Side plank: how to do it, easier and harder versions, and what the studies measured

A side plank is a hold on the side of your body. You support yourself on one forearm and the edge of your feet and lift your hips until you make a straight line from head to feet. The front plank asks your abs to stop your lower back sagging; the side plank asks the sides of your trunk to stop it dropping toward the floor.

In the core workout it is the no-equipment version of the suitcase carry, the "stop the lean" job; in the bodyweight workout it is a harder core option beside the front plank. This page covers the setup, the faults, what the studies measured, the easier and harder versions, how long to hold, and the sets.

How to do a side plank

1. Lie on your side with your legs straight, feet stacked or one in front of the other, and your elbow directly under your shoulder, forearm on the floor.
2. Press into your forearm and lift your hips until your body is one straight line from your head to your feet.
3. Squeeze your glutes and brace your midsection. Keep your ribs down.
4. Look straight ahead, head in line with your spine, and breathe steadily.
5. Hold, and lower your hips when the line breaks. Rest, then switch sides.

The top arm rests along your side or on your hip. These cues are practical, not study findings.

The common faults, and a fix for each

• Hips sagging. Your bottom hip drops toward the floor. End the hold or switch to the easier version.
• Hips rolling forward or back. Your chest should face forward, not the floor or the ceiling. Stack your shoulders and hips.
• Elbow out ahead of your shoulder. Keep it directly under, and push the floor away.
• Head dropping or craning. Keep your neck in line with your spine, and breathe behind the brace.

What the side plank trains

Every study here is a short lab measurement, by ultrasound (how much a muscle thickens during the hold) or by electrical activity (muscle activity, not growth). None trained anyone for weeks.

• The obliques, in an ultrasound comparison. In 13 apparently healthy participants, the external oblique, on the side of the waist, was thicker during the lateral plank (the side plank) than during the bird dog, the glute bridge or a hip extension, and the internal oblique was thicker than during the bird dog or the dead bug. The deep abdominal muscle, the transversus abdominis, showed no difference between the exercises.¹
• The side of the hip, too. In 30 healthy adults, 19 men and 11 women, measured by muscle activity during nine exercises, the authors suggested the side bridge may help strengthen the gluteus medius, on the side of the hip, and the external oblique; they put exercises under 45% of a maximal contraction in the endurance-or-stabilization group.²
• Across ten variations. In 15 recreationally active men doing the side plank, a side plank with the top leg raised and eight Copenhagen plank variations, the right internal oblique showed the most muscle activity, about 38 to 77% of a maximal contraction across the variations, then the right external oblique, about 24 to 47%. The plain side plank was rated the least demanding of the ten, 4.6 out of 10 against 8.1 for the hardest.³
• The deepest muscle, less than the dead bug. In 44 healthy women with at least three years of Pilates experience, the dead bug produced a larger increase in transversus abdominis thickness than a one-knee-down side plank, the hundred, the hip roll or a basic lying position.⁴

Read together: in these small studies the side plank brought in the obliques and the muscle on the side of the hip, and for the deepest abdominal muscle one study found the dead bug beat it, while the other found no difference. Thicker or more active during a hold isn't proof of more benefit over weeks.

An easier side plank

• Knees down: bend both knees and rest them on the floor, so the line runs from your head to your knees. Lift your hips the same way.

No study comparing a knee side plank with the full one turned up in a PubMed search for this page, so the knee version is a practical step, not a measured one.

Harder side planks

• Top leg raised. A 2015 systematic review of 23 studies of hip abduction and rotation exercises in injury-free people found the highest gluteus medius activity during a side bridge with hip abduction, a standing abduction with elastic resistance at the ankle and a side-lying abduction, 81 to 103% of a maximal contraction.⁵ The hip abduction machine covers the gym version.
• Hip dips: from the top, lower your hips an inch and lift again. Feet stacked instead of staggered is harder too.

The practical versions in this list weren't compared in the studies above. In the ten-variation study, the harder ones were the Copenhagen plank variations, particularly the long-lever and raised forms.³

How long to hold a side plank

The studies above give no hold time to aim for. The rule of thumb the core workout and the plank page use for the front plank works here too: if you can't keep the line for about twenty seconds, take the easier version; once forty-five seconds on a side feels easy, make it harder rather than longer. These numbers are practical, not from a study.

Sets, holds and where it goes

• Two or three holds a side of 15 to 30 seconds, each stopped when the line breaks, with about 30 seconds of rest.
• At the end of a session, after your main lifts, in the "stop the lean" slot of the core block; the front plank takes the "stop the arch" slot.
• Progress one thing at a time. (Progressive overload covers the options.)

Common questions

Side plank or front plank?

They train different jobs: the front plank stops your lower back sagging, and the side plank stops your trunk dropping sideways. Use both, as the core workout does.

Does the side plank work the obliques?

In the small studies above, the obliques were the most active muscles measured across the ten plank variations, and the internal oblique was thicker in a side plank than in a bird dog or a dead bug.^3,1

What if my shoulder or hip hurts?

If you have pain, an injury or a medical condition, a doctor or a physical therapist should set the limits before you train; this page is general guidance for healthy adults.

If you'd rather have the week planned

Holds are easy to list; fitting them into a week that already has other work is the part a page can't do. Coaching is the version where your workouts live in Trainerize, built around the days and the equipment you actually have, and a weekly call looks at how the week went and sets the next one. Coaching for beginners explains how the first weeks work, and apply is the first step. Otherwise: at the end of your next session, do two side planks a side and write down the seconds.