RESUMEN
PURPOSE: To identify the effect of allometric scaling on the relationship between running efficiency (R(Eff)) and middle-distance-running performance according to performance level. METHODS: Thirteen male recreational middle-distance runners (mean ± SD age 33.3 ± 8.4 y, body mass 76.4 ± 8.6 kg, maximal oxygen uptake [VO(2max)] 52.8 ± 4.6 mL · kg(-1) · min(-1); G1) and 13 male high-level middle-distance runners (age 25.5 ± 4.2 y, body mass 62.8 ± 2.7 kg, VO(2max) 70.4 ± 1.9 mL · kg(-1) · min(-1); G2) performed a continuous incremental test to volitional exhaustion to determine VO(2max) and a 6-min submaximal running test at 70% of VO(2max) to assess R(Eff). RESULTS: Significant correlation between R(Eff) and performance were found for both groups; however, the strongest correlations were observed in recreational runners, especially when using the allometric exponent (respectively for G1, nonallometric vs allometric scaling: r = .80 vs r = .86; and for G2, nonallometric vs allometric scaling: r = .55 vs r = .50). CONCLUSION: These results indicate that an allometric normalization may improve endurance-performance prediction from R(Eff) values in recreational, but not in elite, runners.