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First published online June 15, 2006
Journal of Experimental Biology 209, 2395-2408 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02310

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The cost of running uphill: linking organismal and muscle energy use in guinea fowl (Numida meleagris)

Jonas Rubenson, Havalee T. Henry, Peter M. Dimoulas and Richard L. Marsh^*

Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA

View larger version (15K): [in a new window]   Fig. 1. Representative organismal oxygen consumption of a guinea fowl during rest and during level running (circles) and incline running (triangles) over a range of speeds. The bird was initially tested running at 1.5 m s–1 on the level and 1.5 m s–1 on a 15% gradient. Subsequent measurements were made over a range of faster running speeds (2.0–3.0 m s–1) in order to determine the speed for which the organismal oxygen consumption matched that at 1.5 m s–1 and 15% gradient (as indicated by arrows). Lines were fitted by eye to illustrate the experimental design.

View larger version (12K): [in a new window]   Fig. 2. Organismal oxygen consumption of guinea fowl at rest, running at 1.5 m s–1 on the level, running at 1.5 m s–1 on a 15% gradient and running at 2.28–2.39 m s–1 on the level. Values are means ± s.e.m. (N=8). *Significant difference (P<0.05) between the level run at 1.5 m s–1 and both the level run at 2.28–2.39 m s–1 and incline run at 1.5 m s–1 and 15% gradient, as measured by paired t-tests. There was no significant difference between the 1.5 m s–1 incline run and the 2.28–2.39 m s–1 level run.

View larger version (12K): [in a new window]   Fig. 3. Organismal oxygen consumption versus total leg muscle blood flow of guinea fowl at rest, running at 1.5 m s–1 on the level, running at 1.5 m s–1 on a 15% gradient and running at 2.28–2.39 m s–1 on the level. Values are means ± s.e.m. (N=8). Total blood flow increases linearly with organismal oxygen consumption (y=8.38x–104.3; r2=0.9997).

View larger version (20K): [in a new window]   Fig. 4. Fractional increases in blood flow (FdQ) above values for moderate-speed level running due to an increase in speed (hatched bars) or incline (black bars). The digital flexors (sDF-II, sDF-III, latDDF, medDDF) and the femorotibialis muscles (FTLD, FTLP, FTI, and FTM) have been combined into a digital flexor group and femorotibialis group, respectively. Muscles are also grouped into those active during swing and stance (Marsh et al., 2004). The femorotibialis group is assigned both swing and stance phase activity (Marsh et al., 2004). Values are means ± s.e.m. (N=8). *Significant difference (P<0.05) in the FdQ values resulting from an increase in speed or incline (Wilcoxon nonparametric test). The red bars represent the fractional increases in flow predicted if the increased flow was distributed according to muscle mass. Abbreviations are defined in Table 1.

View larger version (32K): [in a new window]   Fig. 5. (A) Fractional increases in blood flow (FdQ) above values for moderate-speed level running due to an increase in speed or incline for parallel-fibered stance muscles (black bars; ILPO, FCLA, FCLP, postIF, FCM, PIFL, PIFM, CFC, CFP, ISF) and pinnate-fibered stance muscles (hatched bars; AMB, ITC, sDF-II, sDF-III, latDDF, medDDF, FHL, FDF&FB, FL, LG, MG, IG, FTLD, FTLP, FTI, FTM). *Significant difference (P<0.05, Wilcoxon test, paired samples) in the values of FdQ between pinnate and parallel groups during incline running. (B) Increases in mass-specific blood flow above values for moderate-speed level running due to an increase in speed or incline for parallel-fibered stance muscles (black bars) and pinnate-fibered stance muscles (hatched bars). The broken red lines represent the average mass-specific increase in blood flow to all stance phase muscles. Values are means ± s.e.m. (N=8). **Significant difference (P<0.005; paired t-test) in the increase in mass-specific blood flow between the pinnate and parallel muscle groups during incline running. The increase in blood flow to the FT muscles was divided in half for the fast running condition because it is active during both stance and swing (Marsh et al., 2004). The increase in blood flow to the FT muscles was assumed to occur completely during the stance phase during uphill running. Abbreviations are defined in Table 1.

View larger version (35K): [in a new window]   Fig. 6. (A) Fractional increases in blood flow (FdQ) 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).

View larger version (26K): [in a new window]   Fig. 7. Fractional increases in blood flow (FdQ) above values for moderate-speed level running due to an increase in speed (hatched bars) or incline (black bars) for stance muscles versus swing muscles (for division see Table 1). Stance and swing muscles were assigned following Marsh et al. (Marsh et al., 2004) with two differences. (1) All of the increase in blood flow to the FT during incline running was assumed to occur during stance, and (2) in the present study we measured separately the blood flow to the swing and stance portions of the IF. Values are means ± s.e.m. (N=8). *Significant difference (P<0.05, Wilcoxon test) in the FdQ values for speed and incline conditions.