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Numerous conditions and types of physical activity (e.g., exercise, aging, muscle-related diseases) can influence muscle fiber types and the proteins expressed. To date, muscle fibers can only be characterized by actually obtaining a tissue sample using the invasive muscle biopsy procedure. Mechanomyography (MMG) is the assessment of the vibration properties of contracting skeletal muscle, and has been proposed as a possible non-invasive method for muscle fiber analysis. Therefore, the purpose of this project was to examine the feasibility of using MMG and muscle performance measures to non-invasively assess muscle fiber characteristics. Fifteen men (5 endurance-trained [End], 5 weight-trained [WT], and 5 sedentary [Sed]) provided muscle samples from their vastus lateralis muscle. These samples were analyzed for relative myosin heavy chain protein expression, which is highly correlated with % muscle fiber type areas. Additionally, each subject performed several muscle performance tests, and MMG of the quadriceps was assessed during a knee extension exercise. Multiple regression was used to develop prediction equations for determining relative muscle content of myosin heavy chain (MHC) types I, IIa, and IIx. A combination of MMG and knee extension performance variables estimated types I, IIa, and IIx MHC with approximately 80% accuracy. Although preliminary, these data suggest that muscle performance tests in addition to MMG assessments during a simple muscle performance task (knee extension) can be used to estimate muscle fiber type composition in a healthy male population. Such methods could ultimately be used to non-invasively monitor muscle health and fitness. [ABSTRACT FROM AUTHOR]

The article cites a study which examined the relationship between the fatigue index from an isokinetic fatigue test and the velocityrelated decrease in peak torque for the forearm flexors. The study findings support the possibility of using a multiple-velocity isokinetic test to estimate fiber type composition, just as fatigue-based tests have been used.

The article discusses research which investigated isometric strength, force steadiness, and surface electromyographic (EMG) responses of forearm flexors to concentric and eccentric exercise interventions. Topics explored include the muscle fatigue and damage associated with repeated eccentric exercises, the subject selection and experimental procedures performed, and the use of a customized software for evaluating EMG signal processing and force steadiness.

The article reports on research which investigated the strength and electromyographic (EMG) responses in exercised and nonexercised limbs after concentric (CON) vs. eccentric (ECC) exercise of the forearm flexors. Researchers evaluated 25 male subjects. They found that the CON exercise and ECC exercise interventions caused similar strength losses for the exercised arm and that there was also a strength loss in the contralateral nonexercised arm that was likely because of neural factors.

The article discusses research in applied sports science, with a focus on the role of sample size estimation in experimental design for strength and conditioning research. Topics include calculating statistical power and determining effect size, the G*Power software package, and statistical significance.

The article presents a study on the effectiveness of mental and physical diversion activities on recovery from fatiguing concentric isokinetic muscle exercise. The diverting activities are math problems, contralateral dynamic constant external resistance (DCER) leg extensions, and control or quiet resting. Analysis of peak torque data indicates mental and physical diversions enhance recovery.

The article presents the results of a study which compared two methods of measuring underwater body weight, in terms of their reliability. An overview of related previous research is provided, along with details of the experimental protocol, which involved load cell and mechanical scale versions of hydrostatic weighing.

The article presents the results of a study which investigated the statistical reliability of measurements of barbell velocity during monitoring of the bench press, as performed at various levels of intensity. Details of the experimental protocol, which involved an electronic device called a Tendo Weightlifting Analyzer, are provided.

The article presents the results of a study which investigated the accuracy of techniques for estimating changes induced by a bodybuilding exercise program in the cross-sectional area (CSA) of muscles An overview of related previous research is provided, along with details of the experimental protocol. Two anthropometric-based measurements were found to produce results that correlated significantly with the precise CSA measurements of a peripheral quantitative computed tomography scanner.

The article presents the results of a study which investigated the effect of carbohydrate sports drinks supplemented with leucine on subjects engaged in weight training. An overview of related previous research is provided, along with details of the experimental protocol. It was found that leucine supplementation did not have a significant impact on squat performance or recovery.

The article presents the results of a study on the effects of gender and creatine loading on anaerobic running capacity (ARC). Tests performed are discussed, including a maximal oxygen consumption test on a treadmill used to establish the maximum velocity. Results suggest that creating loading may be an effective strategy for improving ARC in men, but not in women.

The article reports on research conducted to examine the linearity and reliability of the mechanomyographic (MMG) amplitude versus concentric dynamic constant external resistance (DCER) relationships for the bench press exercise. Researchers evaluated 21 resistance exercise trained men. They found that the relationships were not linear and not reliable enough to be used for assessing issues such as the neural versus hypertrophic contributions to training- induced strength gains.

The article presents the results of a study which investigated the use of electromyographic (EMG) fatigue threshold tests as a method to accurately predict ventilatory threshold (VT) after high-intensity interval training. 18 college-aged men performed maximal graded exercise tests which measured oxygen consumption rates. It was found that EMG fatigue threshold is not a valid source for tracking changes in VT.

The article reports on research conducted to determine if the combination of isometric knee extension strength and mechanomyographic median frequency could be used to estimate the percent of myosin heavy chain (MHC) type two isoform content of the vastus lateralis. Researchers evaluated five resistance trained men and five aerobically trained men. They found that the combination could be used to estimate isoform content in well-trained men.

The article reports on research which was conducted to examine the effects four weeks of high intensity interval training and creatine supplementation had on critical power and anaerobic working capacity in college aged men. Researchers found that that creatine supplementation may enhance the effects of intense interval endurance training and increase critical power and aerobic working capacity.

The article reports on the results of research which was conducted in an effort to determine anthropometric estimations of body fat percentage in NCAA division 1 female athletes using a four compartment model of validation and anthropometric equations. The research was also done to compare them with previously validated generalized equations for estimating fat percentage in female athletes. They found that both models were valid and that the new model was not superior to the previously validated model.

The article reports on the results of research which was conducted in an effort to determine the effects creatine monohydrate and polyethylene glycosylated creatine supplementation have on muscular strength, endurance, and power output. Researchers evaluated 58 healthy men. They found that when compared to a group that received placebos, supplementation with either of the drugs did not improve peak power output or muscle endurance.

The article reports on the results of research which was conducted in an effort to determine the effects a thermogenic nutritional supplement had on energy expenditure and cardiovascular function at rest, during low-intensity exercise, and recovery from exercise in sedentary people. They found that the supplement increased energy expenditure and the subjects' exercise oxygen consumption rates and had only minimal effects on blood pressure.

The article presents a study which compared the patterns of responses for plasma ammonia concentration during heavy- and moderate-intensity cycle ergometry. The study also looked at the relationship between plasma and oxygen update. Results indicate a possible relationship between exercise-induced hyperammonemia and oxygen uptake.

The article presents a study which looks at the validity of the Physical Working Capacity at the Heart Rate Threshold and the Physical Working Capacity at the Oxygen Consumption Threshold tests. Tests were evaluated by looking at individual power to duration relationships, estimating the times to exhaustion and comparing power outputs.

The article reports on the study that examines the acute effects of a caffeine-containing supplement (SUPP) on one-repetition maximum (1-RM) bench press strength. The study indicates that the SUPP had no effect on -RM bench press strength or time to running exhaustion (TRE) at 85% of the peak oxygen uptake. However, the findings do not support the use of caffeine as an ergogenic aid in untrained to moderately trained individuals.

The article presents a study which examines whether practical duration of stretching changes muscle strength. According to the article, the experiment have conducted tests on thirteen volunteers who underwent ordered clinical trials before and after the poststretching. In addition, it states that passive stretching (PT) has decreased immediately after all conditions although it is not sufficient enough to alter voluntary force production. Furthermore, it concluded that durations of stretching did not reduced isometric peak torque (PT) as compared with control with no stretching.

The article presents a study which examines the influence of the innervation zone (IZ) on electromyographic (EMG) signals from different bipolar electrodes arrangements that have their center point directly over the IZ. It also investigates the effects of normalization on EMG amplitude and mean power frequency (MPF) values over the IZ. The subject of the study performed isometric muscle action of the dominant leg extensors, and four separate bipolar surface EMG signals were detected simultaneously from the vastus lateralis muscle. The results of the study demonstrated that the patterns for absolute and normalized EMG amplitude and MPF versus isometric torque relationships for the vastus lateralis were affected by electrode location rather than by the IZ.

The article discusses a study to examine the influence of myosin heavy chain (MHC) isoform composition and training status on the mechanomyographic (MMG) amplitude versus isometric torque relationship for the vastus lateralis. There were no consistent patterns of responses for the resistance-trained, aerobically trained or sedentary subjects for MMG amplitude versus torque. The differences in MHC isoform composition and training status did not explain the torque-related patterns.

The purpose of the present study was to use ratings of perceived exertion (RPE) from the Borg (6-20) and OMNI-Leg (0-10) scales to determine the Physical Working Capacity at the Borg and OMNI thresholds (PWCBORG and PWCOMNI). PWCBORG and PWCOMNI were compared with other fatigue thresholds determined from the measurement of heart rate (the Physical Working Capacity at the Heart Rate Threshold: PWCHRT), and oxygen consumption (the Physical Working Capacity at the Oxygen Consumption Threshold, PWCV̇O2), as well as the ventilatory threshold (VT). Fifteen men and women volunteers (mean age ± SD = 22 ± 1 years) performed an incremental test to exhaustion on an electronically braked ergometer for the determination of V̇O2 peak and VT. The subjects also performed 4 randomly ordered workbouts to exhaustion at different power outputs (ranging from 60 to 206W) for the determination of PWCBORG, PWCOMNI, PWCHRT, and PWCV̇O2, The results indicated that there were no significant mean differences among the fatigue thresholds: PWCBORG (mean ± SD = 133 ± 37W; 67 ± 8% of V̇O2peak), PWCOMNI (137 ± 44W; 68 ± 9% of V̇O2peak), PWCHRT (135 ± 36W; 68 ± 8% of V̇O2peak), PWCV̇O2(145 ± 41W; 72 ± 7% of V̇O2peak) and VT (131 ± 45W; 66 ± 8% of V̇O2 peak), The results of this study indicated that the mathematical model used to estimate PWCHRT and PWCV̇O2 can be applied to ratings of perceived exertion to determine PWCBORG and PWCOMNI during cycle ergometry. Salient features of the PWCBORG and PWCOMNI tests are that they are simple to administer and require the use of only an RPE scale, a stopwatch, and a cycle ergometer. Furthermore, the power outputs at the PWCBORG and PWCOMNI may be useful to estimate the VT noninvasively and without the need for expired gas analysis. [ABSTRACT FROM AUTHOR]

The article discusses the effect of the estimated innervation zone (IZ) on electromyographic (EMG) amplitude and mean power frequency (MPF). Participants performed isometric muscle actions of the leg extensors wherein the surface EMG signals were recorded from the vastus lateralis muscle placed over the estimated IZ. Results of the test show the inconsistency on the differences on the patterns of response and mean values for EMG amplitude and MPF versus isometric torque over the estimated IZ from those away from the IZ. Moreover, these differences suggest that normalized EMG amplitude values are not comparable if the EMG signals are detected from different electrode locations.

The purpose of this study was to examine the effects of 2 days of isokinetic training of the forearm flexors and extensors on strength and electromyographic (EMG) amplitude for the agonist and antagonist muscles. Seventeen men (mean ± SD age = 21.9 ± 2.8 years) were randomly assigned to 1 of 2 groups: (a) a training group (TRN; n = 8), or (b) a control group (CTL; n = 9). The subjects in the TRN group were tested for maximal isometric and concentric isokinetic (randomly ordered velocities of 60, 180, and 300°·s-1) torque of the dominant forearm flexors and extensors before (pretest) and after (posttest) 2 days of isokinetic strength training. Each training session involved 6 sets of 10 maximal concentric isokinetic muscle actions of the forearm flexors and extensors at a velocity of 180°·s-1. The subjects in the CTL group were also tested for strength but did not perform any training. Surface EMG signals were detected from the biceps brachii and triceps brachii muscles during the strength testing. The results indicated that there were no significant (p > 0.05) pre- to post- test changes in forearm flexion and extension torque or EMG amplitude for the agonist and antagonist muscles. Thus, unlike previous studies of the quadriceps femoris muscles, these findings for the forearm flexors and extensors suggested that 2 days of isokinetic training may not be sufficient to elicit significant increases in strength. These results may have implications for the number of visits that are required for rehabilitation after injury, surgery, or both. [ABSTRACT FROM AUTHOR]

This investigation examined the effects of a protease supplement on selected markers of muscle damage and delayed-onset muscle soreness (DOMS). The study used a double-blinded, placebo-controlled, crossover design. Twenty men (mean ± SD age = 21.0 ± 3.1 years) were randomly assigned to either a supplement group (SUPP) or a placebo group (PLAC). All subjects were tested for unilateral isometric forearm flexion strength, hanging joint angle, relaxed arm circumference, subjective pain rating, and plasma creatine kinase activity and myoglobin concentration. The testing occurred before (TIME1), immediately after (TIME2), and 24 (TIME3), 48 (TIME4), and 72 (TIME5) hours after a bout of eccentric exercise. During these tests, the subjects in the SUPP group ingested a protease supplement. The subjects in the PLAC group took microcrystalline cellulose. After testing at TIME5 and 2 weeks of rest, the subjects were crossed over into the opposite group and performed the same tests as during visits 1-5, but with the opposite limb. Overall, isometric forearm flexion strength was greater (7.6%) for the SUPP group than for the PLAC group, despite nearly identical (difference = 0.14 N·m, p = 0.940) mean strength values before (TIME1) the eccentric exercise protocol. There were no between-group differences for hanging joint angle, relaxed arm circumference, subjective pain ratings, and plasma creatine kinase activity and myoglobin concentration from TIME1 to TIME5. These findings provided initial evidence that the protease supplement may be useful for reducing strength loss immediately after eccentric exercise and for aiding in short-term strength recovery. The protease supplement had no effect, however, on the perception of pain associated with DOMS or the blood markers of muscle damage. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of a drink containing creatine, amino acids, and protein vs. a carbohydrate placebo on body composition, strength, muscular endurance, and anaerobic performance before and after 10 weeks of resistance training. Fifty-one men (mean ± SD; age: 21.8 ± 2.9 years) were randomly assigned to either the test drink (TEST; n = 23) or the placebo (PLAC; n = 28) and performed two 30-second Win-gate Anaerobic Tests for determination of peak power (PP) and mean power (MP), were weighed underwater for percent body fat (%fat) and fat-free mass (FFM), and were tested for 1 repetition maximum (1RM) dynamic constant external resistance strength and muscular endurance (END; number of repetitions performed with 80% of 1RM) on the bilateral leg extension (LE) and free-weight bench press (BP) exercises. The testing was conducted before (PRE) and after (POST) 10 weeks of resistance training (3 sets of 10 repetitions with 80% of the subject's 1RM performed 3 times per week) on the LE and BP exercises. Body weight, FFM, LE 1RM, LE END, BP 1RM, and BP END increased (p < 0.05), whereas %fat decreased (p < 0.05) from PRE to POST for both the TEST and PLAC groups. Peak power and MP, however, increased for the TEST group, but not for the PLAC group. These results suggested that the creatine-, amino acid-, and protein-containing drink provided no additional benefits when compared with carbohydrates alone for eliciting changes in body composition, strength, and muscular endurance after a 10-week resistance training period. The TEST drink was, however, more effective than carbohydrates alone for improving anaerobic power production. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to determine the validity of the non-exercise-based equations of Davis et al. (13), Jones et al. (20), and Neder et al. (30) for estimating the ventilatory threshold (VT) in samples of aerobically trained men and women. One hundred and forty-four aerobically trained men (mean ± SD age, 41.0 ± 11.6 years; N = 83) and women (37.1 ± 9.0 years, N = 61) performed a maximal incremental test to determine O2max and observed VT on a cycle ergometer. The observed VT was determined by gas exchange measurements using the V-slope method (CO2/O2) in conjunction with analyses of the ventilatory equivalents (i.e., minute ventilation E/O2 and E/CO2) and end-tidal gas tensions (i.e., PETO2 and PETCO2) for oxygen and carbon dioxide. The predicted VT values from 14 equations were compared to the observed VT values by examining the constant error (CE), standard error of estimate (SEE), Pearson correlation coefficient (r), and total error (TE). The results of this investigation indicated that all 14 equations resulted in significant (p < 0.008) CE values ranging from 1.13 to 1.72 L·min-1 for the men and from 0.58 to 1.12 L·min-1 for the women. Furthermore, the SEE, r, and TE values ranged from 0.37 to 0.54, from 0.36 to 0.53, and from 0.68 to 1.81 L·min-1, respectively. The lowest TE values for the men and women represented 45 and 36% of the mean of the observed VT values, respectively. The results of this study indicated that the errors associated with all 14 equations were too large to be of practical value for estimating VT in aerobically trained men and women. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to examine the effects of 3 days of velocityspecific isokinetic training on peak torque (PT) and the electro-myographic (EMG) signal. Thirty adult women were randomly assigned to a slow-velocity training (SVT), fast-velocity training (FVT), or control (CON) group. All subjects performed maximal, concentric, isokinetic leg extension muscle actions at 30 and 270°·s-1 for the determination of PT on visits 1 (pretest) and 5 (posttest). Electromyographic signals were recorded from the vastus lateralis, rectus femoris, and vastus medialis muscles during each test. The training groups performed 4 sets of 10 maximal repetitions at 30°·s-1 (SVT group) or 270°·s-1 (FVT group) on visits 2, 3, and 4. For the SVT group, PT increased from pretest to posttest at 30 and 270°·s-1. The increase in PT at 30°·s-1 was greater than at 270°·s-1. For the FVT group, PT increased at 270°·s-1 only. For the CON group, there were no changes in PT at either velocity. There were no pretest to post-test changes in EMG amplitude or mean power frequency (MPF) for any group at any velocity, with the exception of an increase in EMG MPF from the vastus medialis muscle at 270°·s-1 for the FVT group. The results indicated that 3 sessions of slow velocity (30°·s-1) isokinetic training resulted in an increase in PT at slow and fast velocities (30 and 270°·s-1), whereas training at the fast velocity (270°·s-1) increased PT only at 270°·s-1. The lack of consistent increases in EMG amplitude or MPF suggested that the training-induced increases in leg extension PT were not caused by increased activation of the superficial muscles of the quadriceps femoris. The important implication for coaches, trainers, and physical therapists is that significant muscular performance gains may be achieved even after very short training periods, but determination of the specific physiological adaptation(s) underlying these performance gains requires further investigation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of daily administration of a supplement that contained caffeine in conjunction with 8 weeks of aerobic training on O2peak, time to running exhaustion at 90% O2peak, body weight, and body composition. Thirty-six college students (14 men and 22 women; mean ± SD, age 22.4 ± 2.9 years) volunteered for this investigation and were randomized into either a placebo (n = 18) or supplement group (n = 18). The subjects ingested 1 dose (3 pills = 201 mg of caffeine) of the placebo or supplement per day during the study period. In addition, the subjects performed treadmill running for 45 minutes at 75% of the heart rate at O2peak, three times per week for 8 weeks. All subjects were tested pretraining and posttraining for O2peak, time to running exhaustion (TRE) at 90% O2peak, body weight (BW), percentage body fat (%FAT), fat weight (FW), and fat-free weight (FFW). The results indicated that there were equivalent training-induced increases (p < 0.05) in O2 peak and TRE for the supplement and placebo groups, but no changes (p > 0.05) in BW, %FAT, FW, or FFW for either group. These findings indicated that chronic use of the caffeine-containing supplement in the present study, in conjunction with aerobic training, provided no ergogenic effects as measured by O2peak and TRE, and the supplement was of no benefit for altering body weight or body composition. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the acute effects of a caffeine-containing supplement on upper-and lower-body strength and muscular endurance as well as anaerobic capabilities. Thirty-seven resistance-trained men (mean ± SD, age: 21 ± 2 years) volunteered to participate in this study. On the first laboratory visit, the subjects performed 2 Wingate Anaerobic Tests (WAnTs) to determine peak power (PP) and mean power (MP), as well as tests for 1 repetition maximum (1RM), dynamic constant external resistance strength, and muscular endurance (TOTV; total volume of weight lifted during an endurance test with 80% of the 1RM) on the bilateral leg extension (LE) and free-weight bench press (BP) exercises. Following a minimum of 48 hours of rest, the subjects returned to the laboratory for the second testing session and were randomly assigned to 1 of 2 groups: a supplement group (SUPP; n = 17), which ingested a caffeine-containing supplement, or a placebo group (PLAC; n = 20), which ingested a cellulose placebo. One hour after ingesting either the caffeine-containing supplement or the placebo, the subjects performed 2 WAnTs and were tested for 1RM strength and muscular endurance on the LE and BP exercises. The results indicated that there was a significant (p < 0.05) increase in BP 1RM for the SUPP group, but not for the PLAC group. The caffeine-containing supplement had no effect, however, on LE 1RM, LE TOTV, BP TOTV, PP, and MP. Thus, the caffeine-containing supplement may be an effective supplement for increasing upper-body strength and, therefore, could be useful for competitive and recreational athletes who perform resistance training. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the acute effects of static stretching on peak torque (PT) and the joint angle at PT during maximal, voluntary, eccentric isokinetic muscle actions of the leg extensors at 60 and 1808·s-1 for the stretched and unstretched limbs in women. Thirteen women (mean age ± SD = 20.8 ± 0.8 yr; weight ± SD = 63.3 ± 9.5 kg; height ± SD = 165.9 ± 7.9 cm) volunteered to perform separate maximal, voluntary, eccentric isokinetic muscle actions of the leg extensors with the dominant and nondominant limbs on a Cybex 6000 dynamometer at 60 and 1808·s-1. PT (Nm) and the joint angle at PT (8) were recorded by the dynamometer software. Following the initial isokinetic assessments, the dominant leg extensors were stretched (mean stretching time ± SD = 21.2 ± 2.0 minutes) using 1 unassisted and 3 assisted static stretching exercises. After the stretching (4.3 ± 1.4 minutes), the isokinetic assessments were repeated. The statistical analyses indicated no changes (p > 0.05) from pre- to poststretching for PT or the joint angle at PT. These results indicated that static stretching did not affect PT or the joint angle at PT of the leg extensors during maximal, voluntary, eccentric isokinetic muscle actions at 60 and 1808·s-1 in the stretched or unstretched limbs in women. In conjunction with previous studies, these findings suggested that static stretching may affect torque production during concentric, but not eccentric, muscle actions. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effects of resistance training in combination with a leucine and whey protein supplement or a carbohydrate placebo on strength and muscle cross-sectional area (CSA). Thirty-three men (mean age ± SD = 22.4 ± 2.4 years) were assigned to 1 of 3 groups: (1) supplementation group (SUPP), (2) placebo group (PL), or (3) control group (CON). The SUPP and PL performed unilateral training of the leg extensor muscles with the nondominant limb for 8 weeks. The strength of each limb, muscle CSA of the quadriceps femoris (QF), and body composition were assessed pretraining and posttraining. The results indicated significant increases in strength for both limbs in the SUPP but only the trained limb in the PL. The increase in strength for the trained limb of the SUPP was greater than that for the trained limb of the PL. There was no significant increase in strength for either limb in the CON. There were significant increases in the CSA of all muscles of the QF of the trained limb for the SUPP and PL, and of the vastus lateralis of the untrained limb for the SUPP. The increases in QF CSA did not differ between the SUPP and PL. No significant CSA changes were found for either limb in the CON. There were no significant changes in body composition for the SUPP, PL, or CON. The current findings suggest that leucine and whey protein supplementation may provide an ergogenic effect which enhances the acquisition of strength beyond that achieved with resistance training and a carbohydrate placebo. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to determine the mechanomyography (MMG) and electromyography (EMG) amplitude and mean power frequency (MPF) vs. eccentric isokinetic torque relationships for the biceps brachii muscle. Nine adults (mean ± SD age = 23.1 ± 2.9 years) performed submaximal to maximal eccentric iso-kinetic muscle actions of the dominant forearm flexors. After determination of isokinetic peak torque (PT), the subjects randomly performed submaximal step muscle actions in 10% increments from 10 to 90% PT. Polynomial regression analyses indicated that the MMG amplitude vs. eccentric isokinetic torque relationship was best fit with a quadratic model (R2 = 0.951), where MMG amplitude increased from 10 to 60% PT and then plateaued from 60 to 100% PT. There were linear increases in MMG MPF (r2 = 0.751) and EMG amplitude (r2 = 0.988) with increases in eccentric isokinetic torque, but there was no significant change in EMG MPF from 10 to 100% PT. The results suggested that for the biceps brachii, eccentric isokinetic torque was increased to approximately 60% PT through concurrent modulation of the number of active motor units and their firing rates, whereas additional torque above 60% PT was produced only by increases in firing rates. These findings contribute to current knowledge of motor-control strategies during eccentric isokinetic muscle actions and could be useful in the design of training programs. [ABSTRACT FROM AUTHOR]

The purposes of this study were to (a) determine if the mathematical model used to estimate the physical working capacity at the oxygen consumption threshold (PWCVO 2) and physical working capacity at the heart rate threshold (PWCHRT) for cycle ergometry could be applied to treadmill running; (b) propose new fatigue thresholds called the running velocity at the oxygen uptake threshold (RVVO 2) and running velocity at the heart rate threshold (RVHRT) for treadmill exercise; and (c) statistically compare the velocities at the RVVO2, RVHRT, and ventilatory threshold (VT). Seven aerobically trained adult volunteers (mean ± SD: age 24.0 ± 3.9 years, max = 6.7 ± 7.1 ml·kg-1·min-1) performed a maximal treadmill test to determine VO2 peak and VT as well as four 8-minute submaximal workbouts for the determination of RVVO 2 and RVHRT. One-way repeated-measures analysis of variance indicated that there were no significant (p > 0.05) mean differences among the running velocities for the RVVO 2, RVHRT, and VT. The results of this study indicated that the mathematical model used to estimate PWCVO 2 and PWCHRT for cycle ergometry could be applied to treadmill running. Furthermore, the RVVO 2 and RVHRT test may provide submaximal techniques for estimating the VT. [ABSTRACT FROM AUTHOR]

The purposes of the present study were to (a) modify previously published VO2max equations using the constant error (CE = mean difference between actual and predicted VO2max) values from Malek et al. (28); (b) cross-validate the modified equations to determine their accuracy for estimating VO2max in aerobically trained men; (c) derive a new non-exercise-based equation for estimating VO2max in aerobically trained men if the modified equations are not found to be accurate; and (d) cross-validate the new VO2max equation using the predicted residual sum of squares (PRESS) statistic and an independent sample of aerobically trained men. One hundred and fifty-two aerobically trained men (VO2max mean ± SD = 4,154 ± 629 ml·min-1) performed a maximal incremental test on a cycle ergometer to determine actual VO2max. An aerobically trained man was defined as someone who had participated in continuous aerobic exercise 3 or more sessions per week for a minimum of 1 hour per session for at least the past 18 months. Nine previously published VO2max equations were modified for use with aerobically trained men. The predicted VO2max values from the 9 modified equations were compared to actual VO2max by examining the CE, standard error of estimate (SEE), validity coefficient (r), and total error (TE). Cross-validation of the modified non-exercise-based equations on a random subsample of 50 subjects resulted in a %TE ≥ 13% of the mean of actual VO2max. Therefore, the following non-exercise-based VO2max equation was derived from a random subsample of 112 subjects: VO2max (ml·min-1) = 27.387(weight in kg) + 26.634(height in cm) - 27.572(age in years) + 26.161(h·wk-1 of training) + 114.904(intensity of training using the Borg 6-20 scale) + 506.752(natural log of years of training) - 4,609.791 (R = 0.82, R2 adjusted = 0.65, and SEE = 378 ml·min-1). Cross-validation of this equation on the remaining sample of 40 subjects resulted in a %TE of 10%. Therefore, the non-exercise-based equation derived in the present study is recommended for estimating VO2max in aerobically trained men. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the patterns for the mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) vs. torque relationships during submaximal to maximal isometric and isokinetic muscle actions. Seven men (mean ± SD age, 22.4 ± 1.3 years) volunteered to perform isometric and concentric isokinetic leg extension muscle actions at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC) and peak torque (PT) on a Cybex II dynamometer. A piezoelectric MMG recording sensor was placed between bipolar surface EMG electrodes on the vastus medialis. Polynomial regression and separate 1-way repeated-measures analysis of variance were used to analyze the EMG amplitude, MMG amplitude, EMG MPF, and MMG MPF data for the isometric and isokinetic muscle actions. For the isometric muscle actions, EMG amplitude (R2 = 0.999) and MMG MPF (R2 = 0.946) increased to MVC, mean MMG amplitude increased to 60% MVC and then plateaued, and mean EMG MPF did not change (p > 0.05) across torque levels. For the isokinetic muscle actions, EMG amplitude (R2 = 0.988) and MMG amplitude (R2 = 0.933) increased to PT, but there were no significant mean changes with torque for EMG MPF or MMG MPF. The different torque-related responses for EMG and MMG amplitude and MPF may reflect differences in the motor control strategies that modulate torque production for isometric vs. dynamic muscle actions. These results support the findings of others and suggest that isometric torque production was modulated by a combination of recruitment and firing rate, whereas dynamic torque production was modulated primarily through recruitment. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of static stretching on concentric, isokinetic leg extension peak torque (PT) at 60 and 240°.s-1 in the stretched and unstretched limbs. The PT of the dominant (stretched) and nondominant (unstretched) leg extensors were measured on a calibrated Cybex 6000 dynamometer. Following the prestretching PT assessments, the dominant leg extensors were stretched using 1 active and 3 passive stretching exercises. After the stretching, PT was reassessed. The results of the statistical analyses indicated that PT decreased following the static stretching in both limbs and at both velocities (60 and 240°.s-1). The present findings suggested that the stretching-induced decreases in PT may be related to changes in the mechanical properties of the muscle, such as an altered length-tension relationship, or a central nervous system inhibitory mechanism. Overall, these findings, in conjunction with previous studies, indicated that static stretching impairs maximal force production. Strength and conditioning professionals should consider this before incorporating static stretching in preperformance activities. Future studies are needed to identify the underlying mechanisms that influence the time course of stretching-induced decreases in maximal force production for athletes and nonathletes across the age span. [ABSTRACT FROM AUTHOR]

The use of the “efficiency of electrical activity” (EEA) technique involves plotting EMG amplitude as a function of force at different percentages of one's maximum strength for a given task, and has been used to examine the time course of neural versus hypertrophic contributions to resistance training-induced strength gains. Though several studies have demonstrated a linear EMG amplitude versus force relationship with a reliable slope coefficient under isometric testing conditions, it is unclear whether the EEA technique may be applied to dynamic muscle actions. The purpose of the present investigation was to examine the linearity and reliability of the EMG amplitude versus dynamic torque relationship for the vastus lateralis (VL). Nine healthy men (mean ± SD age = 25.3 ± 4.7 years) and eleven healthy women (mean ± SD age = 22.0 ± 1.3 years) performed concentric isokinetic muscle actions of the dominant leg extensors at 30°·s-1 on two occasions separated by at least 48 hours. The muscle actions were randomly ordered in 10% increments from 10% to 100% of peak torque. During each muscle action, the surface EMG signal was detected from the VL with a bipolar surface electrode arrangement. (See Table 1). The coefficients of determination ranged from r2 = 0.75-0.98 for trial 1 and 0.64-0.99 for trial 2. The results from a paired-samples t-test indicated that there was no mean difference between the linear EMG amplitude versus torque slope coefficients from trial 1 versus trial 2. The linear EMG amplitude versus torque slope coefficient for trial 1 was significantly different from that for trial 2 for 3 (2 were greater, 1 was smaller) of the 20 subjects. The results from a two-way repeated measures ANOVA indicated that there was no significant trial × torque interaction, and no main effect for trial, but there was a significant main effect for torque. In addition, the intraclass correlation coefficient for the linear EMG amplitude versus torque slope coefficients for trials 1 and 2 were 0.730 (SEM = 4.9% of the mean value). The results of the present study indicated that the relationship between EMG amplitude and dynamic torque for the VL did not display an adequate degree of linearity and reliability to be used for the EEA technique. The EEA technique is important in addressing issues such as the neural versus hypertrophic contributions to resistance training-induced strength gains and the mechanisms underlying cross-education. The results of this study suggested that these topics should not be investigated with the use of dynamic muscle actions of the VL.Table 1. Coefficients of determination (r2) and linear slope coefficients for the electromyographic (EMG) amplitude versus torque relationships for trials 1 and 2 for the vastus lateralis (VL) of each subject. [ABSTRACT FROM AUTHOR]

Studies have shown passive stretching may transiently decrease force and alter twitch-related properties. However, the effects of passive stretching on the electromechanical delay (EMD) are still unknown. To examine the acute effects of passive stretching on the EMD, peak twitch force (PTF), rate of force development (RFD), and peak-to-peak M-wave (PPM) for the soleus muscle during evoked isometric plantar flexion muscle actions. Fourteen men (mean ± SD age = 21.2 ± 2.4 yrs; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) volunteered for the study. Five transcutaneous electrical stimuli (each separated by 5 seconds) were delivered to the tibial nerve before and after passive stretching. The stretching protocol consisted of nine repetitions of passive assisted stretching designed to stretch the calf muscles. Each repetition was held for 135 seconds with 5-10 seconds of rest between each passive stretching repetition. An average of three pre- and post-stretching twitches were used to analyze each variable. Dependent-samples t-tests (pre- vs. post-stretching) were used to analyze the EMD, PTF, RFD, and PPM data. There were no significant changes (p > 0.05) from pre-to post-stretching for any of the variables, including EMD (pre- and post-stretching mean ± SE = 29.9 ± 1.1 and 28.8 ± 1.4 ms), PTF (14.5 ± 1.1 and 14.7 ±1.1), RFD (225.1 ± 15.7 and 211.6 ± 19.1), or PPM (3.7 ± 0.5 and 3.4 ± 0.5), Our findings indicated no significant stretching-related changes in EMD, PTF, RFD, or PPM. These findings suggested that passive stretching of the calf muscles did not affect the mechanical aspects of force production from the onset of the electrically-evoked twitch to the peak twitch force. These results may help to explain the mechanisms underlying the stretching-induced force deficit that has been reported as either “mechanical” or “electrical” in origin. These findings suggested that if there is a stretch ing-related decrease in muscle force production, it may be more related to decreases in neural drive (i.e., electrical) than alterations in the mechanical components of muscle contraction. These findings may also be useful for strength and conditioning professionals who are concerned with the potential for performance decreases associated with acute passive stretching. [ABSTRACT FROM AUTHOR]

Many previous studies have reported a temporary decrease in muscle strength following an acute bout of stretching, which has been termed the “stretching-induced force deficit.” It has also been suggested that the stretching-induced force deficit may be joint angle-specific and influenced by initial level of flexibility. To examine the effects of initial flexibility on the stretching-induced force deficit in the plantar flexor muscles at multiple joint angles and ankle joint range of motion (ROM). Fourteen men with limited dorsiflexion ROM (mean age ± SD = 21 ± 2 yrs; stature = 173 ± 9 cm; mass = 75 ± 12 kg; dorsiflexion ROM = 11 ± 6°) and 14 men with a normal ROM (22 ± 2 yrs; 177 ± 8 cm; 75 ± 14 kg; 28 ± 6°) (Roaas et al. 1982, Acta Othropedic 53(2): 205 - 208) performed stretch tolerance assessments and isometric maximal voluntary contractions (MVCs) at -19°, -9°, 1°, and 12° of dorsiflexion (0° = neutral ankle joint angle) designed to examine the ROM and strength, respectively. Testing was performed on a custom-built load cell apparatus attached to a calibrated isokinetic dynamometer before and after a bout of passive stretching. To assess stretch tolerance, the dynamometer lever arm passively dorsiflexed the foot at 5°·s-1 from -20° of dorsiflexion to the maximum tolerable ROM (as acknowledged by the subjects). For the MVC assessments, subjects were instructed to provide maximal force of the plantar flexors for 4 s at each randomly-ordered joint angle. The position signal (°) from the dynamometer and force signal (N) from the load cell were sampled at 1 KHz during the flexibility and strength assessments, respectively. The passive stretching protocol consisted of nine 135-s constant-torque passive stretches, which was held by the dynamometer at each subject's maximum tolerable passive stretching force (the point of discomfort). Five to 10 s was allowed between each stretching repetition. A three way mixed factorial ANOVA [time × angle × group; 2 × 4 × 2] was used to analyze the MVC data, while a two way mixed factorial ANOVA [time × group; 2 × 2] was used to analyze the ROM data. There was a 9% decrease in plantar flexor MVC strength from pre- to post-stretching across all joint angles for both groups (p < 0.001). Conversely, there was a 4% increase in dorsiflexion ROM from pre- to post-stretching for both groups (p < 0.001), however, the normal ROM group had higher dorsiflexion ROM values than the limited ROM group (p < 0.001) at all time points. The magnitude of change for MVC strength and dorsiflexion ROM from pre- to post-stretching was not affected (p > 0.05) by the joint angle or limitations of ROM. These findings suggested that the initial level of flexibility does not influence the force deficit or increases in dorsiflexion ROM following an acute bout of passive stretching in the plantar flexor muscles. These results also indicated that the stretching-induced force deficit occurs at all the ankle joint angles tested. These findings may be useful for strength and conditioning professionals or other allied health practitioners who may incorporate stretching prior to testing or performance. Regardless of initial flexibility, 20 min of passive stretching appears to increase dorsiflexion ROM, but decrease the maximal strength capabilities of the plantar flexors at all of the joint angles tested in the present study. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to evaluate Dual-energy X-ray absorptiometry (DXA) for estimating fat mass (FM), percent fat (%FAT), and fat-free mass (FFM) in older men and women compared to a four-compartment model (4C). Forty men and women (65-84yr, 20 men and 20 women) participated in the study. Body fat calculations included a criterion 4C model and DXA-derived FFM, %FAT, and FFM. The criterion 4C model included body volume from air-displacement plethysmography (ADP), total body water from deuterium dilution, and bone mineral content from DXA. Constant error (CE), standard error of estimate (SEE), total error (TE), and the 95% limits of agreement were used to compare DXA values to the 4C model. All DXA mean values (CE) were significantly different than the 4C model. DXA %fat values were the least accurate with the largest TE and a y-intercept significantly different than zero (p = 0.035). Bland and Altman analysis indicated that no DXA-derived value produced a significant trend. Compared to DXA, the Siri two-compartment (2C) model using ADP produced non-significant (p > 0.106) CE values, lower TE values ( < 1.66), lower SEE values ( < 1.65), and smaller individual errors (95% limits of agreement < 3.17). DXA appears to be biased in older men and women when comparing mean values of FM, FFM, and %FAT compared to a 4C model. %FAT produced the largest individual errors with limits of agreement ± 5.23%FAT. However, DXA produced acceptable TE values and can be considered a valid method for predicting body composition. Nonetheless, regardless of the significant CE values for DXA, using ADP alone in a 2C model produced more accurate, non-biased results compared to the 4C model for all values, as indicated by a reduced SEE and smaller individual errors. FM and FFM DXA values were more accurate than %FAT values compared to a 4C model. However, the Siri 2C model was more accurate than all DXA derived values. Additionally, DXA produced significantly different FM, FFM, and %FAT values compared to a 4C model. Therefore, DXA is not suggested for use in older men and women when attempting to predict FM, FFM, or %fat. Furthermore, choosing ADP for use in the Siri 2C model to predict FM, FFM, and %FAT appears to be more accurate than DXA in this population.Table 1. No Caption Available. [ABSTRACT FROM AUTHOR]

The critical power test provides two measures, critical power (CP) and anaerobic working capacity (AWC). In theory, the CP measurement represents the maximal power output that can be maintained without fatigue, which is regarded as an aerobic measure. AWC is an estimate of work capacity associated with muscle energy reserves adenosine triphosphate (ATP) and phosphocreatine (PCr). High- intensity interval training (HIIT) has been shown to be an effective training method for improving endurance performance, including CP and AWC measures. In addition, creatine (Cr) supplementation has been reported to improve AWC without training; however, Cr had no effect on CP. To date, no one has examined the effect of Cr supplementation during HIIT on CP and AWC. The purpose of this study was to examine the effects of four weeks of HIIT in conjunction with Cr supplementation on CP and AWC in college-aged men. Forty-two recreationally active men (mean ± SD; age 23.62 ± 4.78 yrs; height: 177.48 ± 7.05 cm; weight: 82.23 ± 12.70kg) volunteered to participate in this study. Participants were assigned to one of three groups: Cr (n = 16) 10g Cr + 10g dextrose powder blend; placebo (PL, n = 16) 20g dextrose powder blend; control (CON, n = 10) no treatment. Prior to and following supplementation, each participant performed a continuous maximal oxygen consumption test (o2PEAK) on a cycle ergometer to establish peak power output (PPO). Participants then completed a CP test, consisting of three exercise bouts to exhaustion with the workloads set as a percentage of their PPO to determine CP and AWC. Following initial testing, a 2-week familiarization period of training and supplementing occurred. Baseline values were then measured and all participants in the Cr and PL groups engaged in 4 weeks of HIIT training on a cycle ergometer. Training consisted of either five or six sets of 2-minutes work with 1-minute passive rest, five days per week. Training intensity followed an undulating model starting at 80% PPO and reaching 120%. Significant two-way interactions [time (base- vs. post-) × treatment (Cr vs. PL vs. CON)] were discovered for CP (p = 0.007). Follow-up analyses indicated that the Cr group increased 6.72% ± 2.54%, while PL and CON showed no significant change in CP (3.87% ± 2.30% and -6.27% ± 2.38%, respectively). Furthermore, no changes in AWC were observed in any of the groups following treatment. The current findings suggest that the HIIT and supplementation protocol may be an effective method for improving CP, but had no effect on AWC. It would appear that Cr supplementation may enhance the effect of intense interval endurance training on aerobic performance changes as measure by the CP test. ACKNOWLEGMENTS: This investigation was supported by FSI Nutrition, Omaha, Nebraska. [ABSTRACT FROM AUTHOR]

To examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women following an acute bout of passive stretching. Eight men (mean ± SD age = 20.3 ± 2.0 yrs; body mass = 78.8 ± 12.3 kg; height = 176.6 ± 5.8 cm) and nine women (age = 21.0 ± 2.4 yrs; body mass = 61.7 ± 7.4 kg; height = 166.3 ± 7.5 cm) volunteered for this study. To avoid any menstrual cycle differences, the women were all tested during menses. Each subjects foot was stabilized in a custom-built apparatus designed to measure plantar flexion force with a knee joint angle of 180° and ankle joint angle of 90°. The apparatus was also attached to a powered isokinetic dynamometer that stretched the plantar flexor muscles by passively dorsiflexing the foot at 5°·s-1 until a constant-torque threshold was achieved and held at a point of discomfort as acknowledged by the subject. Nine repetitions of each stretch were held for 135 s with 10 s of rest between repetitions. Before and after the stretching, a maximal, passive flexibility assessment was performed, in which subjects were asked to relax while their foot was maximally dorsiflexed at 5°·s-1. Passive torque and position were recorded from the isokinetic dynamometer. To calculate MTS, the ankle joint angle (°) and torque (Nm) signals were sampled at 1 KHz during the flexibility assessments and plotted as torque-angle curves (i.e., stress-strain curves). Each subject's curve was fit with a 4th-order polynomial regression model (Nordez et al. 2006, Clin Biomech, 21:755-760), and MTS was calculated as the slope (Nm°-1) of the tangent to the curve at a 90° joint angle. MTS decreased by 15.4% (p < 0.001) in men and 36.7% (p < 0.001) in women from pre- to post-stretching. Passive range of motion (PROM) increased by 3.1% (p = 0.018) in men and 7.3% (p = 0.001) in women from pre- to post-stretching. No differences (p > 0.05) were observed between men and women for PROM and MTS prior to and post-stretching. However, the percent change scores from pre- to post-stretching for MTS (p = 0.021) and PROM (p = 0.036) were greater for the women than the men. These findings suggested that 20 min of constant-torque passive stretching increased the PROM and decreased the MTS of the plantar flexors in both men and women, although the magnitude of the change was greater for the women. The greater decrease in MTS and increase in PROM for women may have been due to gender-specific differences in viscoelastic creep during the constant-torque stretching procedures. It has been suggested that a decrease in MTS reduces the total amount of strain through a given ROM, which may reduce the risk of strain injuries. Therefore, the findings of this study suggest that men may have to stretch for a longer duration or at a greater intensity to achieve similar increases in ROM and decrease in MTS as women.Figure 1. No Caption Available. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the mechanomyographic (MMGRMS) and electromyographic (EMGRMS) amplitude vs. force relationships of the vastus lateralis (VL) for aerobically-trained (AT), resistance-trained (RT), and sedentary individuals (SED). Five RT (mean ± SD age = 23 ± 3 yrs; body mass = 101 ± 37 kg; height = 176 ± 8 cm), 5 AT (32 ± 5 yrs; 67 ± 4 kg; 176 ± 2 cm), and 5 SED (23 ± 4 yrs; 93 ± 32 kg; 180 ± 5 cm) men volunteered to perform two 6-s isometric ramp muscle actions from 5% to 100% of their maximal voluntary contraction (MVC) while MMG (m·s-2) and EMG (μV) signals were recorded from the VL muscle. Thigh skinfold measurements and Bergstrom muscle biopsies were taken from the VL. The muscle samples were analyzed for myosin heavy chain (MHC) isoform content. Simple linear regression models were fit to the natural log-transformed EMGRMS and MMGRMS vs. force relationships. The slope (b term) and the antilog of the Y-intercept (a term) were calculated for each relationship. For %MHC, the AT group had a greater percentage of type I fibers than the RT and SED groups (p ≤0.05). The RT group had a greater percentage of type IIa fibers than the AT group (p ≤0.05), and the SED group had a greater percentage of type IIx fibers than the AT and RT groups (p ≤0.05). For both the log-transformed EMGRMS and MMGRMS vs. force relationships, the mean a term for the AT group was higher than the RT and SED groups (p ≤0.05). For the log-transformed MMGRMS vs. force relationships, however, the b term for the AT group was lower than the RT and SED groups (p ≤0.05). There were no differences (p >0.05) among the b terms of the AT, RT, and SED groups for the log-transformed EMGRMS vs. force relationships. In addition, the mean skinfold for the SED group was higher than the AT group (p ≤0.05) (AT = 8.7 ± 2.2mm, RT = 15.4 ± 7.6mm, and SED = 25.4 ± 9.2mm). The group-related differences among the a terms for both the log-transformed EMGRMS and MMGRMS patterns might be best explained by the group differences in skinfold thickness. However, the fact that the AT group had a lower mean b term for the log-transformed MMGRMS vs. force relationships may suggest that the differences in motor control strategies between individuals with predominantly type I vs. type II fibers in the vastus lateralis could be detectible with the MMG signal, but not EMG. The lower b term for the AT group suggested that the MMG-force relationship may have been sensitive to the earlier achievement of rate coding, whereas the RT and SED groups relied more on motor unit recruitment to reach higher force levels. The b terms from the EMGRMS vs. force relationships were unable to differentiate among the groups. The log-transformed MMGRMS, but not EMGRMS, vs. force relationships may be useful as non-invasive measurements to determine the onset of rate coding, which may differ among muscles that are predominantly type I vs. type II fiber types. Therefore, the MMG signal may offer an attractive, simple technique for examining changes in the motor control strategies that govern incremental isometric force production. [ABSTRACT FROM AUTHOR]