33 research outputs found
Regular changes in foot strike pattern during prolonged downhill running do not influence neuromuscular, energetics, or biomechanical parameters
No full textResearch has suggested that a high variability in foot strike pattern during downhill running is associated with lower neuromuscular fatigue of the plantar flexors (PF). Given the popularity of trail running, we designed an intervention study to investigate whether a strategy with regular changes in foot strike pattern during downhill running could reduce the extent of fatigue on neuromuscular, energetics and biomechanical parameters as well as increase an uphill time- to-exhaustion trial (TTE) performance. Fourteen experienced trail runners completed two interventional conditions (separated by 15 days) in a pseudo-randomized and counter-balanced order that consisted of 2.5-h of treadmill graded running with (switch condition) or without (control condition) a change between fore- and rear-foot strike pattern every 30 s during the downhill sections. Pre and Post, neuromuscular tests were performed to assess PF central and peripheral fatigue. Energy cost of running was assessed using an indirect calorimetry system and biomechanical gait parameters were acquired with an instrumented treadmill. TTE was performed after both the graded running conditions. There were not significant condition × time interactions (P ≥ 0.085) for any of the variables considered, and TTE was not different between the two conditions (P = 0.755). A deliberate strategy to alternate between foot strike patterns did not reduce the extent of fatigue during prolonged graded running. We suggest that it is not the ability to switch between foot strike patterns that minimises fatigue; rather the ability to adapt foot strike pattern to the terrain and therefore a better running technique
Biomechanics of Graded Running: Part I - Stride Parameters, External Forces, Muscle Activations
No full textBiomechanical alterations with graded running have only been partially quantified, and the potential interactions with running speed remain unclear. We measured spatiotemporal parameters, ground reaction forces and leg muscle activations (EMG) in nineteen adults (10F/9M) running on an instrumented treadmills at 2.50, 3.33 and 4.17 m·s-1 and 0, ±5o, and ±10o. Step frequency illustrated a significant speed × grade interaction (P < 0.001) and was highest (+3%) at the steepest grade (+10o) and fastest speed (4.17 m·s-1) when compared to level running (LR) at the same speed. Significant interaction was also observed for ground reaction forces (all P ≤ 0.047). Peak ground reaction forces in the normal direction increased with running speed during downhill running (DR) only (+9% at -10o and 4.17 m·s-1). Impulse in the normal direction decreased at fastest speed and steepest DR (-9%) and uphill running (UR) (-17%) grades. Average normal loading rate increased and decreased at fastest speed and steepest DR (+52%) and UR (- 28%) grades, respectively. Negative parallel impulse increased and decreased at fastest speed and steepest DR (+166%) and UR (-90%), respectively. Positive parallel impulse decreased and increased at fastest speed and steepest DR (-75%) and UR (+111%), respectively. EMG showed comparable u-shaped curves across the grades investigated, although only a change in vastus lateralis and tibilias anterior activity was detectable at the steepest grades and fastest speed. Overall, running grade and speed significantly influences spatiotemporal parameters, ground reaction forces, and muscle activations
Individual physiological responses to changes in shoe bending stiffness: a cluster analysis study on 96 runners
No full textInternational audienceBackground Shoe longitudinal bending stiffness is known to influence running economy (RE). Recent studies showed divergent results ranging from 3% deterioration to 3% improvement in RE when bending stiffness increases. The variability of these results highlights inter-individual differences. Thus, our purpose was to study the runner-specific metabolic responses to changes in shoe bending stiffness. Methods After assessing their maximal oxygen consumption ( VO2 max) and aerobic speed (MAS) during a first visit, 96 het- erogeneous runners performed two treadmill 5 min runs at 75% VO2 max with two different prototypes of shoes on a second day. Prototypes differed only by their forefoot bending stiffness (17 N/mm vs. 10.4 N/mm). RE and stride kinematics were recorded during each trial. A clustering analysis was computed by comparing the measured RE and the technical measurement error of our gas exchange analyzer to identify functional groups of runners, i.e., responding similarly to footwear interventions. ANOVAs were then computed on biomechanical and morphological variables to compare the functional groups. Results Considering the whole sample (n = 96), there was no significant difference in RE between the two conditions. Cluster 1 (n = 29) improves RE in the stiffest condition (2.7 ± 2.1%). Cluster 2 (n = 26) impairs RE in the stiffest condition (2.7 ± 1.3%). Cluster 3 (n = 41) demonstrated no change in RE (0.28 ± 0.65%). Cluster 1 demonstrated 1.7 km•h -1 greater MAS compared to cluster 2 (p = 0.014). ConclusionThe present study highlights that the effect of shoe bending stiffness on RE is runner-specific. High-level runners took advantage of increased bending stiffness, whereas medium-level runners did not. Finally, this study emphasizes the importance of individual response examination to understand the effect of footwear on runner's performance.</div
Footwear influences soft-tissue vibrations in rearfoot strike runners
No full textMuscle activity is tuned in response to ground reaction
force to dampen soft-tissue vibrations (Wakeling, Von
Tscharner, Nigg, & Stergiou, 2001) during whole-body
vibrations (Wakeling, Nigg, & Rozitis, 2002) and running
(Boyer & Nigg, 2004). A model study demonstrated this
mechanism may be affected by fatigue and shoe hardness
(Nikooyan & Zadpoor, 2012). Footwear may then influence soft-tissue vibrations, and thus the part of muscle activity affecting the muscle tuning mechanism.La actividad muscular se ajusta en respuesta a la reacción del suelo.
fuerza para amortiguar las vibraciones de los tejidos blandos (Wakeling, Von
Tscharner, Nigg, & Stergiou, 2001) durante todo el cuerpo
vibraciones (Wakeling, Nigg, & Rozitis, 2002) y correr
(Boyer y Nigg, 2004). Un estudio modelo demostró esto
el mecanismo puede verse afectado por la fatiga y la dureza del calzado (Nikooyan y Zadpoor, 2012). El calzado puede entonces influir en las vibraciones de los tejidos blandos y, por lo tanto, en la parte de la actividad muscular que afecta el mecanismo de ajuste muscular
Illustration of the anthropometrics.
No full textGirth (black solid line), length (solid double arrows) and skinfold (dashed circular with X) measurements that were used to calculate the anthropometrics. The position of the EMG and acceleration sensors (grey rectangles) are also indicated. (TIF)</p
Cushioning perception is associated with both tibia acceleration peak and vibration magnitude in heel-toe running
No full textInternational audienceObjective: To investigate the relationship between the perception of cushioning and variable measured using tibia acceleration in heel–toe running. Method: Ten rearfoot strikers’ runners ran at 3.9 m.s−1 on a stiff treadmill in seven footwear conditions presenting different mechanical properties through midsole geometries and/or materials. The perceived cushioning was quantified through a 100-mm visual analogic scale. Tibia accelerations were measured using a triaxial accelerometer from which six variables of interest were extracted based on time and frequency analyses. After pooling data of each subject in each condition (n = 70), Pearson correlation coefficients were calculated to test the correlation between the perceived cushioning and each biomechanical variables. The Cohen’s d effect size was calculated for significant correlation. Results: Significant correlations were found between the perceived cushioning and three axial acceleration-related variables which are the axial acceleration peak (r = −0.246, p = .04, small correlation), the kurtosis coefficient of the axial acceleration peak (r = −0.281, p = .056, small correlation), and the power spectral density of the axial acceleration within the 10–20 Hz bandwidth (r = −0.300, p = .018, small correlation). Conclusion: The present study highlights that the perception of running footwear cushioning was correlated to tibia impact peak and tibia vibration magnitude. Besides, no variable extracted from the transverse component of tibia acceleration was correlated to cushioning perception. These findings could have practical implications in running footwear design
Testing shoes.
No full textThe hard shoe can be seen on the left side, and the soft shoe is on the right side. The overall heel thickness remains the same across shoes, while only the hardness of the EVA foam (yellow/white material) and the thickness of the heel layer (blue material) differed.</p
