This proportion increases to nearly 40% in lesser-trained male and female runners (Figure 1). Specifically, we have estimated that the energy cost of triceps surae muscles contraction during the running stride of highly-trained runners represents nearly 25% of the total metabolic cost of running. Recently, we have estimated that the active skeletal muscle energy cost represents the vast majority of the total metabolic cost of running ( Fletcher and MacIntosh, 2015). None of these reviews has approached E run from a muscle energetics standpoint. It is known that E run is likely influenced by a number of physiological and biomechanical factors and several excellent reviews have been written on the topic in the last 25 years ( Morgan et al., 1989 Morgan and Craib, 1992 Saunders et al., 2004 McCann and Higginson, 2008 Lacour and Bourdin, 2015). But how is an extraordinary E run achieved? min −1, so it is likely the runner who is going to break the sub-2 h marathon will be one with extraordinary E run.m −1 ( Fletcher et al., 2009) would only require a V ˙ O 2 m a x of 77.5 ml.A marathoner, with an excellent E run of 3.77 J E run values this low are frequently reported ( Foster and Lucia, 2007 Fletcher et al., 2009 Shaw et al., 2013), but assuming the marathon distance could be sustained at 85% V ˙ O 2 m a x, this runner would require a V ˙ O 2 m a x near 85 ml Assuming this runner has a body mass of 56 kg and their respiratory exchange ratio is 0.95, this oxygen uptake would equate to an E run of 4.39 J min −1 is required to achieve the current marathon world-best time of 2:02:57.Using the American College of Sports Medicine's metabolic equations for the energy cost of running over level ground, a mean V ˙ O 2 of 71.9 ml
With few exceptions, world-class male marathon running performances are achieved by runners who possess V ˙ O 2 m a x -values above 75 ml These factors include a high maximal oxygen uptake ( V ˙ O 2 m a x), the ability to minimize disturbance to homeostasis while sustaining a higher fraction of V ˙ O 2 m a x and a low energy cost to run (E run) at that high fraction of V ˙ O 2 m a x. Introduction Importance of E run to Distance Running PerformanceĮndurance running performance is determined by a combination of physiological, anthropometric, and biomechanical factors. Here, the key features that dictate the energy cost during distance running are reviewed in the context of skeletal muscle energetics. Other factors affecting E run are altered by training: other anthropometric features, muscle and tendon properties, and running mechanics. It is understood that some determinants of the energy cost of running are not trainable: environmental factors, surface characteristics, and certain anthropometric features. These factors therefore dictate the energy cost of running. The amount of energy needed for skeletal muscle contraction is dependent on the force, duration, shortening, shortening velocity, and length of the muscle. Here, we approach the study of E run from that perspective. E run is determined by the energy needed for skeletal muscle contraction. Fundamentally, the understanding of the major factors that influence the energy cost of running (E run) can be obtained with this approach. The economy of running has traditionally been quantified from the mass-specific oxygen uptake however, because fuel substrate usage varies with exercise intensity, it is more accurate to express running economy in units of metabolic energy. Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.