Fig. 6. (A) Fractional increases in blood flow (F_dQ) above values for moderate-speed level running due to an increase in speed (hatched bars) or incline (black bars) for muscles grouped by their actions in swing or stance. Within the stance-phase group, muscles were further divided according to the joint at which they have their primary action. Values are means ± s.e.m. (N=8). *Significant difference (P<0.05, Wilcoxon test) between the values for speed and incline conditions. (B) Increases in mass-specific blood flow due to an increase in speed (grouped as in A). (C) Increases in mass-specific blood flow due to an increase in incline (grouped as in A). Values are means ± s.e.m. (N=8). The broken red lines in B and C represent the average mass-specific increase in blood flow to all hindlimb muscles. Swing and stance phase muscle groups: the increases in flow to all but one muscle complex were assigned to either swing or stance, as indicated in Table 1. The increases in blood flow to the heads of the FT muscle were divided equally between swing and stance during level running because it is active in both phases. During uphill running, the increase in blood flow to this muscle was assumed to result from increased metabolism during stance only. Grouping of stance-phase muscles by joint action: because the ILPO has extensor moments at both the hip and the knee, the increases in flow to this muscles were divided between the hip (75%) and knee (25%), approximately reflecting the relative moment arms at these two joint. The flow to the other muscles was assigned as follows: Hip: FCLA, FCLP, ITC, postIF, FCM, PIFL, PIFM, CFC, CFP, ISF and ILPO (in part); Knee: FT, and ILPO (in part); Ankle and toes: sDF-II, sDF-III, latDDF, medDDF, FHL, FDL&FB, FL, LG, MG, IG. These assignments are not without ambiguities (see text).