Tuesday 17 September 2013

Snatches and Hinges



The ultimate goal is to pull the bar up high enough for you to get under it. The bar starts on the floor and must finish overhead. You can lift the bar to just above your hip level simply by standing up with enough force. But that will not be a sufficient height for you to slip underneath it.

A lot of emphasis is given to multiple pull sections from the floor to overhead. Breaking down each stage into a different pull. I think this is a poor way to visualise the movement as it (in my mind at least) leads to segmented, non free flowing movement. It can be taught correctly, obviously, as almost all successful weightlifters are taught via the breakdown of the pulls. This is simply another way of looking at it.

Really, it's all a single pull, the only thing that changes is that at certain heights on muscle group is more suitable placed to move the bar higher than another group would be. Or at least, more suitable to do so whilst preserving the ultimate goal in an efficient manner and in a direction that benefits the lifter most.


From the floor to the knees the Quadriceps are the primary movers, they contract, extending the knee joint and forcing the knees to raise upwards and backwards (as the floor is resisting any downward movement of the feet, the force must be released in the only available direction). This conveniently results in the knees moving out of the way of the bars upward path.

Fig 1


The up and backwards travel of the Knees extends the legs, but because of the floor resisting, everything above has to move upwards instead (Fig 1). Like uncoiling a spring underneath something. The angles of the Hips, Shoulders and Back should not change as all that is happening is the whole structure above the Knees is simply travelling upwards. The role of the Shoulder/Hip/Back structure at this point is simply to act as an isometric support for the bar's upwards travel.

Fig 2


After the extension of the Knees by the Quadriceps, they are no longer in a position to generate any more force in order to continue the bars vertical travel. So now, if we want to continue raising the bar, the load must be moved onto another set of muscles. The strongest, nearest muscle group that can raise the bar is now the Posterior Chain. The Hamstrings, being very close to the Quadriceps locationally now take the load. (Fig 2) But being further back in physical space than the Quadriceps, the bar must also travel further back to stay within the centre of gravity of the lifter/bar system.

The only muscle group that can move the bar that can move the bar backwards without compromising the load on the Hamstrings is now the Lats and their surrounding muscles.

Fig 3


The Lats sweep the bar back in line with the centre of gravity (Fig 3). (A degree of upper arm involvement is normal, as the Lats and Triceps/Biceps/Forearms are a connected chain of muscles. So activating one without the other would be difficult).

Now the Hamstrings and Glutes are loaded, the bar is balanced once again and ready to continue its upwards travel.

The Posterior Chain could fire now, hinging around the Glutes. But in this position the path of the bar would be horizontal(Fig 4), as the movement would be identical to a hinge opening quickly. The hips being the centre of the hinge.

Fig 4


So the bar needs to be moved into a position that will allow the vertical movement path to continue. The Glutes and Lower Back could contract, extending the spine vertically(Fig 5). But again this results in the bar swinging out in front horizontally more than vertically as again the movement is rotational around a single hinge point. Remember that we are PULLING the bar off the ground and overhead, not hinging or swinging it.

Fig 5
The most obvious way to impart vertical movement onto an object would be to put it in a position where vertical force can be applied. In this case, repositioning around the bar so that you can move it vertically. We'e already seen how simply using a single hinge results in an omnidirectional generation of force (in this case horizontal). So in order to counteract this, we use opposing hinges to negate the horizontal force and direct it vertically.

The hinges in question are the Hips, Shoulders and Knees (although really the Shoulders are simply the top of the Hip-Hinge). The Hips are the most powerful of these hinges by far, being the largest and connected to the most surrounding muscle groups. But as we have seen, misguided when used alone. So, the Knees and Shoulders must be brought in to counteract the horizontal force of the Hip-Hinge and transfer the force vertically by channelling the force generated by the the ends of the Hips rather than the centre.

But before this happens, the hinges must be placed in positions that allow them to open fully. So they all need to be suitably loaded, ready to fire. So in the real world this looks like (from the side view), the bar being above the front of the Heels, about half way up the Thigh, with hips slightly behind the Heels and Shoulders on top of the bar or very slightly in front of it, with a Spine approaching a nearly vertical angle. The Shoulders in this situation are not so much a direct force generator, instead they channel the force generated from the body into the bar, the body rises upwards, the shoulders do so too, pulling on the bar and transferring the power. (Fig 6)

Fig 6


The bar needs to be roughly centred between all of the hinges prior to opening so that maximal force from each hinge can be  transferred. Now, you 'simply' open all the hinges simultaneously. The Knees travel backwards into extension, forcing everything above them to raise vertically as the floor will not be moved downwards.

At the same time the Hips are opening and generating some horizontal force, but most is negated by the compensating force of the knees (and shoulders to some extent).

They are however generating a lot of vertical force, they have no option as the force must be released but is unable to do so horizontally.

The Shoulders are the point that most of this force in directly transferred into the bar after the hips make contact. However they realistically do more to alter the position of the lifter than the bar, as ideally, the bar weighs more than the lifter. But they do still add a final amount of steering to the ultimate direction of the bar. As we want a vertical direction for the bar, emphasis should be given on a straight pull with the shoulders, rather than a hyper extension/excessive pulling backwards. Or in the other direction, the Shoulders staying in front of the bar will not allow a complete extension of the Hip joint.

Fig 7


From a side view, some amount the Shoulders being behind the Hips will be shown. And this is normal, in fact this is necessary for a  complete extension of the hip hinge. Bio Mechanically, when fully extended, joints do allow their attached limbs to travel past 180 degrees. So for the Hips to be fully opened the thighs and spine will be at an angle of greater than 180 degrees. (Meaning the Shoulder will be slightly behind the Hips)(Fig 7).

Perhaps more relevant to the lifter themselves, if they are hoping for a vertical bar path, then at some point they will need to move themselves out of the way of that bar path, as up until this point the body of the lifter has been held somewhat through the bars path so that balance can be maintained, but once all force has been expelled, the bar does not need supporting in position, the direction has already been determined.

Now that all of this vertical power has been produced; the bar, attached to the generated force by the Arms will be pulled along with this force. The weight used vs amount of force generated will obviously effect the height that the bar travels to.

You can work out the lowest point that the bar must be pulled to by noting the height of the bar when the lifter is in their lowest catch position with locked out arms. (Fig 8)

Fig 8


This is of course assuming a perfectly efficient pull and pull under, which is very rare. In reality most people will pull to a height slightly greater than the lowest required to give some comfort space and allow them room to be certain of getting under the bar correctly. Of course, as the weight increases, this ability to give 'wiggle room' diminishes and the lifter is forced to become more efficient or they will fail.

Once the bar has been raised to the highest point it can reach by extension of the hinges, one more method of pulling must be used to finish. The lifter having exhausted the power of most of his muscle groups gives a final strong tug to the bar with the only group of muscles still attached to the bar and in a position to still contract.

The Upper Back and Arms are used to finish the pull. This effort simultaneously pulls the bar upwards and increases the downward speed of the lifter under the bar.

As with all lifting, the largest muscle groups fire first and the energy production continues down the chain to the smaller muscles. In this case the upper back generates the initial pulling force, pulling the Elbows backwards and upwards. The Arms do exert pull too, but this is more similar to an isometric movement as the result of the upper back activating.

Because the lifter is exerting an up and back  motion on the bar, the bar will be exerting a down and forward motion on the lifter. This will pull them under the bar and pull the bar above them, allowing it to be caught in the correct position with straight arms.

2 comments: