Background of Interval Training
The American Council of Sports Medicine recommends a healthy adult should strive to perform 150 minutes of moderate-intense cardiorespiratory exercise training a week, to maintain a healthy lifestyle. The only problem is, one of the most common reasons why people avoid exercise is they feel they don’t have enough time. During any busy week, who wants to spend two and a half hours on an elliptical staring at a monitor that’s only entertainment value seems to be stacking little yellow dots. What if instead, you could get the same benefits from three 10 minute sessions a week?
Sprint interval training (SIT), or the more popular high intensity interval training (HIIT) are modalities of cardiorespiratory exercise that have been growing in popularity over the last decade. These two methods involve repeating multiple short burst of exercise at a high intensity with rest in between bouts. This form of exercise is considerably different than what we think of as traditional methods of cardio. In the movie Rocky, we see Sylvester Stallone running through the streets of Philadelphia, not performing sprints on a Concept2 rower. So was this prized fighter wasting his time?
If we’re following the principle of specificity, then yes. Rocky would have been better off repeating 12 three minute sprints with one minute rest between rounds, because that would best simulate the work to rest ratio of the fight he was preparing for. But we’re not all Rocky Balboa. What if we are actually looking to get better at endurance running? Well, interval training has a lot to offer!
Increase Aerobic Performance
In a study by Burgomaster et al. (2005) sprint interval training was assessed for its effects on endurance capacity. Before training, the subjects completed a cycle endurance capacity test in which the group on average were able to ride for 26 minutes before reaching fatigue and failing to maintain the necessary cadence. Then they completed three workouts a week (Monday, Wednesday, and Friday) for two weeks. The training sessions included repeating six all out :30 second sprints with four minutes of rest between tests. For my math people out there, that’s nine minutes of intensive exercise a week (141 minutes less than what’s recommended from the ACSM). After the six training sessions were completed, the group's average endurance capacity was 51 minutes! After just 18 minutes of sprint intervals these subjects doubled their endurance capacity!
Doubled Endurance Capacity in 6 workouts!
A year later Gibala et al. (2006) repeated the study comparing the interval group to one that performed 90-120 minutes of continuous steady state cardio three times a week. Although the interval group’s training volume was 10% of the endurance group, and their time commitment was 8 hours less over two weeks, there was no difference between their post training results. Both groups improved the same amount!
At first sight that example might be extremely appealing! Only nine minutes of work and you double your endurance capacity. Well when you factor in the warm ups, rest periods, and cool downs, each training session would take roughly 25 minutes. That adds up to 75 minutes a week, which is still considerably less that the 150 minutes ACSM recommends, but not the 30 minutes I promised you.
Well since the Burgomaster et al. study came out, research of interval training has continued to grow in popularity and scientists have strived to push the limits and find out just how little you can exercise to receive the same benefits as you would from traditional endurance training. In 2014 Gillen et al. published a study in which their interval format consisted of three all out :20 second sprints with two minutes of rest between tests. Including a two minute warm-up and a three minute cool-down, this became know as the ten minute protocol, as the entire training session wouldn’t take more than ten minutes. The interval group trained three times a week for six weeks. This very low volume training routine resulted in a 12% increase in VO2 peak, a 14% increase in maximal workload, reduced mean arterial pressure, and improved skeletal muscle oxidative capacity. All of these improvements came from 1 minute of intense exercise three times per week!
Improvements After 1 Minute 3x a Week!
Burn More Fat
As an added bonus, interval training has also been shown to be significantly more effective at burning fat when compared to long slow endurance. Trapp et al. (2008) compared performing 8 second sprints with 12 seconds rest for a maximum of 20 minutes against performing 40 minutes of steady state training. Both groups trained three times a week for 15 weeks. The interval group not only increased their VO2 peak by more than the steady state endurance group, but they also lost five and a half pounds of fat mass, while the endurance group actually gained a pound of fat!
Interval training has a lot to offer whether you’re looking to get faster, improve your endurance, lose fat, improve your cardiorespiratory health, or just squeeze in a workout during your busy day. There are plenty of variations out there, with one of the most popular being “Tabata”, popularized by Dr. Izumi Tabata in his 1996 study involving Olympic speed skaters. Most any interval format and method of cardio (run, bike, swim, row) will work as long as you remember the key principles. Alternate short periods of near maximal/maximal sprints with less intense recovery periods. Generally, longer rest will be needed to maintain maximal intensity and workouts should not last longer than 30 minutes. For examples of formats mentioned in this paper, see the table below. Happy sprinting!