Does sprinting repetitively increase speed?
Sprinting does help. Weight training can also help. Squats and box jumps not only improve speed, but power and vertical leap as well AND muscle endurance. Lunges also help. Stretch to increase flexibility. Lots of agilities. But I have found the absolute best way is to run hills. Start at the bottom and sprint to the top and walk back down. Continue to do this for a designated period of time. I have a 20 pound weight vest that I also use when running hills and doing vertical jump work outs. You might look into that.