Drug use can cause the spread of diseases.

Yes, drug use can cause the spread of diseases, particularly drugs that involve injections. Drug users usually have sessions with other drug users and tend to use the same paraphernalia that the other is using. The most common disease in drug use is HIV or AIDS. This occurs when direct contact with an infected blood is transferred to another by means of injections. Drug users are at a high risk of contracting this disease and might also easily pass it to others through sexual intercourse. 

It’s a because it says during exercise so they are doing a athletic activity

Target heart rate is the answer