to the editor: It was recently (8) stated that several factors might explain that ultramarathon performance would rely to a higher fraction of V̇o2max (F) sustained at the expense of running energy cost (Cr) compared with shorter distances. So the “sacrificed” economy would be lower in ultramarathon than in marathon runners of similar standard.
Only few data of Cr in ultrarunners have been reported. Treadmill Cr of trained European ultrarunners was 216 ± 14 ml·kg−1·km−1 (7) and is in line with the values of European runners of higher standard, 210–213 ml·kg−1·km−1 (6).
Ultratrail is a new popular sport (e.g., first edition in 1977 for the Western States 100-mile, WS100 and 2003 for the Ultra-Trail-Mont-Blanc, UTMB, France) compared with marathon (e.g., 1897 for Boston, MA), with fewer participants (<2,000 finishers for the UTMB vs. >45,000 in New York marathon), with no prize money for the top finishers (vs. $130,000 in New York) and therefore only few professional athletes. This explains partly why in the last decade the performance density (%time difference with the winner) was much lower in ultratrail [∼10–12% at the WS100 for the 5th place finisher (5); 18.5 ± 6.5% at the UTMB for the 10th place finisher] than in other endurance events (∼4–5% in Berlin, Boston, or London marathons; ∼3–4% at Hawaii ironman, for the 10th place finisher). Therefore, although there is no study comparing the two groups, one may assume that if current “elite” ultramarathon runners would have a higher Cr than elite marathon runners [165–187 ml·kg−1·km−1 (6, 11)], this would be due mostly to the current difference in athletic level between the groups.
This explains also why body mass index and mass can still vary between “elite” ultrarunners and be higher than in elite marathon runners [BMI 18–20 kg/m2; mass ∼54–61 kg (1, 6, 11)]. In mountainous ultratrail, the uphill walking sections represent a very large part of the race. During walking at gradients steeper than 15%, the time course of potential energy becomes a monotonically ascending curve and energy recovery plays a very minor role. So there is a major influence of the body mass that should be minimized as in ski mountaineers, mountain bike, or road cycling uphill specialists. The anthropometric profile is similar (mass <62 kg; BMI 18–20 kg/m2, and height <175 cm) in all these sports where uphill is paramount, and we assume that it will be also the case in ultratrail.
Compared with prevalues, stride frequency (SF) is slightly higher after an ultramarathon [e.g., ∼6% (10)], probably for reducing the mechanical load. However, this is not always observed with a moderate increase in SF because the shock attenuation was significant for a 20% but not for a 10% increase in SF (4). Adaptive change in running gait to reduce the strain cannot be systematically associated to an increased Cr; e.g., a slower peak eversion velocity and a better economy were observed after 10 wk of training in beginner runners (9). Because the adaptations are through a process of self-optimization, one may assume that in ultramarathon runners, mechanical changes are not necessary inducing an increased Cr.
Long-distance runners have a lower flexibility and higher posterior lower limb muscles tightness than nonrunners. Inasmuch as the decrease in calf and lower limb joints flexibility is directly induced by the running activity (9), ultramarathon runners likely have poor flexibility due to their high mileage and low-intensity training. This would have a positive influence on their economy.
Running in mountainous trails requires wearing shoes with a high protective capacity. So the ultratrail shoes tend to be heavier than the cushioned road or minimalist shoes. First, lighter is not necessarily more economical (3). Second, on unstable surfaces, leg stiffness and muscle activation are usually adjusted efficiently (2).
Instead of an adaptation favoring a higher F at the expense of Cr, most of the mechanisms speculating on a deteriorated economy in ultramarathon runners are partly due to the fact that the “elite” athletes in this new nonprofessional sport are not comparable with elite marathon runners.
No conflicts of interest, financial or otherwise, are declared by the author.
Author contributions: G.P.M. conception and design of research; G.P.M. drafted manuscript; G.P.M. edited and revised manuscript; G.P.M. approved final version of manuscript.
- Copyright © 2012 the American Physiological Society