Running Economy from a Muscle Energetics Perspective

Abstract

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. Fundamentally, the understanding of the major factors that influence the energy cost of running (Erun) can be obtained with this approach. Erun is determined by the energy needed for skeletal muscle contraction. Here, we approach the study of Erun from that perspective. The amount of energy needed for skeletal muscle contraction is dependent on the force, duration, shortening, shortening velocity, and length of the muscle. These factors therefore dictate the energy cost of running. It is understood that some determinants of the energy cost of running are not trainable: environmental factors, surface characteristics, and certain anthropometric features. Other factors affecting Erun are altered by training: other anthropometric features, muscle and tendon properties, and running mechanics. Here, the key features that dictate the energy cost during distance running are reviewed in the context of skeletal muscle energetics.

The stiff plate location into the shoe influences the running biomechanics

“…Indeed, during the propulsion phase, the energy from the shoe should be returned in the right direction (Stefanyshyn & Nigg, 2000a), as it was the case in the present study with the resultant GRF more aligned with the runners' leg with the high location. This can enable runners to perform less active muscular work to propel the body upward and forward (Fletcher & MacIntosh, 2017), as it was the case in the present study with less hip, knee, ankle, and MTP joint torques and less positive work at the knee joint with the high location.…”

Effect of habitual foot-strike pattern on the gastrocnemius medialis muscle-tendon interaction and muscle force production during running

“…We observed differences in both GM muscle fascicle contraction velocity and force which can be expected to have opposing effects on metabolic energy consumption between FSP. The metabolic energy consumption of skeletal muscle contraction is higher with higher force, higher contraction velocity (force-velocity relationship) and when the muscle fascicles are operating further away from their optimal length (force-length relationship) (27,70). We found no difference in the GM muscle fascicle length at initial ground contact and, although we did not measure fascicle resting length, there is no direct reason to assume that the GM is working at a different part of its force-length relationship across FSP.…”

Strength and Conditioning for Adolescent Endurance Runners

“…Improvements in RE in the absence of changes in V̇O2max, speed at V̇O2max, blood lactate and body composition parameters suggests that the underlying mechanisms predominantly relate to alterations in intra-muscular co-ordination and increases in stiffness (16). Specifically, ST brings about increases in motor unit recruitment, firing frequency and musculotendinous stiffness, which are thought to optimize the length-tension and forcevelocity relationships of active skeletal muscle, thus reducing the metabolic cost of running (36). It is clear that the inclusion of ST also does not adversely affect V̇O2max, blood lactate markers or body composition (16).…”

“…Resistance training, which should include both ERT and heavy RT, increases motor unit recruitment and firing frequency, thus enhances a runners ability to appropriately control and express force during ground contact. Although changes in fat-free mass appear to be minimal following a ST intervention in distance runners (16), a targeted RT programme, that aims to increase muscle mass specifically around the proximal region of the lower limb may enhance biomechanical and physiological factors, which positively influence RE (36). Exercises, such as squats, deadlifts, step-ups and lunge patterns, which possess similar kinematic characteristics to running gait, are likely to provide the greatest transfer (8) and have been utilized in several previous investigations (9,17,58).…”