Ever had one of those days when your body is willing to work out, but your mind is not?

The reason doesn’t matter: It could be a stressful day at work, or a family matter that you can’t get out of your head. It could even be the “inertia” that comes from missing your previous training session. (Funny how that works.)

Yes, exercise could actually help with all those issues. But it can also add more complexity to an overly complex day.

When that happens, we offer this solution: simplicity.

Each of the four workouts that follow requires only one exercise. They’re fast but effective, and can help you get going—even when your mindset is working against you.

Try one: We think you’ll find it’s so simple that it’s hard not to do—no matter how your day is going.

Workout 1. Lethal lunges

Created by BJ Gaddour, C.S.C.S., Men’s Health Fitness Director.

How to do it: Perform 10 straight minutes of walking lunges. Pause when you need to, but keep rest minimal—the idea is to keep going back and forth between legs for the full 10 minutes.

Why it works: “Not only does this improve your basic level of aerobic conditioning,” says Gaddour, “But the repetitive motion also prepares you for running.” Speed your lunges up to hammer your heart rate, or slow them down to focus on building muscle.

Workout 2. The Iron 300

Created by Dan John, world-renowned strength coach and master kettlebell instructor for StrongFirst.

How to do it: Grab a kettlebell that’s challenging to use, but not too heavy. Do 300 kettlebell swings by starting at the number 300 and counting down to 1. Pause when you’re tired or your grip starts to break.

Why it works: “The swing is one of the best ways to combine high-intensity cardio with a brutal lower-body workout,” says John. It’s a perfect recipe for fat loss.

Workout 3. Brutal Bear Crawl Ladder

Created by BJ Gaddour, C.S.C.S., Men’s Health Fitness Director

How to do it: Get into a bear crawl position. Perform 30 seconds of crawls before resting for 30 seconds. That’s 1 round. Next, do 31 seconds of work and 29 seconds of rest. Repeat, adding 1 second of work and subtracting 1 second of rest with each round for 10 total rounds.

Why it works: “Increasing the amount of work as your muscles fatigue causes your body to turn on the afterburners—using fat for fuel,” explains Gaddour.

Workout 4. Stress-Relieving Slam

Created by Gideon Akande, winner of the 2015 Men’s Health Next Top Trainer—a competition to find the nation’s most skilled and inspiring trainer.

How to do it: Grab a medicine ball—if you don’t have access to one, a couch cushion works just as well. Perform 20 seconds of the overhead slam with as much power as you can muster. Rest for 10 seconds. That’s 1 round. Repeat for 8 total rounds for a heart-hammering 4-minute cycle. Perform multiple cycles for an 8-, 12-, or 16-minute workout.

Why it works: “The explosive movement will jack up your heart rate immediately,” explains Akande. “10 seconds of rest will give you just enough time to attack the next set without slowing down your calorie burn.”