It’s always a bit odd when a study confirms what everyone already knew, or thought they knew. Writing in the NY Times Fitness Blog last week, Gretchen Reynolds reports on recent research into the role of catecholamines (“stress” hormones associated with the body’s “fight or flight” response) on long-term muscular adaptations and improvements in endurance and overall fitness.
The research used mice that had been specially bred to produce more of a protein called CRTC2 that is activated during periods of stress. When the mice were “trained” with frequent strenuous treadmill running, the catecholamines in their bodies set off a sequence of events that resulted in activating the CRTC2 proteins and triggering muscular adaptations that resulted in larger, stronger muscle cells and vastly improved endurance compared with gains seen in normal mice following the same exercise routine.
The researchers concluded, “there is some truth to that idea of ‘no pain, no gain.’ Catecholamines are released only during exercise that the body perceives as stressful, so without some physical strain, there are no catecholamines, no messages from them to the CRTC2 protein, and no signals from CRTC2 to the muscles. You will still see muscular adaptations if your exercise is light and induces no catecholamine release, but those changes may not be as pronounced or complete as they otherwise could have been.”
On the one hand, duh. We’ve always known that effective training requires spending time out of one’s comfort zone.
On the other hand, that’s pretty interesting. The research drills down on the actual mechanisms used by the body to adapt to repeated high intensity exercise and stress. Coaches and athletes might have observed the effects of intense training, but with no understanding of what was going at the cellular level.
This was a study with mice, not with trained runners, so we shouldn’t generalize too much. Nevertheless, the research raises some interesting questions. Is “trainability” related to the genetic “gift” of having higher concentrations of the CRTC2 protein? (I expect it’s an order of magnitude more complicated than that, but perhaps the CRTC2 proteins are part of a much larger physiological substrate that enables adaptation.) What was the exact nature of the strenuous training, and when/how does training stress cease to be beneficial and become toxic?
Reading about this study also got me thinking about how different people have such different feelings about intense exercise. Some people have no use for it whatsoever, although they might thoroughly enjoy low-intensity exercise like walking or jogging. Others, like me, seem to need and enjoy bouts of higher-intensity exercise and chafe when we aren’t able to indulge in moderately hard workouts. Still others seem to crave very intense exercise like races (or sprinting up stadium steps) and can’t seem to get enough of what would be way too stressful for most people.
I hadn’t thought much about it before, but I suppose I had always thought of this variability in behavior as a psychological rather than a physical phenomenon. But now I think that the reality must be much more complicated.
Then there’s the troubling thought that as the mechanism of muscular adaptation is better understood, it will become easier to tamper with that mechanism. After all, the mice who had been specially bred to produce more CRTC2 were “super-mice” after training. If one could find a way to induce the body to make more of that protein, it would be a potent ergogenic aid. Before that happens, though, maybe there’ll be a new trend towards incorporating high-intensity, high-stress training into preparations for endurance events.
In the mean time, old school coaches everywhere are probably saying “we told you so!”