Influence of the muscle-tendon unit's mechanical and morphological properties on running economy

Abstract

SUMMARY The purpose of this study was to test the hypothesis that runners having different running economies show differences in the mechanical and morphological properties of their muscle-tendon units (MTU) in the lower extremities. Twenty eight long-distance runners (body mass: 76.8±6.7 kg, height: 182±6 cm, age: 28.1±4.5 years) participated in the study. The subjects ran on a treadmill at three velocities (3.0, 3.5 and 4.0 m s-1) for 15 min each. The \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{V}}_{\mathrm{O}_{2}}\) \end{document}consumption was measured by spirometry. At all three examined velocities the kinematics of the left leg were captured whilst running on the treadmill using a high-speed digital video camera operating at 250 Hz. Furthermore the runners performed isometric maximal voluntary plantarflexion and knee extension contractions at eleven different MTU lengths with their left leg on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) and vastus lateralis (VL) were visualised by ultrasound during plantarflexion and knee extension, respectively. The morphological properties of the GM and VL(fascicle length, angle of pennation, and thickness) were determined at three different lengths for each MTU. A cluster analysis was used to classify the subjects into three groups according to their \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{V}}_{\mathrm{O}_{2}}\) \end{document}consumption at all three velocities (high running economy, N=10;moderate running economy, N=12; low running economy, N=6). Neither the kinematic parameters nor the morphological properties of the GM and VL showed significant differences between groups. The most economical runners showed a higher contractile strength and a higher normalised tendon stiffness (relationship between tendon force and tendon strain) in the triceps surae MTU and a higher compliance of the quadriceps tendon and aponeurosis at low level tendon forces. It is suggested that at low level forces the more compliant quadriceps tendon and aponeurosis will increase the force potential of the muscle while running and therefore the volume of active muscle at a given force generation will decrease.

Lower-Body Determinants of Running Economy in Male and Female Distance Runners

“…Similar to other studies (2,20), the present data demonstrated that lower-body stiffness is substantially related to running economy of well-trained runners (Table 3; Figure 3). Although it remains to be determined the trainability of stiffness across varying levels of fitness, emerging evidence suggests that runners and coaches may want to focus on strategies to improve lower-body stiffness to enhance performance.…”

Gene Variants that Predispose to Achilles Tendon Injuries: An Update on Recent Advances

“…Finally the 'less flexible' COL5A1 TT genotype has been shown to be significantly associated with improved endurance running performance Brown et al, 2011b). This finding is in agreement with the published inverse relationship between musculotendineous stiffness and running economy (Arampatzis et al, 2006;Dumke et al, 2010;Fletcher et al, 2010).…”

Prevalence of morphological and mechanical stiffness alterations of mid Achilles tendons in asymptomatic marathon runners before and after a competition

“…2). However, it has been shown that the transient reduction in Achilles tendon stiffness after an exercise bout may compromise the mechanical function of the muscletendon unit and predispose the tendon to strain-induced injury during subsequent exercise [24]. Several in-vitro studies also concluded that a prior reduction in tendon stiffness is associated with tendon ruptures, although the exact mechanisms of tendon ruptures remain unclear [25,26].…”