Glen O. Johnson

The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities.

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.

Mechanomyographic and electromyographic responses during submaximal cycle ergometry.

Abstract The purpose of this study was to examine the mechanomyographic (MMG) and electromyographic (EMG) responses during continuous, cycle ergometer workbouts performed at constant power outputs. Eight adults [mean (SD) age, 21.5 (1.6)u2009years] volunteered to perform an incremental test to exhaustion for the determination of peak power (W˙peak) and four, 15-min (or to exhaustion) rides at constant power outputs of 50%, 65%, 80%, and 95% W˙peak. Piezoelectric crystal contact sensors were placed on the vastus lateralis (VL) and vastus medialis (VM) muscles to record the MMG signals. Bipolar surface electrode arrangements were placed on the VL and VM to record the EMG signals. Five-second samples of the MMG and EMG signals were recorded every 30u2009s at power outputs of 50%, 65%, and 80% W˙peak, and every 15u2009s at 95% W˙peak. The amplitudes of the selected portions of the signals were normalized to the first values recorded during the continuous rides, and regression analyses were used to determine whether the slope coefficients for the MMG and EMG versus time relationships were significantly (Pu2009<u20090.05) different from zero. The results indicate that EMG amplitude increased (range of slope coefficients: 0.03–0.56) during the continuous rides for both muscles at all four power outputs (except the VM at 50% W˙peak), while MMG amplitude increased (slope coefficient at 95% W˙peak for VM=0.19), decreased (range of slope coefficients for VL and VM at 50% and 65% W˙peak=−0.14 to −0.24), or remained unchanged (range of slope coefficients for VL and VM at 80% W˙peak and VL at 95% W˙peak=−0.06 to 0.12) depending on the power output. The patterns of the MMG responses, however, were similar for the VL and VM muscles, except at 95% W˙peak. Fatigue-induced changes in motor-unit recruitment and discharge rates, or muscular compliance may explain the differences between power outputs in the patterns of the MMG amplitude responses.

The effect of mathematical modeling on critical velocity

Abstract. The purpose of this investigation was to examine the effects of mathematical modeling on critical velocity (CV) estimates and the oxygen consumption (

The effect of concentric isokinetic strength training of the quadriceps femoris on electromyography and muscle strength in the trained and untrained limb.

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Effects of Arginine-Based Supplements on the Physical Working Capacity at the Fatigue Threshold

n), heart rate (HR), and plasma lactate values that corresponded to the five CV estimates. Ten male subjects performed a maximal, incremental treadmill test to determine maximal

Muscle activation during three sets to failure at 80 vs. 30 % 1RM resistance exercise

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Gender Comparisons of Anthropometric Characteristics of Young Sprint Swimmers

n, and four randomly ordered treadmill runs for the estimation of CV. Two linear, two nonlinear, and one exponential mathematical models were used to estimate CV. Regression analyses were used to determine the

Effects of a protease supplement on eccentric exercise-induced markers of delayed-onset muscle soreness and muscle damage.

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The Effects of Creatine Monohydrate Loading on Anaerobic Performance and One-Repetition Maximum Strength.

n, HR, and plasma lactate values that corresponded to the five CV estimates from the relationships for

Comparison of Critical Force to EMG Fatigue Thresholds during Isometric Leg Extension

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