Scientists are puzzled as to why some people’s bodies respond better to working out than others. According to some studies, genetics must be involved because response to exercise seems to run in families. But which genes are involved? And how exactly do these genes increase or stunt the body’s response?
The NY Times writes about a recent study in rats. In the study, rats with a certain set of genes responded vigorously to exercise; they became much more fit after a few weeks of running. Rats with other genes gained little cardiovascular benefit from the same exercise program; their heart muscles didn’t react as expected.
People who exercise diligently but see no results should consider revising their workout routine. The range of response to exercise can be extremely large. A study published in March examined overweight men and women who enrolled in five months of endurance or weight training. By the end, the men and women were, on average, 8% stronger or more aerobically fit. But 13% of those in the endurance group lost aerobic capacity and 30% of those in the strength-training group were weaker.
Another rodent study conducted at the University of Michigan and the Norwegian University of Science and Technology, scientists created two strains of rats that would or would not respond well to working out. First, they had rats run for several weeks to see how much distance the animals added before tiring out. They also noted how well they were adapting to the workouts. They found that the males who added the most mileage were bred with females who responded similarly. The animals that added the fewest miles to their runs mated to one another.
Several generations later, the scientists had rats that should be significantly high or significantly low responders to exercise. The first part of the experiment supported this. The two different types of rats were set on treadmills with identical workouts. After a two month training program, there was a significant difference with the types of rats. Rats there were bred to respond well to exercise training increased the distance they could run before tiring by 40%. The other rats lost about 2% of their endurance during the training.
To be continued…