The purpose of this study was to investigate the effects of acute fatigue on spring-mass model (SMM) parameters among recreational runners at different speeds. Eleven participants (5 males and 6 females) performed running trials at slower, self-selected, and faster speeds on an indoor track before and after performing a fatigue protocol (60 s of countermovement jumps). Maximal vertical force (Fmax), impact peak force (Fpeak), loading rate (LR), contact time (Tc), aerial time (Ta), step frequency (SF), step length (SL), maximal vertical displacement of the center of mass (ΔZ), vertical stiffness (Kvert), and leg work (Wleg) were measured using a force plate integrated into the track. A significant reduction (–43.1 ± 8.6%; P < .05) in mechanical power during jumps indicated that the subjects became fatigued. The results showed that under fatigue conditions, the runners adjusted their running mechanics at slower (≈2.7 ms–1; ΔZ –12% and SF +3.9%; P < .05), self-selected (≈3.3 ms–1; SF +3%, SL –6.8%, Ta –16%, and Fmax –3.3%; P < .05), and faster (≈3.6 ms–1 SL –6.9%, Ta –14% and Fpeak –9.8%; P < .05) speeds without significantly altering Kvert (P > .05). During constant running, the previous 60 s of maximal vertical jumps induced mechanical adjustments in the spatiotemporal parameters without altering Kvert.
Gabriela Fischer, Jorge L.L. Storniolo and Leonardo A. Peyré-Tartaruga
Francis Degache, Jean-Benoît Morin, Lukas Oehen, Kenny Guex, Guido Giardini, Federico Schena, Guillaume Y. Millet and Grégoire P. Millet
The aim of study was to examine the effects of the world’s most challenging mountain ultramarathon (Tor des Géants [TdG]) on running mechanics. Mechanical measurements were undertaken in male runners (n = 16) and a control group (n = 8) before (PRE), during (MID), and after (POST) the TdG. Contact (t c) and aerial (t a) times, step frequency (f), and running velocity (v) were sampled. Spring-mass parameters of peak vertical ground-reaction force (F max), vertical downward displacement of the center of mass (Δz), leg-length change (ΔL), and vertical (k vert) and leg (k leg) stiffness were computed. Significant decreases were observed in runners between PRE and MID for t a (P < .001), F max (P < .001), Δz (P < .05), and k leg (P < .01). In contrast, f significantly increased (P < .05) between PRE and MID-TdG. No further changes were observed at POST for any of those variables, with the exception of k leg, which went back to PRE. During the TdG, experienced runners modified their running pattern and spring-mass behavior mainly during the first half. The current results suggest that these mechanical changes aim at minimizing the pain occurring in lower limbs mainly during the eccentric phases. One cannot rule out that this switch to a “safer” technique may also aim to anticipate further damages.
Max R. Paquette and Daniel A. Melcher
. Changes in running kinematics, kinetics, and spring-mass behavior over a 24-h run . Med Sci Sports Exerc . 2011 ; 43 ( 5 ): 829 – 836 . PubMed doi: 10.1249/MSS.0b013e3181fec518 21. Derrick TR , Dereu D , McLean SP . Impacts and kinematic adjustments during an exhaustive run . Med Sci Sports
Christian A. Clermont, Andrew J. Pohl and Reed Ferber
, and spring-mass behavior over a 24-h run. Med Sci Sports Exerc . 2011 ; 43 ( 5 ): 829 – 836 . PubMed ID: 20962690 doi: 10.1249/MSS.0b013e3181fec518 32. Moore IS . Is there an economical running technique? A review of modifiable biomechanical factors affecting running economy . Sports Med