Determination of maximal power output at neuromuscular fatigue threshold

Abstract

The purpose of this study was to determine the maximal power output at the neuromuscular fatigue threshold (EMGFT), as estimated from electromyographic (EMG) data from representative leg muscles during cycling. The rate of rise in integrated EMG activity as a function of time (iEMG slope) was calculated at each of four constant-power-output ergometer bouts for 20 subjects. The iEMG slopes were plotted against work rates that were well described as linear functions (0.84 < R2 < 0.99). This iEMG slope vs. work rate relationship was extrapolated to zero slope to give an intercept on the power axis that was interpreted as the highest work rate sustainable without EMG evidence of neuromuscular fatigue (EMGFT). Each individual EMGFT was then expressed in terms of an O2 output (VO2) equivalent on the basis of the individual delta efficiency calculated during a linearly increasing maximal exercise test on the same bicycle ergometer. Results indicated a highly significant correlation (r = 0.92, P < 0.01) between EMGFT VO2 and anaerobic threshold VO2, as determined by conventional gas exchange criteria. The mean EMGFT VO2 (1.84 +/- 0.55 l/min) was, however, significantly greater (P < 0.01) than the anaerobic threshold VO2 (1.72 +/- 0.54 l/min). It was suggested that the EMGFT may provide an attractive alternative to the measurement of the highest work rate that can be sustained without evidence of neuromuscular fatigue.

Influence of duty cycle on the time course of muscle fatigue and the onset of neuromuscular compensation during exhaustive dynamic isolated limb exercise

“…8). In contrast, in trials with levels of force production that exceeded those eliciting the aerobic peaks, we measured progressive increases in EMG activity, as others have (12,15,41). In these trials, which necessarily require a net reliance on anaerobic metabolism, the compensatory behavior began at the outset of each exhaustive trial and continued contraction-by-contraction until the point of failure (Figs.…”

“…This expectation provides a primary rationale for the near-universal practice within the neuromuscular fatigue literature of referencing muscle performance to the force elicited during a maximum voluntary contraction (i.e., MVC). Here, we used surface electromyography (EMG) to identify the presence of impaired muscular force production (7,20,24,37,41) during both sustainable and nonsustainable knee extension exercise. We considered a progressive increase in EMG amplitude occurring while muscle force production remained constant as the indicator of a compensatory response by the nervous system to maintain force output in the presence of fatigue (1,10,17,26).…”

Enhancement of whole body glucose uptake during and after human skeletal muscle low-frequency electrical stimulation

“…Five minutes after all of the settings were adjusted, oxygen uptake and knee extension force measurements were initiated. Our laboratory's method for measuring oxygen uptake has been described in previous communications (34,36). Respiratory gas parameters were continuously monitored throughout a total period of 35 min, including pre-(5 min), during (20 min), and poststimulation (10 min) periods.…”

Endurance Training Of Trained Athletes-An Electromyogram Study

“…One mechanism that has been proposed to explain improvements in endurance performance of athletes is a change in neuromuscular recruitment patterns [5,12]. But there appears to be little known about the neuromuscular response to HIT and hence it is not possible to understand its role in enhancing performance in response to HIT.…”