As an amateur long distance runner, a few days ago I sprinted on a track after a good warmup and after strides and one sprint already. Then at the second sprint I had a nasty hamstring strain (that keeps off running now, probably for two weeks at least). I wore cushioned shoes (kinvara 9). Do you think that sprinting with shoes other than spikes or light flats increases risk of injury do to the extra weight on the foot and the cushioning that takes away the barefoot feeling?