For anyone living above the equator, running presents challenges right now. When the sun rises after you wake up and sets before you eat dinner, it can be hard to resist the call of your bed or couch. In chillier areas, snow and ice can be mental and physical obstacles.

When running outside is unsafe or uncomfortable, many of us hop on the treadmill, but experienced athletes don’t consider it the only indoor option, says exercise physiologist and sports dietitian Marni Sumbal. “Cross-training helps reduce risk of injury but also helps prevent burnout, promotes recovery, and helps you maintain your running fitness,” she says.

What’s more, new research has found that certain types of cardio cross-training can make you a faster runner. Swap out some easy miles or simply add one of these activities to your normal routine to get stronger and speedier by spring.

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Cycling/Spinning

A 2015 study found that doing two weeks of three high-intensity interval sessions on a stationary bike helped runners improve 3K time trial speed by about 3 percent. The workout amps up your aerobic metabolism—your body’s ability to extract energy from carbs—which translates to faster paces. High-intensity running intervals work the same way, but cycling “reduces the amount of joint stress placed on the ankles, knees, and hips,” says study coauthor Rodrigo Aspe.

The Workout: Pedal at an easy speed for three minutes to warm up. Then, increase the resistance until you feel like you’re climbing a hill that, if it were any steeper, you’d need to stand. Pedal as fast as you can for 10 seconds, then drop to a gentle spin. Your rest period can last from 30 seconds (to build endurance) to 80 seconds (to build speed). “Athletes who want to train for power need a longer rest period to ensure they can repeat at their maximum effort,” Aspe says. Do six reps total.

Water-Running

If you associate pool-based cardio with being injured (or retired), think again. Organizations like the New York Road Runners are offering deep-water running programs for athletes of all ages, hurt and healthy. Studies show that running on a treadmill and running in deep water can have similar effects on heart rate and energy expenditure, with the latter activity providing a break from impact forces. And because water is 800 times denser than air, you’ll work opposing muscles more than you would on land, says Ellen Nordberg, a water-running instructor in Colorado.

The Workout: You can adapt any hard workout to the pool. For example, on land you might do eight 800-meter repeats that take four minutes each with a 400-meter recovery. In the pool, try eight four-minute hard-effort repeats with two-minute recoveries. Use a buoyancy belt and keep your body vertical as if you were running on land.

Drills/Plyometrics

A study in The Journal of Strength and Conditioning Research found that six weeks of plyometric training—explosive moves like box jumps and jump squats—helped runners improve time-trial speed by almost 4 percent. They also beat the control group in endurance and strength gains. “The goal of plyometrics is to help you activate the motor patterns used in the motion of running quicker than what you can accomplish in general cardio training,” says Sumbal. “This helps you turn over your legs more quickly and push off the ground with more force.”

The Workout: First, you need to get your muscles warm and limber to absorb the force of these high-impact moves. To do that, start with dynamic drills like hip circles, walking lunges, butt kicks, monster walks, and leg swings—do 10 of each. Then, complete two to four sets of this circuit: toe taps on a step (jump quickly from one foot to the other), hop overs (hop laterally over a low step with feet together), jumps with medicine ball (hop forward as far as you can, holding the ball above your head), squat jumps, and single-leg hops (forward on one leg, then switch). Do each move for 20 seconds before moving to the next; rest for two minutes between sets.