Part of these sets

This exercise rarely works alone. It appears in the following routines, where it is sequenced alongside the others that support it.

What it works

Primary muscles

Obliques and quadratus lumborum
Gluteus medius, on the supporting side

Also involved

Shoulder stabilisers of the supporting arm
Deep abdominals, keeping the midline firm

Equipment: None. A mat, with a folded towel under the elbow for comfort.

How to do it

1
Lie on your side with the elbow directly under the shoulder, forearm flat on the floor. Straighten the legs and stack the feet, or stagger them heel to toe for easier balance.
2
Breathe out and lift the hips until head, shoulders, hips and ankles form one straight line.
3
Press the floor away through the forearm so the shoulder stays strong rather than sagging into its socket.
4
Hold, breathing throughout. The top hip stays stacked over the bottom one, neither dropping back nor rolling forward.
5
Lower with control, rest, and repeat on the other side.

How much to do

3 to 5 holds of 10 to 20 seconds each side

3 to 4 times a week

Progressed gradually is the rule. Several short, well-held repetitions build endurance better than one long shaking one, so add seconds before you add levels.

Stop and get assessed if

Stop and get assessed if the hold produces sharp back or shoulder pain rather than a working burn along the side of the trunk, or, postnatally, if you notice doming along the midline, pelvic heaviness or leaking: drop to the knees version and have the load checked before pushing on.

Common mistakes

Hips sagging towards the floor: A sagged hold trains the sag. The straight line is the exercise, so if it will not hold, drop to the knees version and own that line instead.
Rolling the chest and top hip forward: Imagine being held between two panes of glass. Rotating forward hands the work to the front of the trunk and takes it away from the side you are trying to train.
Hanging in the supporting shoulder: Elbow under shoulder, then push the floor away. A shoulder that sags into its socket ends up sorer than the trunk that was supposed to be working.
Holding the breath: If breathing has stopped, the hold has become a strain. The trunk should hold you up while the lungs keep working; time that only exists breath-held does not count.

Making it harder

Build holds towards 30 seconds, then add repetitions rather than chasing ever longer times.
Slow hip dips: lower the bottom hip towards the floor and lift it back without losing the stack.
Lift the top leg, which sharply increases the work for both the trunk and the supporting hip.

Making it easier

From the knees: bend the knees to a right angle and lift from knee and forearm, keeping head, hips and knees in one line. This is the standard starting version postnatally and after a back flare.
Shorter holds: five seconds well held beats twenty seconds of sag. Build the time before the level.

Side Plank