Biomechanical Principles and General Theory

Anatomy and Complexity

The anatomical parts of the human body which enable movement are surprisingly numerous, incredibly complex and wonderfully sophisticated in their design and interaction. We use a lot of those parts when casting and the longer we cast the more of them we use. Obviously, co-ordinating (timing and controlling) the activation of many parts is a bigger problem than when we are using far fewer parts.

In fly casting the net Force applied in the direction of the cast comes from sum of the force produced by the body parts we use. The amount of force we apply will vary greatly between say, a very short cast and a very long cast. In between short and long there is still plenty of room for variation. Moreover, we are usually striving for finesse as well as power.

Biomechanics is essentially about how force is applied internally. As fly casters it helps to understand how best to externalise that force, applying it ultimately via the rod and line to the fly. The internal application of force to perform fly casting should not be confused with or limited to power and strength as the sole enablers of net Force. Such an approach will be terribly limited and frankly, inadequate. It’s just so much more subtle, elegant and complex than a simple application (and display) of muscle power.

Let’s stop there for a moment because we are on the edge of a precipice that plunges into a deep abyss of detail. That is somewhere you probably don’t want to go and I want to avoid trying to take you. What follows then will simultaneously risk too much and too little simplification, but hey, I can only do my best not to fall off the high wire in either direction. There is, however, an upside to all this. At the very least the complexity signals that it is understandable why we can’t always land the fly where we want to and why we can’t all do it as beautifully as Joan Wulff.

Understanding Muscle Types and Functions

Larger muscle groups are for power. Typical examples include your quads, glutes and biceps. Smaller muscle groups are for finer movements such as by your hands or fingers. Makes sense then that you run with your legs and draw with your hands.

Smaller muscles notably include stabilising muscles. The power muscles enable us to move the skeleton via the joints. The stabilisers add finesse by helping to control the joint movement. They also help protect the joints from injury.

We need to maintain our balance while we cast, not just to avoid falling in the water but to promote efficiency by keeping our movements on track rather than on multiple tracks that change as we wobble about. For this task core stabilisers are going to be important. Weights shifts caused by movement of the upper body require compensatory relaxation and bracing from the lower body.

Summing up. We have larger muscles for power, smaller muscles for finesse and stabilisers for control, balance and joint injury prevention.

Lastly, I can’t in conscience finish this description of muscle function without giving you at least a sniff of the beauty and complexity of even the simplest controlled movement which lie beyond my wilfully simplified account. When we lift an arm out to the side or in front of us it is not just the muscles of that arm and shoulder which produce the movement. A whole range of other muscles facilitate and compensate for that movement, maintaining balance and posture. All this will happen without any conscious awareness of the sweeping extensions and contractions of muscles other than those of the arm we decided to move.

Without these co-ordinated and unconscious activities the voluntary and intended movement would not be feasible even if it were possible at all. For those who might be interested find a copy of Deane Juhan’s 2003 book Job’s Body and read pages 114-115 where he talks about what happens when we lift our right arm out to the side and up to the horizontal.

Proximal and Distal

If you have a quick look around your body you will notice that the bigger muscles are closer to its centre. Technically, they are closer to the axial skeleton – your skull and spine. As you move further away from the centre, out along your limbs, the bone and muscle structures become smaller. The nearer bits are proximal and further away bits are distal. So, now we know that in technical terms the musculoskeletal structures are organised from bigger to smaller and proximally to distally. Oddly enough, it makes biomechanical and fly casting sense to use them in the way they are organised and the purposes for which they were made.

Casting Principles and Biomechanics

Human beings have been in the business and habit of throwing things for a very long time, maybe 2 million years. That seems to be about when we acquired the three anatomical variations from other primates which permit high speed throwing. Only humans can throw fast and accurately. The kicker lies in our ability to store and release elastic energy during the throwing action, known commonly as “cocking” the arm. An early version of rod loading? Just kidding folks. Forget I mentioned it.

Fast forward to the 21^stcentury and now we have the technology of motion capture which allows us to minutely (kinematically) analyse what goes on when we throw things; javelins, baseballs and cricket balls as well as fly lines with a bendy lever. There are significant similarities between all these throwing actions. Of course, the bendy lever we use to propel fly lines introduces some important variations for fly casting but basically what we do and how we do it are neither entirely original nor unique.

Mo-cap of fly casting enables us to see how casters, with varying skill levels perform the task. In particular it shows us what elite casters do differently; what they do more or less of compared with not-so-elite casters. What interests me about the results of kinematic analysis is not the fine detail but the bigger picture – the general points and how they fit with traditional knowledge gained through trial and error, passed on by competent instructors.

No two casters, including elite casters, move in exactly the same way. The finer points of individual style might interest some people but they don’t do much for me or the audience I am writing for. In what follows then I will stick to the salients points of similarity.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.