Prediction of endurance capacity of quadriceps muscles in humans using surface electromyogram spectrum analysis during submaximal voluntary isometric contractions

Abstract

The measurement of endurance time ( t(lim)) is the procedure commonly used to quantify the ability of a muscle to maintain force. The relationship between surface electromyographic (sEMG) manifestations of localised muscle fatigue and t(lim) during an effort at 50% of maximal voluntary isometric torque of the knee extensors (vastus lateralis and vastus medialis) until exhaustion was studied in 14 healthy volunteers. It was carried out to test whether changes in sEMG computed over shorter periods than expected t(lim) could be used to predict t(lim). Changes in mean muscle fibre conduction velocity, mean power frequency, median frequency, root mean square ), in the relative power in the 6-30 Hz and 30-60 Hz frequency bands were monitored using linear slope and area ratio index as statistical indicators. These indicators were computed over fixed periods shorter than t(lim). The subjects were able to maintain the required force level for [mean (SD)] 78.8 (9.5) s. During the fatigue trial, it was the greatest of the increases in the 6-30 Hz frequency band, recorded for either of the two muscles investigated, that was the only variable which correlated with t(lim). Significant relationships between t(lim) and changes in this low frequency band were observed as early as the first 15-30 s of the contraction. These results suggest that sEMG frequency banding may predict mechanical endurance without the need to maintain the contraction until exhaustion. From a clinical perspective, this could be an advantage for patients who might not be able to tolerate contractions to exhaustion.

Differences between young and older women in maximal force, force fluctuations, and surface emg during isometric knee extension and elbow flexion

“…46 Estimates of MFCV were accepted only when cross-correlation values were higher than 0.7, which has been reported to be an acceptable correlation coefficient for VL, due to the fibers' orientation. 34,43 In order to obtain acceptable time resolution, the time delay was computed with a resolution of 10 to 20 s, 36 which was obtained by interpolating the cross-correlation function near the maximum with a sinc function.…”

Influence of exercise intensity and joint angle on endurance time prediction of sustained submaximal isometric knee extensions

“…This calculation time period (i.e., 50% T lim ), therefore, represents a threshold that should not be exceeded for a T lim prediction to remain useful. It also appears that results from spectral parameters of the sEMG signal recorded from the most fatigable muscle established the most reliable relationships between sEMG signal and T lim , and subsequently a better prediction of T lim (Badier et al 1993;Dolan et al 1995;Maisetti et al 2002a;Mannion and Dolan 1996;van Dieen et al 1998;van Dieen et al 1993). However, during a complex multijoint and bilateral task, we have indicated that T lim prediction was not reliable, probably because of the great number of muscles and joints involved (Boyas et al 2009;Maisetti et al 2006).…”

“…(A ? B) is the sum of both areas beneath and above the sEMG parameter-time course delimited by a signal reference value corresponding to the mean value of the sEMG parameter computed over the first 2 s of the test [for further information, see (Maisetti et al 2002a)]. This variable is a dimensionless and regression-free fatigue index that can be applied to any data pattern without previous assumptions.…”

“…These relationships have been illustrated during tasks soliciting back extensors (Dolan et al 1995;van Dieen et al 1998), and limb muscles (Hagberg 1981;Maisetti et al 2002a;Mannion and Dolan 1996;Merletti and Roy 1996). In most of these studies, changes in the sEMG signal computed over the first half of the test duration allowed a prediction of T lim .…”

“…Indeed, T lim prediction has been mainly illustrated during contractions performed at exercise intensities higher or equal to 50% of the maximal voluntary contraction (MVC) (Dolan et al 1995;Maisetti et al 2002a;Mannion and Dolan 1996;Merletti and Roy 1996;van Dieen et al 1998). Only van Dieen et al (1998 investigated T lim prediction of back extensor muscles contractions at lower exercise intensities.…”