Muscle fatigue and archer accuracy: Ibrahim 2024

A single archer from the Egyptian national team shot at 30 metres with surface electrodes on eight muscles, and two consecutive ends of six arrows were recorded, the fifth and sixth of the session.

Between the first and second of those ends the EMG frequency, used as a fatigue index, fell in six muscles out of eight: right upper trapezius from 39 to 33 Hz, left upper trapezius from 41 to 31, right posterior deltoid from 42 to 37, left middle deltoid, the one on the bow arm, from 39 to 16, left triceps from 34 to 32, right wrist extensors from 93 to 80. It rose in two muscles instead: the right biceps from 20 to 37 Hz and the left superficial finger flexor from 35 to 52. The score for the six arrows went from 56 to 54.

The authors read the fall in frequency as the onset of fatigue and the rise in the biceps and finger flexor as those muscles taking over, which they consider undesirable for the score; they add that the two-point drop may not be down to the EMG changes alone.

The paper also reports, as its starting observation, the scores of 42 male archers at the 2023 Arab Championships in Riyadh over the two 70 m rounds. Twenty-one of the 42, that is 50%, scored lower in the second round, with drops of 1 to 18 points. The four Egyptians went 307 to 321, 314 to 320, 321 to 319 and 306 to 319: three up and one down by two points. From this the authors suggest that high-level archers resist fatigue by leaning on different muscles.

A descriptive case study of one international Egyptian archer. Electrical activity was recorded with surface electrodes and a MEGA WIN E 6000 unit, on eight channels: right and left upper trapezius, right biceps brachii, left triceps brachii, right posterior deltoid, left middle deltoid, right wrist extensors, left superficial finger flexor.

The environmental conditions are stated: 34 degrees and 53% humidity. The electrodes were fixed to the chosen sites and the archer shot in his own clothing. The text describes a warm-up of one complete round, 36 arrows in six ends of six, to reach something close to competition conditions and to set the sight; recording started with the whistle at the beginning of the fifth end and covered its six arrows, then was repeated on the sixth end. The score for the six arrows was noted for both.

The distance was 30 metres on an 80 cm face. The index used is what the device returns as the mean frequency in hertz, MF, computed by its own software from the recorded signals; the paper reports no normalisation to maximal voluntary contraction and no statistical test. The results are tables and charts of the values across the two ends, plus a comparison between the right and left sides.

One archer, two ends, twelve arrows in all. The title promises a relationship between muscle fatigue and accuracy, but no correlation coefficient is calculated, because with two measurement points none can be: what the paper contains is a comparison between two sets of numbers read on the same afternoon. The two-point drop over six arrows, from 56 to 54, sits inside the ordinary variation of any archer and cannot be attributed to anything.

The warm-up is described in two incompatible ways: the text speaks of a complete round of 36 arrows in six ends of six, while the protocol diagram gives 48 arrows in four ends of six, figures which do not even multiply out. How many arrows the archer had already shot when recording began therefore remains uncertain.

On the fatigue index the paper is vague. It calls it the mean frequency and labels it MF, which in the literature usually denotes the median frequency of the spectrum, and it does not say how the index was computed or with what filtering. The values reported, from 16 to 93 Hz, sit below the range usually found for surface EMG, and with a single participant there is no way to tell whether that comes from the electrode placement, the software or the archer.

The basic details are missing: age, experience, draw weight, bow discipline and even the dominant hand, which has to be inferred from the muscle labels. The Arab Championship table is a different thing altogether from the study: those are scores from 42 archers on whom no EMG was recorded, and the conclusion about top archers leaning on different muscles is drawn from the points of four Egyptians, with nothing measured on them. The reference list also contains several entries with plainly corrupted years.

What is worth taking from this is the shape of the phenomenon rather than the numbers. In one international archer, between the fifth and sixth ends of the same session, the fatigue index falls in the muscles that hold the shot, the trapezii, deltoids, triceps and wrist extensors, and rises in the biceps of the drawing arm and the finger flexors. Read as the large muscles giving way and the small ones taking over, it describes a feeling many archers know. One archer and twelve arrows are not enough to establish it, and the paper itself does not attempt to with any statistic.

The two points lost between one end and the next mean nothing. The paper's more solid number is the other one: at an Arab championship, half the male archers scored lower in their second 70 m round than in their first, with drops of 1 to 18 points. It is a count from a single competition with no measurements on the athletes, but it does show how common a drop in the second half of a qualification round is.

No training guidance comes out of this. There is nothing on how many arrows that drop costs, whether rest between ends prevents it, or whether the muscles that take over should be strengthened or left alone: these are all questions the paper opens and does not address.