The phrase "avoid strenuous" is correct and usable in written English.
It can be used when advising someone to refrain from engaging in physically demanding activities.
Example: "If you have a heart condition, it's important to avoid strenuous exercise."
Alternatives: "steer clear of intense" or "refrain from vigorous".
Toronto's mayor, Mel Lastman, urged the public to stay calm, stay home and avoid strenuous activities.
Do not bend over, and avoid strenuous activity and heavy lifting for a few hours.
He has no patience with health clubs where the client is constantly warned to avoid strenuous exertion.
Her doctor told her to avoid strenuous activity for at least a week afterward, according to a statement sent by U.S. Figure Skating.
When a thick cloud of air pollution settled in over London last week, experts warned those with health problems to avoid strenuous exercise.
As they prepared to sink another tube, I said, "What's a first-stage smog alert?" "Avoid driving, avoid strenuous activity," Wells answered.
On high pollution days, the government recommends adults and children with respiratory problems such as asthma, adults with heart problems and older people should avoid strenuous exercise.
But Public Health England said it is only those with heart and lung conditions and old people who should avoid strenuous physical activity.
Such people "should avoid strenuous exercise outdoors, particularly around pollution hotspots such as busy roads", said Dr Keith Prowse, the charity's honorary medical adviser.
Those with lung and heart conditions have been told to avoid strenuous activity outdoors while people suffering symptoms of pollution – including sore eyes, coughs and sore throats – should cut down the amount they do outside, health experts said.
"When levels of air pollution are high, people with these conditions, or anyone else who finds themselves coughing or wheezing in times of high pollution, should avoid strenuous exercise outdoors, particularly around pollution hotspots such as busy roads.
