CYCLING PERFORMANCE TIPS
CAN TOO MUCH EXERCISE HARM THE HEART?
I was asked: "How 'healthy' is the high intensity cycling that I've been doing (at over 50's)? By high intensity I mean continuous effort at 85-90% HRMax with touches of 100% HRMax. And then a few days later I ran across this article in the NYT that stated, assuming no family or personal history of heart disease, there was "... no evidence...there is a level of exercise that is dangerous or too much for a normal, healthy person." Although this is generally true, there is sound evidence that there is indeed an upper limit for cardiac healthy exercise. The curve of benefits versus exercise volume doesn't just plateau, it probably starts to drop off as the extremes are reached . A few examples:
There are two potential health risks from high intensity cycling - Musculoskeletal (or overuse) injuries and cardiovascular. The musculoskeletal injuries are known to all of us who exercise and participate in aerobic sports. Overuse leads to injury. And the cure is to listen to your body, and if it hurts when you are using it, decrease your activity level. The cardiovascular risks appear to be from repeated stress at the ultraendurance event level. (Pushing through the pain, as it were.) Although acute stress might cause some modest cardiac muscle injury (and leakage of muscle enzymes into the blood where they can be measured) this heals within a few days, and only with repeated injury/healing/injury does scarring appear to be a risk.
There is no evidence that short term, high level exertion such as 30 to 60 second intervals is harmful and also no sound evidence that intervals longer than this add benefit to cardiovascular fitness.
My Bottom Line? Pushing your limits (within reason) is not harmful to your health. But cardiovascular risk appears as you move to the ultra event level.
The "paradox of exercise" is a low cardiovascular mortality in endurance athletes who have high rates of coronary artery disease (plaques) on imaging studies.
Calcified plaques tend to be stable while non calcium plaques often rupture leading to an acute blockage of the coronary artery and in turn a cardiac event. Perhaps endurance athletes have a more favorable ratio with more calcified plaques and fewer unstable plaques. But this study shows that is not the case. Not only do lifelong endurance athletes have more coronary plaques than fit and healthy individuals with a similarly low cardiovascular risk profile, they have a similar ratio of stable versus unstable plaques as a group with healthy lifestyles.
So the search continues for an explanation for the paradox of more coronary disease but lower cardiovascular mortality. Possibilities such as (my ideas here) that these athletes have better collateral ciculation and are thus better able to withstand an acute obstruction of one of the larger coronary arteries. Or perhaps some other factor that improves the stability of their uncalcified plaques.