THE KAYAKER’S CORE – Part 4: Core Imbalances – When the movers take over
In Part 1-Core 101 we looked at the classification and differences between the muscles of the core; the stabilisers and the movers (mobilisers). In an perfect world (the one sports scientists dream about..), all athlete’s bodies would be well-balanced and functioning optimally, and these muscles would stick to performing the taks they were labelled with.
However, we don’t live in a perfect world, and just because a muscle has been categorised as a stabiliser or mover, doesn’t mean it’s only capable of that one job. These categories just indicate what a muscle’s neuromuscular and physiological characteristics make it most suitable for – but both types of muscles are capable of performing both roles [1].
To examine this in regards to movement, let’s think about the stabilisers as a truck and the movers as a car. If you want to carry a heavy load long distances, then the truck is really useful, but if you want to speed around a Formula 1 track, you’d probably opt for the car. This doesn’t mean you can’t race a truck or heavily load a car…
Most people would agree that driving the car pictured isn’t a particularly good idea, but there are many highly trained athletes driving exactly that ‘car’ around every day, because if the primary core stabilisers are too weak for the job, switched off, or firing incorrectly, but the movers are strong (including movers from other parts of the body), the movers will automatically take over the role of the stabilisers (regardless of the athlete’s best intentions).
This is a very common issue with high level sprint paddlers, not just with the core, but also with other parts of the body, like the shoulders.
(While overloaded cars are common, it’s rare to see a racing truck (stabiliser dominant athlete) among elite paddlers because they spend so much time training the movers (and loading them heavily). Juniors are also rarely stabiliser dominant due to growth patterns. The biggest chance you’ve got of spotting a racing truck in the wild, is the odd coach who doesn’t spend much time in the gym anymore…)
If the job still gets done in the end, why is using the wrong vehicle such a problem?
Let’s first talk about what stabilisation means – this may sound completely obvious, but in this context it’s good to take a moment to remind ourselves as there are many different definitions.
The Cambridge Dictionary defines to stabilise as: To cause something to become fixed or to stop changing.
In exercise science, when talking about general or single joint stability, often a slightly more descriptive version of ‘stop changing’ is used such as: To control joints through their range of motion by preventing excessive movement/s
In scientific literature core stability is often referred to as something like: The ability to maintain spinal equilibrium despite the manifest presence of kinematic disturbances and motor-control errors [2].
or in plain English:
The ability to keep the spine well-balanced in the presence of motion and uncoordinated/erratic movements
What is the one thing that all these definitions have in common? – they are in some way related to preventing or controlling movement.
So what exactly happens if the movers take over the stabilising role?
Four main problems arise when the movers get too heavily involved in the role of stabilisation:
1. To move a body part, the movers shorten and lengthen as they contract and relax. But if a mover is being used to stabilise, then the mover is being forced to work more continuously in a fixed position, which it’s not designed to do (unlike the stabilisers which don’t normally change much in length when contracted). This requires movers to use more energy when in a stabilising role, and they will likely fatigue more quickly (just like the overloaded car..).
2. When we want to stabilise something (in the case of the core, we are talking about stabilising the spine and pelvis) – it’s most efficient to do this with the structures lying closest (the core stabilisers). If instead the movers are trying to stabilise the spine, they will be doing this from a distance as they lie external to the core stabilisers (or in a different part of the body altogether). This is more difficult, and again requires more energy. You could think about it like this:
You’re driving on a bumpy road and there’s a bobblehead going crazy on the dash. It’s annoying and you want to stop it moving (stabilise it). Which is easiest and more efficient?
A) put you hand directly over it, or
B) climb into the back seat and try to stop it moving with a long stick?
(aside from just being difficult and inefficient, if you climb into the back seat of a car while driving and holding a stick you might crash – just like if you overstabilise the core with the movers in the boat).
3. It has been shown that when there is increased postural (stabilising) activity from the movers, there is decreased receptive function (ability to sense movement and force) of the deep stabilisers, which leads to an impairment in the general stabilisation mechanism and balance [3], [4].
4. If the movers are busy preventing movement they were not designed to be involved with, then whichever movement pattern they were supposed to be creating/assisting with will most likely be restricted. To compensate for this restriction, a lot of extra effort will be required to move the body in an alternate way.
When we combine these things together, we get what would be labelled in business world as gross inefficiency..
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In the Part 5 of this series, we’ll look specifically at how stabiliser-mover imbalances and dysfunction affect the sprint paddler.
Alternatively, you might like to look at 9 fundamental core exercises for building a strong stable core.