That kind of workout is excellent, but I would be reluctant to recommend sprinting as an activity unless the person has some experience and training in proper sprint mechanics/form. Most people who aren't trained athletes would be injured in no time if they went from doing nothing or little, to doing the workouts you describe 3x/week. Personally, I put fast running intervals into my training, but almost never go into an all out sprint ('fifth gear'), for this reason.
A safer way to train is to use mixed intervals relying on a variety of activities which can be done all-out with less chance of injury, like jumping rope, stationary bike, steep bike hill-climbs, running up/down stairs, various calisthenics. I do use running as an interval, but I find that tacking a 10-15 second speed-up and slow-down onto each end of 30 second fast running interval has kept me injury free.
Kevin Wilbanks, CSCS