Lack of an effect of judogi colour on the outcome of men's gold-medal final judo matches (1996–2005, n=501). There was also no effect when the gold-medal finals were analysed separately for the Olympic and World Championships (n=63), European Championships (n=64), Super A Tournaments (n=105) and A Tournaments (n=269). Data are from a total of 72 international judo tournaments (for details, see §2). The black line at 0.5 indicates the expected proportion of wins by blue or white under the null hypothesis that colour has no effect on contest outcome. Black bars, proportion won by athletes in blue; white bars, proportion won by athletes in white. No significant differences exist between the number of blue and white wins (p values are indicated at the top).

Contest sheet for the men's 81–90 kg weight category of the 2004 Olympics. The four seed positions are indicated by an asterisk. Each match has a number. Athletes who lost their previous match are indicated by a (–); all other athletes won their previous match. Shown in the upper half is the winner's pool (leading to the gold-medal final) and in the lower half, the loser's pool or repechage (leading to two bronze-medal finals). This figure illustrates two confounding factors. (a) There is a difference in intercontest time interval between athletes in blue and those in white. Every pool is usually allocated to one mat. Matches take place sequentially from top to bottom per pool, with little time between subsequent matches (e.g. in pool A from matches 1 to 4; then 17, 18 and finally 25). Consequently, the intercontest time interval is on average longer for athletes in blue than for those in white, resulting in a longer average recovery time for those in blue. The difference in recovery time between blue and white is approximately the duration of one match. For example, in match 17, the winner of match 1 fights the winner of match 2. The athlete in blue of match 17 had thus the duration of one match longer to recover than the athlete in white. A judo match lasts on average 7.17 min (Sikorski et al. 1987), and this should be almost equivalent to the absolute difference in recovery time between blue and white athletes. The relative time difference was difficult to calculate, because we could not find published estimates of between-round time intervals. Recovery times are equal in the gold-medal final for athletes in white and blue, because the semi-finals are scheduled simultaneously. (b) The repechage contains asymmetries in prior experience and judogi colour. First, in approximately half of the matches, there is an asymmetry in prior win–lose experience and judogi colour; in these matches, the athlete who had lost his previous match starts in white against an opponent in blue who had won his. For example, in match 42, Huizinga, wearing blue, won his previous match while Gordon, wearing white, lost his. However, there are no matches with the opposite bias. Second, in the repechage, the athlete in blue is more likely to have experienced one match less than his opponent in white. For example, in match 29, Kelly, wearing blue experienced one match, whereas Geraldino, wearing white, experienced two matches. This asymmetry may occur in all repechage matches, depending on which colour progresses; it can occur with the opposite bias in the third round and bronze-medal final (overall, the chance that blue experienced one match less than white is 50.00%; the converse 11.11% and both equal number of matches 38.89%).