hmm....hydraulic jacks help with jumping by adding their dice to jumping checks(based on Agility) But running 50 MPH I think is even beyond that.
I had made a guy in another thread for Prime Runners, and he had a modified strength of 13(16 in military armor-and he had qualities and genetech to help with this) with Satyr Legs(equivalent of raptor legs), and military armor with hydraulic jacks. His base move in combat was 37(if running), and he rolled a lot of dice to try to increase that...but I don't think it's 50 MPH. Keep in mind he was also a 800 BP character. Doing this at the start would be very, very, very difficult and said character would be a one trick pony of running and jumping. My fellow could roll his Agility(10), + Gymnastics(modified 6), plus Satyr Leg bonus(2 for gymnastics), and if he had the armor on, +6 more for Hydraulic Jacks, for a total of 24 dice for jumping tests. However, in the SR4 book, characters have a maximum jumping distance based on Agility, so for big jumps, Agility is the stat to tweak. For a running jump, the max distance one can do is Agilityx1.5, so a 10 agility can only hope to jump a max of 15 meters. This is amazingly far(45 feet), but not quite the manga-esque jumps one might think.
To run, a character makes a running + strength test, and each hit adds 2 meters to their run rate(which is measured per turn-not inititative pass, keep in mind, the full turn.)
Honestly? If you want to make a character go fast, get Inline Skates and some sort of rocket booster. I'm sure a clever rigger could rig one up.

If not the boosters(a little out there, I admit), Inline Skates would be a much better bet than plain running.