Younger runners might get away with these imbalances, but gradually, older runners who don't do exercises to improve flexibility and to strengthen their shins are setting themselves up for injury. Alternate activities to achieve a well-rounded workout and avoid overusing particular body parts. For example, alternate running with swimming or bicycling. Give your body a chance to recover from a hard workout by doing an easy workout the next day. Seek advice from a sports medicine professional.
Many injuries arise from faulty technique.
Be sure your equipment is in good shape. Shoes should be replaced every 400 to 600 miles. Check your ego at the gym door. Don't sacrifice good form in trying to lift the same amount of weight you did at age 20. Use lighter weights with good technique.