Ever looked at a trainer's body and thought, I wonder what they do? We wanted answers, so we asked one of our favorite trainers—certified strength and conditioning specialist Tony Gentilcore, founder of CORE training in Boston—to dish on his exact gym routine when he's pressed for time.

I'm a strength guy and like helping get people strong. There’s a lot to be said for training for strength: You build a more resilient body, that body is less likely to break down over time, and you're harder to kill if the zombie apocalypse ever goes down. (The Slim, Sexy, Strong Workout DVD is the fast, flexible workout you've been waiting for!)

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More specifically, I’m a huge believer in hitting a "big" main lift of the day. By that, I mean something that trains the entire body, involves multiple joints and muscle groups, and allows you to burn a ton of calories in a short amount of time. And I like to go heavy. (Good thing, too—a new study published in Frontiers in Physiology found that folks who trained with heavier loads saw a nice bump in muscle size, sure, but also a significantly greater increase in their muscle strength.)

I generally stick to deadlifts or squats, since they hit all those criteria. When I have only a half hour to work with, I'll spend the first half trying to work up to a challenging set of three or five reps.

Bored of ordinary deadlifts? Try these 9 deadlift variations to tone your butt:

preview for 9 Deadlift Variations To Tone Your Butt

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Here’s how that looks:

Let's say I chose to work up to five reps of deadlifts. I'll do however many sets it takes to hit a five-rep max for that specific day. I call it an Estimated Daily Max (EDM) set—I like this approach because it takes into account how I feel on any given day. Some days I feel like a rock star and can be aggressive with the amount of resistance I choose. Other days, not so much and I’ll pick up something a tad lighter. The key is to never go easy, though—whatever weight you select should feel like the absolute maximum load you could possibly handle for five reps that day.

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Once I’ve hit those five reps, I'll knock off 5 percent from the load, then perform another set of five reps with that weight. On the next set, I'll subtract 10 to 15 percent off the original load (or another 5 to 10 percent off the most recent load), and perform a set to one rep shy of failure (that’s when my muscles literally can’t eke out another rep). This allows me to get some additional volume (a.k.a. reps) in, all using the same killer movement pattern.

With the remaining time, I'll set a timer for 15 minutes and perform a full-body circuit. My go-to looks something like this: goblet squat(five reps), pushup (five reps), kettlebell swing (10 reps), TRX row (10 reps), farmer carry (25 yards). I’ll go through the circuit as many times as I can in 15 minutes, with as little rest as possible. When I’m feeling extra-competitive, I’ll record how many rounds I knocked out and try to beat it the next time around. That way I’m always pushing myself... and always improving.