Azevedo et al. 2015, Running drills in an interval training program

Journal of Strength and Conditioning Research 29(7):1796-1802. Thirty recreational runners did 15 weeks of interval training; only the experimental group added running drills. Both groups improved comfortable and maximum speed, but the drills group gained no extra performance, and showed slightly higher impact-load (vertical impulse) parameters. The authors conclude that adding running drills to interval training was not an efficient way to improve mechanical-load or performance parameters. A small controlled trial, but a rare direct test of drills as a training addition. Limited.