Plank + straps for Nordic leg curls and Matrix leg extensions

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Massimo Kokhno
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Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Massimo Kokhno » Sun Jan 13, 2019 8:58 pm

This was just an idea but now I have a working prototype, so this post has been updated. Suggestions to refine the idea are encouraged. It would be great to discover a reliable standard for the dimensions and exact material/wood type of the plank that would guarantee safety and make the plank easily portable.

What are Nordic curls and Matrix leg extensions? They are challenging anchored straight body leg exercises, respectively for the hamstrings and quads. Examples:
Click to show or hide
World record for Nordic curls, as far as I know. They need something heavy to hold the heels down and padding for the knees, optionally for the heels.

Example of Matrix squats with the maximum range of motion allowed by the floor without elevating the feet, certainly not a world record but I don't have better video examples for now. They need something to prevent the shins from falling back and the feet from sliding forward and optionally padding for the back of the knees and for the feet.
Here is an image that summarizes how these exercises could be done with just a plank and one strap (for holding the heels down in Nordic curls) or two (in Matrix squats one to prevent the feet from sliding forward and one to keep the shins vertical):
Click to show or hide
Image
The image shows the "tucked" version of these exercises, which can be used as a progression towards the full lay form.

Here is my first prototype, basically a plank with two holes on one end (the middle hole is not needed), so that the strap for Matrix squats can be removed instead of being nailed down:
Click to show or hide
The plank needs to be robust enough to avoid bending under load (with a straight body the force at the position of the feet is around 115%BW based on someone's calculations of the lever arm, which is from the knees to slightly above the waist). If it starts bending some counterweights can be placed on the end that lifts, like in this example:
Click to show or hide
Also the plank needs a sufficiently long base of support to avoid flipping over, or this can happen:
Click to show or hide
You can see how in his next attempts, to counteract the torque of the straight body and of the added weight, he placed some plates on the end of the machine as a counterweight. So the plank should not be too short or in that case you'll need to put some weight on its end.

It's better if the plank is wider than your knees so that you can put them on it comfortably at the preferred distance.

The straps need to be robust enough too, to be safe you can get some cheap ones rated for more than 200kg/440lbs at a hardware store or use the straps from your gymnastic rings or anything else at your disposal. I'm not sure a belt is always strong enough, I used one in the past but one day it suddenly broke, fortunately I did not faceplant into the floor but after that for safety I used a cheap but robust ratchet strap.

My current setup is not ideal for full range of motion Matrix squats (could be improved by fitting the strap for the feet through a pipe to get better leverage, when using pipes be careful since the edges could fray the strap over time). And it's not suitable for one leg Matrix squats, the strap keeping the shins vertical tends to slide down, using a pipe there too could be a solution. Here are all the setups I've seen for one leg Matrix squats:
Click to show or hide
A bench is a good setup, but it can limit range of motion. A Roman chair (like the one the guy who got flipped over used) would be better I think, if available.

Two pipes worked well for this guy, but the top pipe should be lower to allow full range of motion. Two telescopic bars would work similarly. (at 0:26)

A dip belt against a pillar seems decent, not sure if it's as stable as the setups above. It's a minimalist solution and allows full range of motion since it's easy to elevate the feet. (at 8:48)

This was my best attempt with just a pole and strap, felt quite awkward to balance but I think it's possible to get full range of motion even even with this low amount of support.
Also there are versions of the leg curl and extension that have more range of motion, examples:
Click to show or hide

I have successfully tested incline and decline Nordic curls, but haven't tried this for Matrix squats yet. Below is my test, where the plank slightly bends but holds, to be safer it would need to be reinforced, or have an object under the middle of the plank to bear some weight.
Click to show or hide
I'll keep refining and testing, let me know if you have more ideas or results of your tests.
Last edited by Massimo Kokhno on Sun Jan 27, 2019 3:37 pm, edited 1 time in total.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Vagabond » Mon Jan 14, 2019 5:41 pm

What a great quality post! I did not respond to it right away because I wanted to make sure I had time to see everything.

I really like that idea, and I've seen such planks in the past.

One thing to note is that when the guy's setup failed, it wasn't because the torque was too high, but because it places too much weight outside of the setup's base of support. If you were to put the straps close to one extremity, all you would need is a plank that extends far enough so that your body (or most of it, but let's say your whole body for the sake of safety) stays over the plank. That way, even if you were to do those exercises with 300% BW added... The plank will never flip like that. It can break. But not flip.

Here is the design I suggest:
Image
Make the board thick, and long enough so that your body stays inside of it. You can make it shorter, but you'll have to calculate how much weight there is over the board vs outside, and at what height and leverage. So just make it long enough. I recommend glueing and compressing 2x2s or 2x4s side by side to make it super thick and strong, then planning it so it's perfectly flat, and then cutting the slots for the straps at the desired places. I chose to place many slots because it can be nice to have different straps for each foot/leg so that they're not just squeezed together. Notice that from profile, the bottom of the plank has a different profile where the slots are located. This is to leave space for the straps or ropes to pass underneath.

Also different designs would be cool. Example:

-A shorter board could be made if retractable stabilizers could be added. I can think of many different designs. Could be one or two beams that slide out from the board at the opposing end of the straps. The board could also have dowels sticking out on each side, and two beams with holes in them could be inserted like Lego blocks then strapped to prevent them from falling out if the dowels are short. The whole point of the stabilizers would be to make the plank's base of support longer so that the weight doesn't tip outside of it.

-Make notches underneath the board at either extremity, or place hooks, so that the board could be hooked onto stall bars to modify its inclination/declination. I can see many different possibilities. Even if someone doesn't have stall bars, they could certainly build a small incline ladder onto which the plank could hook to vary its extremities' elevation. Or the plank could have short dowels sticking out on each side, and the structure could have notches on each side in which the dowels could rest. Like that, it would be less expensive than building a ladder using thick dowels, because those are expensive. If I have to build such a contraption, that's probably what I'd do. A thick but short dowel on each side of each extremity, and a foldable triangular structure with notches on each side.

-An other choice could be to add rotating arms at each end of it, and make them lockable like beach chairs to vary the height. But I think it's a fairly limited design, because it gets complicated, makes the board much more bulky, and you can only make those arms so long. I imagine you could make those arms extensible to create bigger differences in height, but it gets even more complicated. Simply making the plank inclinable to fit stall bars is good enough.

-Inclination could be changed by using straps and a door. Find a solid door, have the straps locked above the door using an object too thick to make it through on the other side, and hook the board onto the strap. Advantages: very simple and doable anywhere for cheap. Disadvantage: needs a plain wood door to avoid damage, places stress on the hinges, and might not be the most reliable in terms of solidity, so may be prone to dropping. So, could be dangerous.

-A 2x4 frame can be built, and plywood or boards can be used to cover the top. But the wood around the slots need to be thick and solid. I suggest using 2x4 or 2x2 for this section. Various combinations are possible, such as simple planks held together with 2x4s or 2x2s at a couple different places. One nice possibility would be to laminate wide planks (like 1x6s) in two layers, with two different directions. Could make a nice 2" thick plank that's 2 feet wide and 6 feet long pretty easily. The slots still would need to be reinforced, unless hard wood is used. Do NOT use pine, it will absolutely crack.

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Massimo Kokhno
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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Massimo Kokhno » Mon Jan 14, 2019 8:49 pm

Wow, that's a lot of great ideas, thanks for those! For version 1 I'll just try a sufficiently long plank with only two holes, just to have something I can use at home for now for the unweighted version of the exercises. Then I'll think about applying your improvements. Below I have some thoughts about other setups that could be part of other threads but for now are just a comparison to this method.

The advantage of the simplest design is that it's a great setup for Nordic curls at home. Referring to this list of setups , two other good options are with a door jam or a telescopic pull up bar, but some door frames will deform and get damaged with these. Then there is the option of heavy furniture with space to put the feet under, if available, or making some heavy sandbags and putting them above the feet. Outdoors the simplest options are under a car, pole or tree+strap, park bench + strap or finding low bars from playground equipment etc. So at home it's always possible to use a plank or sandbag + strap, while outdoors a pole or tree + strap since poles and trees can almost always be found. Or a partner holding the heels down, but you can't always find one.

Now regarding the Matrix squat, I think it's a less crucial exercise, since there are other minimalist quad dominant exercises (door frame assisted or freestanding sissy squats, kneeling leg extensions, advanced shrimp squats or other one leg squats with knees far over the toes) but it has its pros, like being able to intensely work the quads with a similar resistance curve to squats without balance being a factor and quantifiyng the resistance precisely (no need to use the hands for balance assistance or friction resisted exercises where the difficulty is less objectively measurable). Outdoors the pole or tree + strap setup is almost always available, while at home aside from a plank a pillar can be used if available, in some cases also very heavy furniture. And if allowed, drilling into a wall to put some kind of hook allows to use it as an anchor point for a strap. Or if there is a narrow corridor or normal door frames that don't deform under pressure, two telescopic pull up bars.

And another point, related to the plank setup, is how much support it allows for one leg Matrix squats. Basically I found that with a pole+strap it was quite awkward to balance, while some others have found more stable setups. Here are some examples:
Click to show or hide
A bench is a good setup, but it can limit range of motion. A Roman chair (like the one the guy who got flipped over used) would be better I think, if available.

Two pipes worked well for this guy, but the top pipe should be lower to allow full range of motion. Two telescopic bars would work similarly. (at 0:26)

A dip belt against a pillar seems decent, not sure if it's as stable as the setups above. It's a minimalist solution and allows full range of motion since it's easy to elevate the feet. (at 8:48)

This was my best attempt with just a pole and strap, felt quite awkward to balance but I think it's possible to get full range of motion even even with this low amount of support.
Maybe for the plank setup to provide stability PVC pipes with padding around them, for the feet and behind the knees, could work.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Vagabond » Mon Jan 14, 2019 10:16 pm

Yeah, that's a good idea! I forgot to add that feet braces would be useful to avoid slipping, too!

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Against Gravity » Tue Jan 15, 2019 8:41 pm

The thing I like the most about BW-based exercises to strengthen legs is that it doesn't require a heavy barbell constantly crushing your spine. I wonder if they are also superior for longevity.

Currently, my goal on barbell squats is 5x20 (+100kg). If I ever achieved that, the most logical thing is to add more weight to the barbell. And repeat this over and over. But this idea doesn't seem very appealing to me when considering longevity factor. Obviously, strength loses associated with aging (or 'sarcopenia') would prevent squatting / deadlifting that heavy, anyway, but I wonder if the accumulated damage through the years may end up causing joints problems.

I mean: theoretically if we keep technique perfect on all reps for all sets (ideal case) no problems should happen. But I can't stop wondering if, even in such ideal case in the very long term (decades) the accumulated damage caused by heavy squatting (or deadlifting) may also have inherent consequences in the form of serious joint issues. There's a lot of powerlifters/weightlifters who seem to be perfectly fine in the old age; but also a lot of others with training-related joint issues.

Sticking to bodyweight leg strength training seem to be much more sustainable for longevity, but I certainly have no idea.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Massimo Kokhno » Wed Jan 16, 2019 3:17 am

I think both bodyweight and weights can help staying healthy at an old age if done in moderation, while with excessive volume or intensity any training tool can cause injuries and long term problems. These bodyweight exercises are quite safe for the back but can damage the knees.

Today a friend helped me make a simple prototype, it worked perfectly for Nordic curls and dragon flags, while for Matrix squats I'm not sure it's safe since it slightly bends and could break in the area between the holes and the place where I put the feet. Reinforcing it could be a good idea. The hole in the middle proved unnecessary.

Here is a video of the setup in action:
Click to show or hide
And a picture of the setup:
Click to show or hide
Image
The straps behind the knees tend to slide down in some cases and when I tried full range of motion I felt like I could not apply good leverage, maybe I'm also weaker at Matrix squats than in the past, I'll test feet against a wall with the strap attached to a pole to compare the leverage. For the one leg version the strap kept sliding down and I felt a lot of pressure even when I tried more padding, so I'll have to refine the design.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Vagabond » Wed Jan 16, 2019 6:35 am

I like it! It's a nice design, but it definitely needs to be made thicker, both for safety and efficient transmission of force while doing moves. I like the size of it tho, it looks easy to put away in a closet or something.

As for longevity, I really think it depends on many factors, including the use of PEDs. Steroids are known to shorten muscles and tendons, and the strength and mass gains associated with them happen so fast that the body's soft tissues lack time to adapt. For natural lifters, it isn't a problem. And for non-competitive people who want longevity, it seems to be fine as long as you don't ego lift, use good form that's adapted to your anatomy and make sure that overall you don't have issues. If anything, heavy-ish weights puts stress on your structural tissues and cause them to grow stronger overtime. As long as you go at it slow but steady, because joints, bones and soft tissues take much more time to repair than muscles do. However, they do recover. After, it's up to good programming. Should you do it? I think so. Should you drive yourself into the ground with it? Hell no. Do you want to spare your back? Yes. So mixing the two is probably the best solution.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Against Gravity » Wed Jan 16, 2019 6:17 pm

Vagabond wrote:
Wed Jan 16, 2019 6:35 am
I like it! It's a nice design, but it definitely needs to be made thicker, both for safety and efficient transmission of force while doing moves. I like the size of it tho, it looks easy to put away in a closet or something.

As for longevity, I really think it depends on many factors, including the use of PEDs. Steroids are known to shorten muscles and tendons, and the strength and mass gains associated with them happen so fast that the body's soft tissues lack time to adapt. For natural lifters, it isn't a problem. And for non-competitive people who want longevity, it seems to be fine as long as you don't ego lift, use good form that's adapted to your anatomy and make sure that overall you don't have issues. If anything, heavy-ish weights puts stress on your structural tissues and cause them to grow stronger overtime. As long as you go at it slow but steady, because joints, bones and soft tissues take much more time to repair than muscles do. However, they do recover. After, it's up to good programming. Should you do it? I think so. Should you drive yourself into the ground with it? Hell no. Do you want to spare your back? Yes. So mixing the two is probably the best solution.
Definitely, since we are not using drugs, we are literally forced to progress slowly - at least, slow enough for giving the bones & soft tissue enough time to adapt to this kind of heavy compression stress. Plus, the fact of not competing like professional powerlifters helps to avoid ego-lifting and the injuries associated with it. So all in all (as long as we learn technique correctly), we are the least likely to get affected by this kind of chronic pain in the old age due to weightlifting.

This is Paul Wade wrote in the 'going beyond' section in the 'Squats' chapter on CC book:
So--assuming you've already reached the expert level in your one-leg squatting-I'm about to tell you how to get stronger and stronger, right? Spill lots of secret prison-guarded tips and tricks for building more and more power in the legs? Wrong. I'm all about strength, but in the case of the lower body I think the instinct of endlessly adding resistance is a mistake. Of course, it's easy to add weight to the one-leg squat if you want. The old school strongmen did it all the time. Just grab a dumbbell and hold it to your chest, or slap a barbell on your back
Training this way, Bert Assirati could do one-leg squats with two-hundred pounds. American female shot-putting champ Connie Price-Smith has used two hundred and forty-five pounds in the exercise.
Big figures look impressive, but in reality they are often associated with injury. All serious powerlifters are constantly plagued by knee and back problems. Most have to go under the knife sooner rather than later, and the majority are crippled into old age because they have whittled away their knee joints and vertebrae in the quest for ponderous poundages. Don't be misled by the idea that strength is everything. For a prison athlete, function is everything. Where the legs are concerned, mobility is more important than strength. Once you have developed the strength to perform unilateral squats, you'll have piston-like legs and your joints will be incredibly powerful. Further resistance work will give you chunkier thighs, but you won't necessarily gain in athleticism. The next stage-if you haven't started already-is to learn to use your lower body strength. Explore stair sprints, jumping, car pushing, etc. These will add conditioning, speed, agility and endurance to legs that are already awesome. Don't get blinded by big numbers in your leg training journey
Probably, by 'don't get blinded by big numbers' he was referring specifically to ego lifting, not necessarily to avoid any kind of weight training for legs. However, 'progress' on barbell squats is always aimed to lift heavier. So eventually, falling into the trap of ego-lifting (aiming for big numbers) may turn into a reality - and that's probably the highest risk of the exercise.
The straps behind the knees tend to slide down in some cases and when I tried full range of motion I felt like I could not apply good leverage, maybe I'm also weaker at Matrix squats than in the past, I'll test feet against a wall with the strap attached to a pole to compare the leverage. For the one leg version the strap kept sliding down and I felt a lot of pressure even when I tried more padding, so I'll have to refine the design.
I'm thinking into adding nordic curls, paired with weighted pistol squats. Based on your experience, what would you recommend for the goal of a full ROM concentric? I'm thinking into three sets of three eccentric attempts per working out session. Once I can successfully control the negative slowly for full ROM, I may try the concentric.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Vagabond » Wed Jan 16, 2019 8:05 pm

For Nordic curls, I've had success with 3x3 eccentric reps with super light hand assistance to come back up not only for myself, but also for students (I have many students who learned to do Nordic curls on a mat).

As for leg training, again, I believe in choosing the right exercise. I think that weighted pistols are great, and have done them for many years. But I also think that regular squats are the best for power development in athletic performance. If you're not trying to jump super high or sprint super fast, then you can probably do away without them. But I've found better increases in my jumping ability when I was doing parkour when I started doing barbell squats vs doing weighted pistols. There is probably a point where this is superfluous, but it would be difficult to pinpoint exactly where.

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Re: Plank + straps for Nordic leg curls and Matrix leg extensions

Post by Massimo Kokhno » Wed Jan 16, 2019 11:05 pm

I've made a thread on Reddit r/bodyweightfitness to get more ideas to improve the setup, I also linked this discussion there.