Building & Maintaining Muscle: The most powerful tool to staying younger, stronger, sharp, and independent into your 70s, 80s, and beyond. Strength training and building strong muscles are critically important for longevity because they directly impact your physical health, metabolic function, mobility, and disease resistance as you age. Preserve Muscle Mass: After age 30, people lose muscle at a rate of 3–8% per decade. Strength training slows or reverses this, maintaining mobility and independence.