Wednesday, 29 June, 2005

How effective is interval training?

I ran across an interesting Associated Press article aggregated on Yahoo today: Intense Interval Training Deemed Effective.  Researchers measured the strength and endurance of two groups of college students, all of whom were healthy and exercised regularly, but weren't really athletes.  One group did three 30-minute interval sessions per week for two weeks.  The other group did no specific training, but continued their normal activities, including basketball, jogging, or aerobics.

It's little surprise to learn that endurance and strength improved in the group that did the interval training.  They nearly doubled their endurance, although how endurance was measured was not specified.  That the control group showed no change also doesn't come as much of a surprise.

The surprising thing about this research is how shallow it is.  Athletes have known for years that focused interval training is a valuable part of an overall training schedule.  If you ever played football or ran track in high school, you probably remember your coach making you run sprints until you thought you were going to puke or pass out.  Working the body at high heart rates (above your lactate threshhold) for brief periods builds strength and increases your ability to use oxygen.  If the measure of endurance is how long you can operate at a high heart rate, then of course interval training will increase your endurance.

The article does state that interval training is not effective as a normal exercise regimen because it's difficult, painful, and doesn't burn enough calories.  Most people do not have the motivation to complete even one interval training session without a lot of encouragement from somebody else who's right there:  a coach or a workout partner.  Four to seven 30-second all-out efforts is hard.  Your lungs burn.  Your legs ache.  Your head spins.  After two or three intervals, you can't believe how long 30 seconds is.  Halfway through the workout you start thinking, "Why am I doing this?  Why should I put myself through such pain?"  Without somebody pushing, only the most highly motivated individuals will push through the pain and complete the interval workout at 100% effort.  I know.  I've done it.  Interval workouts are effective, but they're unbelievably painful.  A 30 minute interval workout in the morning will leave you tired for the rest of the day.

There are other disadvantages to interval training.  The most common problem that athletes experience is over training.  If one interval workout per week is good, wouldn't two or three be better?  All too many athletes--even advanced athletes--over do the interval training by not giving their bodies time to rest and rebuild.  They show improvement for the first few weeks--maybe a month--and then their performance levels off or falls.  The most common reaction then is to increase the intensity, until finally they injure themselves:  pull a muscle, develop a stress fracture, or just run their bodies down to the point that they have no energy.

Endurance cyclists--those who compete in 24-hour races, Paris-Brest-Paris, the Race Across America, and similar events--have tried replacing much of their aerobic conditioning with intervals, and have mostly failed.  Interval training is important for building strength and endurance at high heart rates, but a 30-minute interval workout cannot help with conditioning your back, neck, shoulders, forearms, wrists, butt, and feet for the rigors of spending all day in the saddle.  Believe me, I've tried it.  Although my legs and cardiovascular system were just fine after 100 miles the rest of my body was wiped out.  Interval training is a valuable addition to a training program, but certainly not a substitute for hours on the bike and the aerobic conditioning you need for all around health.