Deadlifts (bent knee)

What it is. The bent-knee (conventional) deadlift starts with the bar on the floor. You grip it with straight arms, then stand up until you're upright with the bar hanging at arm's length, around mid-thigh. It is one of the three powerlifts, with the squat and bench press.

Which muscles work.

• Moments (what the joints must overcome). Escamilla et al. (2000) filmed national-level powerlifters. Conventional lifters generated hip extensor, knee extensor, knee flexor and ankle plantar-flexor moments. Compared with sumo, conventional lifters moved the bar 25–40% farther vertically, with correspondingly more mechanical work.
• Activation (EMG). Martín-Fuentes et al.'s 2020 systematic review found erector spinae and quadriceps activation was higher than gluteus maximus and biceps femoris across deadlift variants. Within the hamstrings, semitendinosus was slightly more active than biceps femoris. In the Romanian deadlift, the pattern flips: erector activity is lower than the hamstrings'.
• How to read that. EMG shows how hard a muscle is working, not which muscle moves the joint. The joint actions are hip extension and knee extension; the spine is held neutral, not extended. The erector spinae work hard, but isometrically, to stop the back rounding.
• How the muscles are classed here. Primary: gluteus maximus, hamstrings and adductor magnus (the hip extensors) and the erector spinae (isometric). Secondary: the quadriceps. This follows the joint demands rather than EMG amplitude: in Escamilla 2000, conventional lifters generated only an extensor moment at the hip, while the knee generated both extensor and flexor moments over the lift. Note the tension with the EMG review, where the quadriceps showed higher activation than gluteus maximus and biceps femoris; neither study measured adductor magnus, which is included for its hip-extensor fibres. The source manual had listed the erector spinae as the only primary muscle, with glutes, upper hamstrings and quads as secondary.

Technique cues (coaching standards; see Safe Lifting Mechanics):

• Set-up: mid-foot under the bar, feet about hip width, hands just outside the legs.
• Brace: take a breath into your belly and brace before the bar leaves the floor. Keep your back in its natural curves throughout.
• Lift: push the floor away. The bar stays close to the shins and thighs, and the hips and shoulders rise together.
• Finish: stand tall with the hips through. Don't lean back.
• Lower: under control, hips back first, then bend the knees once the bar passes them.

Form breaks down most often when the weight is beyond what you can hold in position. Add load only while your back position holds.

The trap-bar option. With a hexagonal (trap) bar you stand inside the frame. Swinton et al. (2011) compared it with a straight bar in 19 powerlifters:

• Lower peak moments at the lumbar spine, hips and ankles; a higher moment at the knee.
• A heavier 1RM (265 vs 245 kg) and more peak power.

This makes the trap bar a sensible way to learn the lift and to train hard pulls with less low-back demand.

Belts. A belt is optional for heavy sets; it raises intra-abdominal pressure. Learn to brace without one first (see Weightlifting Belt — Proper Use & Safety Concerns).

See it. Demo clips in the Fysiqal media library: Conventional Deadlift, Trap Bar Deadlift, Sumo Deadlift, Romanian Deadlift, Dumbbell Deadlift, Rack Pull, Deficit Deadlift.

• Lifters wanting whole-body strength, especially in the hips, back and grip.
• Beginners, via the trap bar, dumbbells or a bar raised on blocks, before moving to the floor.
• Anyone who lifts heavy things in daily life or work and wants a trained hinge pattern.

• Healthy backs. With current back pain, leg pain or numbness, or a recent injury, get individual advice before loading this lift.
• The cues are coaching standards, not trial results. The research here describes muscle activity and joint loads; it doesn't test which cue prevents injury.
• Small, specific samples. Escamilla 2000 had 24 competition lifters; Swinton 2011 had 19 male powerlifters. EMG studies vary in method, as the 2020 review notes.
• Resistance training overall is safe for healthy adults: ACSM 2026 reports no increase in serious adverse events across >38,000 participants. That's a general finding, not specific to heavy deadlifts.

Tom, 6 months into training, wants to start deadlifting.

1. Weeks 1–3: Trap Bar Deadlift, 3 × 6 at a load where every rep looks the same. He films the first set each session from the side.
2. Check: his back holds its natural curve on every rep at 80 kg. At 95 kg, his lower back starts to round on rep 5, so 80–90 kg is his working range for now.
3. Weeks 4–8: he adds 2.5–5 kg a week while the video still looks clean. At week 6 he adds a straight-bar Conventional Deadlift from the floor on a second day, starting at 60 kg.
4. Weeks 9+: he keeps the trap bar as his heavy pull and uses the straight bar for technique practice at moderate loads.

Next lesson: Principle of Progressive Overload. Learn how to keep adding challenge to lifts like this one safely over months.

• Bent-knee deadlift: floor to standing, bar finishing around mid-thigh; one of the three powerlifts.
• Primary: gluteus maximus, hamstrings, adductor magnus (hip extension) and erector spinae (isometric, holding the spine neutral). Secondary: quadriceps. Joint actions: hip extension and knee extension; no spinal extension.
• Erector spinae and quadriceps show higher EMG than gluteus maximus and biceps femoris (Martín-Fuentes 2020); the erectors work isometrically.
• Conventional style moves the bar 25–40% farther than sumo (Escamilla 2000).
• Trap bar: lower lumbar, hip and ankle moments, higher knee moment, heavier 1RM (Swinton 2011).
• Brace, keep the natural curves, bar close, hips and shoulders rise together; add load only while form holds.
• A belt is optional for heavy sets; learn to brace without one first.