Ankle kinetics and plantarflexor morphology in older runners with different lifetime running exposures

Time to stability of treadmill running kinematics in novel footwear with different midsole thickness

Running studies, particularly those examining footwear effects, commonly use warm-up or familiarization periods prior to testing. There is no consensus for how long these familiarization periods should be to ensure stable running kinematics prior to experimental testing in novel footwear. The aim of this study was to assess the time to stability of kinematic variables during treadmill running in novel compared to habitual neutral cushion footwear in distance runners. A cross-sectional analysis of 15 distance runners (seven women, eight men) during 10-minute treadmill running bouts in minimal, neutral cushion, and maximal cushioned footwear was conducted while lower extremity kinematics were recorded for 10 s at the end of each minute. Test-retest intra-class correlation coefficients (ICC, 3, k) were used to detect time to stability in cadence, vertical oscillation, peak dorsiflexion angle, peak eversion angle, and peak knee flexion angle. All kinematic variables were stabilized within two to three minutes (ICC < 0.90) and the type of novel footwear did not influence time to stability. These findings indicate that a two to three minute, ∼310-540 steps, depending on running cadence, familiarization period, regardless of footwear novelty, is sufficient for stabilization of these kinematic variables during treadmill running.

The Influence of Footwear Longitudinal Bending Stiffness on Running Economy and Biomechanics in Older Runners

Purpose: This study assessed the effects of footwear longitudinal bending stiffness on running economy and biomechanics of rearfoot striking older runners. Methods: Nine runners over 60 years of age completed two running bouts at their preferred running pace in each of three footwear conditions: low (4.4 ± 1.8 N·m-1), moderate (5.7 ± 1.7 N·m-1), and high (6.4 ± 1.6 N·m-1) bending stiffness. Testing order was randomized and a mirror protocol was used (i.e., A,B,C,C,B,A). Expired gases, lower limb kinematics, and ground reaction forces were collected simultaneously and lower limb joint kinetics, running economy (i.e., VO2), leg stiffness, and spatio-temporal variables were calculated. Results: Running economy was not different among stiffness conditions (p = 0.60, p = 0.53 [mass adjusted]). Greater footwear stiffness reduced step length (p = 0.046) and increased peak vertical ground reaction force (p = 0.019) but did not change peak ankle plantarflexor torque (p = 0.65), peak positive ankle power (p = 0.48), ankle positive work (p = 0.86), propulsive force (p = 0.081), and leg stiffness (p = 0.46). Moderate footwear stiffness yielded greater peak negative knee power compared to low (p = 0.04) and high (p = 0.03) stiffness. Conclusions: These novel findings demonstrate that increasing footwear longitudinal bending stiffness using flat carbon fiber inserts does not improve running economy and generally does not alter lower limb joint mechanics of rearfoot strike runners over 60 years. Future studies should investigate how other footwear characteristics (e.g., midsole material, plate location, and sole curvature) influence economy and biomechanics in this population.

The effect of exercise modality on age-related changes observed during running

INTRODUCTION

With the increase in participation by older adults in endurance events, research is needed to evaluate how exercising throughout the lifespan can affect the aging process regarding gait and mobility. The purpose of this study was to determine how the type of exercise modality one participates in will affect age-related declines observed during running.

METHODS

Fifty-six individuals between the ages of 18-65 who considered running, resistance training or cycling/swimming as their primary form of activity participated in this study. Kinematics were captured using a 10-camera motion capture system while participants ran at a controlled pace of 3.5 m/s (± 5%) over a 10-m runway with force platforms collecting kinetic data. Eight successful trials were chosen for analysis. A one-way ANOVA assessed differences in mean kinematic and kinetic variables of interest between physical activity groups (α = 0.05).

RESULTS

Older resistance trainers exhibited greater maximal knee power compared to older runners. No other group differences were observed.

CONCLUSION

Despite type of exercise modality, regularly participating in exercise has positive effects. This is evident through the preservation of the function of the lower extremity with age, specifically function of the ankle, and its contribution to healthy movement patterns.