the fat-free weight (FFW) equations derived on nonathletic children and adolescents for estimating mean power (MP) and peak power (PP) in high school wrestlers. One hundred and three male high school wrestlers performed the Wingate Anaerobic Test to estimate MP and PP, as well as underwater weighing to determine FFW. The following equations were used to estimate the MP and PP of the wrestlers in the current study.MP (w) = 9.3 (FFW) - 109.8 EQ.1. PP (W) = 14.1 (FFW) - 162.1 EQ. 2. The results in the current study indicated that as percent of the mean values, the equation that predicted MP resulted in a substantially greater total error (TE; 19.9% of the mean) than the equation that predicted PP (8.3% of the mean). These findings indicated that the equation that was derived on nonathletes did not accurately estimate MP in the high school wrestlers. The equation for estimating PP, however, was valid when applied to the current sample of high school wrestlers. These findings supported previous studies that have shown that in adolescent males, exercise training improves the metabolic capabilities of the anaerobic glycoletic system, but not the phosphagen system.

The purpose of this study was twofold: (1) to determine if the mathematical model used for estimating the EMG(FT) during cycle ergometry was applicable to isometric muscle actions; and (2) to compare the mean torque level from the CF test to that of the EMG(FT) test. The CF was defined as the slope coefficient of the linear relationship between total "isometric work" (W (lim) in N m s) and time to exhaustion (T (lim)). The EMG(FT) was defined as the y-intercept of the isometric torque versus EMG fatigue curve slope coefficient relationship. There was a significant (p < 0.05) mean difference between CF (6.6 +/- 3.2 N m) and EMG(FT) (10.9 +/- 4.7 N m). The results of the present study suggested that, during isometric muscle actions of the forearm flexors, fatigue thresholds estimated from the W (lim) versus T (lim) relationship (CF) are different from those estimated from electromyographic fatigue curves (EMG(FT)).

The purpose of this study was to examine the effects of power output and pedaling cadence on the amplitude and mean power frequency (MPF) of the mechanomyographic (MMG) signal during submaximal cycle ergometry. Nine adults (mean age +/- SD = 22.7 +/- 2.1 yrs) performed an incremental (25 W increase every min) test to exhaustion on an electronically braked cycle ergometer to determine VO2Peak and Wpeak. The subjects also performed three, 8 min continuous, constant power output rides (randomly ordered) at 35%, 50%, and 65% Wpeak. The continuous 8 min workbouts were divided into 4 min epochs. The subjects pedaled at either 50 or 70 rev x min(-1) (randomized) during the first 4 min epoch, then changed to the alternate cadence during the second 4 min epoch. The MMG signal was recorded from the vastus lateralis during the final 10 s of each minute. Two separate two-way [cadence (50 and 70 rev x min(-1)) x %Wpeak (35, 50, and 65)] repeated measures ANOVAs indicated that MMG amplitude followed power output, but not pedaling cadence, whereas MMG MPF was not consistently affected by power output or pedaling cadence. Furthermore, these findings suggested that power output was modulated by motor unit recruitment and not rate coding.

In the past, veterinarians have participated in interprofessional collaboration to support the health promotion and disease prevention goals and objectives described in the United States Department of Health and Human Services' (DHHS) Healthy People 2010. Such projects have resulted from collaboration resulting from a writing competition, the DHHS's Secretary's Award for Innovations in Health Promotion and Disease Prevention (Secretary's Award). The Secretary's Award, which interfaces with Healthy People 2010, has been effectively used as a means of training community-responsive veterinary students in a variety of interprofessional collaborations. All future health care professionals should be trained in innovative interprofessional problem solving, the 'art of thinking outside the box', and the importance of responsiveness to the needs of the community. These health professional students' collaborative efforts are vital for the continual improvement of any nation's health care system in the 21st century.