As a kid, you could easily average seven hours a week playing tag or riding bikes—sans fitness trackers or weight-loss apps. You didn't roll your eyes when teachers called for recess. And you certainly weren't motivated by flatter abs or a firmer butt when you played in the backyard until dark with your friends. What you were motivated by: the sheer fun of it all.

Fast-forward to today, and chances are you've lost a bit of that loving feeling for physical activity. (Case in point: Fewer than half of American adults average even 150 minutes of aerobic exercise per week.) When the "it's a game!" aspect of movement is replaced by regimented fitness, a primary source of positive emotion about exercise is lost, says Kwame Brown, Ph.D., a professor of psychology at Hampton University.

Turning back the clock on your workouts can have some surprising benefits. "If you can learn to associate exercise with feelings of nostalgia, you're more likely to stick to a long-term fitness program," says Clay Routledge, Ph.D., an associate professor of psychology at North Dakota State University.

Take your young-adult-novel-obsessed colleague: Reading The Hunger Games series may not make her brighter or more scholarly, but she's probably reading more pages per week than most of her peers. That's because doing things that are fun can help boost incentive and frequency, which is key for developing a long-term habit. Use these five principles to integrate a more youthful approach to your fitness regimen—without feeling silly—and speed up your shape-up.

Go Back to Basics
If the only "crawl" you do these days is from pub to pub, it's time to put down that pint for a minute. "The fitness industry is taking a cue from the way children learn to move and using more crawling and rolling patterns in workouts," says trainer Mark Fisher, owner of Mark Fisher Fitness in New York City. It builds functional strength and helps increase hip and shoulder mobility, which many adults lack.

Time to Play! Add the bear crawl to your next warmup (or do it at home after a long day of sitting at your desk): Start on all fours, back flat and core tight, then raise your hips to lift your knees off the floor. Crawl forward for 30 to 60 seconds; rest 30 seconds, then repeat up to two times more. Mix things up by alternating giant mama-bear steps (which will help improve flexibility) with short, quick baby-bear steps (to build coordination).

Buddy Up
You ran around with pals when you were a kid, and there's good reason to keep that up: In one study, women who trained with a skilled partner increased their workout time by as much as 200 percent. Exercising with a partner makes you more accountable (you know she'll be pissed if you bail) and less likely to quit early (chatting about Ryan Gosling's current dating status is a helpful distraction). Plus, training with someone else increases the range of options you have to choose from, which can help keep your workouts interesting.

Time to Play! It may sound odd, but hoisting your partner can be a mega calorie burner. Turn her into a piece of equipment for this metabolic finisher at the end of your next workout: Have your partner get into a pushup position; stand behind her and grab her legs by the shins, then lift her feet off the ground, holding her legs on either side of your waist. Have her walk forward on her hands as quickly as possible for 30 seconds, with you following behind. Lower her feet and switch roles. That's one set. Do three total.

Take It Outside
Being stuck inside used to make you stir-crazy. Years later, you may feel the same way, but it's easy to just rely on your go-to gym routine (that elliptical with the built-in TV is always right where you left it). Training outside sans equipment can make your workouts more creative, fun, and fulfilling, says David Jack, performance coach and director of the Activ8 LAB in Phoenix. Not to mention that the change in terrain and wind resistance can give a little jolt to your overall calorie burn.

Time to Play! Find a friend and some open space, and try Jack's version of Mirror, Mirror: Face each other, standing two to three feet apart with an imaginary line separating you. For 30 to 60 seconds, your partner must act like your reflection, mimicking any movement you do. Your job: Move as quickly as possible, doing any exercise you can think of—lunges, jump squats, shuttles (running side to side)—to try to break her "reflection" or tire her out so she has to stop and rest. When time's up, rest at least 30 to 60 seconds, then switch roles. Complete three rounds. Best two out of three wins.

Zig and Zag
As kids, we zoomed all over the place, but most adult fitness routines occur in predictable, repetitive patterns. "The best way to improve overall functional fitness is to move in all three planes of motion, which includes side-to-side and rotational movements," says Fisher.

Time to Play! Inflate three balloons, then throw them as high into the air as possible. You'll need serious coordination and concentration, as well as ninja-like reflexes, to keep all three balloons off the ground for 60 seconds. Repeat three to five times for a heart-pumping warmup.

Bet to Win
Growing up, most of the games you played had a winner and a loser. That competition made you pick up the intensity without even realizing it, says Jack. Tap into that go-for-the-win mentality now. (Bragging rights not enough of an incentive? Place a friendly wager—say, the loser has to buy post-workout smoothies.)

Time to Play! Grab a friend to play Jack's "thigh tag." Stand facing each other, hands in front of your chest. When you say "go," each person tries to tap the other's upper legs. As if you were in a sword fight from Pirates of the Caribbean, jump, squat, and spin to avoid taps, or use your arms to block them (but you can't just keep your arms in front of your legs). The first to land 10 taps wins.

Lettermark
Cristina Goyanes

Cristina Goyanes is a seasoned writer, award-winning editor, and founder of ThisIsRevel.com, a brand editorial agency for companies dedicated to improving people's lives. She is a proud American-Latinx born in Queens, NY, currently living in the Bay Area with her partner and four bikes.