Biomechanics of the deadlift

The deadlift is the cleanest test of hip extension under load

Conventional, sumo, trap bar, Romanian — every variation is a hip hinge with the bar moving in a straight line from floor (or hang) to lockout. The mechanics that matter: torso angle, bar path, joint moment arms, and how the lifter's anatomy decides which variation suits them.

The setup

A conventional deadlift sets up with:

Bar over mid-foot
Shins close to (but not pressing) the bar
Hips higher than knees, lower than shoulders
Shoulders slightly ahead of the bar
Lats engaged, neutral spine

The setup determines whether the lift will go well. A round-back start is the most common cause of failure and injury.

Conventional vs sumo

Conventional: narrow stance, hands outside knees, more forward torso lean. More hamstring and lower-back demand. Suits taller lifters with long arms. Sumo: wide stance, hands inside knees, more upright torso. Less back demand, more quad and adductor demand. Shorter range of motion. Suits shorter lifters or those with hip/back issues.

Neither is "cheating." They load the body differently. Programming choice is about anatomy, not preference.

Trap bar deadlift

The trap bar puts the load in line with the body (instead of in front). This:

Reduces lower-back shear
Lets the lifter stay more upright
Lowers the technical barrier for beginners
Loses some posterior chain emphasis vs straight bar

Trap bar is the safest deadlift variation for most general-population clients.

Common faults

Bar drifts away from body — weak lats, hips rising too fast. Cue "pull the bar into you" and reset the hip angle. Hips shoot up first — the lift becomes a stiff-leg deadlift with no leg drive. Cue "push the floor away" first. Round upper back — usually fine as long as it's intentional and rigid (think: Olympic lifters). Round lower back is the problem — that's where shear injury happens. Hyperextension at lockout — overarching at the top serves no purpose and stresses the lumbar discs. Cue "stand tall, squeeze glutes" — not "lean back."

RDLs (Romanian deadlifts)

Stiff-leg, knees slightly bent throughout, hips travel back. Emphasizes hamstrings and glutes. Cannot be touched to the floor — stop where you feel hamstring stretch without lumbar flexion.

Programming deadlifts

1-2 sessions per week max for most clients
Higher recovery demand than squats
Reset between every rep when teaching — eliminates momentum, builds setup habits
Singles or sets of 3-5 for strength, 5-10 for hypertrophy, 12-20 for RDLs

TL;DR

Deadlift = hip hinge under load. Bar travels over mid-foot from start to lockout. Choose variation based on body proportions and goal. Round lower back = fault; round upper back = often fine. Trap bar is the safest entry point.