In his “sweat science” column, Alex Hutchinson reported on some recent studies that give an update on the question of whether there are health issues associated with excessive endurance training. I have discussed this previously (here, here, and here) it being a matter of some interest to me as I like to endurance train a lot. The first study is a recent one from Sun-Yat-Sen Univerity in China . This confirms that although people that do a high volume of endurance exercise tend to have higher calcium scores in their coronary arteries (an indication of arterial plaque), it is a benign condition because the plaque tends to be stable. This latest study shows that on long-term follow-up, the high-volume athletes have no greater risk of adverse cardiac events.
A second study  disputes the “J-curve” that has been previously reported for all-cause mortality vs. the amount of exercise. It is well-known that exercise reduces the risk of mortality, but some previous studies have shown that the risk of death goes back up for extreme amounts of exercise. This is controversial as some studies have found this effect but others haven’t. The new study highlights a flaw in the methodology of the previous studies that detected a J-curve. Rather than track the actual ongoing exercise habits of the people being followed, the previous results estimated the amount of physical activity just based on a questionnaire administered at the beginning of the study. In the present study, the amount of exercise was continuously tracked for over 30 years in a large (more than 100,000) sample of people. The “J-curve” was not found: exercise reduces the risk of all-cause mortality, including high volumes of exercise.
I still like to hedge my bets on this. I do a high amount of exercise but a large percentage of it is at relatively low intensity, more like brisk walking or equivalent. I do exercise at higher intensities, but at a lower volume. As I’ve discussed previously (here and here) this is a good combination of exercise for effective training, health benefits, and relaxation.
Gao J, Hao Q, Lu L, et al, “Associations of long-term physical activity trajectories with coronary artery calcium progression and cardiovascular disease events: results from the CARDIA study”, British Journal of Sports Medicine 2022.
Hoong Lee, D, et al, “Long-Term Leisure-Time Physical Activity Intensity and All-Cause and Cause-Specific Mortality: A Prospective Cohort of US Adults”. Circulation. 2022.