Fig. 2
The marathon running speed (m s−1) for each genotype was 5.31 (0.08) (median and interquartile range), 5.37 (0.05), and 5.46 (0.07) m s−1 for the I/I, I/D, and D/D genotypes, respectively. Individuals with the D/D genotype had a significantly faster running speed than those with the I/I genotype (Scheffe’s test p = 0.005). A linear trend was observed between the genotype and marathon running speed (Spearman rank correlation coefficients r = 0.833, p = 0.006). The five marathon runners who ran faster than 5.41 m s−1 (i.e., completing the marathon within 2 h 10 min) all exhibited the D/D or I/D genotype (D/D, 4; I/D, 1)