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Table 3 Comparison of main features of lower limb fatigue resistant strategies

From: Advances in selective activation of muscles for non-invasive motor neuroprostheses

Fatigue strategy

Muscle fatigue definition

Fatigue metric

Muscle group

Stimulation strategies & electrodes

Subjects

Results

Popovic et al. 2009 [63]

70 % decrease of max torque

Fatigue Interval

Quadriceps

Synchronous single electrode vs Asynchronous 4 smaller electrodes

6 complete SCI patients

150 % increase of fatigue interval with electrode array

Malesevic et al. 2010 [58]

70 % decrease of max torque

Fatigue Interval

Quadriceps

Synchronous single electrode vs Asynchronous 4 smaller electrodes

6 complete SCI patients

Synchronous: 31 % increase of post-therapy muscle fatigue resistance.

20 daily sessions

Asynchronous: 4 % increase of post-therapy muscle fatigue resistance.

Nguyen et al. 2011 [64]

Torque decrease of 3 dB

Fatigue Index, Fatigue Time, Torque-Time-Interval

Tricep Surae

Synchronous single electrode vs Asynchronous 4 smaller electrodes

1 complete SCI

Asynchronous stimulation: higher torque values for a longer period of time

Sayenko et al. 2013 [67]

Torque decrease of 3 dB

Fatigue Index

Knee flexors/extensors, plantar flexor/dorsiflexor

Synchronous single electrode vs Asynchronous 4 smaller electrodes

15 able-bodied subjects

Asynchronous stimulation higher fatigue resistant than synchronous

Sayenko et al. 2014 [65]

They studied muscle contraction properties

Torque-Rise Time, Rate of torque development, Half-Relaxation-Time, Rate of torque relaxation

Tricep Surae, right gastrocnemius

Synchronous single electrode vs Asynchronous 4 smaller electrodes

15 able-bodied subjects

Amplitude of M-waves depends on the location of the stimulated pad electrodes. Peaks on M-waves on ascending phase of synchronous stimulation are fused as fatigue occurs.