At the same peak force a compound stores far more energy than a recurve and is held at full draw with far less force

The summary today

There is no mechanical comparison between a real compound and a real recurve. The only figure comes from a 2012 model that sets a compound, calculated with the parameters of an experimental bow and checked against photographs to within about 7 per cent, beside two recurves that exist only in the calculation: at the same peak force the compound stores 75 per cent more energy, and at the same energy it is held at full draw with 2.3 times less force. The paper does not explain how the curves of the virtual recurves are built, and the two figures depend precisely on them. Real bows with the same peak, 55 lb, have been compared only from the archer's side, in two master's theses from 2000 and 2001 on seven and six archers: with the recurve the shoulder, arm and forearm work harder, and with the compound activity falls after the let-off, which is what a lower holding force would lead one to expect, but neither force nor energy is measured. The mechanical measurements on real bows concern the compound alone: in 2015 a production compound with a peak of about 200 newtons shed about 65 per cent of the force at full draw, so the archer holds about a third of it while aiming. A 2017 model adds a theoretical constraint: the curve of an eccentric-wheel compound cannot exceed, especially in the first part of the draw, that of the same limbs strung as a traditional bow. That the compound goes in this direction fits everything known about its curve, but the size of the advantage rests on a simulated recurve.

Also phrased as: "compound versus recurve"; "compound bow energy"; "compound holding weight"; "why a compound is easier to hold"; "let-off and the recurve"

Evidence

• 2000
  Context Archers Published later

  7 club archers experienced with both compound and recurve, men aged 36 to 51, six draws each with a compound set to 55 lb with 75 per cent let-off and with a 55 lb recurve at 28 inches, electromyography of 12 shoulder and arm muscles: from the start of the draw to the release every muscle worked harder with the recurve, with the largest differences in the teres major (119.6 per cent) and brachioradialis (116.9) of the drawing arm and in the triceps of the bow arm (111.9), and the smallest in the middle deltoid of the bow arm (30.9). With the compound, activity peaked in the first part of the draw and fell after the let-off; with the recurve, the peak came during the hold at full draw. It compares two real bows with the same peak, but it measures muscles rather than force or energy, the analysis is descriptive only, the hold lasted three seconds with the compound and one with the recurve, and the work is a master's thesis without peer review.

  An Electromyographic and Video Motion Analysis Study of the Drawback and Hold Phases of a Compound Bow versus a Traditional Bow in Experienced Archers · Andrea L. Vagle

• 2001
  Context Archers Published later

  6 experienced club archers, men aged 37 to 51 who had taken part in the previous year's study, a compound set to 55 lb with 75 per cent let-off against a 55 lb recurve, electromyography of the wrist and forearm muscles: with the recurve average activity was higher in both hands, 0.231 against 0.134 volts in the drawing hand and 0.133 against 0.091 in the bow hand, with the largest differences in the wrist and finger flexors of the drawing hand (flexor carpi radialis 89.8 per cent, finger flexors 78.1). The authors put this down to the let-off. Here too muscles are measured rather than force, without statistical tests, with a three-second hold on the compound and a one-second hold on the recurve; it is a master's thesis without peer review.

  Analysis of Wrist and Elbow Muscle Activity in Compound versus Traditional Bows with Experienced Archers · Jesse Fuhrer

• 2012
  For Model Published later

  Mechanical model of a compound, with the parameters of an experimental bow and a discrepancy of about 7 per cent from photographic measurements, compared with two virtual recurves: at the same peak force the compound stores 75 per cent more energy; at the same energy the force to hold while aiming is 2.3 times lower. How the curves of the virtual recurves are built is not described.

  Compound archery bow asymmetry in the vertical plane · Ihor Zanevskyy

• 2015
  Context Equipment tests Published later

  On a real production compound the force rises to about 200 N, stays almost constant over much of the draw and falls by about 65 per cent at full draw; the author notes that in a traditional bow the force instead rises throughout the draw. There is no recurve measured for comparison.

  Applications of Physics to Archery · H. O. Meyer

• 2017
  Context Model Published later

  Static model of an eccentric-wheel compound: the force-draw curve has a theoretical limit, independent of the pulley system, given by the curve of the same bow reduced to a traditional one, with the same limbs and the same distance between the axles; the constraint bears mostly on the first part of the draw. In eccentric-wheel compounds the holding force is usually about a third of the peak.

  The round-wheel compound bow model revisited: a new extension · Marko Tiermas

Status history

1. 2000 Not studied The first comparison between two real bows with the same peak, a compound set to 55 lb with 75 per cent let-off and a 55 lb recurve, looks at the muscles of seven archers experienced with both: with the recurve all twelve shoulder and arm muscles work harder, and with the compound activity falls after the let-off instead of rising during the hold. That is what a lower holding force would lead one to expect, but force and energy are not measured, the analysis is descriptive only and the work is a master's thesis: the claim about the bow has not yet been tested, and the status is not studied.
2. 2001 Not studied The same laboratory repeats the comparison on the wrist and forearm of six of the same archers, with the same 55 lb and the same let-off: with the recurve average activity is higher in both hands, about 70 per cent higher in the drawing hand. It confirms the direction in the muscles, but measures neither the holding force nor the stored energy, and the status stays not studied.
3. 2012 Transferred A mechanical model of a compound, built on the parameters of an experimental bow and checked against photographs to within about 7 per cent, is compared with two recurves that exist only in the calculation: at the same peak force the compound stores 75 per cent more energy, and at the same energy the force to hold while aiming is 2.3 times lower. The benchmark is not a real bow and its curve is not described, so the claim rests on a model: transferred.
4. 2015 Transferred The first measurement on a real compound bears on half the question: a production compound with a peak of about 200 newtons sheds about 65 per cent of the force at full draw, so the archer holds about a third of it while aiming, and the author notes that in a traditional bow the force rises throughout the draw. There is no recurve measured alongside, though, and the comparison is still the model's: the status holds.
5. 2017 Transferred A model of an eccentric-wheel compound adds a constraint: the compound's force-draw curve has a theoretical limit, given by the curve of the same limbs strung as a traditional bow, which bears mostly on the first part of the draw, and in compounds of this kind the holding force is usually about a third of the peak. It is still theory, with no comparison between real bows: transferred.

Related

Related articles

• 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.
• How much energy actually reaches the arrow, and where the rest goesHow much of the drawing work reaches the arrow: models say about three quarters, while the few measurements show where the rest goes and what the arrow changes.
• Barebow / instinctive vs Olympic recurve vs compound: differences in the shot, the equipment and the scoreRecurve, compound and shooting without a sight compared: draw weight, arrow speed and flex, let-off, balance, scoring and injuries in the registry's data.

Research lines

• 12 studiesCompound mechanics: cams, limbs and symmetry
• 22 studiesHow much energy passes from bow to arrow: models and measurements since 1937

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