Duty Factor Reflects Lower Limb Kinematics of Running

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.

A Multivariate Polynomial Regression to Reconstruct Ground Contact and Flight Times Based on a Sine Wave Model for Vertical Ground Reaction Force and Measured Effective Timings

“…3 ) could be used to obtain and when an IMU is used to measure and . Thereby, important parameters to assess running biomechanics such as duty factor ( Lussiana et al, 2019 ; Patoz et al, 2020 ), as well as vertical oscillation and vertical stiffness ( Morin et al, 2005 ), could be calculated more precisely. Having these parameters would allow coaches and practitioners to better evaluate running performance outside the laboratory such as in a coaching environment and during an entire training or race, and to prevent running-related injuries.…”

“…However, force plates could not always be available and used ( Abendroth-Smith, 1996 ; Maiwald et al, 2009 ). In such case, alternatives would be to use a motion capture system ( Lussiana et al, 2019 ; Patoz et al, 2020 ) or a light-based optical technology ( Debaere et al, 2013 ). Nevertheless, even though these three systems can be used outside the laboratory ( Purcell et al, 2006 ; Hébert-Losier et al, 2015 ; Ammann et al, 2016 ; Lussiana and Gindre, 2016 ), they suffer a lack of portability and are restricted to a specific and small capture volume, that is, they do not allow continuous temporal gait data collection throughout the entire training or race.…”

A Single Sacral-Mounted Inertial Measurement Unit to Estimate Peak Vertical Ground Reaction Force, Contact Time, and Flight Time in Running

“…However, a force plate could not always be available and used [ 15 , 16 ]. In such a case, alternatives would be to use a motion capture system [ 17 , 18 ] or a light-based optical technology [ 19 ]. Nevertheless, even though these three systems can be used outside the laboratory [ 20 , 21 , 22 ], they suffer from a lack of portability and are restricted to a specific and small capture volume.…”

Duty factor and foot-strike pattern do not represent similar running pattern at the individual level

“…More recently, runners have been categorized using the duty factor (DF) 19 , 20 , i.e., the ratio of ground contact time ( ) to stride time [ + swing time ( ], with a higher DF reflecting a greater relative contribution of to the running stride 21 , 22 . Considering both and simultaneously provides a better understanding of the global running pattern compared with when these temporal variables are considered separately 19 , 20 .…”

“…More recently, runners have been categorized using the duty factor (DF) 19 , 20 , i.e., the ratio of ground contact time ( ) to stride time [ + swing time ( ], with a higher DF reflecting a greater relative contribution of to the running stride 21 , 22 . Considering both and simultaneously provides a better understanding of the global running pattern compared with when these temporal variables are considered separately 19 , 20 . The authors observed that the 20 subjects with highest DF values and 20 subjects with lowest DF values (among a cohort of 54 participants) used different running strategies but had a similar running economy, showing that these two strategies are energetically equivalent at endurance running speeds 19 .…”