What Muscles Do Stiff Leg Deadlifts Work? Complete Anatomy Guide

The stiff leg deadlift (SLDL) is a hip hinge exercise that maximally stretches the hamstrings by keeping the legs relatively straight. While similar to Romanian deadlifts, the straighter legs and floor start create a different training stimulus.

Let's break down exactly what stiff leg deadlifts target.

Primary Muscles Worked

Hamstrings

The hamstrings are the primary target of stiff leg deadlifts.

Biceps Femoris (Long Head)

• Outer portion of the back of thigh
• Maximally stretched due to straight-leg position
• Primary hip extensor in this movement

Semitendinosus

• Inner portion of the back of thigh
• Also maximally stretched
• Major contributor

Semimembranosus

• Beneath the semitendinosus
• Works alongside other hamstrings

The nearly straight leg position creates maximum hamstring stretch — more than Romanian deadlifts or conventional deadlifts.

Gluteus Maximus

Your glutes work as hip extensors.

• Drive you back to standing
• Work throughout the movement
• Less emphasized than in RDLs due to straighter legs

Erector Spinae

Your spinal erectors work very hard in stiff leg deadlifts.

• Maintain spine position throughout
• Higher demand than RDLs (greater forward lean)
• Significant isometric work

Secondary Muscles Worked

Latissimus Dorsi

Your lats keep the bar close to your body.

Trapezius and Rhomboids

Your upper back maintains posture throughout.

Core

Your core braces to protect the spine:

• Rectus abdominis
• Obliques
• High demand due to forward lean

Forearms

Your grip holds the bar throughout the set.

Adductors

Your inner thigh muscles assist with hip extension.

Stiff Leg Deadlift vs Romanian Deadlift

These exercises are often confused. Here are the key differences:

| Factor | Stiff Leg Deadlift | Romanian Deadlift | |--------|-------------------|-------------------| | Leg position | Nearly straight | Slight knee bend | | Starting position | Floor | Hang (hip level) | | Knee bend | Minimal (~5-10°) | Moderate (~15-20°) | | Hamstring stretch | Maximum | Very high | | Lower back demand | Higher | High | | Range of motion | Deeper (touches floor) | Stops mid-shin typically | | Glute emphasis | Moderate | Higher | | Weight capacity | Lower | Moderate |

Key Difference: The Knees

• SLDL: Legs stay almost completely straight
• RDL: Knees bend slightly throughout

This knee difference changes hamstring stretch and lower back involvement significantly.

Key Difference: Starting Position

• SLDL: Bar starts on the floor each rep (like a deadlift)
• RDL: Bar starts from hang position, never touches floor

Why the Straight Legs Matter

Maximum Hamstring Stretch

With knees nearly locked:

• Hamstrings are stretched maximally at the hip
• Greater tension in lengthened position
• Enhanced hamstring stimulus

Increased Lower Back Demand

Straighter legs mean:

• More forward torso lean
• Greater moment arm on lower back
• Higher erector spinae demand

Flexibility Requirements

SLDLs require:

• Good hamstring flexibility
• Only go as low as you can with a flat back
• Don't force range of motion

Muscle Activation by Phase

| Phase | Primary Activation | What's Happening | |-------|-------------------|------------------| | Setup | Core, lats, grip | Getting tight on the bar | | Initial lift | Hamstrings, glutes, erectors | Breaking bar from floor | | Ascent | Hamstrings, glutes | Hip extension, standing up | | Standing | Glutes (squeeze) | Completing hip extension | | Descent | Hamstrings (eccentric), erectors | Controlled lowering | | Bottom | Hamstrings (stretched), erectors | Maximum stretch position |

Common Mistakes

Rounding the Lower Back

Problem: Lumbar spine flexes to reach the floor. Result: Injury risk, shifts load off hamstrings. Fix: Only go as low as you can with a neutral spine.

Knees Too Bent

Problem: Significant knee bend, turns into an RDL. Result: Reduces hamstring stretch (still good, just different exercise). Fix: Keep legs nearly straight. Slight bend is fine, but minimal.

Going Too Heavy

Problem: Weight exceeds ability to maintain form. Result: Back rounds, injury risk. Fix: Use moderate weight. This is a stretch exercise, not a strength exercise.

Bouncing Off the Floor

Problem: Using momentum at the bottom. Result: Reduces hamstring work. Fix: Control the descent, touch and go or brief pause.

Hyperextending at the Top

Problem: Excessive lean-back at lockout. Result: Lower back stress. Fix: Stand tall, squeeze glutes, neutral spine.

Not Engaging Lats

Problem: Bar drifts forward. Result: More back stress, inefficient. Fix: "Bend the bar around your legs" — keep it close.

How to Maximize Hamstring Activation

Keep Legs Straight (But Not Locked)

Minimal knee bend — enough to avoid hyperextension, no more.

Push Hips Back

Think hip hinge, not bending forward. Hips go back, torso follows.

Feel the Hamstring Stretch

If you don't feel a strong stretch, something's wrong. Check your knee bend.

Control the Eccentric

Lower slowly (3-4 seconds). The stretch under load builds muscle.

Maintain Neutral Spine

Never round your lower back to reach further. Your flexibility determines your range.

Use Appropriate Weight

This is a hamstring stretch exercise. Moderate weight beats heavy with bad form.

Range of Motion Considerations

Full Range (Floor)

• Bar touches floor each rep
• Requires good flexibility
• Maximum ROM
• Only if you can maintain flat back

Elevated/Partial Range

• Bar stops mid-shin or at ankle
• For those with limited flexibility
• Still effective
• Safer for beginners

The Rule

Go as low as you can while keeping your back flat. That's YOUR range of motion for now.

Programming Recommendations

For Hamstring Hypertrophy

• Sets: 3-4
• Reps: 8-12
• Rest: 90-120 seconds
• Tempo: 3-0-1-0 (3 sec down, no pause, 1 sec up)
• Weight: Moderate

For Hamstring Flexibility + Strength

• Sets: 3
• Reps: 10-15
• Weight: Light to moderate
• Focus: Maximum controlled stretch

For Posterior Chain Work

• Position: After main deadlifts or squats
• Sets: 3
• Reps: 8-10
• Purpose: Hamstring emphasis

Position in Workout

• After compounds: When posterior chain is warm
• Not as primary lift: Too demanding on lower back for heavy work
• Hamstring day: Primary hamstring movement

Stiff Leg Deadlift Variations

Barbell SLDL (Standard)

• Most common version
• Allows moderate loading

Dumbbell SLDL

• Each hand holds a dumbbell
• More freedom in movement path
• Good for beginners

Single-Leg SLDL

• One leg at a time
• Adds balance challenge
• Addresses imbalances

Deficit SLDL

• Standing on platform
• Increased ROM
• For advanced lifters with good flexibility

Sample Hamstring Workout Including SLDLs

1. Conventional Deadlifts — 4×5 (posterior chain strength)
2. Stiff Leg Deadlifts — 3×10 (hamstring stretch emphasis)
3. Leg Curls — 3×12-15 (knee flexion)
4. Hip Thrusts — 3×10-12 (glute focus)
5. Back Extensions — 2×15 (lower back endurance)

The Bottom Line

Stiff leg deadlifts primarily work your hamstrings, glutes, and erector spinae, with secondary involvement from your lats, upper back, core, and forearms.

Key takeaways:

• Hamstrings are the primary target (maximum stretch)
• Keep legs nearly straight (minimal knee bend)
• Bar starts from floor each rep (unlike RDLs)
• Only go as low as you can with a flat back
• Higher lower back demand than RDLs
• Moderate weight with good form beats heavy with bad form
• Great for hamstring flexibility + strength
• Different from RDLs — straighter legs, floor start, more hamstring stretch

Stiff leg deadlifts provide a unique hamstring stimulus due to the maximum stretch created by the straight-leg position. Respect your flexibility limits, control the movement, and your hamstrings will grow.