Natural Hamstring Curls are one of the most difficult bodyweight leg exercises that can be performed and are an important part of the toolbox for leg strengthening without weights. The exercise goes by a few different names, you may also see it referred to as Nordic Hamstring Curls, Russian Leg Curls, Ghetto Glute Ham Raises, or Harop Curls, but I prefer to call them Natural Hamstring Curls.
The exercise is a compound exercise that strengthens the entire posterior chain, though primarily the hamstrings and glutes, and does so in a loading plane that is very similar to how leg strength is applied when sprinting. Getting stronger at this exercise will absolutely transfer to sprinting speed.
Small adjustments to form allow you to work with bodyweight alone to very, very high resistances; few people will ever need to (or be able to) add external load to the exercise, and if so very little would be needed. Even the easiest unassisted form variation is still a very difficult exercise, most likely a long period of doing assisted reps will be required before you are strong enough to tackle unassisted reps.
Basics of the Exercise
The exercise is a close relative of the glute ham raise and is in fact often mistakenly called a glute ham raise. The regular glute ham raise however requires a special bench that includes a rounded thigh pad, which makes it a different and much easier exercise, for that reason I prefer to stick to the term natural hamstring curl.
The starting position of each rep is kneeling. There is a support or pad of some sort under your knees, and your feet are vertically restrained at about the same height as your knees (your shins should be roughly parallel to the ground). From there you lower yourself under control so that your body is horizontal to the ground with as little kink in the waist as possible, then reverse the motion back up to kneeling, holding the body as straight as you can, to complete the rep.
Doing this exercise will require some sort of apparatus. A google search on the various names of the exercise will lead to several possibilities. Every good apparatus should have the following traits:
- The vertical heel support needs to be very strong. You are, for all intents and purposes, making yourself into a human crow bar. The upward force of an unassisted rep is a good bit higher than your bodyweight. The support has to be capable of supporting hundreds of pounds. My foot support is a very, very heavy bookcase, by far the heaviest object in my house. A number of possibilities could be built with wood (including as simple as bolting something to the wall).
- There should be some padding on the foot support or shoes of some sort worn. A lot of load is pressing on your heel/Achilles, a little padding goes a long way for safety and comfort. I simply use a blanket.
- The knee support, like the heel support, needs to be very strong (if elevated). By turning the body into a lever, quite a bit of downward force is generated.
- The knee support should be roughly even with the heel support, minus the width of your leg. You don’t need it to be exact, but the closer the better. It is much better for the knee support to be too low than too high. When it is too high its easier for your legs to get perfectly straight or even hyperextend, something to be avoided for safety reasons.
- Padding the knee support is a must. On top of that there should be a good force transfer point just below the kneecap. The kneecaps should be able to freely move. In my setup this is accomplished by placing a rolled up towel just below my kneecaps, on top of the pillow I use. This will make the exercise far more comfortable to perform. Restricting the movement of the kneecaps under high loads is not particularly good for the knees.
- The knees don’t have to be off the ground, but elevating them does give you some additional space to allow for the full range of motion at the point of peak contraction. On the flipside with elevation comes some risk of knee hyperextension, and being too high up will require the use of an elevated object for the hands for assisted reps.
- A toeplate or some form of horizontal foot restriction will allow you to use your calves to assist with the exercise, making it a little bit easier. Without horizontal foot restriction your calves can’t be used to aid with closing the knee. The calves don’t provide a lot of assistance, but it does make a difference, plus it is some additional work for your calves. I do not usually use any sort of horizontal foot restriction in my apparatus, though I have stacked up some books in the past to give it a try.
There is some real risk of injury involved with this exercise; always approach this exercise with caution and respect the potential risk. There are four main points to be aware of:
1) Keep your hands in front of you so that failing doesn’t mean a broken nose or jaw. Your hands should always be in front until you are confident doing unassisted reps and confident you are not going to fail. Do not think that you can get your hands under you quick enough to catch yourself. Even once you are confident doing unassisted reps, keep your hands ready just in case.
2) Do not fully extend the knee. Always keep a kink in the knee. If you fully extend the knee you run the risk of hyperextending the knee and loading/overloading your anterior cruciate ligament (ACL). Tearing the ACL is one of the main major sports injuries. There is nothing to be gained by fully extending the knee, avoid it at all costs. As long as your lower leg is horizontal or even a little slope down from the heel to the knee in your apparatus, the risk of hyperextending the knee isn’t that great. Be mindful of this however when doing the exercise, always keep a kink in the knee.
3) Allow your kneecap to move freely. You should have some sort of support below the kneecap. Even if it isn’t taking 100% of the load going through your knees, the support below your knees should take enough of the load off your kneecaps that they can move freely. A tightly rolled towel works excellent for this purpose.
4) Do not point load your Achilles tendon. If your apparatus has hard edges for the foot support, provide some sort of padding so that the load is spread out throughout the heel area. This will make the exercise much more comfortable and prevent injury to your Achilles.
Don’t let me scare you away from doing this exercise, it is perfectly safe if you keep these danger points in mind and always exercise caution, and respect what your body is capable of.
When starting out, unless you are already very strong, it is highly unlikely that you will be able to do a full unassisted rep. Fortunately this exercise is very easy to add assistance to with the arms. To do an assisted rep, keep your arms out in front of you, catch yourself with your arms then do a pushup to assist getting back up. Doing assisted reps is really all that you need to do to work up to unassisted reps.
The problem with assisted reps is that the amount of assistance you are providing is unknown and fairly variable. It can be difficult to track progress when doing any sort of assisted reps for any exercise; without a means of tracking progress it can be easy to second guess that what you are doing is working.
Fortunately there is a way to track progress with assisted natural hamstring curls. Place a bathroom scale (analog or quick reading digital) under your shoulders, and at the bottom of a rep place your hands on the scale instead of the floor. Hold yourself as parallel as possible (the most difficult point in the rep), then flex your leg muscles as hard as you can to try to get back up. When you flex your muscles the number on the scale will decline, the lowest number you see is the minimum amount of assistance your arms need to provide with each rep. You can track your progress every workout this way. Eventually that number will decline to zero, when it does you can do the concentric (positive) portion of each rep without assistance. You’ll still need assistance to stop the negative (that is a bit harder), but not much; you’re very close to being able to do unassisted reps once the scale goes to zero.
When you first start out, this exercise will likely cause epic cramps in the hamstrings. This will pass in time, it took me a couple months to work through it before I stopped getting them. When you do get them, don’t worry, it is perfectly normal.
This is a little dab’ll do ya exercise. Something about this exercise (the negative) is really rough on the body (not necessarily a bad thing, but use sparingly). It causes unusually strong DOMS and can make the leg tendons sore. There is no need to be doing more than 2-3 sets in a workout, and no need to do the exercise more than once a week. Always err on the side of too little with this exercise.
To manage the soreness and aid recovery, I highly suggest when doing assisted reps that you don’t try very hard during the negative. Put some resistance into the negative, but don’t put forth maximum effort every rep (or even on any reps). Instead put your effort into the concentric (positive) portion of the rep. You’ll get most, if not all of the strengthening benefits without as much muscle and tendon soreness. Once you can do unassisted reps, the negative portion isn’t nearly as damaging (all exercises are this way, but this one in particular really magnifies the effect).
I personally see less value in doing partial reps than doing assisted reps. Trying to control your depth can be really tough, especially since the load greatly increases the deeper you go.
When doing assisted reps keep your body as straight as you can. You’ll need a little kink at the hips, but try to minimize it. I found it helps to took up at the wall in front of you to straighten out.
Once you can do unassisted reps, arm position will have a big impact on the load. By your sides is the easiest. The further forward you move your arms, the harder they become. Possible arm positions include by your sides, out wide like you are flying, tucked up against your chest, behind the neck prisoner style, and overhead like Superman (the hardest position).
If somehow doing the exercise with bodyweight alone becomes too easy, a weight of some sort (kettlebell, dumbbell, weight plate, etc…) can be held goblet style against the chest to add additional load.
The natural hamstring curl is an awesome and very difficult bodyweight exercise used for developing the posterior chain, especially the hamstrings and the glutes, that will translate to sprinting speed. To do it will require some sort of apparatus. Progress to doing full unassisted reps by using hand assistance, and tracking your progress with a scale. Don’t overdo it with the exercise and keep the danger points in mind to stay safe.
Good luck and happy training.
Bodybuilder/Powerlifter/Smart Guy Layne Norton performing the exercise in a gym setting holding weights.
(Note he does not have a contact point under the kneecap to allow for motion and he’s allowing the knee to extend a bit more than I’d be comfortable with, but all in all he’s doing the exercise with very high quality form).
T-Nation Tutorial for Nordic Hamstring Curls (same exercise)