Muscle silence before the release: Nishizono 1984

This is the paper that first described at length the electrical silence appearing in some muscles just before release. It contains two separate experiments. In the first, five archers: two beginners with three months of practice, one intermediate with five years, and two world-level archers, one Japanese and one American. In the second, twelve university students from the same club, split into four beginners, four intermediates and four at high level on the basis of years of practice and competition results.

In the first experiment the difference between levels lies in how tension is distributed. In the beginners the biceps of the drawing arm fires heavily from the draw onwards, activity shifts towards the trunk unsteadily, and at release the two sides are out of balance. In the two top archers the biceps stays almost out of the action, the deltoids on both sides work at high and steady levels from the start of the draw, and the trunk is engaged symmetrically. In the Japanese archer activity collapses 1.50 seconds after release, in the American the high level is held for 1.71 seconds and then falls, and in both that duration was nearly the same on every shot. In both, just before release, the electrical silence appears: in the deltoids of both arms and in the trapezius of the bow arm, lasting between 0.03 and 0.05 seconds.

The second experiment counts how often that silence appears as level rises. In the four beginners it shows in only two archers, in one of them on 15 per cent of shots, and the time from the clicker to release is long and scattered. In the intermediates it shows in three of four, in two of them on 45 to 60 per cent of shots, with clicker response times between 150 and 210 milliseconds. In the four high-level archers it shows in all of them, on 70 to 100 per cent of shots, and the two times tighten: on average 115 milliseconds from the clicker to the onset of the silence and 175 milliseconds from the clicker to release, with the abstract giving the ranges 110 to 120 and 170 to 180.

One further detail, seen almost only in the high-level archers: when the deltoid of the drawing arm falls silent, the trapezius on the same side increases its activity, and the latencies of the two events coincide within ten per cent. The authors note that these are two muscles that are not antagonists and have different innervation, and read the whole as a programme built by training, with the response to the clicker being not a simple reaction but an anticipation, since the archer feels in muscles and joints that the click is coming.

In the first experiment surface electromyography covered eleven sites: the descending part of the trapezius on both sides, the acromial part of the deltoid on both, biceps brachii on both, the lateral head of the triceps on the right, flexor carpi ulnaris on both, and extensor digitorum on the right. In the two top archers the left flexor carpi ulnaris was replaced by the transverse part of the trapezius on both sides. Bow deformation was picked up by a strain gauge glued to the upper front face, and the moment of release is read off that curve. The beginners and the intermediate used a test bow, the two top archers their own, with a clicker, which the paper describes as a seven millimetre steel blade under which the arrow passes and which snaps at the end of the draw.

The trials took place in a gymnasium, at ten metres, on a target 0.8 metres across with its centre 1.3 metres from the ground, in competition format: about ten shots per archer in the first experiment, twenty in the second. A 35 millimetre camera placed to the side, with a shutter speed of one thousandth of a second, filmed the sequence in step with the electromyography, and the movement analysis was done by tracing the prints on paper. Height, weight and arm span were also measured, along with draw force isometrically, with the bow hand resting against a fixed bar while the other pulled a cable attached to a strain gauge.

In the second experiment the muscles come down to five: transverse trapezius on both sides, acromial deltoid on both, and extensor digitorum on the right. An electrical contact was added to the clicker, a metal plate fixed to the side of the handle, to give an exact signal. Signals went to magnetic tape and were replayed through an electromagnetic oscillograph, so that the duration and latency of the silence could be read precisely. The release response time is defined as the interval between the clicker contact and the onset of the rise in the bow deformation curve. For each archer and across the twenty shots the mean and standard deviation were computed, and the results are reported by group.

The numbers are small and the design is descriptive. The first experiment compares two top archers with three club archers, and the two top archers are individuals rather than a group: the authors note that they differ from each other, since the Japanese archer shot with a square, symmetric posture while the American used an open stance with a rotation of the torso that raised his right trapezius. The second experiment has four archers per level and reports no statistical test between groups: the appearance rates and means sit in a chart, and the differences are read by eye.

Neither experiment measured a score. The shots were at ten metres on an eighty centimetre face in a gymnasium, a setting chosen for recording rather than for discriminating accuracy, and the level of the participants was defined by years of practice and past results. The link between the electrical silence and the quality of a shot is therefore measured nowhere: it is inferred from the more advanced archers showing it more often.

What that silence is remains an interpretation. The authors themselves write that the phenomenon had been read in two opposite ways in the literature, as useless activity in beginners in one earlier paper and as a mark of skill in experts in another, and they offer an explanation, a programme organised above the peripheral level, that their data do not test. The trapezius firing while the deltoid is quiet is an observation; the reciprocal inhibition that would explain it is a hypothesis, as the authors themselves acknowledge, since the two muscles are not antagonists.

Finally the instrumentation is that of 1984: magnetic tape, an oscillograph, movement analysis traced by hand from photographs, and a single camera to the side. The paper is in Japanese, with an English title and abstract.

For someone who shoots, the contribution of this work is a figure for timing. In the more advanced archers, an average of 175 milliseconds passes between the click and the arrow leaving, and the interval is tight from shot to shot; in beginners the same time is longer and varies a great deal. It is the measure of an action that cannot be steered by watching: too short to correct while it happens, and regular enough, in the more advanced, to resemble something prepared in advance.

The other finding concerns where the tension sits. In the two world-level archers the biceps of the drawing arm is almost out of the action and the load sits on the deltoids and the back, symmetrically; in the beginners the biceps works hard and the two sides do not match. After release the muscles of the top archers stay active for a long and consistently equal period, about a second and a half, which the authors call the follow through.

What the study does not say is that the electrical silence should be sought or trained. There is no score in either experiment, and nobody tried to bring the silence about: the phenomenon accompanies a high level, and that leaves both directions open. Nor does it say that a quicker release is better, since what was measured is the regularity of the timing rather than its brevity.