Prept

Muscle reference

Every muscle group, mapped

The human body has more than 600 muscles, but training is organised around roughly 17 major groups. This interactive map covers all of them: what each muscle does, where it attaches, and the exercises that actually train it. Click any region to start.

Tap a muscle to read about it. Switch to the back view for the muscles you can't see from here.

Upper body

Chest

Pectoralis major

The chest is dominated by the pectoralis major, a large fan-shaped muscle running from the collarbone, sternum and upper ribs to the upper arm bone. Its main job is pulling the arm across the body — horizontal adduction — which is why every press and fly trains it. Beneath it sits the smaller pectoralis minor.

What it does

  • Horizontal adduction — bringing the arm across the front of the body (the flye motion).
  • Shoulder adduction — pulling the arm down toward the side from overhead.
  • Internal rotation of the humerus.
  • Shoulder flexion, via the clavicular head — raising the arm forward.

Top exercises

Barbell bench pressIncline dumbbell pressDumbbell flyeCable crossover
Full chest guide

Visible from the front

All 17 muscle groups

Each guide covers anatomy, origin and insertion, functions, a table of the best exercises, weekly volume guidance, stretches and common mistakes.

Upper body

Chest

Pectoralis major

The chest is dominated by the pectoralis major, a large fan-shaped muscle running from the collarbone, sternum and upper ribs to the upper arm bone. Its main job is pulling the arm across the body — horizontal adduction — which is why every press and fly trains it. Beneath it sits the smaller pectoralis minor.

Read guide →

Upper back

Latissimus dorsi, rhomboids and middle trapezius

The upper back is not one muscle. The latissimus dorsi is the large fan that pulls the arm down and back and creates width; the rhomboids and middle trapezius sit between the shoulder blades and pull them together. Vertical pulls bias the lats, horizontal rows bias the mid-back.

Read guide →

Shoulders

Deltoideus

The deltoid is a three-headed muscle capping the shoulder. The anterior head raises the arm forward, the lateral head raises it out to the side, and the posterior head pulls it backward. Each head needs a different movement, which is why pressing alone never builds complete shoulders.

Read guide →

Traps

Trapezius

The trapezius is a large diamond-shaped muscle spanning the neck, shoulders and mid-back. Its upper fibres elevate the shoulder blade, the middle fibres retract it, and the lower fibres depress and upwardly rotate it. Shrugs only train the upper third.

Read guide →

Neck

Sternocleidomastoid, splenius and deep cervical flexors

The neck is a layered group rather than one muscle. The sternocleidomastoid runs down the front-side and turns and tilts the head; the splenius group at the back extends it; and the deep cervical flexors hold the head in position. Combat and contact-sport athletes train it directly; most people do not need to.

Read guide →

Arms

Biceps

Biceps brachii

The biceps brachii has two heads running from the shoulder blade to the forearm, crossing both the shoulder and elbow. It bends the elbow and rotates the palm upward. Underneath sits the brachialis, a pure elbow flexor that contributes more to arm size than most people realise.

Read guide →

Triceps

Triceps brachii

The triceps brachii is the three-headed muscle on the back of the upper arm, and it makes up roughly two thirds of the arm's mass. All three heads extend the elbow, but only the long head crosses the shoulder — which is why overhead extensions train it in a way pushdowns cannot.

Read guide →

Forearms

Flexor and extensor compartments of the antebrachium

The forearm contains roughly twenty muscles in two compartments. The flexors on the palm side bend the wrist and fingers and drive grip strength; the extensors on the back side straighten them. The brachioradialis, the thick muscle on the thumb side, flexes the elbow rather than the wrist.

Read guide →

Core

Abs

Rectus abdominis

The rectus abdominis is the long flat muscle running from the pubic bone up to the lower ribs — the one that shows as a six-pack. Its job is flexing the trunk and resisting extension. The visible segments come from tendinous bands crossing the muscle, and how many you have is genetic.

Read guide →

Obliques

Obliquus externus and internus abdominis

The obliques are two layers of muscle running diagonally along the sides of the abdomen. The external oblique's fibres run down and inward; the internal oblique's run the opposite way underneath. Together they rotate the trunk, bend it sideways, and — most importantly — resist rotation.

Read guide →

Lower back

Erector spinae, quadratus lumborum and multifidus

The lower back is built around the erector spinae, three columns of muscle running either side of the spine that extend the trunk and, more often, stop it from bending forward. The quadratus lumborum handles side bending, and the deep multifidus provides segment-by-segment stability.

Read guide →

Lower body

Glutes

Gluteus maximus, medius and minimus

The glutes are three muscles. Gluteus maximus is the largest muscle in the human body and extends the hip — driving you up out of a squat and forward in a sprint. Gluteus medius and minimus sit higher and to the side, abducting the hip and stopping the pelvis dropping when you stand on one leg.

Read guide →

Quads

Quadriceps femoris

The quadriceps is a four-headed muscle group on the front of the thigh that straightens the knee. Three heads — the vastus lateralis, medialis and intermedius — attach to the femur. The fourth, rectus femoris, crosses the hip as well, so it also flexes the hip and needs different training.

Read guide →

Hamstrings

Biceps femoris, semitendinosus and semimembranosus

The hamstrings are three muscles on the back of the thigh: biceps femoris, semitendinosus and semimembranosus. They cross both the hip and the knee, so they do two jobs — bending the knee and extending the hip. Training only one of those leaves half the muscle undertrained.

Read guide →

Adductors

Adductor magnus, longus, brevis, pectineus and gracilis

The adductors are five muscles on the inner thigh that pull the leg toward the midline. The largest, adductor magnus, is also one of the body's most powerful hip extensors — it contributes meaningfully to squats and deadlifts, which is why the inner thigh is far more than a stability muscle.

Read guide →

Calves

Gastrocnemius and soleus

The calf is two muscles. The gastrocnemius is the visible two-headed muscle that crosses both the knee and the ankle, so it only works fully with the leg straight. The soleus lies underneath, crosses only the ankle, and takes over when the knee is bent — which is why seated calf raises are not optional.

Read guide →

Tibialis anterior

Tibialis anterior

The tibialis anterior is the strap-like muscle running down the outside of the shin. It lifts the foot upward — dorsiflexion — and controls how the foot lowers to the ground with every step. It is the direct antagonist to the calf, and it is almost universally undertrained.

Read guide →

Common questions

How many muscle groups are there in the body?
The human body contains over 600 individual muscles, but for training purposes they are usually grouped into around 15 to 20 major muscle groups. This guide covers the 17 trainable groups: chest, upper back, shoulders, traps, neck, biceps, triceps, forearms, abs, obliques, lower back, glutes, quads, hamstrings, adductors, calves and tibialis anterior.
What are the main muscle groups to train?
Most training programmes organise around chest, back, shoulders, arms, core and legs. Within those, the largest and highest-priority muscles are the glutes, quadriceps, latissimus dorsi, pectoralis major and hamstrings — they carry the most mass and respond most to training.
Which muscles are on the front of the body?
The main front-facing muscle groups are the chest (pectoralis major), abs (rectus abdominis), obliques, biceps, quadriceps and tibialis anterior. The shoulders, forearms, calves, neck and adductors are visible from both the front and the back.
Which muscles are on the back of the body?
The main rear muscle groups are the latissimus dorsi and rhomboids (upper back), trapezius, lower back erector spinae, glutes, hamstrings and triceps. Shoulders, calves, forearms and neck are visible from both sides.
How many sets per muscle group per week should I do?
Current evidence points to roughly 10 to 20 hard sets per muscle group per week for most trainees, with the dose-response relationship flattening beyond that. Larger muscle groups such as the back and legs tend to tolerate the higher end; smaller ones such as the biceps and calves need less direct work because they also get trained indirectly.

References

This page is general educational information about exercise and anatomy. It is not medical advice, and it is not a substitute for assessment by a qualified clinician.