Skin vascular reaction to short durations of normal seating

The effects of duration and compliance of seating surfaces on reactive hyperemia within the skin overlying the ischial tuberosities was determined in four normal, one paraplegic and one cerebral palsy subject. Reactive hyperemia was demonstrated thermographically after short durations (ie, 5, 10, and 15 minutes) of seating on a hard surface. The magnitude of hyperemic response increased significantly (p < .001 for 15 v 5 minutes; p = .019 for 15 v 10 minutes; p = .001 for 10 v 5 minutes) with increased duration of seating. In all six subjects studied, the maximum postseating blood flow continued to increase with up to 15-minute seating on a hard surface, and the mean maximum response was positively correlated with duration of seating (4 = 0.918, p < 0.001). Although there was good correlations between magnitudes of interface pressures measured and vascular responses within each individual, there was no such direct correlation between individuals.