Most all top sprinters squat. Including Bulgarian squats, step-ups and other one legged versions, and with heavy weight. Most all track & field athletics also. Any of their weight programs include heavy ham, lower back work and weighted ab . Ben Johnson was squatting around the 500lb range if I remember correctly, when in was on top of his game (juiced or not)..
Far as Bolt's 700lb squat goes, not likely. Though he may support a loaded bar off a PR...some will do that and take a slight break at the knees.
Back in the 50's the open secret of how the Russians (even the women) dominated so many Olympic events was weight training. American coaches use to think that would cause an athletic to become muscle bound so no such training for them. Those injected sports "vitamin's" given by Russian doctor was maybe the really "big secret", along with weight training, for the Russian athletes.. Funny how the women Russian athletes would grow facial hair, take on masculine qualities and develop a deep voice with these "vitamin" injections.