"Short bouts of very intense exercise improved muscle health and performance comparable to several weeks of traditional endurance training," says Martin Gibala, an associate professor in the department of kinesiology of McMaster.
The training program consisted of between four and seven 30-second bursts of "all out" cycling followed by four minutes of recovery three times a week for two weeks. Researchers found that endurance capacity in the sprint group increased on average from 26 minutes to 51 minutes, whereas the control group showed no change. The muscles of the trained group also showed a significant increase in citrate synthase, an enzyme that is indicative of the tissue's ability to utilize oxygen.
MY COMMENTS: This was published in 2005- pointing out a potential alternative to long slow miles- I would worry about injuries if you run the high intensity intervals. Remember the subjects here carried out their high intensity training on a bike- not a bad idea for runners runners to add 60 sec. uphill repeats on the bike regularly as a second workout. I've done that but not on a consistent basis. Something to consider for a runner as an alternative to a planned 30 minute easy run. The results shown here were demonstrated in just 2 weeks!