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The purpose of this study was to investigate the pacing pattern and associated physiological effects in competitive cyclists who performed a 30-minute maximal cycling test. Measurements included oxygen uptake (V O2), heart rate (HR), blood lactate concentration (BLC), rating of perceived exertion (RPE), and work rate in watts. Twelve well-trained amateur cyclists (seven men and five women) whose mean age was 32.4 +/- 8.6 years participated in this study. They performed a 30-minute self-paced maximal cycling test using their own performance road bike attached to a CompuTrainer Pro, which allowed the assessment of work rate (W). During the test, work rate, V O2, and HR were measured every 30 seconds. Subjects' BLC and RPE were obtained every 5 minutes. Results indicate that no significant differences existed across three 10-minute periods for work rate, HR, or V O2. However, RPE at 30 minutes was significantly greater than RPE at 10 and 20 minutes (both p < 0.05). The RPE at 20 minutes was also greater than the RPE at 10 minutes (p < 0.01). Work rate remained relatively constant, with minimal fluctuations occurring throughout the test except for a surge during the final 30 seconds of the test. The associated V O2 was fairly constant over time, whereas HR rose linearly and gradually. It was concluded that pacing in a 30-minute maximal exercise bout performed in the laboratory in experienced cyclists varies minimally until the last 30 seconds. Knowledge of pacing strategy and the linked physiological responses may be helpful to exercise scientists in optimizing performance in the endurance athlete. [ABSTRACT FROM AUTHOR]

Previous studies have indicated that skinfold thickness (SKF) acts as a low-pass filter to the mechanomyographic (MMG) signal. PURPOSE: The purpose of this study was to examine the effects of SKF at four different locations on the vastus lateralis (VL) muscle on MMG amplitude and mean power frequency (MPF) responses during incremental cycle ergometry. METHODS: Twenty adults (age ± SD = 23.8 ± 3.0 years) volunteered to participate in the investigation. An orientation session was performed to determine the location of the innervation zone (IZ) for the VL using a linear electrode array. The MMG signals from the VL muscle were detected during an incremental cycle ergometry test using four accelerometers placed on the right VL proximal (Prox1), over (Over IZ), and distal (Dist IZ) to the IZ. A fourth accelerometer was placed at the site recommended by the SENIAM Project (Prox2) for the placement of EMG electrodes. Prior to the test, three SKF were taken at each accelerometer placement site. The mean of the three SKF at each site were used for the analysis. The subjects were divided (at the median SKF value) into two groups of smaller (n = 10) and larger (n = 10) SKF values. Simple linear regression analyses were performed for SKF vs. MMG amplitude and MPF at each location for power outputs of 50, 75, 100, 125, 150, and 175W. Independent t-tests were also performed between the smaller and larger SKF groups for SKF measurements, MMG amplitude, and MMG MPF values at each accelerometer placement site. An alpha of p ≤ 0.05 was considered statistically significant for all analyses. RESULTS: For the 48 regression analyses, there were only 2 significant relationships (r = -0.461 and -0.519) between the SKF values and MMG MPF and 3 significant relationships between the SKF values and MMG amplitude (r = -0.535, -0.456, and -0.443). The independent t-tests showed that there were significant mean differences between the smaller and larger SKF groups for SKF measurements for all accelerometer placements sites. Of the 48 mean comparisons, only 1 was significantly different between the smaller and larger SKF groups for MMG MPF and 4 for MMG amplitude. CONCLUSIONS: The present study showed that, in general, SKF values were not correlated with the MMG signal. Only 10% of the regression analyses for SKF versus MMG MPF and MMG amplitude were statistically significant. In addition, only 10% of the mean comparisons between smaller and larger SKF groups for MMG MPF and MMG amplitude were significantly different. Thus, the results of the present study indicated that the larger SKF values did not attenuated the MMG signal. Other factors, including changes in force production and muscle length, as well as factors related to the accelerometer location, such as amount of muscle mass, muscle architecture, and/or motor unit territorial distribution may have had a greater effect on the MMG signal than SKF. PRACTICAL APPLICATIONS: These findings indicated that, in generall, smaller and larger SKF values did not correlate with the amplitude and frequency parameters of the MMG signal. Thus, there may be other anatomical, physiological, or methodological factors that have a greater effect on the MMG signal. These findings provide information about a methodological consideration necessary for the interpretation of the MMG signal. [ABSTRACT FROM AUTHOR]

It has been suggested that the thickness of the subcutaneous tissue layer affects time and frequency domain parameters of the surface electromyography (EMG) signal. PURPOSE: The purpose of the present study was to examine the effects of skinfold thickness on the amplitude and mean power frequency (MPF) of the EMG signal from the vastus lateralis (VL) muscle during cycle ergometry. METHODS: Twenty adults (13 men and 7 women; mean age ± SD = 23.8 ± 3.0 yr) volunteered for this study. A bipolar surface EMG electrode configuration (30 mm center-to-center distance) was placed over the vastus lateralis (VL) muscle at one-third of the distance from the lateral border of the patella to the anterior superior iliac spine. EMG amplitude and MPF values were measured during incremental cycle ergometry at 50, 75, 100, 125, and 175 W. The incremental cycle ergometry test began at 50 W and increased by 25 W every 2 min. In addition, three skinfold measurements (mm) were taken from the VL at the site of the EMG electrode placement with the average value used in subsequent analyses. Simple linear regression was used to determine the relationships for EMG amplitude and MPF versus skinfold thickness at each power output. In addition, independent t-tests were used to compare the mean values for EMG amplitude and MPF between the 10 subjects with the largest skinfold values (mean ± SD = 16.7 ± 5.2 mm) and those (n = 10) with the smallest skinfold values (mean ± SD = 6.6 ± 1.2 mm). RESULTS: The simple linear regression analyses revealed no significant (p > 0.05) correlations between skinfold thickness and EMG amplitude (r = 0. 18 - 0.40) or MPF (r = 0. 17 - 0.41) at any of the power outputs. Furthermore, there were no significant mean differences (p > 0.05) in EMG amplitude or MPF between the subjects with the largest skinfold values and those with the smallest skinfold values. CONCLUSIONS: The results of the present study indicated that skinfold thickness did not affect absolute values for EMG amplitude or MPF from the VL muscle during cycle ergometry at five power outputs. These findings suggest that there maybe differences between the results of simulation studies and measured findings from surface EMG studies. PRACTICAL APPLICATIONS: Subcutaneous tissue thickness is just one of many possible factors that can affect the amplitude and frequency domains of the EMG signal. Other factors include the conductivities of the tissue, interelectrode distance, and the number of recruited motor units. The current findings provide information regarding a methodological consideration associated with the application of surface EMG measurements. [ABSTRACT FROM AUTHOR]

PURPOSE: To examine the influence of electrode placement on the physical working capacity at the fatigue threshold (PWCFT). The PWCFT test estimates the highest power output that can be maintained without neuromuscular evidence of fatigue and is determined from the rate of increase in the amplitude of the electromyographic (EMG) signal. METHODS: Fifteen college-aged males and females (mean age ± SD = 22.6 ± 3.4 yr; BW = 74.3 ± 11.2 kg; HT = 176.1 ± 9.0 cm) performed an incremental test to exhaustion on a cycle ergometer. A linear electrode array was utilized to determine the location of the innervation zone (IZ) and muscle fiber pennation angle (MFPA) of the vastus lateralis (VL). For determination of the PWCFT values, surface EMG signals were recorded from 3 bipolar electrode arrangements at different locations over the VL during the incremental tests. The first electrode arrangement was placed on the VL at one-third of the distance between the lateral border of the patella and the anterior superior iliac spine, and oriented parallel to the MFPA. The second electrode arrangement contained the same center point as the first electrode arrangement, but was oriented parallel to the long axis of the femur. A third electrode arrangement was placed over the IZ and oriented parallel to the MFPA. RESULTS: The results of a one-way ANOVA indicated there were no significant (p < 0.05) mean differences in PWCFT values among the 3 electrode placements (parallel to the MFPA = 181 ± 40 W; parallel to the long axis of the femur = 185 ± 44 W; and over the IZ = 189 ± 54 W). In addition, there were significant correlations in PWCFT values for the electrode placement parallel to the MPFA vs. parallel to the long axis of the femur (r = 0.94) and over the IZ (r = 0.88), as well as for the electrode placement parallel to the long axis of the femur vs. over the IZ (r = 0.81). CONCLUSIONS: These findings indicated that the PWCFT test is not influenced by the placement of a bipolar electrode arrangement in relation to the MFPA or over the IZ. Practical Applications: The results of the current study suggested that the onset of neuromuscular fatigue (PWCFT) can be estimated without identification of the MFPA or IZ. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine the effects of daily administration of two different arginine-based supplements for four weeks on the physical working capacity at the fatigue threshold (PWCFT). The PWCFT test estimates the highest power output that can be maintained without neuromuscular evidence of fatigue. The study used a double-blind, placebo-controlled design. Fifty college-aged males (mean age ± SD = 23.9 ± 3.0) were randomized into one of three groups: 1) placebo (n = 19); 2) 1.5 gm arginine (n = 14); or 3) 3.0 gm arginine (n = 17). The placebo was microcrystalline cellulose. The 1.5 gm arginine group ingested 1.5 gm of arginine and 300 mg of grape seed extract, whereas the 3.0 gm arginine group ingested 3.0 gm of arginine and 300 mg of grape seed extract. All subjects performed an incremental test to exhaustion on a cycle ergometer prior to supplementation (PRE) and after 4 weeks of supplementation (POST). Surface electromyographic (EMG) signals were recorded from the vastus lateralis using a bipolar electrode arrangement during the incremental tests for the determination of the PRE and POST supplementation PWCFT values. There were significant mean increases (PRE to POST) in PWCFT for the 1.5 gm (22.4%) and 3.0 gm (18.8%) supplement groups, but no change for the placebo group (-1.6%). These findings supported the use of the arginine-based supplements for improving neuromuscular performance and delaying the onset of fatigue during cycle ergometry. [ABSTRACT FROM AUTHOR]