Strength training in your fifties is highly recommended to support better aging.
It is important to recognize that strength is relative and not an absolute number. Too much pressure is put on lifting 315, or 405 or whatever. It does not matter.
The philosophy should be:
Can you lift a little bit more today than you could two days ago?
MARK LOWE - STRENGTH COACH
The term "Stronger" is relative and unique to each and every one of us. If you are gaining muscle mass, or training yourself to maximize the muscle mass you have then you, by definition, are stronger.
This doesn't happen by accident or in a slap-dash way. To work, it needs to be trained in a systemic way regardless of age and gender.