The energetics of ultra-endurance running

Our objective was to determine the effects of long-lasting endurance events on the energy cost of running (Cr), and the role of maximal oxygen uptake (VO2max), its fractional utilisation (F) and Cr in determining the performance. Ten healthy runners (age range 26-59 years) participated in an ultra-endurance competition consisting of three running laps of 22, 48 and 20 km on three consecutive days in the North-East of Italy. Anthropometric characteristics and VO2max by a graded exercise test on atreadmill were determined 5 days before and 5 days after the competition. In addition, Cr was determined on atreadmill before and after each running lap. Heart rate (HR) was recorded throughout the three laps. Results revealed that mean Cr of the individual laps did not increase significantly with lap number (P = 0.200), thus ruling out any chronic lap effect. Even so, however, at the end of lap 3, Cr was 18.0% (P<0.001) greater than before lap 1. In addition, a statistically significant acute lap effect on Cr was observed at the end of the second and third laps (by 11.4 and 7.2%, respectively). The main factors determining performance were VO2max, F, as estimated from the average HR, and the average Cr-mean throughout the three laps; the grand average speed over the three laps being described by vend-mean = F 9 VO 2max 9 Cr-mean-1 . We concluded that (1) the substantial increase of Cr-mean during the competition yields to marked worsening of the performance, and (2) the three variables F, VO2max and Cr-mean combined as described above explaining 87% of the total competition time variance. © 2011 Springer-Verlag.