Activities that involve jumping can also be uncomfortable and painful for people for a wide variety of reasons. Anything from knee or foot pain to past spinal cord injuries or gender dysphoria can make jumping an inaccessible experience. So if your instructor has your class skipping rope or doing jumping jacks, feel free to experiment with what feels best for your body: bouncing up and down on the balls of your feet might be helpful if you’re avoiding impact due to a spinal cord injury, but it might hurt worse if you have plantar fasciitis. It also depends on your goals: are you trying to build your calves or cardiovascular system with jumping? If it’s about getting your heart rate up, then grab a sandbag, kettlebell, or dumbbell, set your feet about hip-width apart, and do some kettlebell (or sandbag or dumbbell) swings. Just make sure you’re keeping good kettlebell swing form. You should be breathing, keeping a neutral back, maintaining soft elbows, and initiating movement with your hips as you send the bell back behind you (between your legs) and — again, leading with your hips — exploding the weight up to about your eye level and back down again. No impact, but it’ll get your heart rate up quite nicely.

If you’ve rolled your ankle in the past, or if your knees aren’t quite what they used to be — or if, like me, your knees hate sudden starts and stops in unpredictable directions — then you might get nervous when your instructor announces skating-type movements that require hopping from side to side. If the lateral aspect of the movement doesn’t feel right, feel free to keep the movement more stable: lateral movements are wonderful for increasing long-term stability, but if they’re causing you current pain or making you nervous, you can hop back and forth or up and down instead of side-to-side for motions that your knees and ankles will be more used to. If that’s too high-impact, that’s alright! Lunges or reverse lunges (essentially, lunges while you’re standing in one place) can wake your legs and heart rate up without giving your body that lateral instability.

When your instructor tells everyone to lunge or squat, know that your knees are not alone in getting scared! Know also that squatting to depth is actually good for pained knees, because the rest of your lower body (your hamstrings and inner groin muscles) pitch in to get you back up instead of just shearing at your knee itself. That assistance won’t kick in unless you get low enough into the squat. But, if you can’t or don’t want to get into that low of a squat, that’s more than okay: if your group fitness room has a rower or cycle, these low-impact activities can fire up your quads while keeping the pressure off the stabilizer muscles you need to squat and lunge. You can also do these movements while holding onto TRX handles if they’re available, which will help you increase your range of motion and your confidence. If your room has none of that, or if you’re not comfortable asking for it, you’re still okay: do your squats against a wall, stand with your heels elevated on a weight plate, or simply widen your stance to get the most out of the movement with the least bodily stress.

Sometimes, instructors will have you get on the ground and then back up: think burpees, Turkish getups, or squats. That vertical change can be disorienting and even dangerous for people who experience vertigo, who have high blood pressure, who are new to exercise, or who are recovering from a cold or flu. So, pick a part of the movement and stick to it! If you’re asked to do a burpee, for example, stick to the parts you can complete on the ground (pushup, squat thrust, and plank), or stick to the parts you can complete standing up (jump or jumping jack). Break the complex movement into little pieces that don’t require your head to be changing elevation so rapidly, and you’ve got this.

If you have any shoulder impingements, or even if you slept weirdly last night, movements that bring your arms out to the sides — like jumping jacks, any kinds of chops, or any kinds of lateral arm circles — might twinge in your shoulder. You can modify these movements by thinking about the purpose of the exercise. With chops, for example, the goal is promoting core stability: so getting on the ground to do some v-holds or planks can help you out. With jumping jacks, you’re trying to elevate your heart rate: instead of engaging your shoulders laterally, pretend you’re jumping rope so you can keep your shoulders near your body. Lateral arm circles are meant to wake up your shoulders, but you can always wake them by shrugging in circles, first forward, then backward. It’s a more subtle movement, but it’ll do the trick!

If you have any history of shoulder pain or injury, you always want to be careful of any exercises that require you to reach, lift, or pull in a vertical direction (e.g., above your head). Customize these movements by changing assisted pull-ups, for example, to inverted rows (in other words, changing it from a vertical pull to a horizontal pull). Similarly, if you’re pressing dumbbells up into a shoulder/overhead press, grab a bench or a mat and press them out into a bench press instead (again, from a vertical push to a horizontal push). These customizations have the added benefit of rehabilitating your shoulder: I’ve torn my left shoulder rock climbing over and over again, and horizontal pulling exercises (and eventually, horizontal pushing exercises) were my best friends during rehab!

Your instructor is telling everyone to do a pushup, but your body doesn’t like those. Or everyone is squatting but that’s not what your body needs right now. Find similar movements that feel right to your body. With pushups, you can keep your knees on the ground, but you can also push up while leaning on an inclined surface (a wall, a bench, etc.). As long as you keep your core tight and your hips in line with your shoulders, this will activate the same muscles as other kinds of pushups. Similarly, using a wall (perhaps with a Swiss ball between your back and the wall) or TRX bands to help with your squat is a badass way to get low.

And here I’ve reached my own least favorite part of group fitness classes: timed activities, or working in stations. As a powerlifter, this timed aspect, often borrowed from CrossFit, can be fun once in a while, but it never fails to make me feel like the least fit person in the room. That can be so demoralizing! But, the best way to customize timed activities is to rest as often as you need to, clock on the wall be damned. If you’d like to and can, keep your body moving while you rest: walk in place or cycle slower or row less intensely, whatever the case may be. There has been many a time when, working out with personal training colleagues, I’ve had to stay in a plank, on my knees, while they were all still cranking out weighted pushups. The more I rested like this, the more I learned that my workout was about me and my body, no one else’s. It’s the hardest lesson of group fitness to learn, but the most valuable: because, each workout, I got better. And that personal achievement was the best feeling of all.