Mean power frequency and integrated electromyogram of repeated isokinetic plantar flexions

Abstract

Peak torque (PT), contraction work (CW), mean power (CP), and time for contraction (t) were recorded for each of 200 full range-of-motion repetitive isokinetic (maximum effort) plantar flexions at the preset angular velocity 60 degrees s-1 (degrees X s-1). The subjects were 12 healthy males (42-46 years). Simultaneous recordings of electromyographic activity of the three parts of the triceps surae muscle were made. The electromyograms were truly integrated and the mean power frequency was also calculated for each of the contractions. The mechanical variables decreased steeply during approximately the first 70 contractions (the fatigue phase) followed by a steady-state level (the endurance level) with no further significant decrease. The fatigue phase was composed of two parts. The first was characterized by decreases in CW, MPF and in the ratio CW/iEMG, while iEMG and iEMG/t were unaltered. During the second part decreases in iEMG and iEMG/t occurred while MPF and CW/iEMG had stabilized. During the endurance level all the variables were stable but lowered when compared with the initial contractions of the fatigue phase. The results indicated that the mechanical fatigue went through two parts before the steady-state level was established.

Electromyographical assessment on muscular fatigue—an elaboration upon repetitive typing activity

“…From our study, significant differences in EA values between the pre-and post-MVC tests are seen (Fig. 1), and is similar to the findings of Komi [30] and Gerdle et al [21].…”

“…Decrease in MDF and/or MPF has been demonstrated in the quadriceps during isokinetic knee extensions [22], the gastrocnemius during isokinetic plantar flexions [21], some leg muscles during uphill running [1], the shoulder muscles during repetitive arm works [49], and in the biceps brachii during repeated elbow flexion-extension movements [9,37]. On the other hand, the EMG amplitude has been observed to increase during repetitive, dynamic submaximal efforts [21,31,36], and decrease during maximal efforts [21,31]. Luttmann proposed a new joint analysis of spectra and amplitude (JASA) method to assess fatigue of muscular activity [35,36].…”

Intramuscular pressure and electromyographic responses of the vastus lateralis muscle during repeated maximal isokinetic knee extensions

“…RMS throughout the contractions did not change although a tendency to decrease was apparent. RMS has varied widely between studies due to the fact that it appears to be dependent both on the muscle group investigated (largely due to fibre‐type constitution), and on the velocity of contraction (Gerdle et al . 1987, Elert & Gerdle 1989, Masuda et al .…”

“…1999). The RMS may decrease, increase or even remain unchanged during repetitive isokinetic contractions (Gerdle et al . 1987, Elert & Gerdle 1989, Masuda et al .…”

Fatigue in the shoulder muscles during static work at two different torque levels

“…However, several studies have shown that the shift in MPF occurs early in exhaustive performance. Our recent studies of repeated maximum dynamic contractions of the shoulder and the plantar flexors, respectively, have demonstrated simultaneous parallel steep decreases in mechanical performance and MPF during the initial 40-70 contractions followed by stable levels during the remaining 100 or more contractions (Fugl-Meyer et al, 1985a, 1985bGerdle et al, 1987Gerdle et al, ,1989Elert & Gerdle, 1989;Elert et al, 1989). In some of our studies the subjects rated their perception of fatigue in the working muscles using the 10-graded scale of Borg (1982).…”