With a mechanical release the arrow flexes far less than it does off the fingers
3 studies
The summary today
A single experiment has compared the two releases on the same arrows, and the difference is large. With a recurve bow mounted on a robot, competition arrows launched with a mechanical release oscillate with a mean amplitude of 1.22 mm just clear of the bow; shot by two Japanese national-level archers they oscillate by 6.86 mm, more than five times as much, and with a mechanism that imitates the fingers they reach 14.8 mm. The frequency stays about the same, around 86 hertz, so what changes is how far the arrow bends, not the way it vibrates. A model published two years earlier describes why: as the grip relaxes, the string slides sideways across the fingers, by 4.7 mm on average in 12 top archers, and forward by 9 or 10 mm, and that slide is what starts the arrow flexing. On a compound, as early as 2011, a model and a few photographs gave a flex of about 2 millimetres with a release, perhaps 5 on bows with more nocking point movement, but with no comparison against the fingers. There is only one test, though, with 72 shots in all and only two archers, and nobody has measured whether the extra flex turns into a wider group. The model also points out that on a recurve the flex is what lets the rear of the arrow pass the riser, and the authors of the experiment find air drag more repeatable precisely on the archers' shots.
Also phrased as: "release aid and archer's paradox"; "with a release the arrow leaves straight"; "finger release and arrow flex"; "mechanical release"
In practice
It is said that with a release aid the archer's paradox almost disappears and the arrow leaves straight, whereas off the fingers the string has to slide over the fingertips and the arrow snakes.
Evidence
-
2011
Context Equipment tests Published later
With a single-cam compound and a mechanical release, the model of an Easton Protour 470 gives a maximum flex of about 2 millimetres along the arrow, almost all in the fundamental mode, and photographs of a compound with more nocking point movement show perhaps 5, roughly the diameter of the shaft; the typical frequency is around 80 hertz. There is no comparison with a finger release.
The aerodynamic drag and axial rotation of an arrow · J L Park
-
2012
Context Model Published later
The recurve model starts from the way the string leaves the fingers: as the grip relaxes the string slides sideways towards the body and forward, and that is why the arrow starts to flex. From high-speed video of 12 top archers the mean sideways slide is 4.7 mm and the forward slide is of the order of 9 to 10 mm, against the 2.9 and 3.5 mm used in an earlier model. The author adds that the flex is needed: it is what lets the rear of the arrow pass the riser without striking it.
Arrow behaviour in the lateral plane during and immediately following the power stroke of a recurve archery bow · James L Park
-
2014
For Equipment tests Published later
Easton A/C/E arrows launched in four ways and filmed with two high-speed cameras, 72 shots in all: the mean flex amplitude just clear of the bow is 1.22 mm with a mechanical release on a robot with a recurve bow, 6.86 mm on the shots of two Japanese national-level archers and 14.8 mm with a finger mechanism on the same robot; with the compressed-air launcher, without a bow, the arrow does not flex. The release gives about a fifth of the archers' flex (0.18 times), the finger mechanism more than double (2.2 times).
J0520102 Aerodynamic properties of an archery arrow : Influence of flexural oscillation · Ryu Ando, Kyouhei Okawa, Takeshi Miyazaki, Hiroki Sugiura
-
2014
Context Equipment tests Published later
The flex frequency is about the same with every launch method, 84.8 hertz with the finger mechanism, 87.0 with the release and 86.8 with the archers: the same vibration mode is excited. For air drag the lowest variability is on the archers' shots, and the authors put forward the hypothesis that flex of a suitable amplitude makes the flight more repeatable.
J0520102 Aerodynamic properties of an archery arrow : Influence of flexural oscillation · Ryu Ando, Kyouhei Okawa, Takeshi Miyazaki, Hiroki Sugiura
Status history
- 2011 Not studied The first figure concerns the release aid alone, on a compound bow: modelling the arrow as it leaves the bow and looking at photographs, the flex with a mechanical release comes out small, about 2 millimetres in the model and perhaps 5 in the photographs, at around 80 hertz. It says how little an arrow shot with a release flexes, but nobody has yet compared it with the fingers on the same arrow.
- 2012 Not studied The first figure on the finger release comes inside a recurve model: as the grip relaxes, the string slides sideways towards the body and forward, and that is why the arrow starts to flex. From high-speed video of 12 top archers the mean sideways slide is 4.7 mm and the forward slide is of the order of 9 or 10 mm, more than an earlier model assumed. It says that the finger release is where the flex begins, but nobody has yet compared fingers and release.
- 2014 Reported An experiment with high-speed cameras compares four ways of launching the same arrows: with a mechanical release on a robot-mounted recurve the flex amplitude is 1.22 mm, on the shots of two national-level archers 6.86 mm, with a mechanism that imitates the fingers 14.8 mm. The frequency stays around 86 hertz in every case. It is a single test on equipment, with two archers and 72 shots, and it does not measure where the arrows land: reported.
Related
Related articles
- The archer's paradox: the physics of the flexing arrowAt full draw the arrow points to one side and still reaches the centre: how it flexes and clears the riser in the first twenty milliseconds, and how spine matches it to the bow.
- The compound on the draw: what the cams, the limbs and the nocking point doCompound cams, limbs and nocking point: what shapes the force-draw curve, the let-off and the path of the nock, according to what studies have measured.
- Bow tuning in archery: how to tune your bow, backed by scienceBow tuning and the research: spine, centre shot, button, nocking point, brace height and tiller. What models and machine tests show, and how precise you need to be.
Research lines
Cite
Campagna, M. (2026). With a mechanical release the arrow flexes far less than it does off the fingers (Version 3). In Evidence Registry. Retrieved 16 October 2026, from https://matteocampagna.com/en/registry/equipment/mechanical-release-arrow-flex
@misc{campagna2026_sganciomeccanicoflessionefreccia,
author = {Campagna, Matteo},
title = {With a mechanical release the arrow flexes far less than it does off the fingers},
year = {2026},
howpublished = {Evidence Registry, matteocampagna.com},
url = {https://matteocampagna.com/en/registry/equipment/mechanical-release-arrow-flex},
note = {Version 3; accessed 2026-10-16}
}
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