question about allan wells training

Hi Youngy, do you use any tempo running workouts in your system, or do you find the circuits and speedball are good enough alternatives for that sort of work?

The reason I ask, is that I only have time to get to the track twice per week due to family/work commitments, but have a garage in which I work out. I have previously used a shortened, modified version of the system (no speedball, and only pressups, chinnies, alternate squat thrusts and squat jumps) which I got from this book:

http://www.amazon.com/Sprinting-Hurdling-Skills-Peter-Warden/dp/1852232994

which got me in great shape.

Due to lower limb injuries I am looking for conditioning routines which will give the same benefits of tempo, with less impact.

Thanks.