Are 8-Minute Intervals Uniquely Effective?

I’ve just finished reading a new paper that’s easy to turn into a neon, attention-grabbing headline. But first, a quick reminder of several important points.

1. We know little about successful training programs except to say that Olympians and world-record-setters train a lot--100+ miles a week for the best distance runners. They also tend to have Alter-G treadmills, chiropractors, massage therapists, nutritionists, sports psychologists, and Nike-Adidas-XYZ sponsorship. This is great for them, but not so instructive for you, if you happen to have a job and time to run only 30 miles a week.

2. There are no secret workouts or training programs. All training programs contain the same limited tools, just as our number system contains only 10 numerals, 0 to 9.

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3. There are no bad workouts. All workouts are good. It’s the way you mix things together that’s important. I’d rather have 100 dollars than 001 dollars. Same numerals, different mix.

4. There have been few controlled experiments with workouts and training programs. That's why we don't know much about training except that Olympians train a lot.

This is a report on a new training experiment, and therefore it's immediately interesting. It comes from exercise physiologist Steve Seiler and colleagues in Norway. Seiler is a transplanted American who has devoted a fair amount of his time to studying the actual training programs of actual runners, cyclists, skiiers, rowers, and swimmers. Granted, he has mostly looked at world-class athletes, but at least he’s looking and comparing.

This time around, he looked beyond the best of the best. That's another reason to appreciate the new study. The subjects in the trial were fit but recreational cyclists. On average, they were about 40 years old, and cycling six hours a week. They had the type of VO2 max that, if they were runners, would put them around 1:28 for a half-marathon.

Seiler then randomized his 36 subjects to one of four training programs: 1, all slow training, five to six times a week; 2, twice-a-week intervals, 4 x 16 minutes with 3-minute rests; 3, twice-a-week intervals, 4 x 8 minutes with 2-minute rests; 4, twice-a-week intervals, 4 x 4 minutes with 2-minute rests. Groups 2-3-4 also did an additional two or three easy rides per week.

Importantly, each interval group was told to do each interval workout at 100 percent effort. That doesn’t mean they did each repeat as fast as they could. But they did each total session as fast as they could. The total minutes of repeats-riding per session were 64, 32, and 16.

Other controlled training experiments have tried to achieve “equivalent calorie burn” between workouts to eliminate total miles (calories burned) as a variable. Seiler took a different approach. You could say he aimed for “equivalent effort” since he asked all the interval riders to go at 100 percent for their interval workouts. I like his approach since the equivalent-calorie method puts a premium on easy, slow miles. The equivalent-effort method doesn't penalize people for training harder, which doesn't allow you to cover as many miles. Seiler is thinking outside the box. Good for him.

He thought the 4 x 4 group might turn out to be the “winners,” as other studies and recent emphasis on high-intensity training have made this a popular approach. He also thought the 4 x 16 group group might “win” as it seemed the closest to popular tempo or lactate threshold training runs.

Surprise. Neither came out on top. The 4 x 8 group produced the best results, by a significant margin. See the table below for key data.

* Range of session perceived exertion is 1 to 9

** Lactate measured in mmol/L of circulating blood

*** Time to exhaustion at 80 percent of peak power output

The table shows that the longer repeats produced a lower perceived exertion, lower heart rate, and lower lactate accumulation than the faster repeats. Just as you would expect. The big surprise was that the mid-range efforts, the 8-minute repeats, led to a much longer (better) performance test-ride. That's roughly equivalent to saying they should produce a faster race time.

Could the 8-minute repeats work for you? There's only one way to find out: Give them a try.