On the Importance of “Front-Side Mechanics” in Athletics Sprinting

Abstract

Practitioners have for many years argued that athletic sprinters should optimise front-side mechanics (leg motions occurring in front of the extended line through the torso) and minimise back-side mechanics. This study aimed to investigate if variables related to front-and back-side mechanics can be distinguished from other previously highlighted kinematic variables (spatiotemporal variables and variables related to segment configuration and velocities at touchdown) in how they statistically predict performance. Twenty-four competitive sprinters (age 23.1 ±3.4 yr, height 1.81 ±0.06 m, body mass 75.7 ±5.6 kg, 100-m personal best 10.86 ±0.22 s) performed two 20-m starts from block and 2-3 flying sprints over 20 m. Kinematics were recorded in 3D using a motion tracking system with 21 cameras at a 250 Hz sampling rate. Several front-and back-side variables, including thigh-(r=0.64) and knee angle (r=0.51) at liftoff, and maximal thigh extension (r=0.66), were largely correlated (p<0.05) with accelerated running performance (ARP), and these variables displayed significantly higher correlations (p<0.05) to ARP than nearly all the other analysed variables. However, the relationship directions for most front-and back-side variables during accelerated running were opposite compared to how the theoretical concept has been described. Horizontal ankle velocity, contact time and step rate displayed significantly higher correlation values to maximal velocity sprinting (MVS) than the other variables (p<0.05), and neither of the included front-and backside variables were significantly associated with MVS. Overall, the present findings did not support that front-side mechanics were crucial for sprint performance among the investigated sprinters.

Kinematic stride cycle asymmetry is not associated with sprint performance and injury prevalence in athletic sprinters

“…Sprint running is a fundamental skill in many sport disciplines. An optimal sprint running technique is regulated by a complex interaction of numerous variables, including mass‐specific force application, spatiotemporal variables, body configuration, and lower limb segment velocities prior to and during ground contact . However, the human running pattern is also associated with bilateral asymmetry, most likely due to imbalances in the neuromuscular and skeletal system .…”

Kinematics of Maximal Speed Sprinting With Different Running Speed, Leg Length, and Step Characteristics

“…Employing a large number (n = 79) of sprinters across a broad range of performance levels (10.30-12.14 s), multiple regression equations which took into account difference in running speed, leg length and spatiotemporal variables to predict kinematics of maximal speed sprinting were successfully obtained, and leg kinematics of greater maximal running speed based on leg length and step characteristics were elucidated using the multiple regression equations. Although there were previous studies that examined the relationship between running speed and each of kinematic variables (Kunz and Kaufmann, 1981;Alexander, 1989;Ae et al, 1992;Bushnell and Hunter, 2007;Ito et al, 2008;Yada et al, 2011;Toyoshima and Sakurai, 2016;Haugen et al, 2018), this study is the first to demonstrate kinematic features for faster sprinting performance, taking into account the characteristics of individuals in terms of leg length and spatiotemporal variables. Moreover, as the adjusted R 2 for all predicted kinematic variables were greater than R 2 for each of simple linear regression analyses (Supplementary Table 1), it is evident that not only running speed, but also leg length and spatiotemporal variables (step frequency and swing/support ratio), relate to leg kinematics.…”

“…Leg length was obtained as sum of average thigh and shank lengths which were taken by the digitized data across the whole stride cycle in reference to a previous study (Toyoshima and Sakurai, 2016). In reference to variables used in previous studies (Kunz and Kaufmann, 1981;Alexander, 1989;Ae et al, 1992;Hunter et al, 2004;Bushnell and Hunter, 2007;Ito et al, 2008;Yada et al, 2011;Toyoshima and Sakurai, 2016;Haugen et al, 2018), the kinematic variables listed in Table 1 were extracted.…”

“…Associations of leg kinematics and maximal speed sprinting performance have broadly been investigated (Kunz and Kaufmann, 1981;Alexander, 1989;Ae et al, 1992;Bushnell and Hunter, 2007;Ito et al, 2008;Yada et al, 2011;Toyoshima and Sakurai, 2016;Haugen et al, 2018). For joint kinematics, greater maximal running speed was associated with more extended knee joint angle at the mid-support (Yada et al, 2011), smaller knee joint angle at toe-off (Bushnell and Hunter, 2007;Yada et al, 2011), greater minimal knee joint angle during the swing phase (Ito et al, 2008), greater hip extension velocity during the support phase (Ae et al, 1992;Ito et al, 2008), and smaller knee extension velocity during the support phase (Ito et al, 2008).…”

“…Knowledge of difference in magnitudes of changes in kinematic variables associated with changes in running speed, leg length, and spatiotemporal variables would be of great value to coaches when training a sprinter to improve maximal speed sprinting performance. Moreover, because each of previous studies investigated relationships between maximal speed sprinting performance and kinematic variables for small number of variables (Kunz and Kaufmann, 1981;Alexander, 1989;Ae et al, 1992;Bushnell and Hunter, 2007;Ito et al, 2008;Yada et al, 2011;Toyoshima and Sakurai, 2016;Haugen et al, 2018), the data as normative information which can be used by coaches and sprinters are limited. Adopting a large number of kinematic variables therefore would provide normative information for considering faster maximal sprinting performance based on individual-specific factors.…”