The warning applies to people with cardiovascular disease. The thing is, snow removal is a very stressful job. Physical efforts are accompanied by the effect of low temperatures on the body. This raises blood pressure and at the same time narrows the coronary arteries. This combination of circumstances is dangerous for cores. The stress on the heart when clearing snow can be even higher than when running fast.
Experts noted that even two minutes of active cleaning may be enough for the pulse to rise to the upper limit. People with minimal physical fitness are at risk the most.