The Biomechanics of Strength 2: Measuring Movement.

Our first biomechanics of strength article focuses around the key terms that are banded around in relation to strength and conditioning and performance, what these key terms mean in reality and how the way we train can influence things like strength and power… Ultimately, we should now know a little about the ‘physics’ of training, and in this article we are going to show you how researchers tie the physics to the physiology of movement and how this information can help optimise performance efficiency, assess areas of weakness and be used to guide injury prevention and rehabilitation strategies.

We are going to (hopefully) explain what key biomechanics terms are and, with through a few examples, hopefully you will see why these measures are important, help you understand the scientific literature, see its strength and limitations and for the geeks amongst us, take a more methodological view to the way we see our training and programming. When we consider our main biomechanics outcomes that are widely researched across a variety of different sports, exercises and activities we are talking broadly in two main areas; these are kinematics and kinetics. Although these terms sound similar and are in fact closely related, the main difference is that kinematics is the study of movement or motion, whereas kinetics is the study of movement, but it also investigates the underlying forces that influence or generate changes in movement and for our purposes is the most in-depth and useful type of analysis. The methods by which this measurement is achieved, we will get back to shortly…

When we discuss kinematics we are fundamentally talking about measuring the positions of the body in space and the changes in the angles at each joint. Strength and conditioning coaches can now very easily use this kind of analysis on site in order to assess movement patterns, look for shifts in angles and faulty technique quite simply with the use of a video camera. Even mobile phones and various other software offer this basic analysis which can be used to track joint angles, the bar path, variations in technique, movement efficiency and to give ‘live feedback’ and demonstrations in order to correct faulty technique right there in the gym environment. One thing as coaches we need to consider is using all tools available to us to get the best results for our athletes and clients, and these ‘plug and play’ tools offer simple and effective methods to work quickly and effectively at analysing movements; although this may not be as thorough as more complex methods, there is always a trade-off between functionality, speed and ease of use and the amount and depth of information technology can give you.

In order for more detailed information to be collected that allows kinetic measurements, including moments (rotational forces at the joint), joint powers and various other outcomes can give a more detailed assessment of movement. Obviously kinetics relies on some pretty serious technology, with most systems now being able to record movement in three dimensions using multiple specialised cameras picking up markers located at specific anatomical landmarks. The tracking of these markers and some fancy processing is what is often used in CGI in movies to convert human or animal movement into digitised characters and in fact, the hardware is often the same, but it is the video data and how it is processed that is different. Of course, the video data can only give us the kinematics; it is this video data when combined with force collecting devices that can be then used to calculate the loading that takes place across the joints of the body.

The most common method to collect the forces that the body generates is using force platforms. These are basically glorified weighing scales that measure changes in loading as your body acts through the floor thousands of times per second and in both the vertical, horizontal, anterior and posterior directions. Once we have these forces, we can combine this with the joint angles and accelerations at any specific point of a movement and work out the loading at each joint, if we consider that the load transfers through the joints of the body from the ankles upwards. This makes measurement of the lower body forces and loading fairly reliable, but as the forces are dissipated/redistributed at each joint and through the muscles, the measures of true loading become more challenging to measure. However, with some clever positioning of equipment, we can analyse movements like the bench press effectively, but this can require some outside the box thinking and multiple force platforms to measure loading in the upper and lower body.

One thing that is missing to complete this movement picture is muscle activation. Although we can have an educated guess from our knowledge of anatomy as to which muscles are likely to be activated, the use of electromyography (EMG) is a commonly used tool to measure muscle activity. EMG uses electrodes placed on the muscle of interest which picks up the electrical activity in that muscle. This data can then be synchronised with 3D video cameras, marker sets and force platform data to give us a pretty thorough analysis of human movement and performance that enables us to assess how different groups of people perform tasks. From a clinical/medical perspective, this might be used to assess how people with a disability move compared to those who don’t and identify areas of loading that might be prone to injury, it might identify subtler indicators of a movement adaptation or dysfunction that the naked eye alone just cannot detect. All of this can be used to improve patient care, but what about from a strength training perspective?

Well, if we consider groups that are elite athletes we can investigate what makes them ‘better’ than recreational ones; this could be from a technical perspective, but also the ability to co-ordinate movement and muscle activation at the right time in the right way means that we can use this information to think about how we might advance an athletes training. We can also analyse groups that have had injury or are at risk of injury and see what they do differently, and develop strategies to reduce injury risk. A really important thing we can investigate is the amount of variation there is within the performance of a task, and do these variations matter for athletic performance? At a basic level, this can be used to select the most effective exercise for physique development. If we know what exercise causes what loading and activation in what amounts, then we can use this to direct our training either for muscle growth as an end to itself, but also to identify exercises that might best develop weaker parts in our movement chain or act as the best accessories to sports specific movements.

Thanks for reading,

Team TTC.