Comparison of electrical and magnetic stimulations to assess quadriceps muscle function

Abstract

This study aimed to 1) compare electrical and magnetic stimulations for quadriceps muscle function assessment, and 2) ascertain whether the ratios of the second twitch elicited by supramaximal electrical and magnetic femoral nerve stimulation at 10 and 100 Hz (T2(10:100)) and the total twitch force elicited by the same types of stimulations (Fpaired(10:100)) are equivalent to the standard low- to high-frequency force ratio associated with submaximal electrical tetanic stimulations (Ftet(10:100)). Quadriceps force and vastus lateralis EMG were recorded at rest (n = 21 subjects), immediately after, and 30 min after a 30-min downhill run (n = 10) when 1) supramaximal electrical nerve stimulation (ENS), 2) magnetic nerve stimulation (MNS) and 3) submaximal electrical muscle stimulation (EMS) were delivered in random order at 1 (single stimulation), 10, and 100 Hz (paired stimulations). Ten- and 100-Hz 500-ms tetani were also evoked with EMS to determine Ftet(10:100). Before exercise, contractile properties with single and paired stimulations were similar for ENS and MNS (all intraclass correlation coefficients k > 0.90), but smaller for EMS (P < 0.001). M-wave characteristics were also similar for ENS and MNS (all k > 0.90). After exercise, changes in all parameters did not differ between methods. With fatigue, the changes in Ftet(10:100) were inconsistently correlated with the changes in T2(10:100) (r(2) = 0.24-0.73, P = 0.002-0.15) but better correlated with the changes in Fpaired(10:100) (immediately after exercise: r(2) = 0.80-0.83, P < 0.001; 30 min after exercise: r(2) = 0.46-0.82, P = 0.001-0.03). We conclude that ENS and MNS provide similar quadriceps muscle function assessment, while Fpaired(10:100) is a better index than T2(10:100) of low- to high-frequency fatigue of the quadriceps in vivo.

Original Research: Central and peripheral quadriceps fatigue in young and middle-aged untrained and endurance-trained men: A comparative study

“…The following parameters were calculated from the mechanical responses to stimulation: peak force for Tw p , Db 100 , Db 10 , and the ratio Db 10 :Db 100 (Db 10:100 as an index of lowfrequency peripheral fatigue 27 ) to characterize peripheral mechanisms of neuromuscular function. Peak force during superimposed Db 100 was used to calculate voluntary activation (VA, characterizing central mechanisms of the neuromuscular function, see below).…”

“…Supramaximality was confirmed since unpotentiated quadriceps twitch and M ampl were not significantly reduced until 80% of the maximal power output in all subjects as previously reported. 27 Quadriceps surface EMG signal was recorded from the vastus lateralis as a surrogate for the whole quadriceps. 28 EMG signals were amplified (BioAmp, ADInstruments, Sydney, Australia) and 5 to 500 Hz filter was used.…”

“…33 However, in some individuals, Db 10:100 values were above 1 suggesting lower temporal summation during stimulation at 100 Hz compared to 10 Hz. Although changes in Db 10:100 have been shown to provide similar estimation of high-versus ....................................................................................................................... low-frequency fatigue compared to ratio obtained with tetanic stimulation trains, 27 this variable should not be used to describe muscle contractile properties in the unfatigued state.…”

Comparison of neuromuscular adjustments associated with sustained isometric contractions of four different muscle groups

“…Resting PS100 and PS10 amplitudes were analyzed for the trials, yielding the highest MVC in the prefatigue. The PS10/PS100 ratio was calculated both pre-and postfatigue as an index of low-frequency fatigue (74). Mean force was quantified for every 10% period of endurance time.…”

Impact of preinduced quadriceps fatigue on exercise response in chronic obstructive pulmonary disease and healthy subjects

“…The results of t2 at 10 Hz (t2 10Hz) and at 100 Hz (t2100Hz) were then reported as a ratio to determine t210:100. This ratio has recently been validated on the quadriceps muscle (42). V E and HR were measured by a portable device (Jaeger Oxycon Mobile; VIASYS Healthcare, Yorba Linda, CA) at rest and during the electrostimulation protocol.…”