Back in the day, when I was a young buck, lean and mean, I worked out with weights four days a week:
Monday, Tuesday, Thursday, Friday.
Monday and Thursday was chest, shoulders, triceps.
Tuesday and Friday was back, biceps, legs.
About two hours a day.
Always.
Why?
Glad you asked.
The body needs about 48 hours of rest between exercises targeting the same muscle groups. I first learned this from the guys at the gym I worked out with. We hit it pretty hard in those days and so Wednesday was a complete rest day.
Now, my regular workout schedule is more like Monday, chest and shoulders; Wednesday, back and arms; Friday, legs.
I mix it up sometimes just to keep things interesting. And core is always part of the equation.
There are other good ways to schedule workouts, too.
For my older clients who do strength training two days a week (the recommended minimum), we do a full-body circuit workout on Tuesdays and Thursdays. Both workouts target the same muscle groups, but we do different exercises to mix things up, and also to teach them different ways of working the same muscles.
So there ya go.
Two days a week is minimum; three is better.
Four or five days a week?
That’s fine, but I’d recommend making those other days strictly cardio, flexibility, and balance days.
You can do it!