Razor Curl
How to Do a Razor Curl
Set up securely in a GHD with the feet locked in and knees positioned comfortably on or near the pad.
Flex the hips so the torso is approximately parallel to the floor and brace the trunk to maintain that position.
Begin with the knees bent and keep the hips and torso controlled rather than allowing the body to unfold into a standard GHR.
Slowly extend the knees, lengthening the body lever while maintaining the hip-flexed torso position.
Stop before the knees lock completely or before you lose neutral spine and pelvic control.
Flex the knees forcefully with the hamstrings to pull the body back toward the starting position.
Reset the hip angle and trunk brace before each repetition.
Form Check & Technique
DO THIS (Technique Tips)
- Secure the feet and test the GHD setup first.
- Keep a deliberate hip-flexed torso position.
- Maintain a neutral spine.
- Extend the knees slowly.
- Avoid hard knee lockout.
- Pull back with the hamstrings.
- Use the razor curl as a progression toward GHRs.
AVOID THIS (Common Mistakes)
- Extending the Hips Into a Standard GHR — Fix: maintain the planned hip-flexed torso position throughout the razor curl.
- Rounding or Hyperextending the Spine — Fix: brace the core and use a smaller knee-extension range.
- Locking the Knees Hard at the End — Fix: stop just short of passive lockout and keep hamstring tension.
- Using Momentum — Fix: control the eccentric and initiate the return with knee flexion.
- Poor GHD Setup — Fix: secure the feet and adjust the pad so the knees can move comfortably.
- Treating Study EMG Numbers as Proof of Universal Superiority — Fix: use the razor curl as one effective hamstring option rather than claiming it beats every alternative.
About Razor Curl
The razor curl is a GHD-based hamstring exercise and variation of the glute-ham raise performed with the hips flexed and torso held approximately parallel to the floor. You extend and flex the knees while maintaining the shortened body lever, which makes it a useful progression toward a full glute-ham raise. Research on the razor curl has shown very high hamstring activation in a small group of collegiate athletes, particularly from a hip-flexed position into greater knee flexion.
Razor Curl Muscles Worked
The razor curl places the hamstrings under high knee-flexion demand while the hips remain flexed.
- A 2009 EMG study in eight female intercollegiate athletes reported very high medial-hamstring and biceps-femoris activation, with maximum hamstring and gluteal activation observed from about 90 degrees of hip flexion into knee flexion beyond 90 degrees.
Sets & Reps Guidance
Technique / Learning
Technique: 2–4 sets of 4–6 assisted or partial-range reps while learning the fixed torso position.
Strength Focus
Strength: 3–5 sets of 4–6 controlled reps with a stable hip angle and long rest.
Muscle Growth (Hypertrophy)
Muscle growth: 3–4 sets of 6–10 reps, using assistance if needed to preserve form.
General training baseline. Need.fit automatically adjusts exact sets, reps, and working weight based on your individual fitness level, recovery, and progress over time.
Exercise Variations & Alternatives
Glute-Ham Raise
Longer-lever GHD hamstring movement that the razor curl can help you progress toward.
Nordic Hamstring Curl
Floor-anchored long-lever eccentric knee-flexion exercise.
Slider Leg Curl
Scalable bodyweight floor curl useful as an easier regression.
Swiss Ball Leg Curl
Bridge-and-curl hamstring exercise with an unstable ball.
Romanian Deadlift
Learn Romanian deadlift form, muscles worked, hip-hinge and bar-path cues, proper depth, common mistakes, RDL vs deadlift differences, and sets and reps.
Lying Leg Curl
Learn lying leg curl form, muscles worked, hip & knee setup, pad placement, common mistakes, lying vs seated leg curl, and optimal sets and reps.
Razor Curl vs Glute-Ham Raise
Muscle & Strength describes the razor curl as a variation and progression toward the full GHR. The razor curl starts with more hip flexion and a shorter effective body lever, while a standard GHR keeps the hips more extended through much of the knee-flexion phase.
Razor Curl vs Nordic Curl
The Nordic curl is usually performed from the floor with the body aligned from knees to shoulders and the ankles anchored. The razor curl uses a GHD and a flexed-hip torso position, shortening the lever and changing hamstring length and joint angles.
Why Hip Flexion Changes Hamstring Demand
Most hamstrings cross both the hip and knee.
- Flexing the hip lengthens them proximally while they continue producing knee-flexion force.
- The razor-curl study was specifically designed around this functional hip-flexed position.
What the Razor Curl Study Actually Found
The 2009 study measured eight healthy female intercollegiate athletes.
- It reported peak medial-hamstring activation up to 220% of MVIC and biceps-femoris activation up to 140% of MVIC during the tested movement.
- These findings demonstrate high activation in that small sample, not a guarantee that the razor curl is universally superior to every other hamstring exercise.
How to Use Razor Curls as a GHR Progression
Because hip flexion shortens the effective lever, Muscle & Strength recommends razor curls for lifters who cannot yet complete normal GHRs. As strength improves, gradually reduce the hip flexion and transition toward a longer, more demanding GHR position.
How to Regress the Razor Curl
Use band assistance, shorten the knee-extension range, or emphasize slow eccentric repetitions. If maintaining a neutral trunk is difficult, regress further to slider or Swiss-ball curls before returning to the GHD.
How to Program Razor Curls
Treat them as a demanding hamstring accessory rather than a high-fatigue conditioning movement. Low-to-moderate rep sets allow you to preserve the hip angle and controlled eccentric that make the exercise distinct.
Sources & References
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