It was traditionally thought that endurance training that relied on aerobic activities was the best way to induce physiological adaptations necessary to improve endurance performance. More recently, numerous studies have shown that high intensity interval training (HIIT) can significantly improve both VO2 max and skeletal muscle mitochondrial enzyme production when a training program is carried out for as little as six weeks.
What is High Intensity Interval Training?
An enhanced version of interval training, HIIT involves completing at number of brief intervals close to VO2 max interspersed with recovery periods at low intensities. HIIT can be very physically demanding, as it involves exercising for short intervals of maximum intensity where the anaerobic system is pushed to its limit by reaching the lactate threshold. These intervals are combined with longer, lower-intensity intervals where the athlete can recover by using the aerobic system. Tabatha intervals are a particularly hardcore form of HIIT.
The Gibala/McGee Study
Research has shown that HIIT dramatically improves VO2 max and other exercise performance capabilities in athletes who rely on aerobic energy metabolism for their chosen sport. In addition, HIIT is shown to directly improve exercise performance in real situations, as shown in lab tests simulating bicycling races lasting from anywhere between 2 minutes to an hour.
VO2 max and other metabolic adaptations are induced faster than was originally believed with just a small amount of HIIT. In study conducted by Gibala and McGee, participants were able to double the amount of time they could exercise after just six HIIT sessions over two weeks; subjects were able to bicycle at 80% of their VO2 max (as calculated prior to beginning the study) for 51 minutes on average, up from 26 minutes.
The most significant point of the Gibala/McGee study was its use of a far smaller quantity of HIIT than in similar investigations. Subjects bicycled at “all out” effort using a braking force on an ergometer for 30 seconds, completing four to six intervals with a four-minute recovery between each interval.
How to Train with HIIT to Improve VO2 Max
For many athletes, it’s possible to improve VO2 max through HIIT training.
Active suggests some of the following interval training methods:
30/30 and 60/60 Intervals
Developed by the exercise physiologist Veronique Billat, 30/30 and 60/60 intervals are more widely used by amateur athletes, particularly runners. The athlete begins with a 10-minute warm up and then runs at maximum effort for 30 seconds. He or she then rests for another 30 seconds with a low intensity jog. It is recommended that the athlete start with no less than 12 intervals in his or her first session, increasing every session until reaching 20. When the athlete is ready, begin 60/60 intervals, starting with 6 intervals, increasing gradually to 10.
Hill intervals involve running up a gradient for a set period of time, and then jogging down as recovery. 2 to 3-minute intervals are considered most effective for VO2 max training. After a warm up, the athlete runs uphill for a predetermined time at “all out” effort, and then returns to the starting point using a gentle jog. This process is repeated up to 10 times using 2-minute intervals or 7 times with 3-minute intervals.
Lactate intervals are the hardest exercise for VO2 max improvement. These are only attempted by elite athletes who have already mastered the above two methods. After at least a 10-minute warm up, the athlete runs hard for a distance between 800 meters (two laps on a full size running track) to 1200 meters (three laps).
The athlete recovers with an easy jog of 400 meters (one lap). Athletes should begin with 800 meters, gradually increasing the length of the high-intensity interval. Each session should total around 5000 meters of high-intensity running, which is the equivalent of 6 to 7 intervals at 800 meters, 5 intervals at 1000 meters, or 4 intervals of 1200 meters.