Only a minority of elite archers have the arrow leave the string on the bow's median plane

The summary today

There is a single study, but on world-class archers and with a direct method. In footage at 4,000 frames per second of sixteen national-team recurve archers, eight men and eight women, only four have the nock leave the string on or very close to the bow's median plane; for the others the separation point scatters, with a mean close to zero but a standard deviation of 4.9 millimetres and one case at fifteen. The difference shows after separation too: when it happens away from the plane the string keeps swinging sideways, when it happens on the plane the string stops almost at once. A 1998 model points to separation on the median plane as the condition of a well-tuned bow and arrow, and the authors read the scatter as equipment not adjusted at its best, even in athletes of that level. The limit is twofold: a single sample, and nobody has yet shown that separating on the median plane leads to tighter groups or higher scores.

Also phrased as: "the arrow should leave in the centre of the bow"; "centre shot and arrow departure"; "the string swings sideways after release"; "nock separation from the string"; "bow median plane"

Evidence

• 1998
  Context Model Published later

  A model of a competition recurve with an Easton X7 1714 arrow, compared with footage of a single shot: the string releases the arrow at roughly the moment the nock crosses back over the bow's median plane, before the tail passes the grip, and this coincidence is the criterion of a well-tuned bow-arrow system. It describes the ideal condition, not how many archers reach it.

  Bow-arrow interaction in archery · B. W. Kooi

• 2012
  For Archers Published later

  16 world-class recurve archers, eight men and eight women, all national-team members, filmed at 4,000 frames per second: only 4 have the nock leave the string on or very close to the bow's median plane. The separation point lies on average 0.6 mm from the plane, with a standard deviation of 4.9 mm, one extreme case at 15 mm and others at 5 and 6 mm on either side. When separation happens away from the plane the string swings widely sideways after leaving the arrow; in the case closest to the plane the string stops almost at once. The authors read the scatter as equipment not adjusted at its best, but they do not link the position to scores.

  High-speed video analysis of arrow behaviour during the power stroke of a recurve archery bow · James L Park, Oliver Logan

Status history

1. 1998 Not studied A model of a competition recurve, compared with footage of a single shot, predicts that the string releases the arrow at roughly the moment the nock crosses back over the bow's median plane, and that this takes the tail past the grip without striking it: it is the condition of a well-tuned bow-arrow system. How many archers actually achieve it nobody has yet measured.
2. 2012 Reported Footage at 4,000 frames per second of sixteen world-class recurve archers gives the first measurement: only four have the nock leave the string on or very close to the median plane, the separation point has a standard deviation of 4.9 millimetres with one case at fifteen, and when separation is off the plane the string swings widely sideways, while on the plane it stops almost at once. A single study, on high-level archers and with a direct method: 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.

Research lines

• 29 studiesThe archer's paradox in research: from 1987 to today
• 24 studiesThe passive release: fifty years to take an idea apart

Other claims in this domain

• CorroboratedAlong its flight the arrow loses an appreciable part of its launch speed12 studiesStatus since 2011
• CorroboratedAs it leaves the bow, the arrow flexes and snakes around the riser instead of leaving straight19 studies · 47 archers measuredStatus since 2012
• ReportedA camera-based scoring system misreads some arrows: the ones barely sticking out and the ones that shift the target face7 studies · 2 archers measuredStatus since 2017
• ReportedA chest band with fibre optic sensors measures breathing and mean heart rate with small errors, and an archer can wear it while shooting2 studiesStatus since 2019
• ReportedA compound bow stores between 70 and 100 joules and sheds about two thirds of the force at full draw4 studiesStatus since 2015

See all claims on equipment and tuning