Three days a week of strength training

After 30, men lose 3–5% of muscle mass per decade if they don't actively train. By 75, an untrained man has lost 30%+ of the muscle he had at 30. Muscle mass is the single most reliable predictor of healthy aging.

The protocol

Day A: Squat 3×5, Bench Press 3×5, Bent-over Row 3×8, Romanian Deadlift 3×8, Plank 3×45 sec.

Day B: Deadlift 3×5, Overhead Press 3×5, Pull-up 3×8, Reverse Lunge 3×8, Hanging Knee Raise 3×10.

Three sessions per week. Add 2.5kg to a lift when last week's session was clean.