Differential of inertia, the importance of pulling under the bar

This one is a topic for the physics lovers and those like myself who have spent far too much time thinking about the Olympic lifts, their movements and just what exactly is happening during a lift.

Let me just start off by stating that this article is a little bit of the science behind an often overlooked area, getting into that lovely full squat position and catching a lift under the bar.

Often times coaches, S&C instructors and even athletes are really caught up in the triple extension, getting the bar high enough to snatch or clean. This in itself is great, getting that powerful pull is absolutely crucial to a good lift, max weights and proper form; but it’s not where the exercise ends.

Image

A fine example of all of the above from the World Championships ©Neil Dougan 2011

If you’ve been at any of the coaching courses with me as a tutor you’ve probably heard me asking the question, “at what point does the lift finish” the vast majority of the time the answer I hear, is when the athlete is at rest with the bar overhead. For those same people I say what about practicing correctly setting it down and getting twice the amount of work from your lifts, but that’s for another article.

At this point of triple extension, a lot of beginner athletes take the foot off the gas, they think the hard work is done and drop under the bar, floating eloquently into a nice stable position with a comfortable weight.

I call Shenanigans…there’s so much more to be done… your lift isn’t finished yet!

I can almost hear the coaching cries [read excuses] ring out now; Hell we’re doing it for sport, we want good sprints, the triple extension is the most important part… and yes, for power generation that’s true.

Take this picture for example… lovely triple extension on the left leg – Hip, knee and ankle all opened out to drive powerfully and accelerate…

Image

Now look closer, the right leg is in triple flexion. Toe in dorsiflexion, hip flexor and hamstring all in concentric contraction. Both actions need to be performed fluidly, at speed and with as little lost effort as possible to maximise acceleration.

Nobody sprints with two straight legs after two steps, the sharp contraction of the iliopsoas (hip flexor) mimicked by the squat position, having received the bar, is essential for quick turn around and reutilisation of the limb, it is the second amortisation phase, the second stretch shortening powerful fast movement that is replicated time and again on the pitch, field, track, and yes… in the gym. Weightlifters, for you it’s actually just as, if not more important. If it’s not working at 100%, then nor are you. That 100kg snatch you were looking for when 95 sails into place… that’s only 5% guys and girls, it’s time to get efficient, it’s time to lift big.

This action, of getting quickly under the bar is where the physics comes into play. I use the physics because it so beautifully sums up why it is so important to actively pull under a bar rather than drop or flop; after all it’s the law… so it’s time to dust off the lifting shoes, it’s time to take on physics, and one of the biggest hurdles we face as lifters… Gravity.

The efficient lifter instinctively knows when to use gravity to their advantage; we’ll accelerate from standstill towards earth at 9.81 m/s², but why wait?

Image

Here at the 2011 world championships, we can see how little movement there is in the bar after the triple extension, but it still moves… it is moving under it’s own momentum at this stage, frame 3 shows the feet off the floor, therefore nothing to pull against to add height but empty space; or is there?

As Jennifer Aniston once said, here comes the science…

[Glossary:  M=Mass,  V=Final Velocity, U= Initial Velocity, F= Force, t= time]

The athlete is moving upwards, driving themselves up and taking the bar along for the ride, accelerating to max velocity a la frame 1. – They now have velocity… to make it simple but roughly accurate, lets call it 2m/s.

When calculating the change in inertia, or impulse Mv-Mu would be different for pulling under the bar, than an object at rest. Basically letting gravity do the work for you, slowing you to a stop, then accelerating you towards earth at 9.81ms² takes too long; bearing in mind… gravity’s doing this to the bar as well, the idea is to be under that bar when it starts plummeting to the ground.

The main difference here is the time it takes to get under the bar, which is directly affected by how much force you put into pulling under the bar once those toes of yours get a sniff of hang time leaving the floor.

If the athlete weighs 50kg (490n mass), reaches the top of their pull moving up at 2m’s and hits the bottom of their squat moving down at 2 m/s the change in speed is 4m/s or: (v-u)=4.

In the above frames, they are shot at 60 frames per second which means that it takes 4 frames to get from [V] to [U] which is 0.07 seconds to get under the bar… trust me when I say, this guy was really frickin quick

So if there is space under your feet, and only air around you, what exactly do you have to pull against? – the only object left is the bar.

The bar is travelling upwards under its own momentum at this stage, so what you in fact do by pulling against it is transfer your upward momentum [V] into the bar, increasing it’s velocity, reducing your own by creating downward impulse in your body. This gets the 2m/s speed under the bar or final velocity [U]

The harder you pull, the faster you decelerate, and therefore transfer more force, and upward momentum into the bar as a result. This is the differential of inertia – you defer your inertia into the bar by actively pulling against it like it was nailed to the damn floor. When those deodorant ads said men can’t help acting on impulse, I wonder if they knew the secret to epic lifts…

This means you accelerate down under the bar quicker, take less time to do it, and there is more upward force going into the bar as a result. All of which means… heavier weights!

Just in case there’s a few thinking… I’ve done the analysis, I have the figures: The bar doesn’t get any quicker after triple extension. This is true, but it will decelerate slower with an athlete pulling under the bar, the actual upward momentum gained by the bar during pull under is very minimal.

In any case, the bar is not what’s important in this equation, but the speed of the lifter, if they are under the bar much sooner, the bar has less time to come to rest and head earthbound under gravity, which means the lifter has a much better chance of snatching or cleaning that weight.

There is also an added benefit to this, the psychological one gained by teaching that this is an active part of lifting rather than an addendum to a clean or a snatch.

When the athlete has to focus on actively pulling under the bar then they’re more engaged, less relaxed and just that little bit sharper when it comes to performing the movements.

The action of pulling under the bar, even the language used, lets the lifter know that they are expected to maintain form, continue to lift until the bar is overhead, and not simply coast after Vmax/triple extension.

There are no thoughts of relaxation, or lesser effort, max effort must be maintained until the bar is secured overhead and successfully recovered.

This translates to faster athletes under the bar, more powerful contractions at the hips (great for sprinters and getting those muscles up to standard for good running mechanics) and more weight being lifted due to the increased efficiency of the lifter.

This minimises the distance the bar drops, lowering the force transferred into the lifter when it is caught as it is moving slower, and allows the lifter to again lift heavier as a result.

So why overlook this one small aspect when even small percentages play such a massive role at the high end of lifting.

The less scientific explanations is simply this;

The harder you pull under the bar once the feet leave the floor, the quicker your momentum is transferred into it, with more force, which gets you under the bar quicker, into a stronger position [psychological effect], and even has the added benefit of scraping that little bit of extra height into the bar.

No matter what way you look at it, the bar will be higher when you catch it, you’ll be under it quicker and therefore able to do heavier weights as a result.

Advertisements

Coaching semantics and the misconception of the one true path

Image

As many of you know it’s not like me to be opinionated or controversial, but I thought I’d kick off the new blog with this one.

It’s a subject that comes up time and again regarding various methods of coaching, ideas, and just what really is the best way to achieve results.

There are a number of examples that spring to mind, the Double knee bend, a favourite bone of contention amongst many sports scientists, driving up on to the toes (finishing the triple extension) and actively using this technique to lift, argued amongst weightlifting coaches…. The list does go on; but what are coaches really actually arguing about?

Almost every coach I’ve spoken to over the last decade has agreed that both the movements I used as an example above do happen, the problem comes in do you actively teach this? Are they actions to be performed, or are they reactions which happen automatically?

This is where that grey area tends to appear, and tempers tend to disappear.

I’m going to give you my coaching methodology now to save you reading on while guessing; I personally relate all my coaching back to the end user… the athlete/client.

If the athlete needs something explained or corrections made, I do it. If they don’t, I don’t. As a weightlifting coach, who’s been practicing, performing and competing in the Olympic movements for almost 15 years, these are the movements I coach most often. They are complicated, intricate and there is a hell of a lot involved in getting the movements right.

So one of the idioms I use most often when teaching new coaches, is – “do you as a coach need to know everything there is to know about the lifts?” – I personally believe coaches do, but my follow up question “ok, does your athlete?” usually gets the same response every time, the simple answer is no, there’s enough to think about, and even the action of thinking through a lift inevitably makes performing it harder.

Focusing on one, sometimes two key areas or technical aspects is plenty, any more than that and you’re asking for things to go wrong.

So what do we teach? – my answer, only what’s needed at that time, anyone can get a good grounding in the movements with drills and technique bars/brush handles provided they have the proper mobility and stability.

This brings me to the core of the article… the misconception of the one true path

This idea seems to go unnoticed, glossed over and altogether undervalued as a core principle governing a coaches’ willingness to be open, learn and improve their skills.

The idea being as Liam Moggan summed up so eloquently…. Who says there’s only one right answer?

This small nugget of truth in an absolute quagmire of knowledge, learning and teaching shone above all else. The simplicity of it struck me… Why are we arguing over whether to introduce movements we all agree happen or not, when what we could be looking at is… when is it time to introduce these movements, if ever?

There are so many different body shapes, sizes, motor skill levels, areas of stability, tightness and weakness that teaching one set method would never logically work for everyone.  There will always be those who benefit, and those who would benefit more from a different approach.

The statement is so small in structure, but so far reaching in nature, it’s one of those Zen moments, the answer to a question I didn’t know my subconscious was asking, but yet there it was right in front of me.

It was never that one coach was right, and another was wrong; it was simply that both ideas are correct, it’s the one size fits all application that made the ideas incompatible. When you find an athlete that the coaching method works for, the idea is perfect, when it doesn’t fit, then it’s not the idea that’s incorrect, it’s not adapting your coaching to suit your athlete that’s the problem.

The same can be said for the ideas of coaching the top down method, the bottom up method, whole part whole (compartmentalisation) and so on. The methods are all sound, they work…. But only for those athletes that need that particular method to progress. The method is a tool, it’s the skilled coach who can wield more than one at any given time.

Ask a plumber to fix a broken pipe with only a hacksaw and they may do it, but give them all the tools and parts at their disposal, not only will it get done quicker, but it’ll probably be a much better job as well.

Being a coach is an art form, getting the best tools is what a good coach does, and knowledge is one hell of a tool when in the right hands.

So in looking at the how’s and why’s of coaching; talking about movement skills or even something much bigger or more profound, taking each and every athlete as the unique individual they are, not trying to apply the one size fits all scenario to them to me seems not only logical, but simple, effective, and quite possibly the only way of getting the results that each individual wants.

It’s not that [in this case] there are better ways of teaching, just that some athletes learn better one way, others another. It is the coach who is willing to stretch their own capabilities, push their own teaching boundaries and get out of their comfort zone who will have the most successful athletes. Ask yourself, what does my athlete need, not what was I taught, so I’ll use that.

The more tools you have at your disposal, the more teaching methods, skills and personal attributes you can call on, will mean that you arrive at the answer that’s best for your client or athlete, whatever answer that may be for them.

… there may also be more than one successful way of achieving it; the more I’ve looked, the more I’ve realised; there is no one true path, there are many. They cross, intertwine, some are quicker, some dead ends even help you find the route you were looking for, but it’s never a straight road, and there’s always another path if you get lost.