It’s essential for fitness instructors to know where their students are in terms of how their bodies are feeling before class begins. For starters, this helps instructors have a baseline for how far they’re able to challenge each student based on their individual limitations. Having this information upfront also allows instructors to come up with modifications that meet the needs of the ambitious students who are working through a mild injury or existing condition as the class progresses.

However, a class full of students with different needs can be challenging to lead. On one hand, you want to conduct a class that’s challenging for the students who are feeling good and ready to go. But you also want to be sure that the ones who need to be careful about overworking certain muscles or body parts don’t end up hurting themselves, too.

We asked a few seasoned fitness instructors for their best advice on modifying their workouts for injured students. Here’s what they had to say about how to assess an injury and provide alternate moves for an effective workout.

In order to keep the workout moving smoothly, evaluate each member before class gets started, and take time to speak with each attendee about the nature of their injury or limitation. “Ask the crew before class begins if anyone has any injury or range of motion issue in order to flag any athletes who might need some additional eyes,” says Rob Sulaver, founder and CEO of Bandana Training and founding trainer of Rumble Boxing. “Chat with them personally about their injury, walk them through appropriate regressions for the workout, and remind them that above all else, they must respect the signals they’re getting from their body.”

To make sure your students are being upfront about what’s bothering them, Daphnie Yang, certified personal trainer and creator of HIIT IT!, suggests doing this process individually to encourage honest responses. “I’ve found that when an instructor begins the class and yells out, ‘Does anyone have any injuries?’ many students won’t say anything,” she says. “Some will, but most won’t in order to not draw attention to themselves, or to not appear weak. It works better for me to go up to a student, shake their hand, introduce myself and then check in about injuries and pain in the body. I’ll always write down a quick note on my clipboard when they do, and let them know I’ll make modifications. ”

Maybe you had planned to go through an intensive upper body workout with your students — but more than one participant is dealing with a shoulder injury. Or you’ve got a high-intensity cardio routine to teach, but there’s a student that’s working with a problem ankle. You don’t need to rethink your entire workout, of course. But you do need to make note of the moves that injured participants will need modifications for. “When someone does have an injury, my brain works like a computer,” says Yang. “I quickly memorize their injury, and go over my mental checklist of the workout I have planned and make some quick notes on what needs to be adjusted. Every exercise we do in class has a modified version already, so it’s up to me, the instructor, to demonstrate it before the students perform it.”

So, you’ve established the places in your routine where you’ll need to make adjustments. Now, it’s time to figure out what those recommendations should look like. George Foreman III, fitness instructor and founder of Everybody Fights says to aim for modifications that still accomplish the goal of the move without putting stress on the injury. “When cueing a specific modification, first attempt a modification that is similar to the original movement pattern,” he says. “For instance, if the exercise is a jump squat, the modification would be an air squat, goblet squat, or maybe even a lunge. If the exercise is a deadlift or kettlebell swing, the modification might be a glute bridge.”

To get a step ahead of the modification process, Yang recommends being knowledgeable about the most frequent injuries, and having alternate moves ready to go before class starts. “The most common injuries I hear of are knee issues, wrist pain, shoulder issues and ankle injuries,” she says. “For knee issues, I make sure all my students are performing squats and lunges properly with the knees never extending past the toes. This keeps the exercise in the muscle versus the joints. I also have students with knee issues do modified versions of some of our jumping exercises.  I’ll either take out the jump or have them limit their range of motion.” For wrist issues, Yang recommends that students use their forearms when performing plank exercises, and their knuckles or fingertips for burpees. “For students with shoulder issues I’m careful with push ups,” she says, “making sure students perform them correctly with their shoulders locked down and back to get the push up into their chest muscles and out of their shoulders — or have them hold a plank on their hands and eliminate the push up completely for burpees.” To minimize impact, Yang suggests students dealing with ankle issues do single leg lateral exercises without jumping from side to side.