The Short and the Long of It – Applied Biomechanics

Fly fishing involves casts of greatly varied lengths, from the leader only to a few feet of fly line and the leader, to way out as far as we can make it sail. In between very short and very long there is plenty of space. Each of us will have marked out that space in our heads. We will know, at least roughly, where short gives way to medium, medium to long and so on out to the maximum distance we can cast. It isn’t a matter of quantitative prescription by me but rather of qualitative experience by you.

• A short cast is about finesse. Power isn’t a problem except for not using too much of it.
• A medium cast will be a nice balance of power and finesse.
• A long cast will begin to test seriously the strength of our technique. It will be about increasing power (a bit) without losing finesse.
• A very long cast will be right at the limits of technique and getting it to fully extend won’t be entirely predictable. Finesse of the delivery landing will be the least of our worries. However, finesse in the sense of staying smooth remains critical – always.

I was going to break distance into 5 categories and give a biomechanical analysis for each category beginning with very short and ending with very long. However, when I started writing this up it turned into a detailed description, getting ever longer, more detailed and thus ever more like instructions on how to make the casts. As the range of movement extended so did the written description. Detailed casting instructions are not my objective. There is no shortage of instructions out there and watching a video clip would probably be lot more useful. So let’s turn it around and avoid a lot of the detail by starting with the bigger picture.

As we cast longer we need to make longer casting strokes. Sooner or later the basic casting stroke will have run its race, even with leans at the start and a thrust extension at the finish. Put another way, adding ever more power to a limited range of movement will eventually become counterproductive. You know, the bendy lever problem again.

At this point, we have to extend the stroke by progressively recruiting more and more proximal parts of the body. The stance will be opened up by the stepping the casting side leg backwards. The torso and hips can then begin to rotate without us losing our balance and falling over. Weight will be shifted between the front and back legs providing some linear movement of the upper body and some momentum, eventually, to the line.

Meanwhile, the elbow will have moved away from the side of body (abducted). The upper arm and forearm will now form something close to a right angle with the upper arm being in line with the shoulder. Freeze frame right there and what do we see? Dang, looks a lot like someone about to throw a ball in from the outfield or a spear into a fish. We’ve been here before I think.

[Edit] Five years further on I’m not inclined to recommend abducting the elbow as we rotate the torso but rather to keep it more tucked in until quite late in the torso rotation. This will reduce strain on the shoulder in general and the rotator cuff in particular.  (Yep, personal experience.) I now prefer to wait until the torso has turned far enough to permit arm extension, particularly forearm extension, in straighter lines which aids tracking. Right angles turned out to be wrong angles for me.

On then to the 5 categories.

Very Short

Little or no fly line outside the tip. It will most likely be a wrist flick with a tiny bit of forearm. Still needs to be smooth. Still possible to form a nice loop. No haul. It’s a very distal thing.

Short

At least one rod length of line and perhaps several outside the tip now. Maybe a little bit of upper arm movement but it’s mostly done by forearm extension and a gentle straightening of the hand. No real need to haul but a short one is acceptable if you must or you want a short stroke and slightly more zippy turnover. It’s still a bit constrained and distal but it’s starting to feel a bit more like a “real cast”.

Medium

This is where we can start to move more expansively and with rhythm – back cast to forward cast and repeat as necessary. Using a basic stroke the upper arm is fully mobilised and the proximal to distal sequence of the arm is complete. The stroke is extended far enough to comfortably manage the carry. Hauls can be added routinely to share the workload. We aren’t straining and we aren’t feeling constrained.

I find this range extremely helpful for refining technique whether that be correct tracking, smooth power application, full finish, variations to haul timing, length and speed, line release timing and so on. Time and again I come back here to get the feel of how effortless a good cast is to make and how good it feels to make one. Then I try to keep that sweet feeling as I progressively extend the carry and the cast. Keep the flow and finesse, add just enough power to increase the distance.

Long

Around this point it will become necessary to start using some torso (shoulder) rotation and eventually that will start to involve weight transfer. Hauls will become pretty much essential. The biomechanical point is to observe that the proximal part of the casting sequence now includes an axial movement of the whole upper body and possibly the hips as well. The largest muscles and bones we have are becoming involved. As it gets more complicated it gets harder to maintain control, especially if we use too much power too soon. As ever the trick is to follow the sequence and the flow – that is, to stay smooth.

Very Long

This is where it gets much harder to do well. Technique is at or very close to its limit. If it hadn’t already, the sequence will now recruit our leg muscles. The vast expansion of the proximal recruitment has about reached its practical limit.

You may want to fully extend the forearm into the back cast, finishing with a straight arm. If so, you will have to rotate your torso/shoulders through a full ninety degrees. That’s because the elbow is a hinge joint (not a ball joint) so your forearm can only move (flex and extend) in the line of your upper arm. Failure to rotate far enough or premature forearm extension will see the fly line fired partly sideways instead of straight behind you. Bingo, tracking error.

As you move into the forward cast you reverse the weight transfer and the rotation of the upper body. The rod is translated but not significantly rotated while this part of the sequence is executed. In fact rod rotation by extension of the forearm and then hand will be largely delayed until the upper body is again facing the target and weight is transferred almost entirely to the front foot. After rotation is complete you can further extend the movement with a thrusting action, as though pushing into the bend of the rod to prolong it. This is will help increase Work done and to narrow the loop.

The greater the extent of our movements the less the margin for error in sequence timing, in flow and in effort. That’s the bad news. The good news is that fly lines don’t weigh much and we can throw them a surprisingly long way with the application of surprisingly little net Force provided we stay smooth and move in the correct order of the sequence.

The total range of movement and the body parts involved both change a lot but the sequence stays the same from the very short to the very long cast. Proximal to distal, ok?

Applying all this doesn’t mean reciting or consciously thinking about the exact order of the body parts in the movement sequence for every cast. What it means is practicing to habitualise (groove) leading the stroke with the proximal bits and following with the distal bits. As we will see later on  slow motion exercises, pantomimes and even just mental rehearsal of the movements will help entrench the correct order, effort and flow of the movement until most of it becomes unconscious. On the water then, we can see the target and take the shot. The cast just happens.

Rod Translation and Rotation

If we are making a short cast with a short, basic casting stroke there will be a limited amount of rod translation. For medium casts the translation phase will become more distinct and as we get into long casts with body rotation so rod translation will become far more pronounced and important. It is commonly accepted that to make seriously long casts we must learn to delay rotation of the rod and execution of the haul.

By now it will be obvious that this is in keeping with the proximal to distal sequence. Rod rotation is performed by the smaller structures of the forearm and hand. Translation is performed by the larger more proximal structures – whatever those might be according to the extent of recruitment as discussed above.

The Haul

In the Einstein Series hauling got a number of mentions and was examined in more detail here . Hauls share the Work done on the fly line between the rod hand and the line hand. That means in a hauled cast we can use less Force applied to the rod and thus a shorter stroke than we would in a non-hauled cast. We achieve the same line speed and distance in both casts. The hauled cast means less effort from the rod hand and that improves control and therefore accuracy.

Hauling accelerates the line in the direction of the cast if we do it before loop formation and it promotes loop propagation if we do it after loop formation. If you haul at least partly after loop formation then you are now pulling back on the rod leg instead of forward on the “fly leg”. This will enhance loop propagation velocity but diminish loop travel velocity. You will get zippier turnover but a tad less distance.

Hauling can also give us tighter loops because the stroke length can be reduced and rod flex (bend) and counterflex (bend the other way) will also be reduced. Tighter loops mean less opposition from drag.

Lastly, haul timing and completion affects when we release the line for shooting purposes. Obviously you don’t release before the haul is finished and you can play around with release timing but for maximum distance you will want a clean release about when the rod straightens.

From a biomechanical perspective, hauls of varying lengths are similarly made with a proximal to distal sequence. You might do more Work on the line with a longer haul but against that you can produce harder, faster hauls using just forearm and hand movements. Different casters make different choices for different casts. I do and I encourage you to do the same. I find it easier to stay smooth when the tempo of the hauls matches the cast movements and since I very rarely go to maximum distance when fishing I reserve the right to improvise the combinations and vary the haul length and speed.

Just a couple of years ago some guys in a Swedish lab made a very detailed and informative biomechanical study of elite fly casters casting with various lines and rods of differing stiffness and weight ratings. The results for the Trout Distance casts using a 5wt SA MED line and three different 9’ rods are particularly interesting. You can read the whole article here.

Their focus was on co-ordination of haul and rod contributions to line speed but of course they captured and analysed both using a 3D motion analysis system. For our purposes their conclusion is affirming as well as informative.

“Among elite casters, single-handed fly casting with double haul is coordinated in an order of events whereby the peak speed occurs first for the translation of the rod, then for the rotation of the rod and finally for the line haul.”

The succession of peak speeds speaks to each building on the Work of the previous stage, progressively accelerating the fly line. It implicitly confirms the mechanical effects of the proximal to distal sequence for both rod and line hands. Less obviously, it affirms the flow and integration of the body movements, including the overlaps between activation of the body parts.

And just because I can’t resist, checkout the range of rods used for the Trout Distance casts – from stiff competition rods to a bit of a noodle they weren’t too familiar with. The mean difference between the length of the casts? About 3m with most casts being 30m or more. Technique is what matters, not the gear.

And Another Thing

I have tried to give you general principles combining biomechanics and traditional casting knowledge, linking both back to physics and the mechanical requirements for efficient fly casting. General principles apply generally and that means across the range of single handed casts. Equally, it implies the possibility of exceptions. What is optimal or ideal for one person or one situation will not be exactly the same for different people and situations.

People come in different shapes, sizes, physical prowess and functionality. A tall, fit, young, muscular athlete may well have different ranges of movement, strength and learning/skill acquisition capabilities to a short, unfit and ageing non athlete. Sensible expectations and adaptions need to be adopted.

The purpose of the cast and the order of the casters priorities will similarly vary and these variations will both affect and be affected by biomechanics. If, for example, delicate presentation is paramount the biomechanics of your cast will change and change further with the range to target. As the range increases the caster might have to choose between movements which promote finesse and movements better suited to power. Contrastingly, if there is no fish in sight and the purpose is simply maximum distance then finesse is unlikely to be a big deal. In both cases, however, the general principles apply equally albeit differently. Efficiency is the link. If it is a missing link, general principles will always be a good place to look.

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