Relative changes in blood flow with functional electrical stimulation during exercise of the paralyzed lower limbs

Eight spinal cord injured (SCI) patients performed three sets of exercise with two conditions, 60% and 80% of VO2peak, with an arm crank ergometer. Functional neuromuscular stimulation was used to induce static leg contractions in two of the above sets of exercise. The three exercise sets were performed with no functional neuromuscular stimulation (NOS); with functional neuromuscular stimulation at 40 milliamperes; and with functional neuromuscular stimulation at 80 milliamperes (HIS). The lower limb blood flow was estimated by a photoelectric plethysmograph. Results showed that the lower limb blood flow was consistently reduced across both functional neuromuscular stimulation levels (17.4% from NOS to LOS; 13.8% from LOS to HIS; and 28.8% from NOS to HIS), and work loads (15.3% from rest to 60% VO2peak; 38.0% from 60% VO2peak to 80% VO2peak; and 47.5% from rest to 80% VO2peak). Rate-pressure product was decreased by 8.3% between NOS and HIS at 60% VO2peak (15.7 +/- 3.4 to 14.4 +/- 3.8), by 6.8% between NOS and HIS at 80% VO2peak (18.9 +/- 53 to 17.6 +/- 4.8), and by 12.4% between LOS and HIS at 80% VO2peak (20.1 +/- 6.7 to 17.6 +/- 4.8). These data indicate that in SCI (a) functional neuromuscular stimulation-induced contractions of the lower limb muscles can increase blood flow and thus reduce venous blood pooling in the paralyzed muscles, and (b) such improvements are associated with a reduced rate pressure product.(ABSTRACT TRUNCATED AT 250 WORDS)