Abstract
The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.
Highlights
In both well-trained athletes and recreational runners, a U-shaped curvilinear relationship between running economy and self-selected stride length [1,2,3,4,5,6,7], stride rate [3,7], and contact time or leg stiffness [8] has been reported
Using the duty factor (DF; an objective parameter representing the proportion of time spent in contact with the ground during a running stride), Lussiana et al (2019) observed global biomechanical differences when classifying runners in two groups called DFlow (a low mean DF (DF) averaged over different running speeds) and
The increase of the running speed from 8 to 18 km/h was accompanied with a decrease of the DF from 35.5 ± 2.4% to
Summary
In both well-trained athletes and recreational runners, a U-shaped curvilinear relationship between running economy and self-selected stride length [1,2,3,4,5,6,7], stride rate [3,7], and contact time (tc ) or leg stiffness [8] has been reported. This highlights that runners seem to self-optimize their running gait to minimize the metabolic cost of running [1,9,10,11]. Using the duty factor (DF; an objective parameter representing the proportion of time spent in contact with the ground during a running stride), Lussiana et al (2019) observed global biomechanical differences when classifying runners in two groups called DFlow (a low mean DF (DF) averaged over different running speeds) and
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