Gym & Training

Squat

The squat is the foundational lower-body strength movement, primarily driving through the quadriceps and glutes to extend the hips and knees. The hamstrings and adductors assist throughout the range of motion, while the core and lower back maintain an upright torso. Depth and stance width shift emphasis between muscle groups.

Primary Muscles

quadricepsgluteshamstrings

Supporting Muscles

lower backabdominalsadductorscalves

Primary Muscles

Thigh

rectus femoris

The rectus femoris is the central quad muscle crossing both hip and knee, visible as the teardrop above your knee. It flexes the hip and extends the knee, powering sprints, jumps, and squats. Balanced development prevents knee pain in athletes.

Thigh

vastus intermedius

Deep central quad muscle under rectus femoris, extends knee powerfully. Core quad for squats and jumps.

Thigh

vastus lateralis

Largest quad on outer thigh, massive knee extender for lateral stability in lunges and sprints.

Thigh

vastus medialis

Teardrop inner quad (VMO) stabilizes patella, key for knee health in deep squats.

Hip

gemellus inferior

Small deep rotator in the hip, gemellus inferior laterally rotates and stabilizes the thigh. Works with piriformis in squats and pivots. Crucial for hip control in sports.

Hip

gemellus superior

Tiny hip muscle above ischial spine, gemellus superior laterally rotates femur. Assists in twisting sports and hip stability. Part of deep six rotators.

Hip

gluteus maximus

Largest hip muscle, gluteus maximus extends and externally rotates thigh for powerful hip thrust in squats, deadlifts, running. King of posterior chain.

Hip

gluteus medius

Side hip muscle for abduction and stabilization during single-leg stance in running, squats. Prevents Trendelenburg gait.

Hip

gluteus minimus

Deepest glute under medius, minimus abducts and internally rotates hip. Key stabilizer for balance in yoga, hiking.

Hip

piriformis

The piriformis is a deep hip rotator in the glutes, externally rotating the hip for balance in squats and deadlifts. Tightness often causes sciatica-like pain. Essential for hip mobility in athletes.

Hip

quadratus femoris

Deep hip external rotator between ischium/femur for leg stability in single-leg work. Prevents twisting injuries in sports.

Thigh

biceps femoris

The biceps femoris is the lateral hamstring on the back of the thigh, with long and short heads forming a thick band from hip to knee. It flexes the knee, extends the hip, and rotates the leg outward, vital for running, jumping, and deadlifts. Key for posterior chain power and injury prevention.

Thigh

gracilis

Long, thin medial thigh muscle adducting and flexing knee. Aids cutting movements in soccer, stabilizing in squats.

Lower Leg

popliteus

The popliteus is a small knee muscle behind the joint that 'unlocks' the knee from full extension for flexion. Crucial for downhill running and pivoting in sports. Prevents knee hyperextension.

Thigh

semimembranosus

The semimembranosus is a posterior thigh hamstring forming the teardrop at knee back, flexing knee and extending hip. Powers deadlifts, lunges, and deceleration in sports. Prevents ACL strains by stabilizing.

Thigh

semitendinosus

Semitendinosus is the slender medial hamstring with a long tendon, flexing knee and extending hip. Aids in medial knee stability for cutting sports. Complements semimembranosus for balanced posterior chain.

Supporting Muscles

Pelvis

iliococcygeus

The iliococcygeus forms the back part of the pelvic floor, spanning from pelvis to tailbone, supporting organs and pelvic stability. Important for core integrity in heavy lifts and preventing incontinence. Weakness shows in squats or postpartum.

Lower Back

iliocostalis lumborum

Iliocostalis lumborum is the lumbar erector spinae muscle along the back, from iliac crest to lower ribs, maintaining upright posture and spinal extension. Critical for deadlifts, squats, and anti-rotation core work.

Upper Back

longissimus thoracis

The longest erector spinae muscle, running parallel to the spine from sacrum to mid-back, it extends the spine and maintains upright posture. Essential for deadlifts, squats, and spinal stability in powerlifting. Weakness leads to back rounding under load.

Lower Back

lumbar rotator

Lumbar rotators (multifidus and rotatores lumborum) are deep spinal muscles that rotate and stabilize individual lumbar vertebrae. They prevent twisting injuries during rotational lifts like Russian twists. Essential for core stability in CrossFit and golf swings.

Upper Back

semispinalis thoracis

Semispinalis thoracis is a deep erector spinae muscle from thoracic spine, extending the vertebral column. Maintains thoracic posture during deadlifts and rows. Prevents slouching in prolonged sitting.

Lower Back

serratus posterior inferior

Deep muscle from lower thoracic spine to lower ribs, draws ribs down and back for exhalation. Aids breathing in heavy lifts like deadlifts.

Lower Back

Set of interspinales lumborum

Small muscles between lumbar spinous processes that extend and stabilize the lower back. Key for spinal integrity during squats and deadlifts. Fitness pros target them for back health.

Upper Back

Spinalis

Medial erector spinae column spanning thoracic/cervical, extends spine unilaterally/ bilaterally. Core for upright posture in lifts.

Pelvis

Tendinous arch of levator ani

The tendinous arch of levator ani is a fibrous white line on the pelvic sidewall anchoring levator ani muscles for pelvic floor support. It transmits fascia for stability during lifts. Critical for core integrity in squats and deadlifts.

Abdomen

Diaphragm

The diaphragm is the dome-shaped breathing muscle separating chest from abdomen, contracting to inhale. Central tendon anchors it, essential for core bracing in lifts and endurance.

Pelvis

External anal sphincter

The external anal sphincter is a skeletal muscle ring around the anus that you can consciously control for bowel movements. It maintains continence during daily activities and is strengthened via Kegels for pelvic floor health. Important for athletes in high-impact sports to prevent incontinence.

Abdomen

external oblique

External obliques form the outer 'V' of your abs on each side, rotating and side-bending the torso while compressing the abdomen. They're powerhouse muscles for rotational power in sports like golf, boxing, and throws. Train them for a defined waist and core stability.

Hip

iliacus

The iliacus is the fan-shaped hip flexor filling your pelvis bowl, partnering with psoas to lift the thigh. Crucial for running, kicking, and rising from sits. Tight iliacus contributes to anterior pelvic tilt and lower back strain in fitness enthusiasts.

Abdomen

psoas major

The psoas major is a deep hip flexor from spine to thigh, lifting knees in running/squats. Core to posture and power; tightness causes low back pain.

Pelvis

pubococcygeus

Part of pelvic floor, the pubococcygeus supports bladder/bowel, aids continence and core stability. Crucial for intra-abdominal pressure in heavy lifts like squats.

Hip

adductor brevis

Short inner thigh muscle adducts the thigh and assists rotation, key for lateral stability in squats and sprints. Middle adductor, it prevents groin pulls in dynamic sports. Essential for balanced leg power.

Hip

adductor longus

Prominent inner thigh muscle adducts and flexes the hip, powering lateral lunges and cutting moves. Prone to strains but key for athletic power. Gym staple for groin strength.

Hip

adductor magnus

Largest inner thigh muscle, with adductor and hamstring-like parts, adducts and extends hip powerfully. Mimics hamstring in deadlifts. Crucial for posterior chain balance.

Hip

adductor minimus

Small deep inner thigh muscle above magnus, aids adduction and rotation. Stabilizes hip in single-leg work. Often overlooked but prevents imbalances.

Thigh

gracilis

Long, thin medial thigh muscle adducting and flexing knee. Aids cutting movements in soccer, stabilizing in squats.

Hip

obturator externus

Deep hip external rotator and adductor originating from the pelvis obturator foramen. Stabilizes hip in deep squats and lateral movements. Often overlooked but prevents groin strains in agility training.

Hip

pectineus

The pectineus is a flat muscle on the inner upper thigh that flexes and adducts the hip, helping drive knees up in running or squats. It's crucial for lower body power in athletes. Tightness contributes to groin strain prevention.

Thigh

sartorius

The sartorius is the longest muscle in the body, spiraling from hip to inner knee, forming a 'tailor's muscle' for crossing legs. It flexes, abducts, and rotates the hip plus flexes the knee, key for soccer kicks and agility drills. Balances quad-dominant training.

Foot

Abductor digiti minimi of left foot

This small muscle on the outer edge of the left foot spreads the little toe away from the others, aiding balance and push-off in gait. It's vital for foot arch stability during running or lateral movements. Runners and athletes appreciate its role in preventing foot pronation issues.

Foot

Abductor digiti minimi of right foot

This muscle runs along the outer arch of the right foot, abducting the little toe to support lateral stability and toe-off in walking. Essential for preventing supination injuries in trail running. It matters for overall foot mechanics in dynamic sports.

Foot

abductor hallucis

This medial foot muscle abducts and flexes the big toe, supporting the arch and propulsion in walking or sprinting. Key for preventing flat feet and plantar fasciitis. Runners target it for injury prevention and efficiency.

Foot

adductor hallucis

Inner foot muscle adducts the big toe, stabilizing the transverse arch during toe-off. Prevents hallux valgus and aids propulsion. Important for barefoot training enthusiasts.

Foot

extensor hallucis brevis

The extensor hallucis brevis is a small muscle on the top of the foot that specifically extends the big toe (hallux). It works alongside other extensors to lift the toes during walking or running, preventing toes from dragging. For fitness enthusiasts, it's key for foot stability in activities like sprinting or plyometrics.

Lower Leg

extensor hallucis longus

The extensor hallucis longus runs down the front of the lower leg and extends the big toe while also assisting in dorsiflexion of the ankle. It's crucial for clearing the foot during the swing phase of gait in runners and athletes. Strong EHL prevents foot drop and enhances explosive movements like jumping.

Lower Leg

fibularis brevis

The fibularis brevis, aka peroneus brevis, lies low on the outer lower leg and everts the foot while plantarflexing it. It's essential for lateral stability in running, surfing, or agility drills. Fitness athletes strengthen it to prevent ankle rolls.

Lower Leg

fibularis longus

The fibularis longus runs along the outer lower leg, crossing under the foot to evert and stabilize the arch. It powers push-off in sprinting and side-to-side movements. Crucial for runners to avoid ankle sprains and maintain foot alignment.

Lower Leg

fibularis tertius

The fibularis tertius is a small muscle on the front-outer lower leg that assists in dorsiflexion and eversion. It's active in quick foot lifts during running or hiking. Often absent, but when present, aids ankle agility in sports.

Foot

First lumbrical of left foot

The first lumbrical of the left foot is a small worm-like muscle that flexes the big toe's base and extends its tip, stabilizing during gait. It fine-tunes toe position for balance in yoga or barefoot training. Key for foot intrinsic strength.

Foot

First lumbrical of right foot

The first lumbrical of the right foot flexes the big toe's proximal joint and extends the distal one for precise foot control. Essential for push-off in unilateral sports like kicking. Builds foot dexterity for minimalist shoe training.

Foot

flexor accessorius

Flexor accessorius (quadratus plantae) is a flat muscle in the sole of the foot that assists flexing the lateral toes. It aligns toe flexors for even toe curl in gripping surfaces. Useful for climbers and martial artists needing foot grip.

Foot

Flexor digiti minimi brevis of left foot

This small muscle in the left foot's sole flexes the pinky toe at its base. It aids toe grip for balance on uneven terrain. Relevant for barefoot runners enhancing foot intrinsics.

Foot

Flexor digiti minimi brevis of right foot

Right foot's flexor digiti minimi brevis flexes the pinky toe base, aiding lateral stability. Supports arch in lateral movements. Train for foot resilience.

Foot

flexor digitorum brevis

Flexor digitorum brevis in the foot sole flexes the four lateral toes at their base for propulsion and balance. Critical for arch support and barefoot stability in fitness.

Lower Leg

flexor digitorum longus

The flexor digitorum longus is a powerful muscle in the deep posterior compartment of the lower leg, running from the tibia down to the toes. It flexes the four smaller toes and assists in plantarflexion at the ankle, helping with push-off during walking, running, and jumping. Strong flexors like this are crucial for balance, propulsion, and preventing foot drop in athletes.

Foot

flexor hallucis brevis

The flexor hallucis brevis is a short muscle in the sole of the foot that flexes the big toe's proximal joint. It stabilizes the arch during walking and running, crucial for propulsion and balance in barefoot training or sprinting. Weakness contributes to flat feet and poor push-off power.

Lower Leg

flexor hallucis longus

Running deep in the calf's posterior compartment, the flexor hallucis longus flexes the big toe and plantarflexes the ankle. It's essential for powerful push-off in sprinting, ballet, and hill running. Athletes rely on it for toe grip on uneven terrain.

Foot

Fourth lumbrical of left foot

The fourth lumbrical of the left foot is a small intrinsic muscle flexing the 4th toe's base and extending its middle/distal joints. It fine-tunes toe position for balance on uneven surfaces during hikes or agility drills. Helps prevent claw toes.

Foot

Fourth lumbrical of right foot

Small worm-like muscle in right foot sole, the fourth lumbrical flexes metatarsophalangeal joint and extends IP joints of 4th toe. Aids precise foot control in sports like soccer. Prevents toe curling issues.

Lower Leg

gastrocnemius

The gastrocnemius forms the visible calf bulge, crossing knee and ankle for explosive plantarflexion. Key for sprinting, jumping, and calf raises. Two heads make it powerful for athletic propulsion.

Lower Leg

plantaris

The plantaris is a thin, vestigial calf muscle aiding knee flexion and plantarflexion, like a minor gas pedal muscle. Often ruptured without issue due to redundancy. Useful for explosive calf power in jumping.

Lower Leg

soleus

Broad flat muscle deep to gastrocnemius in calf, plantarflexes ankle for standing/walking. Powers propulsion in running/squats; endurance king.

Lower Leg

tibialis posterior

Hidden deep in the calf behind the tibia, the tibialis posterior supports your arch and stabilizes the ankle. It inverts the foot and assists plantarflexion, vital for push-off in running and preventing flat feet. Weakness leads to overpronation and foot pain during activity.