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First published online November 30, 2007
Journal of Experimental Biology 210, 4418-4427 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.004481
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Effects of independently altering body weight and body mass on the metabolic cost of running

Lennart P. J. Teunissen1,2, Alena Grabowski1 and Rodger Kram1,*

1 Department of Integrative Physiology, University of Colorado, Boulder, CO 80309, USA
2 Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands


Figure 1
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  		Fig. 1. Reduced gravity apparatus.

 

Figure 2
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  		Fig. 2. Net metabolic rate for running as a percentage of normal body weight from the rolling trolley method (half-solid squares), the fixed pulley method (open circles), the Farley and McMahon (Farley and McMahon, 1992Go) data (solid line), and normal running (open square). Net metabolic rate decreased substantially when we reduced body weight. The dashed line indicates an extrapolation to zero weight. Lines are linear least squares regressions. Rolling trolley: (%NNMR) = 0.73 x %BW + 26.18; R2=0.88; and fixed pulley: %NNMR = 0.81 x %BW + 19.36; R2=0.84; where %NNMR is the percentage of normal net metabolic rate and %BW is the percentage of normal body weight. Error bars are s.e.m. Within the rolling trolley and fixed pulley methods, metabolic rates were all significantly different from each other (P<0.0001). However, at a given percentage of body weight, there was no significant difference between rolling and fixed trolley methods (P>0.08). Statistics were calculated on absolute values.

 

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  		Fig. 3. Net metabolic rate for running with added mass and weight (solid squares), with added mass at normal body weight (half-solid squares), and with normal weight and mass (open square). Net metabolic rate increased slightly more than in direct proportion to added mass and weight. Net metabolic rate increased only slightly when we added mass alone. Error bars are s.e.m. (W kg–1). Metabolic rates at all levels of added mass and weight were significantly different from each other and from normal (P<0.004). For the added mass alone trials, the only significant difference was between 110% added mass and normal (P=0.005). Statistics were calculated on absolute values.

 

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  		Fig. 4. Normalized net metabolic rate (solid squares), vertical impulse (open triangles pointing up) and horizontal impulse (open triangles pointing right) for running with reduced body weight. Body weight support resulted in significant and substantial linear decreases with nearly similar slopes for all variables. At 25% body weight, the vertical impulse data diverged slightly from net metabolic rate.

 

Figure 5
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  		Fig. 5. Normalized net metabolic rate (solid squares), vertical impulse (open triangles pointing up) and horizontal impulse (open triangles pointing right) for running with added mass and weight. Net metabolic rate increased significantly and more than proportionally with added mass and weight, while both horizontal and vertical impulses increased significantly and slightly less than proportionally with added mass and weight.

 

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  		Fig. 6. Normalized net metabolic rate (solid squares), vertical impulse (open triangles pointing up) and horizontal impulse (open triangles pointing right) for running with added mass alone. Net metabolic rate, vertical impulse and horizontal impulse increased only slightly when we added mass alone.

 

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  		Fig. 7. (A) Net metabolic rate (% normal) for walking with reduced body weight (open triangles), walking with added mass and weight (solid triangles), running with reduced body weight (half-solid squares), running with added mass and weight (solid squares), and walking and running normally (open square). Net metabolic rate decreased only modestly in reduced weight walking, but substantially in reduced weight running (21% vs 55% at 25% body weight, respectively). Net metabolic rate increased more than proportionally with added mass and weight in walking, and nearly proportionally with added mass and weight in running. (B) Net metabolic rate (% normal) for walking with added mass alone (open triangles), running with added mass alone (half-solid squares), and walking and running normally (open square). Net metabolic rate increased substantially with added mass in walking, but did not substantially increase with added mass in running. Data for walking were obtained from Grabowski et al. (Grabowski et al., 2005Go).

 




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