The study description: Sixteen young men performed six training sessions over two weeks. Eight subjects performed between four and six 30-second bursts of "all out" cycling separated by four minutes of recovery during each training session. The other eight subjects performed 90 to 120 minutes of continuous moderate-intensity cycling.
Total training time commitment, including recovery, was 2.5 hours in the sprint group, whereas the endurance group performed 10.5 hours of total exercise over two weeks. Both groups showed similar improvements in exercise performance and the muscles ability to resist fatigue.
8 subjects per group, 6 total treatment sessions. This is not exactly high-power research.