HIIT (High Intensity Interval Training)–Less may be more…

“I felt amazing…It was one of those days on a bike you dream of.”

There’s one thing about cyclists; we like to recall memorable performances. It’s as if retelling—and I say re-telling because any good performance has no doubt been told at least once—jolts our feel-good centers. I bet it’s the same chemicals that get released when someone writes “good post.”

Another reason such shows of force are retold: because ‘good legs’ are so mysterious. They couldn’t hurt me today. What gives? Was it the bee pollen? The blue, not red, sports drink? My new coach? The new bike? No…it’s never the bike.

Now…we know what brings bad legs. Competing stress in life, not enough sleep and too much pizza and beer are common leg-sappers. Under-training and over-training are often cited as well.

But what of the dose of training?

How much causes the staleness of over-training and how little can be called under-training? And for that matter, what’s the right mix of intensity, distance and rest? Does the mind play a role? Recent research suggests the brain adds more watts than once thought. And to complicate the good-legs equation further, everyone knows humans respond differently to training.

Shoot, it would be tough to be a coach.

Recent research on the right dose of exercise only adds to the cloudiness of training formulas. As chronicled nicely by Gretchen Reynolds in the NYTimes today, High-Intensity Interval Training (HIIT) looks to be tinkering with cycling dogma. The same horse-hockey that says cyclists must wear knee-warmers to protect our synovial capsules from cold weather has held that getting fit in the early season means slogging around for hours at conversation pace. They call it building a base. I call it boring, and BS. All of it. Non-evidence-based dogma in cycling is just as shaky as non-evidence-based stuff in Medicine.

It turns out that “lacerating” HIIT sessions seem to produce equal or better results than standard endurance training sessions. I have read (some of) the raw data from the physiology journals; the results are eye-opening.

First: The definition of HIIT: The original studies on HIIT called for subjects to do half-hour sessions with 4-6 30-second sprint efforts interspersed with 4 minutes easy. Here in Louisville, such efforts are called ‘pukers.’ As most people, including athletes, can’t tolerate pukers, the researchers modified the HIIT protocol to rotating 60 sec of  intense (but not lacerating) effort with 60 sec easy.

Second: The Results: Though preliminary and small, many studies from multiple centers have shown that subjects that do just 3 short HIIT sessions per week (90 minutes of total exercise) perform as well, or better than those who exercise up to 80% longer but at lesser intensity.

Third: HIIT appears useful in a wide range of patients: It’s not just cyclists that improve time-trial performance; diabetics achieve better sugar control; cardiac patients (post-stent and bypass) improve arterial function and quality of life scores and obese patients boost metabolism and lose fat.

Fourth: The believability of HIIT’s effect is bolstered by real biology. HIIT looks to have easily demonstrated effects at the cellular level. It greatly boosts a ‘master-regulator’ (PGC-1) of mitochondria growth. Having more PGC-1 is a good thing; as PGC-1 also improves muscle oxygen uptake, anti-oxidant defense, sugar uptake, resistance to age-related atrophy and yes, it even fosters anti-inflammatory pathways. At the muscle level, athletes will be happy to know HIIT helps muscles burn fat, use glycogen more efficiently and produce less lactate.

I have led with the good stuff. There are limitations on this research. The studies involve small numbers of subjects, who are often healthy and motivated. Also, the duration of HIIT sessions studied is weeks, not months or years. It’s therefore way too early to make far-reaching claims.

But that said, I can’t help but wonder why I feel so good on the road after doing only 30-60 minute trainer sessions all winter. Every year, the same thing happens: short intense sessions on the indoor bike seem to translate to having ‘good legs’ out there on the road.

Of course, the implications of HIIT reach farther than just toppling cycling dogma—though it’s always cool to see dogma overturned—or explaining why I have good legs each February.

From a public health standpoint, as the richness and modernization of society push us deeper into a health crisis, the discovery that effective exercise requires less of a time commitment is exciting.

Now put down that magazine, turn the fan on high, crank the tunes, prepare the mind and then…sweat!

JMM

Disclaimer:

Please note: Safely starting and maintaining an exercise program is like anything else in life; it’s best accomplished with heaping doses of common sense. Starting slow, warming-up, listening to your body, being mindful of joints and tendons and by all means, consulting with your doctor are just a few examples of such common sense.

References:

Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance JPhysiol 2006

Effects of different interval-training programs on cycling time-trial performance. Med Sci Sports Exerc. 1999 May;31(5):736-41.

How 1-Minute Intervals Can Improve Your Health. NY Times, 2012

Physiological adaptations to low-volume, high-intensity interval training in health and disease. J Physiol. 2012 Jan 30. [Epub ahead of print]–Amazingly complete list of references.