Fit to Play: Continuous or Interval Training?

  • Jim Johnson

Published: 12/5/2022 3:51:13 PM
Modified: 12/5/2022 3:50:51 PM

I clearly remember the first time I tried to run a mile as an adult. The night before, a group of my colleagues and I went to hear Ken Cooper talk about his new book, “Aerobics.” Cooper made such an inspirational presentation that most of us wanted to run home rather than drive, but I waited until the next afternoon. My neighbor and colleague, Roy, and I drove to the park and mapped out one mile. Roy and I were both in decent condition, playing tennis and badminton regularly. I also swam, but this was no preparation for a continuous mile run. The exhilaration soon ended as we lumbered around the park wondering when the mile would end.

Our approach to running a continuous mile should have been to use interval training, an exercise protocol involving repeated, relatively intense exercise interspersed with rest. While athletes and coaches had been using interval training for years, the first formal studies of interval training were not published until 1960, and were all conducted in Sweden.

The results of the Swedish studies were very clear; interspersing exercise with rest is easier than continuous exercise, especially if the exercise is more intense. Further, longer exercise intervals are more difficult than short duration. For example, a 60 second exercise followed by a 60 second rest is more difficult than a 30 second exercise, 30 second rest protocol.

Since most sports are interval in nature, it is common sense to train for most sports with interval protocols. A soccer game may last 90 minutes, and players often run about five miles or more, but the distance is comprised of intense running, jogging, walking, and standing. Naturally, training for soccer should be interval in nature. Sports such as swimming and track are just the opposite. Conditioning for these sports should involve interval and continuous training.

Many studies on interval training have been conducted, but one study conducted in Japan in 1996 by Izumi Tabata became of note. Tabata’s protocol involved 20 seconds of very intense exercise on a laboratory ergometer followed by 10 seconds of rest, repeated 8 times. The effects on aerobic power were equal to or better than one hour of moderate exercise. The Tabata protocol became attractive since it took only four minutes. Many trainers started advocating so-called Tabata workouts, labeled as high intensity interval training (HIIT).

Common HIIT workouts use the same 20-second exercise, 10-second rest, but have participants doing things like running in place or squat thrusts. A true Tabata protocol is more intense, grueling. On a personal note, I’ve used a HIIT protocol for cycling and rowing, but can’t think of anything more boring than running in place or doing squat thrusts. They may get you fit, but I daresay most people will find them tedious.

Interval training works, making difficult tasks easier. Similarly, working intervally reduces the toil of many tasks. As winter approaches, snow shoveling is a common and strenuous task. To reduce the effort, use the interval approach. Shovel for short intervals of about 30 seconds and rest. Don’t use a huge shovel and don’t fill it up. The interval approach to exercise and work allows you to get a lot done without undue stress.

Exercising continuously is a common goal for many exercisers, a goal that is in reach for most of us. Dr. George Sheehan, the well-known cardiologist, runner, and philosopher spoke eloquently about living at our best, to make the most of our abilities. “When I’m on the road I feel like a saint,” he said. Sheehan said we should tap into our animal side, to move as we were born to. I wondered about the animal side until one day when I took off on a run. It was chilly when I left the house, down Elm St, around Child’s park and back home. Running felt natural, effortless, unforced. As I lay on the porch recovering, water vapor rose from my body into the cold air. I had a vision of my old dog, Gus, running endlessly on the beach chasing seagulls. I said to myself, “I’m an animal.”

There’s something special about continuous exercise, a flow experience; these feelings are possible, but we need to develop the capacity to do this. One way is to interval train until you have acquired the adaptation necessary to run, cycle, swim, or row continuously. The effort is worth it.

Jim Johnson is a retired professor of exercise and sport science after teaching 52 years at Smith College and Washington University in St. Louis. He comments about sport, exercise, and sports medicine, and his column runs monthly. He can be reached at


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