An investigation was carried out into how stimulation frequency and stimulation history affect the potentiation of muscle force during 20 s of constant stimulation of the two knee extensors in isometric conditions. Stimulation frequency significantly affected the potentiation pattern: low-frequency (2.5-10 Hz) stimulation showed a reduction and subsequent enhancement of force, and high-frequency (14.3-25 Hz) stimulation showed only enhancement of force. The degree of enhancement in force and time-to-peak decreased with the stimulation frequency. Whereas 40 Hz conditioning stimulation enhanced the muscle force, 14 Hz stimulation after 10 s of rest induced little force enhancement (8% in both muscles). When the frequency of the conditioning stimulation was 14 Hz and the main 14 Hz stimulation was applied after 50 s of rest, the initial force at the main stimulation was similar to the final force value of the conditioning stimulation (above 90% similarity). The potentiated twitch force slowly decayed during rest, with an average time constant of 2.4 min. These observations indicate that muscle potentiation depends on the stimulation frequency and stimulation history, and therefore a computer model of potentiation can play an important role in predicting muscle force and body movement induced by electrical stimulation.
- Frequency dependence
- Functional electrical stimulation
- Muscle potentiation
- Stimulation history dependence
ASJC Scopus subject areas
- Biomedical Engineering
- Computer Science Applications