Mountain Climbers: Muscles Worked, Proper Form and Variations

The mountain climber is one of the few exercises that costs nothing, needs no equipment and will have you out of breath inside thirty seconds. You hold a high plank and drive your knees towards your chest one at a time, as if you are running horizontally. It trains your core hard, gets your heart rate up fast, and works as a warm-up, a conditioning finisher or the centrepiece of an interval circuit. It is also very easy to do badly, and done badly it turns into a hip-swinging shuffle that trains almost nothing. Here is how to do it properly.

How to do a mountain climber

All you need is a bit of floor. A yoga or exercise mat makes it more comfortable on the hands.

1. Set up in a high plank. Hands directly under your shoulders, arms straight, legs extended behind you, feet about hip-width apart. Your body should form one straight line from your head to your heels.
2. Brace before you move. Tighten your abs as if you are about to be poked in the stomach, and squeeze your glutes. Push the floor away so your upper back is slightly rounded rather than collapsed between your shoulder blades.
3. Drive one knee forward. Bring one knee towards your chest without letting your hips lift. The foot can lightly touch the floor or hover just above it.
4. Switch legs. Return that leg to the start as the other knee drives forward. Both feet should never be forward at the same time.
5. Find a rhythm. Once the pattern feels stable, speed up to a controlled run. Keep your shoulders stacked over your hands and your hips low throughout.
6. Breathe. Do not hold your breath. Short, steady breaths, in through the nose and out through the mouth.

Muscles worked

The clever thing about the mountain climber is that the core has to work statically while everything else moves.

• Rectus abdominis and obliques. They resist your hips dropping towards the floor and resist rotation as each leg moves independently. This anti-movement work is exactly what the core is for.
• Transversus abdominis. The deep stabilising layer that wraps the trunk. It is switched on the entire time you hold the position.
• Hip flexors, including the iliopsoas and rectus femoris. These drive each knee towards the chest and are usually the first thing to feel it the next day.
• Shoulders, chest and triceps. They hold you up in the plank. Anterior deltoid and pectoralis major do most of that work, with the triceps keeping the elbows locked.
• Serratus anterior. Holds the shoulder blades flat against the ribcage. This is why pushing the floor away matters.
• Quads, glutes and calves. They stabilise the trailing leg and contribute to the drive, so the lower body is far from passive.

Benefits

• They raise your heart rate fast. Because so much muscle is involved at once, a 30 second set gets you breathing hard. That makes them ideal for interval work, and interval training delivers comparable or greater gains in aerobic capacity than longer steady sessions for a fraction of the time (review of high-intensity interval training).
• They train the core the way it actually works. Real-world core strength is mostly about resisting movement rather than creating it, and that is precisely what a mountain climber demands.
• No equipment and no impact. Nothing to buy, nothing to store, and no jumping, which makes them a good option for flats and shared houses where burpees would annoy the neighbours.
• They are easy to scale. Slow them down and they are a beginner core exercise. Speed them up and they are a conditioning tool. Elevate your hands and they get easier, elevate your feet and they get much harder.
• They warm you up efficiently. Thirty seconds gets the shoulders, hips and core moving and the heart rate up, which is a good use of the first few minutes of a session.
• They contribute to your weekly activity target. Vigorous work like this counts at roughly double the rate of moderate activity towards the NHS physical activity guidelines.

Common mistakes

Hips riding up. The most common fault by far. When you tire, your hips drift towards the ceiling, which shortens the lever and lets your core off the hook. It looks like you are working harder and it is doing less.

Hips sagging. The opposite problem, and the one that puts load into your lower back. Squeeze your glutes and keep your ribs pulled down towards your hips.

Hands too far forward. If your hands creep out in front of your shoulders, your shoulders take a beating and the plank gets much harder to hold. Stack the shoulders directly over the wrists.

Bouncing on the toes. Pushing off the back foot to launch each rep turns it into a hopping motion. Drive the knee forward with the hip flexor instead and keep the movement smooth.

Going too fast too soon. Speed is the reward for control, not a substitute for it. Nail a slow, stable version before you chase pace.

Not going far enough. A knee that barely leaves the floor is not doing much. Drive it towards your chest through a full range on every rep.

Variations

Slow mountain climber. Two seconds per leg, holding the knee at the top. Far more of a core exercise and the right place for beginners to start.

Hands-elevated mountain climber. Put your hands on a bench, a step or the arm of a sofa. This reduces the load on the shoulders and core considerably and is the easiest useful version.

Cross-body mountain climber. Drive each knee towards the opposite elbow. This adds rotation and brings the obliques in much harder.

Feet-elevated mountain climber. Rest your feet on a bench or a plyo box. Substantially harder on the shoulders and core.

Sliding mountain climber. With sliders, a towel on a hard floor or your socks on laminate, keep both feet in contact and slide them in and out. This removes the bouncing entirely and makes the movement much stricter.

Spider climber. Drive the knee to the outside of the same elbow rather than towards the chest. A brutal hip and adductor stretch under load.

Weighted mountain climber. Wear a weighted vest once bodyweight sets stop being challenging.

How to program them

Mountain climbers work best in time, not reps, because the quality of the position matters more than the count.

• As a warm-up: 2 rounds of 20 seconds at a moderate pace, early in the session.
• As conditioning: 4 to 6 rounds of 30 seconds hard with 30 seconds rest. Simple and very effective.
• In a circuit: 40 seconds of mountain climbers between strength moves such as push ups and goblet squats, for 3 to 4 rounds.
• As a core finisher: 3 sets of 20 slow, controlled cross-body reps at the end of a session.
• For beginners: 3 sets of 15 seconds at a slow tempo with hands elevated, resting as long as you need between sets.

Stop the set when your hips move, not when the timer says so. A clean 20 seconds beats a sloppy 45 every time, and the whole point of the exercise disappears once the position collapses. If you want to build the underlying position strength, the plank is the obvious companion, and hanging leg raises cover the other end of the core.

Recommended reads

1. Plank: how to do it and muscles worked
2. Burpees: technique and variations
3. Hanging leg raise guide
4. The best exercise and yoga mats in the UK
5. The best plyo boxes in the UK