Bioimpedance in para-archery: Harjianto 2024 study

Five Indonesian para-archers, three men and two women, were measured with bioelectrical impedance (InBody S10): total body water, split into water inside and outside the cells, water in each segment (arms, trunk, legs), muscle mass, fat mass, body mass index and estimated basal metabolic rate. Mean age was 31.40 years and mean shooting experience 7.20 years.

No difference between men and women was significant. The men had on average more total water (41.53 against 33.15 litres), more skeletal muscle mass (30.77 against 23.30 kg) and a higher estimated basal metabolic rate (1,572.67 against 1,348.00 kcal); the women had more fat mass (22.25 against 14.67 kg) and a higher body fat percentage (31.50 against 20.93%). The ratio of extracellular to total water was 0.39 in the men and 0.41 in the women. The segment data show strong asymmetries: in the men the left leg averages 10.04 litres, with a standard deviation of 7.54, and the right 6.70, differences probably linked to the participants' impairments, which the paper does not describe.

The study is cross-sectional, with one measurement per athlete. The device, with eight electrodes on hands and feet, measures impedance over five segments at six frequencies (1 to 1,000 kHz) and derives body composition with the manufacturer's equations, following the standard manual. Before testing, athletes were to avoid exercise for 6 to 12 hours, food for 3 to 4 hours and alcohol and caffeine for 24 hours, and not to use lotions on hands or feet. Differences between men and women were tested with an independent-samples t-test, that is, with three values on one side and two on the other.

The paper does not say what impairments the athletes had, which class they competed in, what bow they shot or at what level. The data are given as means and standard deviations by sex, with no individual values.

Five people are not enough to compare two groups: with three against two, even large differences, such as the roughly 7.5 kg of muscle mass, do not reach significance, and the lack of significant differences does not mean that men and women are alike. The women's means come from two people.

There is also a measurement problem the paper does not address. Standard bioimpedance equations are built on people without impairments; with an amputation, paralysis or a limb carrying less muscle, estimates of lean mass, fat and segmental water can be unreliable. The authors cite a study that developed specific equations for amputees, yet use the manufacturer's. Some readings go beyond the data: basal metabolic rate is an estimate of resting expenditure, not the number of calories to eat in order to lose fat or gain muscle, as the paper presents it; and the judgements on the women's health risk rest on body mass index thresholds developed for other populations, and on two people. The dates do not agree either: the paper is listed as received in September 2024 and approved in November 2023.

For archers, and for those who coach para-archers, the study changes nothing. It is a snapshot of the body composition of five athletes with no link to shooting: there are no scores, no performance measures and no information on bow or class. The differences between men and women are those found in any adult population.

The most interesting point is indirect: in para-archers the distribution of water and tissue across body segments can be highly asymmetric, which makes comparison with general reference values, using instruments calibrated on people without impairments, of limited meaning. For a para-athlete, comparing the same athlete's measurements over time looks more informative; that is our reading, not a conclusion of the study.