So, you don’t like to exercise? Maybe you could blame it on your great-great-grandparents. Similarly, if you’re a practiced and proud couch potato who suddenly woke up to the fact that you’re a “natural” athlete, the credit could also belong to your genes.
Exercise research traditionally has focused on the effects of training, rather than underlying genetic mechanisms. But physiologists wondered what would happen if they took a single strain of rats – meaning they all had the same basic genetic background – and bred two separate lines purely on the basis of “continued selecting of untrained rats with either high- and low-running endurance.” In other words, the genetic role in endurance performance and oxygen delivery systems.
Results of this large longitudinal study have been coming out generation by generation, and now a group of researchers at the University of California, San Diego have found some surprising results at generation #15 (G15), compared with G7. The G7 untrained rats from the “athletic” line had a greater running endurance and increased oxygen consumption (12%) than the “couch potatoes.” These differences were mainly due to peripheral improvements (skeletal muscle) rather than central physiological changes in the cardiovascular or respiratory systems.
Wider endurance, oxygen usage differences reflect system-wide changes
As would be expected, the UCSD physiologists found that the continued selection led to significantly greater differences in endurance and oxygen consumption (44%) between the two groups of G15 rats than were seen at G7.
“This enhanced divergence at G15 was due in part to an increased skeletal muscle oxygen conductance that allowed for better transport of the oxygen to the muscle mitochondria of the athletic rats.” according to Richard A. Howlett, lead author of one of three papers on the experiment. Howlett and the other two lead authors, Scott D. Kirkton and Patrick G. Giuliano are all from UCSD’s Department of Medicine, Division of Physiology.
They are presenting their research at the 35th Congress of the International Union of Physiological Sciences in San Diego, March 31 - April 5, 2005.
Howlett continued: “However, we found that in addition the G15 ‘athletic’ rats had increased performance due to central changes in oxygen delivery.” Specifically, the running rats had improved cardiovascular systems (proportionally larger hearts (16% ) and increased blood flow (33%), reported in Kirkton et al., below) and respiratory systems (proportionally larger lungs (17%) and better oxygen diffusing capacity, reported in Giuliano et al., below) over the G7 stage, the researchers pointed out.
Oxygen delivery system maximized over time; support for ‘controversial thesis’