ABSTRACT
The initial contact and midstance angles may influence injury risk. Previous literature has not assessed these angles under the influence of new footwear for a non-exhaustive prolonged run or the relationship between the angles. To assess lower extremity kinematic changes and the relationship between kinematic parameters at initial contact and midstance with prolonged running under the influence of different types of footwear. Twelve experienced, recreational runners (6 male; 6 female; 24.8 ± 8.4 years; 70.5 ± 9.3 kg; 174.1 ± 9.7 cm) ran for 31 minutes at a self-selected pace for three testing sessions wearing maximalist, habitual, and minimalist shoes. Sixteen anatomical retroreflective markers and seven tracking clusters were placed on the participants' lower extremities. Kinematic data were collected every five minutes beginning at minute one. Initial contact angle (IC), maximum angle (MAX) during midstance, and latency (Tmax) between IC and MAX were calculated for the ankle and knee joints in the frontal and sagittal planes. No significant differences were observed between footwear. Rearfoot inversion (F3,33 = 9.72, p < .001) and knee flexion (F6,66 = 5.34, p < .001) at IC increased over time. No significant differences were detected for MAX over time. Tmax for dorsiflexion (F6,66 = 10.26, p < .001), rearfoot eversion, (F6,66 = 7.84, p < .001) and knee flexion (F6,66 = 11.76, p < .001) increased over time. Maximum eversion during midstance is related to the angle at initial contact, and regardless of footwear type, IC and Tmax increased over the duration of the run. No differences in the ankle and knee sagittal or frontal plane kinematics between minimalist, habitual, and maximalist footwear were observed During a self-paced run.
ABSTRACT
Muscle fatigue is a common consideration when evaluating and rehabilitating athletic injuries. The presence of muscular fatigue has been previously determined by quantifying median frequency (MF) through a power spectral analysis on EMG signals collected throughout an endurance task. Research has not yet determined if a prolonged isometric test in a standing position generates muscular fatigue of the hip. The purpose of this study was to determine the reliability and fatigue characteristics of a standing hip isometric endurance test. Twenty healthy participants completed one 60-s Maximum Voluntary Isometric Contraction of standing hip flexion, extension, adduction, and abduction. MF of the participants' dominant limb rectus femoris (RF), biceps femoris (BF), gluteus maximus (GMax), gluteus medius (GMed) and adductor longus (ADD) was determined via surface electromyography during two sessions, 30-min apart. Reliability values (ICC2,1) were moderate-to-excellent for all time intervals of each action (FlexionRF: >0.80; ExtensionBF: >0.89; ExtensionGMax: >0.60; AdductionADD: >0.78; AbductionGMed: >0.60) and MF significantly decreased over time for all actions. Results suggest the endurance test is a reliable technique to generate muscular fatigue for hip flexion, extension, adduction and abduction. It can be used as a time efficient fatigue protocol specific to the RF, BF, GMax, ADD and GMed.
