{"schemaVersion":1,"id":"en-hub-muscles","type":"hub","pillar":"body","locale":"en","translationGroupId":"hub-muscles","slugPath":"body/muscles","title":"The muscles","shortTitle":"Muscles","summary":"Twenty-two pages, grouped by what they do rather than where they sit. A muscle only means something once it is tied to an action: that is the order used here.","level":"beginner","estimatedMinutes":3,"synonyms":["muscles","muscular anatomy","muscle groups","prime movers"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"The "},{"kind":"link","value":"Body","href":"/en/body","external":false},{"kind":"text","value":" pillar describes twenty-two muscles. Arranging them by region — arm, trunk, leg — would have been simpler, and less useful: what helps you remember a muscle is what it does, not where it sits."}]},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"They are therefore grouped by function. Several appear in two groups, which is not a filing error but a property of the subject."}]},{"id":"b3","type":"heading","level":2,"text":"The prime movers of pushing","anchor":"the-prime-movers-of-pushing"},{"id":"b4","type":"list","ordered":false,"items":[[{"kind":"link","value":"Pectoralis major","href":"/en/body/muscles/pectoralis-major","external":false},{"kind":"text","value":" — the driver of horizontal pushing."}],[{"kind":"link","value":"Deltoids","href":"/en/body/muscles/deltoids","external":false},{"kind":"text","value":" — three heads carrying the arm in three directions."}],[{"kind":"link","value":"Triceps brachii","href":"/en/body/muscles/triceps-brachii","external":false},{"kind":"text","value":" — elbow extension, in every push."}],[{"kind":"link","value":"Serratus anterior","href":"/en/body/muscles/serratus-anterior","external":false},{"kind":"text","value":" — keeps the shoulder blade flat on the ribs, a condition of overhead pushing."}]]},{"id":"b5","type":"heading","level":2,"text":"The prime movers of pulling","anchor":"the-prime-movers-of-pulling"},{"id":"b6","type":"list","ordered":false,"items":[[{"kind":"link","value":"Latissimus dorsi","href":"/en/body/muscles/latissimus-dorsi","external":false},{"kind":"text","value":" — the fan running down to the pelvis."}],[{"kind":"link","value":"Trapezius","href":"/en/body/muscles/trapezius","external":false},{"kind":"text","value":" — three portions with opposing actions."}],[{"kind":"link","value":"Biceps brachii","href":"/en/body/muscles/biceps-brachii","external":false},{"kind":"text","value":" — flexes the elbow and supinates the forearm."}],[{"kind":"link","value":"Rhomboids","href":"/en/body/muscles/rhomboids","external":false},{"kind":"text","value":" — beneath the trapezius, draw the shoulder blades together."}]]},{"id":"b7","type":"heading","level":2,"text":"The lower body","anchor":"the-lower-body"},{"id":"b8","type":"list","ordered":false,"items":[[{"kind":"link","value":"Quadriceps","href":"/en/body/muscles/quadriceps","external":false},{"kind":"text","value":" — four heads, one insertion."}],[{"kind":"link","value":"Hamstrings","href":"/en/body/muscles/hamstrings","external":false},{"kind":"text","value":" — brake the leg before every foot strike."}],[{"kind":"link","value":"Glutes","href":"/en/body/muscles/glutes","external":false},{"kind":"text","value":" — hip extension, the driver of the hinge."}],[{"kind":"link","value":"Calves","href":"/en/body/muscles/calves","external":false},{"kind":"text","value":" — propulsion, and the spring of running."}],[{"kind":"link","value":"Tibialis anterior","href":"/en/body/muscles/tibialis-anterior","external":false},{"kind":"text","value":" — lifts the toes on every step."}],[{"kind":"link","value":"Hip adductors","href":"/en/body/muscles/hip-adductors","external":false},{"kind":"text","value":" — draw the thigh back towards the midline."}]]},{"id":"b9","type":"heading","level":2,"text":"The trunk and pressure","anchor":"the-trunk-and-pressure"},{"id":"b10","type":"list","ordered":false,"items":[[{"kind":"link","value":"Abdominal wall","href":"/en/body/muscles/abdominal-wall","external":false},{"kind":"text","value":" — four layers whose fibres cross."}],[{"kind":"link","value":"Erector spinae","href":"/en/body/muscles/erector-spinae","external":false},{"kind":"text","value":" — flank the spine and hold it back."}],[{"kind":"link","value":"The diaphragm","href":"/en/body/muscles/diaphragm","external":false},{"kind":"text","value":" — the one muscle charged with two incompatible tasks."}]]},{"id":"b11","type":"heading","level":2,"text":"The deep plane","anchor":"the-deep-plane"},{"id":"b12","type":"paragraph","content":[{"kind":"text","value":"These four are visible on no silhouette. They orient and stabilise more than they move, and the body map keeps a layer for them."}]},{"id":"b13","type":"list","ordered":false,"items":[[{"kind":"link","value":"Rotator cuff","href":"/en/body/muscles/rotator-cuff","external":false},{"kind":"text","value":" — holds the head of the humerus against the shoulder blade."}],[{"kind":"link","value":"Iliopsoas","href":"/en/body/muscles/iliopsoas","external":false},{"kind":"text","value":" — the only muscle linking the lumbar spine to the femur."}],[{"kind":"link","value":"Gluteus medius","href":"/en/body/muscles/gluteus-medius","external":false},{"kind":"text","value":" — keeps the pelvis from tipping at every step."}],[{"kind":"link","value":"Tensor fasciae latae","href":"/en/body/muscles/tensor-fasciae-latae","external":false},{"kind":"text","value":" — pulls on a band, not on a bone."}]]},{"id":"b14","type":"heading","level":2,"text":"The distal segments","anchor":"the-distal-segments"},{"id":"b15","type":"list","ordered":false,"items":[[{"kind":"link","value":"Forearm muscles","href":"/en/body/muscles/forearm","external":false},{"kind":"text","value":" — drive the hand from a distance, and often give out first."}]]},{"id":"b16","type":"heading","level":2,"text":"What they are made of","anchor":"what-they-are-made-of"},{"id":"b17","type":"paragraph","content":[{"kind":"text","value":"Describing a muscle assumes you know what a muscle is. Four cross-cutting pages take that on: "},{"kind":"link","value":"muscle fibres","href":"/en/body/muscle-fibres","external":false},{"kind":"text","value":", "},{"kind":"link","value":"the tendon","href":"/en/body/the-tendon","external":false},{"kind":"text","value":", "},{"kind":"link","value":"fascia","href":"/en/body/fascia","external":false},{"kind":"text","value":" and "},{"kind":"link","value":"contraction regimes","href":"/en/body/contraction-regimes","external":false},{"kind":"text","value":", which explains why a muscle produces more force lengthening than shortening."}]},{"id":"b18","type":"shapierAction","actionId":"exercises-catalogue","label":"Browse exercises by muscle","description":"Looking up which exercises train a given muscle happens in Shapier; Body Lab only explains what each muscle does.","webTarget":"https://shapier.app/en/exercises","appTarget":"shapier://exercises"},{"id":"b19","type":"relatedContent","title":"The twenty-two muscles","targetIds":["en-anatomy-pectoralis-major","en-anatomy-deltoids","en-anatomy-triceps-brachii","en-anatomy-serratus-anterior","en-anatomy-latissimus-dorsi","en-anatomy-trapezius","en-anatomy-biceps-brachii","en-anatomy-rhomboids","en-anatomy-quadriceps","en-anatomy-hamstrings","en-anatomy-glutes","en-anatomy-calves","en-anatomy-tibialis-anterior","en-anatomy-hip-adductors","en-anatomy-abdominal-wall","en-anatomy-erector-spinae","en-anatomy-diaphragm","en-anatomy-rotator-cuff","en-anatomy-iliopsoas","en-anatomy-gluteus-medius","en-anatomy-tensor-fasciae-latae","en-anatomy-forearm"]}],"relations":[],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02"},"limitations":["This index page describes how a set is organised; the anatomical descriptions, their sources and their limits sit on the pages themselves.","The groupings below are reading aids. A muscle rarely belongs to a single category, and several appear in two groups for that reason."],"seo":{"title":"The muscles — an index of the twenty-two structures described","description":"An index of Body Lab's muscle pages, grouped by function: prime movers of pushing and pulling, the lower body, the deep plane and the distal segments.","canonicalPath":"/en/body/muscles","image":"/og/en/hub-muscles.png"},"app":{"offlineEligible":true},"version":1}