Can the level of high volume endurance exercise above which mortality risk increases be defined.
An important study with data from the Cooper Clinic in Dallas provides some information on that question.
Defina et al (1) presented data from a large cohort of men ( 21,758) with ten years of more of followup. In the group there were 432 men with an exercise history of equal to or greater than 3000 met-min per week .This is approximately equivalent to one hour of vigorous activity per day ( at a level greater than 7 Mets which is the oxygen uptake required to finish Stage 2 on the Bruce protocol).This is a level of exercise about 6 times the minimal level of vigorous ( greater than 7 Mets) exercise per week recommended by the 2018 guidelines.
Men in this group had a greater risk of having a coronary calcium score of 100 or greater but their risk for cardiovascular mortality (CVD) and all cause mortality was not greater than men exercising at lower levels and was lower than the least active men in that cohort. This was the case even though they had higher CAC scores which generally predicts a higher cardiovascular risk.
Franklin and co-authors (2) said this about the DeFina study:
" These finding refute the notion that high-volume endurance activity ( greater than one hour/day) increases mortality regardless of CAC level"
The issue in the De Fina article was the signficance of increased CAC in long time endurance exercisers on cardiovascular mortality but it also provides some information regarding the title question .
1)DeFina,LF et al Association of all-cause and cardiovascular mortality with high levels of physical activity and concurrent artery calcification. JAMA Cardiology 2019 42 (2) 174
2)Franklin, BA Exercise related acute cardiovascular events and potentially deleterious adaptations
following long term exercise training. Placing the risks into perspective-An update A scientific statement from the American Heart Association. Circ 2020 Feb 26 PMID 32100573
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