Why Adam Peaty’s body looks like this

Shoulder
Trapezius and deltoids
Shoulder stability is generally important in breaststroke as strength is required around the glenohumeral joint in a number of positions to allow effective application of force to the water. Furthermore the trapezius is involved in the shrugging of the shoulders at the start of the recovery phase.

Chest
Pectoralis major/pectoralis minor
The pectorals act as one set of the primary propulsive muscles involved in the application of power to water during all active arm phases and are also vital in the effective recovery of arms into the body prior to their extension into the next stroke.

Back muscles
Latissimus dorsi (lats)
Another primary propulsive muscle group involved in producing power in the catch and down-sweep phases, strength and mobility in this group is key to swimming performance.

Upper arm
Biceps brachii/triceps brachii
The biceps are involved at a range of lengths during arm phases to maintain and transfer force to the water; they also assist with the recovery of arms after which the triceps extend the arms into the next catch phase.

Forearms
Brachioradialis/flexors, extensors
A combination of feel, strength and endurance is required within the musculature of the forearm to achieve correct hand position and maintain pressure on the water throughout the catch phase, down-sweep and in-sweep.

Anterior abdominals
Rectus abdominis
The abdominals play an important role in controlling lumbar extension and minimising drag throughout the phases of breaststroke. In combination with the muscles of the lower back they provide the connection between the upper and lower body.

Oblique abdominals
External obliques/serratus anterior
While breaststroke is a linear event there is the requirement for stability in the water and a well developed midsection is vital. The obliques do not actively contribute to propulsion but provide support across the duration of the race.

Groin
Gracilis/adductors
While the quads act as knee extensors the muscles of the groin effectively finish the kick by squeezing the legs together and maximising the propulsive output from each cycle.

Quadriceps
Rectus femoris/vastus medialis/vastus lateralis
The quads which extend the knee in the kick phase are more vital in breaststroke than any other stroke because approximately 70 per cent of the propulsive power is produced by the kick. Lower body strength and power are also vital in the start and in the turn.

Calves
Gastrocnemius/tibialis
The muscles responsible for ankle plantarflexion assist with the application of power to the block and wall in starts and turns, they also help achieve effective positions at the end of the kick and glide phases. Additionally, ankle dorsi-ti flexion is required at the start of the kick phase alongside effective tibial external rotation to maximise the kick propulsive area.

● John Watson is national performance services manager for Swim Ireland. He was the strength and conditioning coach at Bath national performance centre until this year and was on the Great Britain staff at Rio 2016. He has worked with British medallists including Siobhan- Marie O’Connor, Jazz Carlin and James Guy.