Sprint intervals improve insulin sensitivity. In the youngsters, it improves their lipids, too. Sprint intervals also reduce postprandial lipemia (temporary elevation of blood triglycerides after a meal), and they improve the circulatory function of obese, sedentary women. Sprinting also boosts growth hormone.
Sprinting doesn’t just make you better at sprinting. Even though it’s wholly anaerobic, sprinting increases the oxidative (fat burning) potential of muscle and improves endurance capacity. It also improves the efficiency of muscle during exercise, so you can conserve more glycogen and rely on more fat, instead of using up the former right away (perfect for fat-burning beasts). Incorporating sprint training with jump training improves both speed and vertical leap in handball players better than jumping alone.
It’s even an effective way to improve agility and speed in young (11 and 12 year olds) kids. 10 and 20 meter runs are effective in making kids more athletic, because that’s exactly how they naturally play – by running around in short bursts! Play-restricted adults, take heed.