interval training 
noun [mass noun]
Physical training consisting of alternating periods of high- and low-intensity activity.The other training a successful cross-country runner needs is long interval training....
- A typical day at the track includes a 10-15 minute jog, stretching and drills, pole vaulting for two hours, interval training, weight lifting, and some gymnastics training in the evening.
- Training should involve short distances/sprints, longer runs as well as interval training that will combine various distances and short rest periods.