Abstract
Based on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s-1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = -0.68, P = 0.014 and r = -0.70, P = 0.01). In addition, Achilles tendon moment arm length correlated with the amplitude of the ankle flexion at both speeds (r = -0.59, P = 0.03 and r = -0.60, P = 0.03) and with the electrical activity of the medial gastrocnemius muscle at 3 m s-1 speed (r = -0.62, P = 0.02). Our finding supports the concept that a longer moment arm could be beneficial for distance runners.
Highlights
Running economy (RE) is defined as the oxygen or energy cost of transport at a given speed and distance [1], as a better RE refers to a smaller rate of oxygen consumption
The main aim of this study was to examine the connection between RE and Achilles tendon moment arm (AT-MA), and the effect of AT-MA on joint kinematics, muscle electromyography activity (EMG) activity and fascicle behavior during submaximal running
Confirming our expectation, the results showed that a longer AT-MA was related to a superior RE among our participants, i.e., marathon runners with longer AT-MA length have had less oxygen consumption during constant running speed
Summary
Running economy (RE) is defined as the oxygen or energy cost of transport at a given speed and distance [1], as a better RE refers to a smaller rate of oxygen consumption. RE is influenced by several biomechanical factors [2] that include structural parameters of the lower leg [3,4,5,6]. The lower leg produces most of the propulsive force, and it consumes a large portion of the energy cost of running [7]. The amount of energy stored in a tendon depends on the force that stretches the tendon. The magnitude of force production during running depends on the running velocity and the joint angular displacement [10]
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