Forearm muscles, compound vs recurve: Fuhrer 2001

Six experienced archers from a North Dakota club shot a recurve and a compound of the same draw weight, 55 lb, while surface electromyography recorded six forearm muscles on each arm, the flexors and extensors of the wrist and fingers. The aim was to see which muscles work from the draw to the release and how much their effort changes between the two bows.

With the recurve the average activity was higher in both hands: 0.231 volts against 0.134 in the string hand and 0.133 against 0.091 in the bow hand. In the string hand the largest differences were in flexor carpi radialis (89.8% more with the recurve), the radial wrist extensors (85.5%) and the finger flexors (78.1%); in the bow hand in extensor carpi ulnaris (64.6%), flexor carpi ulnaris (47.9%) and the finger flexors (39.6%).

The compound, on the other hand, demanded more work in the first part of the draw, up to about 30% of the time, before the let-off took the weight off. With both bows almost every muscle of the bow hand showed a sharp peak right at release, and in the string hand the finger extensors rose suddenly while the flexors faded.

The archers were right-handed men aged 37 to 51 (44.8 on average), with at least three years of shooting and at least three tournaments in the past year, the same men who had taken part in an earlier study of the shoulder by the same department. The recurve was a Martin Hatfield takedown, 55 lb at 28 inches; the compound a Hoyt Raider Intruder set at 55 lb, with 75% let-off and each archer's stated draw length. Both were shot with a glove and three fingers on the string, with no release aid, at a target about a metre and a half away, with 4-6 shots per bow and the first bow chosen at random. The hold was timed with a metronome: 3 seconds with the compound, 1 second with the recurve, drawn to 28 inches against a mark on the arrow.

The muscles recorded were flexor carpi ulnaris and radialis, extensor carpi ulnaris, extensor digitorum, the long and short radial wrist extensors and the superficial and deep finger flexors, the last two pairs read together because surface electrodes cannot tell them apart. The signal (Noraxon Telemyo 8) was synchronised with a 60 Hz camera following three markers on the bow to obtain the string angle and the moments of full draw and release. Each archer's trials were averaged as a percentage of the time from start to release. There is no statistical test: the results are means and percentage differences.

The values are raw volts, not normalised to each muscle's maximal contraction, as the author acknowledges: the two bows can be compared on the same muscle, but the muscles cannot be compared with each other. The hold differed between the bows (3 seconds against 1) and the comparison is made on the average over the whole shot, so part of the difference depends on how long each phase lasted.

The compound was shot with fingers, which almost no compound archer does, and with a bow that was not the archer's own; the recurve, too, was a single borrowed bow used by everyone. A target a metre and a half away rules out aiming anything like competition aiming. Six archers, few shots per bow, no statistics and possible crosstalk between neighbouring electrodes complete the picture. It is an end-of-course physiotherapy project that has not been peer reviewed, and the exercise programme in the appendix is a generic example the study did not test.

The study puts figures on something anyone who has shot both bows knows: at full draw the compound, thanks to the let-off, asks far less of the forearms than a recurve of the same draw weight, while the effort is concentrated at the start of the draw. For a recurve archer the more interesting finding is a different one: the bow hand, quiet during the hold, switches on sharply at release, and the string hand opens the fingers partly with the extensors, not only by letting go.

It says little about competition technique, since the hold was very short, the target very close and the compound shot with fingers; as for the strengthening exercises suggested in the appendix, nobody evaluated them.