The following report, titled "Sporadic Exercise, Even Sex, May Boost MI, Death Risk" does not come from the primary scientific literature, but from a medical newsletter to which I subscribe for professional reasons.
Here is the link: Sporadic Exercise, Even Sex, May Boost MI, Death Risk
One may read the article for free, but one may be required to sign up to do so.
Here's some of the text, if you don't want junk mail.
Couch potatoes beware: Episodic bouts of physical or sexual activity may carry a risk of heart attack or sudden cardiac death, researchers reported.
But the risk drops with regular physical activity, according to Issa Dahabreh, MD, and Jessica Paulus, ScD, both of Tufts Medical Center in Boston.
And because periodic physical and sexual activity tends to be transient and infrequent, the absolute risks involved are small, Dahabreh and Paulus reported in the March 23/30 issue of the Journal of the American Medical Association.
"There is a link between episodic physical activity and sexual activity with the risk of heart attack and death from sudden cardiac events" within one or two hours after the episode, Paulus said in a video prepared for the journal...
The report indicates that the study was difficult since the normal tools of epidemiology do not apply. (One of the more difficult things to do - unless you're in Greenpeace and feel endowed by God by an intrinsic right to ignore things like "control groups" is to compare a population with no confounding factors like, say, exposure to gasoline.)
But studies using a case-crossover design, in which the patient acts as his or her own control, can eliminate many confounding factors, they noted.
A systematic review of the literature found 14 such studies investigating the cardiac effects of episodic physical activity, sexual activity, or both, Dahabreh and Paulus reported.
The primary outcomes were myocardial infarction in 10 studies, sudden cardiac death in three, and acute coronary syndrome in one.
The meta-analysis showed:
Episodic physical activity was associated with more than a threefold increase in the risk of heart attack. The relative risk was 3.45 with a 95% confidence interval from 2.33 to 5.13.
By the same token, episodic sexual activity was associated with a relative risk of heart attack 2.70 with a 95% confidence interval from 1.48 to 4.91.
Episodic physical activity was associated with nearly a five-fold increase in the risk of sudden cardiac death. The relative risk was 4.98 with a 95% confidence interval from 1.47 to 16.91...
...The researchers also estimated that the absolute risk increase for MI associated with an hour of additional physical or sexual activity every week was two to three per 10,000 person-years. For sudden cardiac death the corresponding figure was one per 10,000 person-years.
Dahabreh and Paulus cautioned that the studies in their analysis had significant differences in design and protocols.
They also cautioned that the findings should not be interpreted "as indicating a net harm of physical or sexual activity."
Instead, they concluded, the results suggest that such exposures are associated with a "temporary short-term increase in the risk of acute cardiac events."
One hesitates, of course, to discuss this matter, given the public's spectacular misapprehension of risk.
If you're out of shape, start slowly and work your way up, doing the work consistently and constantly is what I guess would be better than "sporadic."
I'd love to stay and chat, but I have to go discuss with a loved one the dangers of "sporatic."