Keeping your muscles strong in your 40s, 50s, and on is still absolutely possible. There are some things to consider that will keep your physique strong and healthy, such as injury prevention and physical limitations that change as you age. Training smart means you can keep pushing long past your 40s.
Cardiovascular Health

A simple test for checking your cardio health is to climb stairs. It should take around one and half minutes to climb four flights of stairs. If it takes more than that, you should consult a doctor to check your heart health more in depth.
Tendon and Ligament Health
Tendons and ligaments will gradually deteriorate over time. As you enter your 40s and 50s, your tendons are more likely than ever to become injured from trauma or overworking. A simple glucosamine supplement can help support your joints, tendons, and ligaments to keep everything moving smoothly. Turmeric and Omega-3s can help reduce joint pain without using anti-inflammatory medications.
Muscle Breakdown
As your body ages, your muscles and tendons lose elasticity which can contribute to injuries but can also contribute to a loss in muscle strength. Sarcopenia is a condition where strength, muscle mass, and stamina are decreased with age. To combat this condition, eat more protein. This can be found in eggs, lean meat, and beans. Keeping your strength training consistent will also help keep your muscles strong and healthy.
Work Up Slowly

There is no reason to go crazy hard immediately. You want to start at an easy level, work through it, rest, and work through the next level. It’s important that you feel comfortable with the level of difficulty before you move to the next level. This is essential to making safe gains, where you can eventually work up to the level you want to be at.
Keep Going
As you age, it will become more difficult to work back up to your younger physique. The best way to keep your physique is to keep moving and to keep working it. That doesn’t mean you need to max out or stretch for personal bests all the time, but keeping your body challenged will help keep it in shape and looking and feeling good.