The higher metabolic rate that results from an increase in lean muscle mass can help the dieting individual. Fat just sits there, but muscle burns energy to sustain itself. Strength training also improves self confidence, self image and might even make you look a bit better at the beach. Long distance runners have primarily aerobic slow twitch fibers that do not enlarge as do the Fast Twitch muscles found in most body builders and in sprinters. This training is a requirement to compete at a high level.
Runners frequently develop muscle imbalances that lead to pain.
The runner with low back pain may benefit from strengthening of the abdominal muscles, lower back muscles and stretching of the hamstrings. Posture is an important component for both optimal running performance and elimination of pain. Strength training can help with this. A variety of knee and hip problems can also be helped by strength training. Imbalances between the Quadriceps and Hamstrings can be corrected by strength training.