There has been a lot of commotion lately about interval training. Once the training secret of the world’s best runners, interval training has become the new buzz term in the fitness industry. It seems as if everyone is doing it, from competitive athletes to grandma next door.
Interval training originated in the 1930s by coach Waldemar Gerschler and physiologist Hans Reindell of Germany’s Freiburg University to develop fitness in runners. That’s right—this activity that has the fitness industry buzzing all started with running. Gerschler and Reindell focused their attention on its cardiovascular aspects and believed that the stimulus for cardiovascular improvement occurs during the recovery intervals between work periods rather than during the periods of activity, as the heart rate decreases from an elevated value. Thus, the emphasis of the workout was placed on the recovery interval, prompting Gerschler and Reindell to call it an “interval workout” or “interval training.”
Gerschler and Reindell’s original interval training method consisted of running periods ranging from 30 to 70 seconds at an intensity that elevated the heart rate to 170 to 180 beats per minute, followed by sufficient recovery to allow the heart rate to decrease to 120 beats per minute, signifying the readiness to perform the next work period.
During the recovery interval, the heart rate declines at a proportionally greater rate than the return of blood to the heart, resulting in a brief increase in stroke volume (the amount of blood the heart pumps with each beat). The increase in stroke volume places an overload on the heart, which makes the heart stronger. Since stroke volume peaks during the recovery interval, and because there are many recovery intervals during an interval workout, stroke volume peaks many times, providing a stimulus for improving maximum stroke volume and thus the capacity of the oxygen transport system.
Also during the recovery intervals, a significant portion of the muscular stores of quick energy—adenosine triphosphate (ATP) and creatine phosphate (CP)—that were depleted during the preceding work period is replenished via the aerobic system. During each work period that follows a recovery interval, the replenished ATP and CP will again be available as an energy source.
In the late 1940s and early 1950s, interval training was brought into the global spotlight by distance runner Emil Zatopek of Czechoslovakia, the only runner to win the 5,000 meters, 10,000 meters, and marathon in the same Olympics. Also during that time, Hungarian coach Mihaly Igloi developed the concept of sets of short distances run quickly to permit a greater total training stimulus. His coaching centered on large amounts of interval training, believing that a large amount of speed training also built stamina. This opinion was echoed by Zatopek himself in response to those who told him he was spending too much time training with short distances: “…but if I run 100 meters twenty times, that is two kilometers and that is no longer a sprint.”
It wasn’t until the 1960s that famous Swedish physiologist Per-Olaf Åstrand discovered, using a stationary bicycle in a laboratory, what Coach Igloi, Zatopek, and many other coaches and runners already knew—by breaking up a set amount of work into smaller segments with recovery intervals, you can perform a greater volume of work at a higher intensity. For example, you can run 5 x 1,000 meters faster than you can run 5,000 meters; you can run 10 x 500 meters faster than you can run 5 x 1,000 meters; and you can run 20 x 250 meters faster than you can run 10 x 500 meters. Sounds obvious, but Åstrand’s simple observation is important when designing workouts at specific intensities to achieve specific results.
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