Troxell, Michael Lee, Steven Loyal Britton, and Lauren Gerard Koch. Selected Contribution: Variation and heritability for the adaptational response to exercise in genetically heterogeneous rats. J Appl Physiol 94: 1674-1681, 2003. First published November 1, 2002 10.1152/japplphysiol.00851. 2002-Adaptational response to aerobic exercise was artificially selected for across one generation in a founder population of 20 female and 20 male genetically heterogeneous rats (N:NIH). Selection for low and high response was based on the change in treadmill running capacity, assessed by meters (m) run to exhaustion before and after 24 days of modest treadmill running. The training response of the founder population averaged ϩ222 m, with wide variation from a negative gain (Ϫ) of Ϫ110 m to a positive gain (ϩ) of ϩ430 m. Six pairs of the lowest (ϩ13 m) and highest (ϩ327 m) responders were mated. Mean response to training of the lowline (ϩ242 m) offspring did not differ from the founder. The high-selected line gained 383 m from training, ϩ161 m above the founder population. Narrow sense heritability estimated from regression of offspring on midparent values for response to training was 0.43 (P Ͻ 0.007). One generation of selection resulted in a 58% divide between the low and high lines. Selectively bred models of both intrinsic (untrained) and adaptation response can be useful in resolving the genetic basis of variation in aerobic capacity.

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