Figure 2
Torque traces and oxygenation/deoxygenation profiles during neuromuscular electrical stimulation and recovery. The signals, recorded from a representative subject during a frequency ramp contraction (from 2 to 50 Hz in 7.5 s) and the subsequent recovery phase, refer to tibialis anterior muscle stimulation via the motor point (MP stimulation) and stimulation following anatomic reference charts for electrode placement (conventional stimulation). Note that MP stimulation results in greater mechanical stress and metabolic demand than conventional stimulation. O2Hb = oxyhemoglobin; HHb = deoxyhemoglobin; TOI = tissue oxygenation index; THI = total hemoglobin index. The bottom panels are related to subject perception of discomfort evaluated with a numeric rating scale (NRS) and show group mean ± SD values for the two conditions studied in 10 healthy subjects: MP stimulation induces significantly (* P < 0.05) less discomfort than conventional stimulation. NRS scores: 0 = no discomfort; 10 = maximum discomfort. (Modified from Gobbo et al. [6]. Copyright © 2011 Springer. Used with permission provided by Copyright Clearance Center, license number: 2913660233993).