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The new interval strategy

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Employ the 85 percent rule.

Movement sparks progress. For high performers, this forward momentum is powered by currents in science, technology, and subculture. To celebrate the launch of the INNOVATION IN MOTION Collection, Furthermore and ASICS have partnered to harness the power of these currents and show you how to channel them into actual results.

Interval training is having a long-lasting moment, but athletes are starting to recognize that hitting their max isn’t necessarily the best strategy.

“I think people go all-out when they’re slightly lacking confidence or patience in the process, trying to force progression,” says Michael Olzinski, a Precision Run coach at Equinox locations in San Francisco. Max-effort intervals can over-stress the muscles, ligaments, tendons, and joints and require more recovery time between sessions—time that, he notes, most people don’t take, which only adds to their injury risk.

Plus, at 100 percent, “technique and form go out the window,” says Rob McCabe, Tier X manager at Kensington in London.

Those are just some of the reasons sub-max speedwork is gaining popularity among high-level coaches and runners. Their new strategy: hitting 85 percent instead of 100, which allows people to practice intelligent running, says Diana Katsikaris, a Precision Run instructor at Equinox Chestnut Hill in Boston. “By scaling back slightly, you can ultimately improve your speed and speed maintenance over time.” To log your best intervals, you’ll also need a shoe that provides high-energy return and shock absorption, like the ASICS GEL-NIMBUS® 21 from the INNOVATION IN MOTION Collection.

Calculating your 85 percent

Think about it in terms of your hardest effort for a given distance or time. Since you’ll run at different paces in a 30-second interval and in a 5K, this means your 85 percent will change depending on your goals or interval length.

McCabe recommends first finding your 100 percent with a time trial, then doing some math. For example, to find your 85 percent speed for one-minute treadmill intervals, find the fastest mph pace you can hold for that period and multiply it by 0.85. For mile intervals, find your best in mph for that distance and do the same equation. (So if you can hang onto 10 mph for a full mile, your 85 percent is 8.5 mph.) Katsikaris recommends increasing your recovery speed or reevaluating your 100 percent max every month to progress.

To build an aerobic base (important for endurance athletes), use a one-to-one work-to-rest ratio, McCabe says. For anaerobic power (crucial for short bursts of energy, like sprints and heavy lifts), shorten your work periods (thus reaching a faster pace) and lengthen your rest period. Recoveries should be active but easy enough that you can fully catch your breath before the next interval.

Remember, speed, incline, and work-to-rest ratios all affect intensity. When you manipulate these three variables, the 85 percent calculation isn’t as straightforward. Katsikaris developed a 25-minute interval run (captured in the video below) that will help you get faster, perfect your form, and stay injury-free—all without reaching your 100 percent. Throughout the workout, you’ll run at speeds as fast as 0.2 mph below your one-minute best and up eight-percent incline hills.

“I love the ever-changing pace of the routine,” she says. “It keeps your body guessing and challenges you in a short block of time.”

The workout

In this session, you’ll work at different inclines and speeds for multiple benefits. Running at an 8 percent incline, for example, activates your posterior chain, Katsikaris says, important for proper posture.

How often you perform the routine depends on your goals. If you’re training for an endurance race like a marathon or triathlon, aim for twice a week. To simply add variability and cardio to your plan, once a week is enough to get the benefits.