Strength train at least three times a week for best results. Ultimately you can strength train every day if you really like it. The key is to get the proper rest for each individual muscle group in between. For instance, do your legs and chest one day and your back and arms the next day. You need 48 hours of rest for any body part you train. Most people, however, like to get everything done in one session, so three total-body strength sessions per week is a good solution.