Alternating Side Plank
From a high plank, turn onto one side, top arm up towards the ceiling, hold for a moment — then back through the plank and onto the other side. It trains the side of your trunk. All you need is floor space.
A basic trunk exercise that works for beginners and for people who've been training for years — and it travels: at home, in a hotel room, on the road.
The moment you turn onto your side, your trunk holds the hip up from the side. That job belongs to the obliques and to quadratus lumborum, the lateral stabiliser beside the spine. The turn from one side to the other is the demanding part — it's the exercise itself.
Starting position
Start in a high plank: hands under your shoulders, arms straight, body long. From there, turn onto one side, stack your feet, and reach your top arm up towards the ceiling. Hold briefly, come back through the plank, then turn the other way. One thing stays the same throughout: the supporting shoulder sits directly over the wrist.
The three cues
- Start in a high plank with straight arms — from there, turn onto one side, then the other
- Shoulder stacked over the wrist, otherwise there's no solid base underneath you
- Feet stacked, one on top of the other — hold one side for a moment, then turn to the other
Common faults
| Fault | How to fix it |
|---|---|
| The hips drop towards the floor | Turn sooner and shorten the hold. The position only counts while the line from shoulder to foot stays straight. |
| Your hand is too far forward or too far back | Stack the shoulder directly over the wrist. Anywhere else and your arm ends up working against a long lever — that gives out long before your trunk does. |
| The chest rotates down towards the floor | Open your chest upwards, so it faces the wall you're turning towards. The sideways work happens as long as your chest stays open. |
| You roll straight through without actually holding | Stay up there for a breath or two. The hold is the exercise; the turn is how you get into it. |
| In the leg-raise version, the leg drifts forward or back | The leg lifts straight up towards the ceiling, in line with your body — not ahead of it or behind it. If you need to find that feeling first, lie on your side on the floor and lift and lower the top leg a few times. |
Variations
| Variation | When to use it |
|---|---|
| Feet staggered instead of stacked | Top foot in front of the bottom one. A wider base and less balance to manage — the calmer way into the position. |
| On the forearm instead of the hand | If your wrist or shoulder doesn't tolerate the straight-arm position. |
| Alternating side plank on the hand | What we do in the studio: from a high plank, turning onto one side, then the other, feet stacked, shoulder over the wrist. |
| With a leg raise | Once about 20 turns, or a minute of alternating, feels easy. The top leg lifts while you're on your side, which brings the hip muscles in. |
| Lie on your side and lift only the leg | To learn the movement before you have to hold yourself up at the same time. Lift, lower, lift, lower — that's all there is to it. |
Reps and load
A rough marker: once you can do about 20 turns, or a full minute of alternating, you've got the basic version — then add the leg raise.
"Hold briefly" means briefly: a breath or two per side, then move on. The position sets the limit, not the rep count — the moment your hips drop or your top shoulder rolls forward, the set is over. Left and right should feel much the same.
Which muscles do the work
| Muscle | Role | What it does here |
|---|---|---|
| External obliques M. obliquus externus abdominis | Prime mover | Stop the trunk dropping sideways and stop it rotating back towards the floor |
| Internal obliques M. obliquus internus abdominis | Prime mover | Draws the waist in and keeps the pelvis steady in the side position |
| Quadratus lumborum M. quadratus lumborum | Prime mover | The lateral stabiliser beside the lumbar spine — this is exactly what it's built for |
| Rectus abdominis M. rectus abdominis | Synergist | Contributes most as you pass through the plank |
| Lats M. latissimus dorsi | Synergist | Links the arm to the pelvis as you turn from one side to the other |
| Glute med M. gluteus medius | Synergist | Keeps the hip up; the moment the top leg lifts, it takes the lead |
| Delts M. deltoideus | Stabiliser | Carry the support on the hand |
| Spinal erectors M. erector spinae | Stabiliser | Keep the spine long while everything around it turns |
The heart of it is the direction of the work: on your side, the trunk holds the hip up from the side, not from above. That's the job of the obliques and quadratus lumborum. Gluteus medius sits here as a synergist — the moment the top leg lifts, it takes the lead.
Ways to do it — on video
The equipment changes, the movement pattern stays the same. What you learn on the cable applies to the band just as much — only the resistance differs.
On the hand, alternatingStandard
The studio standard. From a high plank onto one side, a short hold, back through the plank and onto the other. Feet stacked, shoulder over the wrist.
With a leg raise
The step up: while you're on your side, the top leg lifts, alternating side to side. That brings the hip muscles in.
Explained in full
How it grows out of a high plank, why the shoulder has to sit over the wrist, and when to add the leg raise — including the side-lying lead-in. · 1:25
Seeing it done right is not the same as doing it right
Video, cues and variations take you a long way. What they cannot give you is an outside eye at the moment the movement isn't quite there yet. That is what training with me is for — in the studio or in a workshop.
See the workshopsNew exercise pages are added all the time — the newsletter keeps you posted.
Sources
McGill S, Juker D, Kropf P. (1996). Clin Biomech 11(3):170–172. DOI: 10.1016/0268-0033(95)00056-9 — Fine-wire EMG recorded directly from quadratus lumborum: in the side-support position it was more active than in any other task tested. The authors explicitly recommend the side support for training this muscle. Only four people were measured. (Evidence type: EMG)
Kinney AL, et al. (2020). J Sport Rehabil 30(2):255–260. DOI: 10.1123/jsr.2018-0442 — The largest sample on the question, 63 people: the side plank produced strong oblique activation. The version measured was on the forearm. (Evidence type: EMG)
McGill SM, Karpowicz A. (2009). Arch Phys Med Rehabil 90(1):118–126. DOI: 10.1016/j.apmr.2008.06.026 — The closest evidence for the alternating version: rolling from one side, through the plank, to the other was the most demanding of the progressions tested. Eight people, forearm version, feet staggered; the roll passed through the plank, as it does here. (Evidence type: EMG)
Boren K, et al. (2011). Int J Sports Phys Ther 6(3):206–223. Volltext (PMC3201064) — Of 18 exercises tested, the side plank with abduction produced the highest gluteus medius demand of all: 103 per cent of maximum for the bottom leg and 89 per cent for the top — first and second place. Plain side-lying abduction came in at 63 per cent in the same dataset. The side plank without the leg raise was not among the exercises measured. (Evidence type: EMG)
McGill SM, Childs A, Liebenson C. (1999). Arch Phys Med Rehabil 80(8):941–944. DOI: 10.1016/S0003-9993(99)90087-4 — A reference database of 75 healthy young adults for side-bridge hold times, reported as ratios against the other trunk tests. (Evidence type: Reference data)
A note on context: EMG studies show which muscles an exercise recruits — that is a good reason to pick it, but it does not replace adjusting things to the person in front of you. See a doctor for persistent or severe pain.