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First published online December 14, 2005
Journal of Experimental Biology 209, 115-127 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.01883

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Maximum aerobic performance in lines of Mus selected for high wheel-running activity: effects of selection, oxygen availability and the mini-muscle phenotype

Enrico L. Rezende^*, Theodore Garland, Jr, Mark A. Chappell, Jessica L. Malisch and Fernando R. Gomes

Department of Biology, University of California, Riverside, CA 92521, USA

View larger version (32K): [in a new window]   Fig. 1. Maximum aerobic capacity (O2max) measured during forced exercise in a hypoxic (14% O2), normoxic (21% O2) and hyperoxic atmosphere (30% O2) for 59 mice from lines selected for high voluntary wheel running (S) and their non-selected control lines (C). Each point represents the highest 60-s average obtained in two measurements on the treadmill performed on consecutive days (see Materials and methods). (Left panels) Aerobic capacity in relation to selection history - i.e. S (closed circles) versus C (open circles). Adjusted means for S and C in each PO2 are listed in Table 2. (Right panels) The same graph, but highlighting individuals with the mini-muscle phenotype (all in S lines) versus normal phenotypes. Effects of size, selection history and mini-muscle are summarized in Table 2.

View larger version (23K): [in a new window]   Fig. 2. (A) Maximum aerobic capacity (O2max), (B) carbon dioxide production, (C) respiratory exchange ratio at O2max (RER=CO2/O2max) and (D) maximum running speeds, measured in S and C mice (N=35 and 24, respectively) during forced exercise on a treadmill with a hypoxic (14% O2), normoxic (21% O2) or hyperoxic atmosphere (30% O2). Values are shown as adjusted means ± s.e.m. Statistical differences between hypoxic, normoxic and hyperoxic trials are shown in lowercase letters; effects of selection history for each trait at a given PO2 are shown in Table 2; overall effects of selection on the entire dataset (i.e. across PO2) are listed in Table 4.

View larger version (26K): [in a new window]   Fig. 3. Individual consistency of maximum aerobic performance (O2max) measured across different PO2. Points represent the highest 60-s averages for each individual obtained from either of two treadmill trials each in hypoxia (14% O2), normoxia (21% O2) and hyperoxia (30% O2). The broken line represents equality (x=y) in each plot. Pearson product-moment correlations are also reported for residuals calculated from nested ANCOVAs performed separately for each PO2, including mass and age as covariates and batch as a cofactor.