above the neck rule

A guideline for deciding whether to exercise when sick, which posits that if symptoms (like a runny nose, sneezing, or mild sore throat) are only "above the neck," light to moderate activity may be permissible, but "below the neck" symptoms (chest congestion, body aches, cough) indicate one should refrain from exercise to avoid worsening illness.

Definition source: English Wiktionary via Wiktextract