Biomechanics FOR Fly Casting: Part 1


Having made my way through the physics of fly casting it made sense to look at biomechanics and the sensory motor system as the next stops in the knowledge journey. Why? Because the mechanics (physics) of fly casting defines the most efficient outcomes of casting. It also enables us to measure them. The essential outcome is line speed achieved with an optimally efficient application of Force in the intended direction of the cast.

Knowing what we need to produce, however, is not the same as knowing how to produce it. Physics might explain why good casting technique works and even why bad technique is fugly, but it doesn’t come up with many original ideas in the what to do and how to do it departments. Physics won’t tell us what bodily movements to make in order to achieve optimally efficient application of Force. Neither will it tell us how to learn, revise, create, recreate and improvise those movements.

Secondly, it is the sensory motor system, not Newton’s Laws of Motion, that we use to control those movements. It tells our bodies which bits to move, when, how much and how forcefully. The sensory motor system (SMS) is central to how we learn, remember, reproduce, refine and vary those movements. There is extensive scientific literature on biomechanics and the SMS. As with mechanics I want to extract the knowledge most useful to fly casters and explain it as accessibly as I can.

So, for me, there is a logical and compelling sequence to understanding this stuff and telling the story meaningfully. Mechanics => Biomechanics => Sensory Motor Learning. What organises and connects them all is the concept of efficiency. That is the conceptual framework for my research and the story I will try to tell.

The Context

What I write about fly casting is anchored in the context of fly fishing with a single handed rod. Most often that will involve a standard overhead cast. This is the context for most people who fly cast.

If you are a competition fly caster, accuracy or distance, you might well find some useful information and ideas here but I am not writing for you directly. One important implication (among others) of this approach is that I don’t accept competition casting as the dominant model or sole arbiter of how fly casting ought to be performed.

To be clear, I’m not saying people who win casting competitions can’t cast for fishing or that competing won’t improve your casting or that we can’t learn from what the best competition casters do. That would be silly. What I am saying is that competition casting is not the only source of fly casting knowledge. In this game no individual, organisation or pastime holds all the cards and has all the answers, including me of course.

When we fish or practice casting we throw lines of many different lengths. We might also intentionally throw lines of many different shapes and degrees of turnover. I won’t be covering specialty casts directly. Some of the principles of “normal” single handed casts covered in what follows apply to specialty casts but I see those casts essentially in the improvised casting department.

Getting back to the length variations, when needed , these will be conveniently divided into short, medium and long casts. You will know what lengths of your casting fall into those categories as I do for my casting but we will both understand the actual lengths won’t be the same for everyone, no matter where they sit on the continuum of skill level . For some folks a 50’ (15m) cast is long and for others it is barely medium.

In all cast lengths, we have to manage both power and finesse to reach the target efficiently. In short casts power is never a problem, except perhaps in trying to avoid using too much of it. Finesse is the main game. For medium casts finesse and power will be nicely balanced. In long casts the emphasis will shift slightly toward power or, more particularly, how we can increase line speed without destroying finesse. Of course we can all make casts of similar lengths with varying amounts of power (to say nothing of finesse!) and that is perfectly legitimate. However, the point is to offer a qualitative framework of general and subjective application rather than quantitative prescriptions for how everyone should define, say, a long cast.

What Use is Science?

If we take that question broadly then I hope the Einstein Series has scored a few points for the home team. If we consider it more narrowly, with biomechanics as the science of human movement, then a more difficult problem arises. Throughout most of the history of our species we have managed to hunt, fish and express ourselves athletically and artistically in movement with little or no help from science.

In my country, for example, the first people populated Australia some 60,000 years ago and survived as hunter gatherers often in very challenging environments. I don’t know for how much of that time they used woomeras (spear throwers) but they didn’t have any need of Newtonian mechanics or biomechanical (kinematic) analysis of motion capture footage to sort out the design of their spears, woomeras or throwing techniques. Trial, error, intelligence and survival motivation did a pretty good job for them.

Traditional knowledge of fly casting has also been produced largely by experiential learning though in a comparatively short space of time. What value can science add to what we know already? During my research for this project I came across an article by Bruce Elliot.

Concluding this article about biomechanics and tennis he wrote in part:

“There is no question that players striving for more power, more control, or more variety in stroke production through trial and error are the primary determinants in changes to stroke mechanics. However, I have shown that biomechanics certainly plays a role in the process of change. General theory provides a base on which modifications can be made, and an understanding of individual stroke mechanics inevitably leads to improved performance.”

There is a lot in that paragraph and still more in the whole article if you are up for it.

Here is my interpretation. Science is an add-on to the fruits of experiential learning which means:

  • It is not a substitute for experiential learning, it is an aid.
  • We should only discount and discard knowledge from shared experience when and to the extent that it is proven wrong.
  • General theory provides a foundation for understanding which can be modified as and when required.
  • Understanding individual stroke mechanics can lead to improved performance.

These days it is alarmingly fashionable to try to marginalise and ridicule science as inferior to what “normal” people “know”. My objective is to grasp how science fits with and trial and error. My answer for the fly casting context is that science is a valuable accessory to experience which can significantly reduce the iterations of trial and error. It can also polish performance in ways that practice alone might not be able to achieve. Endless practice and field experience might (or might not) result in sound technique. We lack the survival motivation.

Traditional casting instruction/knowledge can also shortcut the trial and error process (what and how departments) to a considerable extent. Let’s also remember that the why department can both test the veracity of received wisdom and supply insight beyond trial and error.

Of course there are practical and financial limits to scientific exploration of an individual’s casting technique. For example, if an athlete has access to the facilities and expertise required to accurately measure and scientifically analyse what they are doing their performance might be significantly improved. This would be especially useful within elite competition. However, that’s a pretty expensive “if” beyond the reach of me and most of my readers, even if it was of interest to them – another fair sized “if”. Meantime, we get by with astute observation and video footage which tells no lies even if it doesn’t reveal the whole truth. Oh, and speaking of truth in casting, a measuring tape is very good idea too.

In what follows I am going to try to remember that biomechanics is an add on, use general theory to generate and/or affirm general principles of casting and, to a necessarily limited extent, shed some light on individual (casting) stroke mechanics.

Science based insight might be useful to casters at all stages of proficiency though I expect it is at the upper levels and specifically, where the margin for error in technique grows slim, that it will be of greatest practical benefit and therefore more readily accepted.


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