Try This 35-Minute HIIT Workout That's Gentle on Achy Knees

The health and fitness benefits of HIIT (aka high-intensity interval training) are well documented: In addition to improving your overall fitness, torching belly fat and building muscle mass, it also helps you maintain healthy blood pressure, cholesterol and insulin sensitivity.

But if you've suffered an injury, incorporating HIIT into your fitness regimen can be a challenge. With the help of American Council on Exercise-certified group fitness trainer Stephanie Thielen, we've assembled a high-octane workout that will increase your heart rate, burn some serious calories and tone you up all over — and it's safe for your knees!

The goal of any HIIT workout is to exercise at almost maximum effort, Thielen says. To start, perform each of the exercises in order. First, establish the movement for 15 seconds, then give it maximum speed and effort (but with precision and control) for 45 seconds and, finally, recover for 90 seconds.

"Be careful to move into the exercises slowly to start to be sure you're able to complete the them correctly and safely as you proceed," says chiropractor Jeffrey Ptak, owner of Ptak Chiropractic in Los Angeles. "And do things at your own pace. There is no exercise routine that fits all."

Follow along below with Heather Dorak, owner of Pilates Platinum in Los Angeles, but be sure to make adjustments as needed for your own fitness level. Stop if you notice pain or other issues within the first 15 seconds.

‌Read more:‌ 5 Common Myths About High-Intensity Interval Training (HIIT)

Before jumping into a HIIT routine, warming up is essential to prepare your muscles and prevent injury. For this workout, start with marching. You can add hand weights to increase the intensity slightly (otherwise go weight-free). Be sure to wear supportive shoes.

"Whenever bending the knees, point the bent knee toward the second toe to safeguard against future knee pain," says Michael Mills, Los Angeles-based personal trainer.

1. March in place, swinging your bent arms as you do so.
2. Move with precision and control at a moderately fast pace.
3. Perform this move for 90 seconds.

‌Read more:‌ 7 Reasons to Do Moderate Intensity Exercise More Often

The knee lift warm-up is similar to marching in place, but much bigger and a little slower.

1. Standing up straight, contract your abs and begin your knee lifts in place, imagining you are stepping up onto a stair.
2. Alternate legs as your bent arms move naturally.
3. Continue this, lengthening your breathing as you go, focusing on core strength, the control of your limbs and moving with precision and balance.
4. Perform this move for 90 seconds before moving to the next warm-up exercise.

‌Read more:‌ 10 Dynamic Warm-Up Exercises to Prime You for Your Workout

1. Stand with your knees slightly bent and feet shoulder-width apart while holding light weights (optional).
2. Tap your right heel out in front of you while raising your straight arms in the same direction (shoulder height, arms parallel to the floor). If you find yourself hunching over, don't raise your arms quite as high.
3. Repeat, alternating heels, for 90 seconds.

‌Read more:‌ 12 Easy Anytime Moves to Strengthen Your Feet and Ankles

1. Stand with your feet together and arms bent, holding hand weights if you prefer.
2. Engage your core and step your right foot out wide to the right side, then bring the left foot in to meet it.
3. As you step, raise your arms at the elbows in a reverse-fly motion.
4. Next, step your left foot out to the left, then bring your right foot in.
5. Repeat for a full 90 seconds at a rapid pace, maintaining core engagement throughout.

Starting your full HIIT routine with this exercise increases your heart rate and strengthens your quads, abdominals and upper body. To add intensity, hold a set of hand weights or a medicine ball during this exercise.

1. Starting with your feet hip-distance apart and your arms overhead, contract your abs and draw one knee up to your chest as you pull your elbows down.
2. Return your arms up overhead as you set the lifted foot down and switch sides.
3. Keep your core tight, and don't turn your feet or knees outward or inward as you move.

Thielen likes this exercise for "its ability to strengthen the lateral muscles of the hips, which can help keep the knees aligned and stable." You'll also work your obliques and deltoids.

1. Stand with feet together and arms down along your sides, palms facing your legs.
2. Engage your core with a very slight bend in the knees, then take both arms overhead until they touch above you.
3. At the same time, lift the left leg out to the left side. Alternate legs with each arm swing.
4. Contract your abs to prevent your hips and torso from swinging with your legs.

1. Stand with your arms fully extended in front of your chest.
2. Take two steps to the left, pulling your arms back with each step, and then take two steps with arm rows to the right.
3. Initiate any movement by contracting your abs and pulling through your inner thighs.

"Sustaining a partial squat helps to improve lower-body endurance and activates the entire lower body while keeping the hips and knees in pain-free range of motion," says Thielen. Feel free to add hand weights to amp up the intensity.

1. Stand with your feet together, knees slightly bent, torso tilted forward and arms down at your sides.
2. Open your arms and lift your elbows into a reverse fly and tap the left heel out at a 45-degree angle and bring it back.
3. Do the same with your right foot.

1. Start in a split stance — right foot forward and left foot back. Load about 80 percent of your body weight on the front leg with the front knee slightly bent.
2. Lean your torso forward (in line with your back leg) and extend your arms overhead. Your arms, head, torso and back leg should form a single line.
3. Draw your left knee up and into your chest as your hands come down to tap the knee.
4. Return your arms overhead and the left leg back.
5. Repeat for one full round before switching legs (it will take a total of four minutes to complete this exercise on both sides).

‌Read more:‌ 4-Minute Tabata-Inspired Fat-Blasting Workout

1. Stand with your feet together in front of an elevated surface, such as a step, bench or chair.
2. Contract your abs, bend your knees and place your hands on top of the step.
3. Walk your feet back into a high-plank position.
4. Walk the feet back and return to standing, raise your arms overhead and bring them down for one full rep.
5. If your knees can stand doing so, try hopping the feet back and forth, instead of walking them.

1. Stand with your feet hip-distance apart and arms bent at 90 degrees.
2. Leading with the right foot, march your feet out wide to the sides then back to the center, pumping your bent arms as you go.
3. Move with precision and control, especially as you go into full effort.
4. Do a full HIIT set leading with the right leg then repeat the round leading with the left leg.

1. Stand with your feet hip-width apart and your arms at your sides.
2. Bend at the waist and place your hands on the floor.
3. Walk your hands out until you are in a full plank before doing a push-up.
4. Walk your hands back to your feet, using your abdominal muscles to lift your hips up toward the ceiling.
5. Engage your back muscles to come back to standing.

‌Read more: ‌Why You Should Add Body-Weight HIIT Workouts to Your Routine

1. Stand with your feet wider than hip-width.
2. Keeping your feet planted, lean the torso to the right, bending your right knee into a partial side lunge and keeping your left leg straight.
3. At the same time, drive the left arm forward and the right arm back.
4. Shift your weight to the other side, coming into a partial side lunge on the left and straightening the right leg.
5. The right arm will drive forward as the left arm goes back.
6. Add hand weights, widen your stance more, deepen the lunge or push off from your straight leg to amp up the intensity.

1. Stand with your feet together and arms angled toward the left hip.
2. Moving with precision and control, circle your arms up and overhead from the left to the right as you take the left leg back and behind the right leg into a curtsy.
3. Reverse the windmill to the other side.

‌Read more: ‌HIIT for Beginners: 7 Tips to Jump-Start Your Workouts

1. Stand with your feet together and knees slightly bent.
2. Lean forward a bit with your weight evenly distributed across each foot from side to side.
3. Take your arms up overhead as you extend and lift the right leg back behind you.
4. Return the right foot to the floor and switch legs.
5. Keep your head and neck in line with your spine and your abs contracted to protect your lower back as you do this exercise.
6. To add intensity, hold a medicine ball or hand weights.

‌Read more:‌ 20 Best Body-Weight Exercises