It is important to incorporate strength-based exercises into your weekly routine to help prevent muscle loss and even build new muscle. Strength-based exercises can help prevent heart disease, arthritis, and osteoporosis, and also reduce your risk of falling. Try incorporating body weight squats with a chair, wall pushups, and deadbugs, described below.
Body weight squat with a chair:
Stand with your feet hip-width apart directly in front of a chair. Keeping your chest upright, push your hips back and bend your knees to lower your body toward the chair. Either touch your bum to the chair or sit down on it. At the bottom of the squat, your upper body should be leaning forward only slightly. Pause, then push through your feet and squeeze your bum to return to start. During squats, keep your weight mostly distributed over you heels and mid-feet (you should be able to wiggle your toes throughout the entire movement). to prevent putting unwanted pressure on your knee joints.
Wall pushup:
Stand about 2 feet away from the wall (move closer to the wall to make the exercise easier) and put your hands against the wall at shoulder height and shoulder-width apart. Keeping your body in a straight line, bend your elbows diagonally to your sides to lower your chest to the wall. Let your heels come off of the floor. Pause, then slowly press through your hands to straighten your elbows and return to start.
Deadbug:
Lie flat on your back with your arms and legs up in the air and your knees bent. Maintaining contact between your lower back and the floor, lower one leg until your heel just about touches the floor while also lowering the opposite arm toward the floor above your head. Lift them back up to return to start and repeat on the opposite side. You can make this exercise harder by keeping your legs straight rather than bent.
References
Strength and Power Training for Older Adults. (2019). Harvard Health Publishing. https://www.health.harvard.edu/exercise-and-fitness/strength-and-power-training-for-older-adults
Fetters, K.A. & Esposito, L. (2020, September 30). . U.S. News. https://health.usnews.com/health-news/health-wellness/articles/best-equipment-free-strength-exercises-for-older-adults