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Muscle and body-part reference
A page for each of 34 muscles, joints and load-bearing structures: where it is, what it does, which exercises load it, how it is stretched and what usually goes wrong with it.
This is a reference, not a diagnosis. It describes what each structure is and what problems typically feel like; it does not tell you what is wrong with you. Pain that is severe, that is getting worse, that follows an injury, or that comes with numbness, weakness or fever belongs with a clinician.
How to read these pages
Each page opens with the attachments — where the structure starts and where it ends — because almost everything else follows from them. A muscle can only pull its two ends together, so knowing the two ends tells you what it does. The nerve supply is given with its spinal root levels, which is what makes the difference between a muscle that is weak because it is untrained and one that is weak because a nerve is not reaching it.
After that comes function, the exercises in the TempoLife exercise library that load the structure, how it is lengthened, and what commonly goes wrong. The injury notes are deliberately descriptive: what a problem typically feels like and the setting it usually appears in. There are no incidence figures, because good ones are hard to find and bad ones spread easily, and there is nothing here about what treatment to have.
Where a popular claim is weakly supported, the page says so. Several of the ideas that circulate widely about the body — that the iliotibial band can be stretched, that a specific deep abdominal muscle must be isolated to protect the back, that a disc can slip — are wrong or much weaker than they sound, and a reference that repeats them is not worth reading.
Every body part, by region
34 pages, grouped by where they are in the body. The plain-English column is there because the Latin is precise but unhelpful when you are trying to work out which muscle you can feel.
Shoulder and shoulder blade
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Deltoid | Musculus deltoideus | The cap of the shoulder | Abduction of the arm |
| Rotator cuff | Musculi supraspinatus, infraspinatus, teres minor, subscapularis | The four small muscles that hold the shoulder in its socket | Holding the head of the humerus centred in the socket |
| Trapezius | Musculus trapezius | The big diamond across the upper back and neck | Upper fibres elevate and help rotate the shoulder blade upward, middle fibres retract it, lower fibres depress it and complete the upward rotation |
| Rhomboids | Musculi rhomboideus major et minor | The straps that pull the shoulder blades together | Retraction of the shoulder blade toward the spine, downward rotation, and holding the medial border against the rib cage |
| Serratus anterior | Musculus serratus anterior | The finger-like muscle on the ribs that pins the shoulder blade down | Protraction of the shoulder blade, upward rotation of the socket, and holding the blade flat against the rib cage |
Arm and forearm
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Biceps brachii | Musculus biceps brachii | The two-headed muscle at the front of the upper arm | Supination of the forearm, flexion of the elbow, and weak flexion of the shoulder |
| Triceps brachii | Musculus triceps brachii | The three-headed muscle at the back of the upper arm | Extension of the elbow |
| Forearm and grip | Musculi antebrachii | The muscles below the elbow that close your hand | Flexion and extension of the wrist and fingers, deviation of the wrist, and pronation and supination of the forearm |
Chest and back
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Pectoralis major | Musculus pectoralis major | The big chest muscle | Adduction and internal rotation of the arm |
| Latissimus dorsi | Musculus latissimus dorsi | The broad muscle of the back | Extension, adduction and internal rotation of the arm |
| Erector spinae | Musculi erector spinae | The columns of muscle either side of the spine | Extension of the spine when both sides work, side flexion when one side works, and controlled lowering of the trunk when bending forward |
Core, breathing and pelvic floor
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Rectus abdominis | Musculus rectus abdominis | The straight abdominal muscle, the six-pack | Flexion of the trunk, posterior tilt of the pelvis, and raising intra-abdominal pressure with the other abdominal muscles |
| Abdominal obliques | Musculi obliquus externus et internus abdominis | The side abdominal muscles that twist the trunk | Trunk rotation and side flexion, compression of the abdomen, and resisting rotation under load |
| Transversus abdominis | Musculus transversus abdominis | The deepest abdominal layer, a corset around the waist | Compression of the abdominal contents, raising intra-abdominal pressure, and tensioning the thoracolumbar fascia |
| Diaphragm | Diaphragma | The dome of muscle that does your breathing | Contracts and flattens to draw air into the lungs |
| Pelvic floor | Diaphragma pelvis | The sling of muscle at the base of the pelvis | Supports the pelvic organs, maintains continence, contributes to sexual function, and works with the diaphragm and abdominal wall to manage pressure |
Hip and buttock
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Iliopsoas | Musculus iliopsoas | The deep hip flexor that runs from the lower spine to the thigh | Flexion of the hip |
| Gluteus maximus | Musculus gluteus maximus | The main buttock muscle | Extension of the hip, particularly from a flexed position |
| Gluteus medius | Musculus gluteus medius | The side-hip muscle that keeps the pelvis level | Abduction of the hip |
| Piriformis | Musculus piriformis | The deep rotator behind the hip, next to the sciatic nerve | External rotation of the extended hip |
| Tensor fasciae latae | Musculus tensor fasciae latae | The small front-of-hip muscle that tightens the IT band | Flexion, abduction and internal rotation of the hip |
| Hip adductors | Musculi adductores | The inner thigh muscles | Adduction of the hip, assistance with flexion or extension depending on hip position, and stabilisation of the pelvis in the frontal plane |
Thigh
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Quadriceps femoris | Musculus quadriceps femoris | The four muscles at the front of the thigh | Extension of the knee |
| Hamstrings | Musculi ischiocrurales | The three muscles at the back of the thigh | Extension of the hip and flexion of the knee |
Lower leg and foot
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Gastrocnemius and soleus | Musculus gastrocnemius et musculus soleus | The calf muscles | Plantarflexion of the ankle |
| Tibialis anterior | Musculus tibialis anterior | The shin muscle that lifts the foot | Dorsiflexion of the ankle and inversion of the foot |
Neck
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Sternocleidomastoid | Musculus sternocleidomastoideus | The rope of muscle down the side of the neck | Turns the head to the opposite side and side-bends it to the same side |
| Levator scapulae | Musculus levator scapulae | The strap from the neck to the top corner of the shoulder blade | Elevates the shoulder blade and rotates the socket downward |
Joints, tendons and fascia
| Body part | Latin | In plain English | Main job |
|---|---|---|---|
| Shoulder joint | Articulatio humeri | The ball and socket at the top of the arm | Flexion, extension, abduction, adduction, internal and external rotation, and circumduction |
| Knee joint | Articulatio genus | The hinge between thigh and shin | Flexion and extension, with a small amount of rotation available when the knee is bent |
| Hip joint | Articulatio coxae | The ball and socket where the leg meets the pelvis | Flexion, extension, abduction, adduction, internal and external rotation |
| Lumbar spine | Vertebrae lumbales | The five vertebrae of the lower back | Flexion and extension freely, side flexion moderately, rotation only slightly because the facet joints face largely front-to-back |
| Achilles tendon | Tendo calcaneus | The thick cord at the back of the ankle | Transmits calf force to the heel, and stores and returns elastic energy during walking and running |
| Plantar fascia | Aponeurosis plantaris | The thick band along the sole of the foot | Supports the medial longitudinal arch and stiffens the foot for push-off |
Which muscles work in each exercise
The same information read the other way round. Every body-part page lists the movements that load it, and this table inverts those lists, so it can never say something different from the pages themselves. Each exercise links to its own page in the library, where the MET value and the calorie estimate live.
The lists are not exhaustive anatomy — almost every movement involves almost everything to some degree. They name the structures a movement loads enough to be worth knowing about.
Where this sits next to the rest of the site
The body map is a visual index of the systems TempoLife measures — heart, sleep, digestion — and what a tracker can and cannot say about each. This reference is the other thing: an encyclopedia of the moving parts, with no connection to your own data. The exercise library covers the movements themselves, the fitness norms page covers reference values for strength and capacity, and training plans cover how to structure a week of it.
Sources: descriptive anatomy from Gray's Anatomy of the Human Body, 20th US edition (1918), which is in the public domain; Latin names follow Terminologia Anatomica, published by the Federative International Programme for Anatomical Terminology. Nerve root levels are the conventional ranges taught from those sources and vary between individuals and between textbooks. Exercise cross-links use the TempoLife exercise library. Checked 2026-09-06.
Frequently asked questions
Which muscles work in a squat?
On this site the bodyweight squat is listed on the pages for gluteus maximus, gluteus medius, hip adductors, quadriceps femoris, knee joint. A squat is a hip and knee extension pattern, so the buttock and thigh muscles do the moving while the trunk resists being folded forward.
What is the difference between origin and insertion?
By convention the origin is the attachment that moves least and the insertion the one that moves most. It is a teaching convention rather than a law of nature: in a pull-up the hands are fixed and the body moves, so the muscle that normally pulls the arm down ends up pulling the trunk up instead.
Why use the Latin names at all?
Because they are unambiguous. Everyday names for body parts differ between languages and even between regions, while Terminologia Anatomica gives one agreed term that a clinician anywhere will recognise. Each page prints the Latin next to the plain-English name for that reason.
Can I work out which muscle is injured from where it hurts?
Often not. Pain is referred between structures, nerves send symptoms far from their source, and several different tissues can produce identical symptoms in the same spot. These pages describe what problems typically feel like so you can have a better conversation with a clinician, not so you can replace one.
Is this medical advice?
No. It is a reference on anatomy and how movement loads the body. It contains no dosing, no diagnosis and no treatment plan, and every page says when a symptom is a reason to be examined in person.
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