Effects of short-term resistance training and subsequent detraining on the electromechanical delay.

INTRODUCTION: The purpose of this study was to examine and compare the effects of 3 days of dynamic constant external resistance (DCER) and isokinetic (ISOK) training and subsequent detraining on the electromechanical delay (EMD). METHODS: Thirty-one men [age 22.2 ± 4.2 years, body mass 77.9 ± 12.9 kg, height 173.9 ± 5.4 cm (mean ± SD)] were randomly assigned to a DCER training group, ISOK training group, or control (CONT) group. RESULTS: No significant changes were found for EMD from pre- to posttraining assessments 1, 2, and 3 [4.5 ± 0.2 ms, 4.7 ± 0.2 ms, 4.5 ± 0.1 ms, 4.5 ± 0.2 ms, respectively (mean ± SE)] (P > 0.05). CONCLUSIONS: It can be hypothesized that increases in strength observed after a short-term resistance training program may not be attributed to stiffness changes in the series-elastic component.

Consistency of rapid muscle force characteristics: influence of muscle contraction onset detection methodology.

The purpose of this study was to investigate the consistency of commonly reported rapid force characteristics utilizing both automated and manual muscle contraction onset detection methods. Twenty-four healthy volunteers performed isometric strength testing of the plantar flexor muscle group on two nonconsecutive days. Test-retest reliability was evaluated using intraclass correlation coefficients (ICCs), standard errors of measurement (SEM), and the SEM as a percentage of the mean (SEM%) for rate of force development (RFD), relative RFD, contractile impulse, and absolute force-time values at various epoch durations using automated and manual onset detection methods. For all rapid force variables, ICC and SEM% values ranged from 0.52 to 0.96 and 7.56% to 37.56%, respectively. For the majority of these variables (20 of 23), the automated onset detection method resulted in higher ICC and lower SEM% values compared to the manual onset detection method. Regardless of onset detection methodology, the consistency of relative RFD values declined following 50% of MVC. Collectively, these findings indicated that commonly evaluated rapid muscle force variables demonstrated acceptable relative and absolute consistency values. However, these values were generally superior for the automated onset detection methodology. Additionally, the consistency of relative RFD values declines following 50% MVC and therefore should be evaluated with caution.

Acute effects of passive stretching on the electromechanical delay and evoked twitch properties: a gender comparison.

This study examined the acute effects of passive stretching on electromechanical delay (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 age ± SD = 21.2 ± 2.4 years; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) and 20 women (20.9 ± 2.5 years; 61.3 ± 8.9 kg; 165.3 ± 7.5 cm) volunteered for the study. Five single-square, supramaximal transcutaneous electrical stimuli (each separated by 5 s) were delivered to the tibial nerve before and after passive stretching. A time × gender interaction was observed for EMD, and the post hoc dependent-samples t tests indicated that EMD increased 4% for the women (p = .023), but not for the men (p = .191). There were no other stretching-related changes for PTF, RFD, or p-p M-wave for either the men or women (p > .05). These findings tentatively suggested that mechanical factors related to the stiffness of the muscle-tendon unit may contribute to the explanation for why stretching caused an acute increase in the EMD during evoked twitches in the women, but not in the men.

Percent voluntary inactivation and peak force predictions with the interpolated twitch technique in individuals with high ability of voluntary activation.

The purpose of this study was to examine the sensitivity and peak force prediction capability of the interpolated twitch technique (ITT) performed during submaximal and maximal voluntary contractions (MVCs) in subjects with the ability to maximally activate their plantar flexors. Twelve subjects performed two MVCs and nine submaximal contractions with the ITT method to calculate percent voluntary inactivation (%VI). Additionally, two MVCs were performed without the ITT. Polynomial models (linear, quadratic and cubic) were applied to the 10-90% VI and 40-90% VI versus force relationships to predict force. Peak force from the ITT MVC was 6.7% less than peak force from the MVC without the ITT. Fifty-eight percent of the 10-90% VI versus force relationships were best fit with nonlinear models; however, all 40-90% VI versus force relationships were best fit with linear models. Regardless of the polynomial model or the contraction intensities used to predict force, all models underestimated the actual force from 22% to 28%. There was low sensitivity of the ITT method at high contraction intensities and the predicted force from polynomial models significantly underestimated the actual force. Caution is warranted when interpreting the % VI at high contraction intensities and predicted peak force from submaximal contractions.

Differences in the log-transformed electromyographic-force relationships of the plantar flexors between high- and moderate-activated subjects.

The present study examined the log-transformed electromyographic amplitude (EMG) versus force relationships for the medial gastrocnemius (MG) and soleus (SOL) in high- and moderate-activated subjects. Twenty-five (age=21±2 year; mass=62±12 kg) participants performed six submaximal contractions (30-90% maximal voluntary contraction [MVC]) with the interpolated twitch technique (ITT) performed at 90% MVC to calculate percent voluntary activation (% VA). Sixteen participants with>90% VA at 90% MVC were categorized high-activated group; the remaining nine were the moderate-activated group. Linear regression models were fit to the log-transformed EMG-force relationships. The slope (b value) and the antilog of the Y-intercept (a value) were calculated. The b values from the MG EMG-force relationships were higher (P<0.05) for the high-activated group (1.27±0.13) than the moderate-activated group (0.88±0.06). The a values and p-p M-wave amplitude values (collapsed across twitches [superimposed and potentiated]) were larger (P<0.05) for the MG (1.17±0.40 and 8.98±0.46 mV) than the SOL (0.24±0.07 and 4.48±0.20 mV) when collapsed across groups. The b value from the log-transformed EMG-force relationships is an attractive model to determine if a subject has the ability to achieve high activation of their MG without muscle or nerve stimulation.

Effects of two modes of static stretching on muscle strength and stiffness.

PURPOSE: The purpose of the present study was to examine the effects of constant-angle (CA) and constant-torque (CT) stretching of the leg flexors on peak torque (PT), EMGRMS at PT, passive range of motion (PROM), passive torque (PAS(TQ)), and musculotendinous stiffness (MTS). METHODS: Seventeen healthy men (mean ± SD: age = 21.4 ± 2.4 yr) performed a PROM assessment and an isometric maximal voluntary contraction of the leg flexors at a knee joint angle of 80° below full leg extension before and after 8 min of CA and CT stretching. PASTQ and MTS were measured at three common joint angles for before and after assessments. RESULTS: PT decreased (mean ± SE = 5.63 ± 1.65 N·m) (P = 0.004), and EMG(RMS) was unchanged (P > 0.05) from before to after stretching for both treatments. PROM increased (5.00° ± 1.03°) and PASTQ decreased at all three angles before to after stretching (angle 1 = 5.03 ± 4.52 N·m, angle 2 = 6.30 ± 5.88 N·m, angle 3 = 6.68 ± 6.33 N·m) for both treatments (P ≤ 0.001). In addition, MTS decreased at all three angles (angle 1 = 0.23 ± 0.29 N·m·°(-1), angle 2 = 0.26 ± 0.35 N·m·°(-1), angle 3 = 0.28 ± 0.44 N·m·°(-1)) after the CT stretching treatment (P < 0.005); however, MTS was unchanged after CA stretching (P > 0.05). CONCLUSIONS: PT, EMG(RMS), PROM, and PASTQ changed in a similar manner after stretching treatments; however, only CT stretching resulted in a decrease in MTS. Therefore, if the primary goal of the stretching routine is to decrease MTS, these results suggest that CT stretching (constant pressure) may be more appropriate than a stretch held at a constant muscle length (CA stretching).

Mechanical scale and load cell underwater weighing: a comparison of simultaneous measurements and the reliability of methods.

Both load cell and mechanical scale-based hydrostatic weighing (HW) systems are used for the measurement of underwater weight. However, there has been no direct comparison of the 2 methods. The purpose of the current investigation was to simultaneously compare a load cell and mechanical scale for use in HW. Twenty-seven men and women (mean ± SD, age: 22 ± 2 years) participated in the 2-day investigation. Each subject completed 2 HW assessments 24 hours apart. Single-day comparisons of all trials for both days revealed no significant difference between the mechanical scale and the load cell (mean difference < 0.016 kg, p > 0.05). True underwater weight values were not significantly different between methods for either days (mean difference < 0.014 kg, p > 0.05) and accounted for a mean difference in percent fat (%FAT) of <0.108%. The 95% limits of agreement indicated a maximum difference between methods of 0.53% FAT. Both methods produced similar reliability SEM values (mechanical SEM < 0.72%FAT, load cell SEM < 0.75%FAT). In conclusion, there was no difference between mechanical scale and load cell measurements of underwater weights and the added precision of the load cell only marginally (<0.16%FAT) improved day-to-day reliability. Either a mechanical scale or load cell can be used for HW with similar accuracy and reliability in young adults with a body mass index of 18.7-34.4 (5-25%FAT).

Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching.

The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean ± SD age = 21 ± 2 years; body mass = 79 ± 15 kg; and height = 177 ± 7 cm) and 19 women (21 ± 3 years; 61 ± 9 kg; 165 ± 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means ± SD pre to post: 109.39° ± 10.16° to 116.63° ± 9.63°; p ≤ 0.05) but not for the men (111.79° ± 6.84° to 113.93° ± 8.15°; p > 0.05). There were no stretching-induced changes in MTS (women's pre to postchange in MTS: -0.35 ± 0.38; men's MTS: +0.17 ± 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 ± 0.41 vs. 0.97 ± 0.38; p ≤ 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p ≤ 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS.

Reproducibility and validity of bioimpedance spectroscopy for tracking changes in total body water: implications for repeated measurements.

Bioimpedance spectroscopy (BIS) has been used to track changes in total body water (TBW). Accurate TBW estimations can be influenced by both methodological and biological factors. One methodological variation that contributes to BIS TBW errors is the electrode placement. The purpose of the present study was to compare the reproducibility and validity of fixed-distance electrode placements (5 cm) with the standard single-site electrode placements. Twenty-nine subjects (fifteen men and fourteen women) participated in the reproducibility study, while sixty-nine subjects (thirty-three men and thirty-six women) participated in the validity study. The reproducibility study included two measurements that were taken 24 h apart, while the validity study consisted of a 12-week exercise intervention with measurements taken at weeks 1 and 12. TBW was estimated using BIS and 2H techniques. Reproducibility results indicated that fixed-distance electrodes reduced the day-to-day standard error of the measurement in men (from 1·13 to 0·81 litres) but not in women (0·47 litres). sem values were lower for women than for men, suggesting that BIS TBW estimates are sex dependent. Validity results produced similar accurate findings (mean difference < 0·21 litres). However, fixed-distance electrodes improved delta TBW errors (mean difference improvements>0·04 litres in men, women, and men and women combined). When tracking changes in TBW, fixed-distance electrodes may reduce reproducibility errors and allow for smaller changes to be detected. However, the reduction of reproducibility errors may be greater for men than for women. Therefore, reproducibility calculations should be based on the sex of the sample population.

Six weeks of high-intensity interval training with and without beta-alanine supplementation for improving cardiovascular fitness in women.

The purpose of the present study was to evaluate the effects of cycle ergometry high-intensity interval training (HIIT) with and without beta-alanine supplementation on maximal oxygen consumption rate (VO2 peak), cycle ergometer workload at the ventilatory threshold (VT W), and body composition. Forty-four women (mean +/- SD age = 21.8 +/- 3.7 years; height = 166.5 +/- 6.6 cm; body mass (BM) = 65.9 +/- 10.8 kg; VO2 peak = 31.5 +/- 6.2 ml x kg(-1) x min(-1)) were randomly assigned to 1 of 3 groups: beta-alanine (BA, n = 14) 1.5 g + 15 g dextrose powder; placebo (PL, n = 19) 16.5 g dextrose powder; or control (CON, n = 11). Testing was conducted at baseline (week 0), after 3 weeks (week 4), and after 6 weeks (week 8). VO2 peak (ml x kg(-1) x min(-1)) and VT W were measured with a metabolic cart during graded exercise tests on a corival cycle ergometer, and body composition (percent fat = % fat and fat-free mass = FFM) were determined by air displacement plethysmography. High-intensity interval training was performed on a corival cycle ergometer 3 times per week with 5 2-minute work intervals and 1-minute passive recovery with undulating intensities (90-110% of the workload recorded at VO2 peak) during each training session. VO2 peak increased (p 0.05) for the CON group. VT W increased (p

Viscoelastic creep in the human skeletal muscle-tendon unit.

The purposes of the present study were to (1) characterize viscoelastic creep in vivo in the human skeletal muscle-tendon unit and (2) to examine the consistency of these responses during a single 30-s stretch. Twelve volunteers (mean +/- SD = 22 +/- 3 years; height = 169 +/- 11 cm; mass = 70 +/- 17 kg) participated in two separate experimental trials. Each trial consisted of a 30-s constant-torque stretch of the plantar flexor muscles. Position (degrees) values were quantified at every 5-s period (0, 5, 10, 15, 20, 25, and 30 s) and the percent change in position was quantified for each 5-s epoch (0-5, 5-10, 10-15, 15-20, 20-25, and 25-30 s) relative to the total increase in the range of motion. In addition, the intraclass correlation coefficient (ICC) and standard errors of the measurement (SEM) were calculated for test-retest reliability. These results indicated that position increased over the entire 30-s stretch (P < 0.05), while the majority of the increases in position (73-85%) occurred during the first 15-20 s. ICC values were >or = 0.994 and SEM values (expressed as percentage of the mean) were

Validity of electromyographic fatigue threshold as a noninvasive method for tracking changes in ventilatory threshold in college-aged men.

The submaximal electromyographic fatigue threshold test (EMG(FT)) has been shown to be highly correlated to ventilatory threshold (VT) as determined from maximal graded exercise tests (GXTs). Recently, a prediction equation was developed using the EMG(FT) value to predict VT. The aim of this study, therefore, was to determine if this new equation could accurately track changes in VT after high-intensity interval training (HIIT). Eighteen recreationally trained men (mean +/- SD; age 22.4 +/- 3.2 years) performed a GXT to determine maximal oxygen consumption rate (V(O2)peak) and VT using breath-by-breath spirometry. Participants also completed a discontinuous incremental cycle ergometer test to determine their EMGFT value. A total of four 2-minute work bouts were completed to obtain 15-second averages of the electromyographic amplitude. The resulting slopes from each successive work bout were used to calculate EMG(FT). The EMG(FT) value from each participant was used to estimate VT from the recently developed equation. All participants trained 3 days a week for 6 weeks. Training consisted of 5 sets of 2-minute work bouts with 1 minute of rest in between. Repeated-measures analysis of variance indicated no significant difference between actual and predicted VT values after 3 weeks of training. However, there was a significant difference between the actual and predicted VT values after 6 weeks of training. These findings suggest that the EMG(FT) may be useful when tracking changes in VT after 3 weeks of HIIT in recreationally trained individuals. However, the use of EMG(FT) to predict VT does not seem to be valid for tracking changes after 6 weeks of HIIT. At this time, it is not recommended that EMG(FT) be used to predict and track changes in VT.

Acute effects of passive stretching on the electromechanical delay and evoked twitch properties.

The purpose of this study was to investigate the acute effects of passive stretching on the electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and compound muscle action potential (M-wave) amplitude during evoked twitches of the plantar flexor muscles. 16 men (mean age +/- SD = 21.1 +/- 1.7 years; body mass = 75.9 +/- 11.4 kg; height = 176.5 +/- 8.6 cm) participated in this study. A single, square-wave, supramaximal transcutaneous electrical stimulus was 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 s separated by 5-10 s of rest. Dependent-samples t tests (pre- vs. post-stretching) were used to analyze the EMD, PTF, RFD, and M-wave amplitude data. There were significant changes (P < or = 0.05) from pre- to post-stretching for EMD (mean +/- SE = 4.84 +/- 0.31 and 6.22 +/- 0.34 ms), PTF (17.2 +/- 1.3 and 15.6 +/- 1.5), and RFD (320.5 +/- 24.5 and 279.8 +/- 28.2), however, the M-wave amplitude did not change (P > 0.05). These findings suggested that passively stretching the calf muscles affected 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 have been reported as either "mechanical" or "electrical" in origin.

Acute effects of a thermogenic nutritional supplement on cycling time to exhaustion and muscular strength in college-aged men.

BACKGROUND: The purpose of the present study was to examine the acute effects of a thermogenic nutritional supplement containing caffeine, capsaicin, bioperine, and niacin on muscular strength and endurance performance. METHODS: Twenty recreationally-active men (mean +/- SD age = 21.5 +/- 1.4 years; stature = 178.2 +/- 6.3 cm; mass = 76.5 +/- 9.9 kg; VO2 PEAK = 3.05 +/- 0.59 L/min-1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. All testing took place over a three-week period, with each of the 3 laboratory visits separated by 7 days (+/- 2 hours). During the initial visit, a graded exercise test was performed on a Lode Corival cycle ergometer (Lode, Groningen, Netherlands) until exhaustion (increase of 25 W every 2 min) to determine the maximum power output (W) at the VO2 PEAK (Parvo Medics TrueOne(R) 2400 Metabolic Measurement System, Sandy, Utah). In addition, one-repetition maximum (1-RM) strength was assessed using the bench press (BP) and leg press (LP) exercises. During visits 2 and 3, the subjects were asked to consume a capsule containing either the active supplement (200 mg caffeine, 33.34 mg capsaicin, 5 mg bioperine, and 20 mg niacin) or the placebo (175 mg of calcium carbonate, 160 mg of microcrystalline cellulose, 5 mg of stearic acid, and 5 mg of magnesium stearate in an identical capsule) 30 min prior to the testing. Testing included a time-to-exhaustion (TTE) ride on a cycle ergometer at 80% of the previously-determined power output at VO2 PEAK followed by 1-RM LP and BP tests. RESULTS: There were no differences (p > 0.05) between the active and placebo trials for BP, LP, or TTE. However, for the BP and LP scores, the baseline values (visit 1) were less than the values recorded during visits 2 and 3 (p

Anthropometric estimations of percent body fat in NCAA Division I female athletes: a 4-compartment model validation.

Anthropometric equations, based on 2-compartment models, have been routinely used to estimate body composition in female college athletes; however, these equations are not without error. In an attempt to decrease the error associated with anthropometric equations, updated equations were developed using multiple-compartment models, although the validity of these equations has not yet been established. The purpose of the current investigation was to determine the validity of the updated anthropometric equations and compare them with previously validated generalized equations for estimating percent fat (%fat) in female athletes. Twenty-nine white female NCAA Division I athletes (20 +/- 1 years) volunteered to have their %fat estimated using anthropometric measurements. Skinfold equations included generalized and updated equations and a height and weight-based equation. %fat values were compared with a criterion 4-compartment model. All equations produced low total error (TE) (< or =3.38%fat) and SEE values (< or =2.97%fat) and high r values (r > or = 0.78). The 2 updated skinfold equations produced the highest constant error (CE) values, but the tightest limits of agreement (< or = -1.58 +/- 4.86%fat; CE +/- 2SD) compared with the 3 generalized Jackson et al. equations (< or =0.92 +/- 5.34%fat), whereas the limits of agreement for the height and weight-based equation (+/- 6.00%fat) were the widest. Compared with the updated skinfold equations, the generalized Jackson et al. skinfold equations produced nearly identical TE values. Results suggest that the updated skinfold equations are valid but not superior to the generalized Jackson et al. equations, and the height and weight-based equation of Fornetti et al. is not recommended due to the large individual error in this population. Additionally, more than 3 skinfold sites did not improve %fat values. Therefore, the Jackson et al. sum of 3 skinfold equation is the suggested skinfold equation in the white female NCAA Division I athletes.

Reliability of absolute versus log-transformed regression models for examining the torque-related patterns of response for mechanomyographic amplitude.

This study examined the test-retest reliability of the slopes (b) and y-intercepts (a) of the absolute and log-transformed regression models applied to the mechanomyographic amplitude (MMG(RMS)) versus torque (TQ) relationship. Fifteen participants (mean+/-SD age=23+/-4 yrs) performed two isometric maximal voluntary contractions (MVCs) and ten randomly ordered isometric leg extensions from 5% to 95% of their MVC during three separate trials. MMG(RMS) was recorded from the vastus lateralis during each MVC. Intraclass correlation coefficients (ICCs) and standard errors of measurement (SEMs) were calculated for test-retest reliability. ICCs for the b and a terms were 0.89 and 0.90 for the log-transformed and 0.85 and 0.76 for the absolute relationships, respectively. The SEM values (expressed as a percentage of the mean) for the b and a terms were 9.7% and 16.4% for the log-transformed and 18.9% and 57.1% for the absolute relationships, respectively. These results indicated that the b and a terms from both the absolute linear and log-transformed MMG(RMS) versus TQ relationships were relatively reliable (ICCs), however, the SEMs for the log-transformed relationships were lower than the absolute linear models. Furthermore, the b term from the log-transformed relationships may provide unique information regarding the nonlinear characteristics (plateau points) of the MMG(RMS) versus TQ relationship, whereas the a term may indicate upward or downward shifts in MMG(RMS) across the TQ spectrum. Thus, the log-transformed MMG(RMS) versus TQ relationships may offer an attractive alternative method for reliably quantifying and tracking changes in the TQ-related patterns of response for MMG(RMS) on a subject-by-subject basis.

Effects of creatine monohydrate and polyethylene glycosylated creatine supplementation on muscular strength, endurance, and power output.

The purpose of this study was to examine the effects of a moderate dose of creatine monohydrate (CM) and two smaller doses of polyethylene glycosylated (PEG) creatine on muscular strength, endurance, and power output. Fifty-eight healthy men (mean +/- SD: age, 21 +/- 2 years; height, 176 +/- 6 cm; body mass [BM], 75 +/- 14 kg) volunteered and were randomly assigned to 1 of 4 groups: (a) placebo (PL; 3.6 g of microcrystalline cellulose; n = 15), (b) CM (5 g of creatine; n = 13), (c) small-dose PEG creatine (1.25 g of creatine: PEG1.25; n = 14), or (d) moderate-dose PEG creatine (2.50 g of creatine: PEG2.50; n = 16). Testing was conducted before (pre-) and after (post-) a 30-day supplementation period. Measurements included body mass, countermovement vertical jump (CVJ) height, power output during the Wingate test (peak power [PP] and mean power [MP]), 1 repetition maximum bench press (1RMBP), 1RM leg press (1RMLP) strength, and repetitions to failure at 80% of the 1RM for bench press (REPBP) and leg press (REPLP). BM and MP (W) increased (p

Acute effects of a thermogenic nutritional supplement on energy expenditure and cardiovascular function at rest, during low-intensity exercise, and recovery from exercise.

The purpose of present study was to examine the acute effects of a thermogenic nutritional supplement on energy expenditure (EE) and cardiovascular function at rest, during low-intensity exercise, and recovery from exercise. Twenty-eight healthy sedentary participants (mean +/- SD; age, 22.3 +/- 1.9 years; body mass index, 24.0 +/- 3.7) volunteered for this randomized, double-blinded, placebo-controlled, crossover study. Each experimental trial was divided into 4 phases: (a) 30 minutes of initial resting, followed by the placebo or thermogenic nutritional supplementation, (b) 50 minutes of postsupplementation resting, (c) 60 minutes of treadmill walking (3.2-4.8 km x h), and (d) 50 minutes of postexercise recovery. Gas exchange variables measured by indirect calorimetry and heart rate (HR) were recorded during all 4 phases, blood pressure was only measured at rest, and rating of perceived exertion (RPE) was only recorded during exercise. EE and oxygen consumption rate (Vo2) were greater for the supplement than the placebo at 50 minutes after supplementation. Also, during the postsupplementation period, diastolic blood pressure (DBP) was higher at all time periods, whereas the respiratory exchange ratio (RER) was higher at 20 and 30 minutes for the supplement. During exercise, only Vo2 and minute ventilation (VE) were greater for the supplement than the placebo, with HR being less than the placebo at 20 minutes for the men. Postexercise EE, Vo2, systolic blood pressure (SBP), DBP, and HR (men only) at 10, 20, 30, and 50 minutes were greater for the supplement than the placebo. These findings indicated that the thermogenic nutritional supplement increased resting EE and exercise Vo2 with only minimal effects on blood pressure and HR and no meaningful effects on RER or RPE. These results suggested that the combination of thermogenic ingredients in this nutritional supplement may be useful to help maintain a negative caloric balance but may not influence substrate use or perceived exertion.

Effects of beta-alanine supplementation and high-intensity interval training on endurance performance and body composition in men; a double-blind trial.

BACKGROUND: Intermittent bouts of high-intensity exercise result in diminished stores of energy substrates, followed by an accumulation of metabolites, promoting chronic physiological adaptations. In addition, beta-alanine has been accepted has an effective physiological hydrogen ion (H+) buffer. Concurrent high-intensity interval training (HIIT) and beta-alanine supplementation may result in greater adaptations than HIIT alone. The purpose of the current study was to evaluate the effects of combining beta-alanine supplementation with high-intensity interval training (HIIT) on endurance performance and aerobic metabolism in recreationally active college-aged men. METHODS: Forty-six men (Age: 22.2 +/- 2.7 yrs; Ht: 178.1 +/- 7.4 cm; Wt: 78.7 +/- 11.9; VO2peak: 3.3 +/- 0.59 l.min-1) were assessed for peak O2 utilization (VO2peak), time to fatigue (VO2TTE), ventilatory threshold (VT), and total work done at 110% of pre-training VO2peak (TWD). In a double-blind fashion, all subjects were randomly assigned into one either a placebo (PL - 16.5 g dextrose powder per packet; n = 18) or beta-alanine (BA - 1.5 g beta-alanine plus 15 g dextrose powder per packet; n = 18) group. All subjects supplemented four times per day (total of 6 g/day) for the first 21-days, followed by two times per day (3 g/day) for the subsequent 21 days, and engaged in a total of six weeks of HIIT training consisting of 5-6 bouts of a 2:1 minute cycling work to rest ratio. RESULTS: Significant improvements in VO2peak, VO2TTE, and TWD after three weeks of training were displayed (p < 0.05). Increases in VO2peak, VO2TTE, TWD and lean body mass were only significant for the BA group after the second three weeks of training. CONCLUSION: The use of HIIT to induce significant aerobic improvements is effective and efficient. Chronic BA supplementation may further enhance HIIT, improving endurance performance and lean body mass.

The consistency of ordinary least-squares and generalized least-squares polynomial regression on characterizing the mechanomyographic amplitude versus torque relationship.

The primary purpose of this study was to examine the consistency of ordinary least-squares (OLS) and generalized least-squares (GLS) polynomial regression analyses utilizing linear, quadratic and cubic models on either five or ten data points that characterize the mechanomyographic amplitude (MMG(RMS)) versus isometric torque relationship. The secondary purpose was to examine the consistency of OLS and GLS polynomial regression utilizing only linear and quadratic models (excluding cubic responses) on either ten or five data points. Eighteen participants (mean +/- SD age = 24 +/- 4 yr) completed ten randomly ordered isometric step muscle actions from 5% to 95% of the maximal voluntary contraction (MVC) of the right leg extensors during three separate trials. MMG(RMS) was recorded from the vastus lateralis during the MVCs and each submaximal muscle action. MMG(RMS) versus torque relationships were analyzed on a subject-by-subject basis using OLS and GLS polynomial regression. When using ten data points, only 33% and 27% of the subjects were fitted with the same model (utilizing linear, quadratic and cubic models) across all three trials for OLS and GLS, respectively. After eliminating the cubic model, there was an increase to 55% of the subjects being fitted with the same model across all trials for both OLS and GLS regression. Using only five data points (instead of ten data points), 55% of the subjects were fitted with the same model across all trials for OLS and GLS regression. Overall, OLS and GLS polynomial regression models were only able to consistently describe the torque-related patterns of response for MMG(RMS) in 27-55% of the subjects across three trials. Future studies should examine alternative methods for improving the consistency and reliability of the patterns of response for the MMG(RMS) versus isometric torque relationship.