# Open Book (Thoracic Rotation): how to do it

- Main muscles: upper back
- Also works: chest
- Equipment: bodyweight
- Level: beginner
- 3D demo (side view): https://media.trainaq.com/exercises/open_book/4bf5c3f892/side-m-720.mp4

## Steps

1. Lie on your side with your hips and knees bent to right angles and your head on a cushion.
2. Stretch both arms out in front of you at chest height, palms together.
3. Breathe out and sweep your top arm up and over, turning your chest and head to follow your hand.
4. Pause where it feels comfortable, then bring the arm back to the start.
5. Do 5–10 reps, then switch sides.

## Cues

- Knees stay glued together.
- Follow your hand with your eyes.
- Turn from your upper back.

## Common mistakes

- Knees coming apart: squeeze your thighs together to keep your hips still.
- Forcing the arm to the floor: stop where the stretch feels comfortable.
- Bending the elbow: keep the arm long as it sweeps round.

## The version in our demo

Lying on the left side, hips and knees bent to 90° and pressed together, arms straight in front at chest height; the top arm sweeps up and over to open out behind, the chest following it. ACE's "side-lying books" uses the stacked 90° knees (it locks the pelvis, beginner-safe); Physitrack's version with the bottom leg straight is a variant.

## Starting position

Lying on the left side on a mat, head on a small pillow or folded towel (5–10 cm) so the neck is level. Hips flexed about 90°, knees bent 90° and stacked, thighs squeezed together. Both arms straight out in front at shoulder height, palms together, top hand resting on the bottom hand.

## The movement

Breathe out and lift the top (right) hand up towards the ceiling, keeping the arm straight, then continue the arc over and back towards the floor behind, turning the chest and head to follow the hand with the eyes. Stop at the end of comfortable rotation, ideally with the arms in a T. Pause, then sweep the arm back along the same arc to the start. The knees stay together and on the floor, the bottom arm stays on the mat, the pelvis does not roll back.

## Breathing

Breathe out as you open; breathe in as the arm returns.

## Tempo

One rep, 8 s: 3 s opening (breathe out), 2 s pause at the end (one breath), 3 s closing. Real sets: 5–10 reps per side.

## Form in numbers

- Top arm stays straight at shoulder height (about 90° from the torso) throughout.
- Head turns 45–70° with the chest, eyes on the top hand.
- Knees stay stacked, pelvis rotation under 5°; the bottom knee does not lift.

## Sources

1. [ACE, "Thoracic Mobility Exercises to Address Shoulder Pain" (side-lying books)](https://www.acefitness.org/resources/pros/expert-articles/7960/thoracic-mobility-exercises-to-address-shoulder-pain/)
2. [Physitrack, "Thoracic rotations in side lying (open book) – Version 1 (exercise video)"](https://uk.physitrack.com/home-exercise-video/thoracic-rotations-in-side-lying-(open-book)

Source: https://trainaq.com/exercises/open-book