Three-dimensional kinematic comparison of treadmill and overground running

The treadmill is an attractive device for the investigation of human locomotion, yet the extent to which lower limb kinematics differ from overground running remains a controversial topic. This study aimed to provide an extensive three-dimensional kinematic comparison of the lower extremities during overground and treadmill running. Twelve participants ran at 4.0 m/s ( ± 5%) in both treadmill and overground conditions. Angular kinematic parameters of the lower extremities during the stance phase were collected at 250 Hz using an eight-camera motion analysis system. Hip, knee, and ankle joint kinematics were quantified in the sagittal, coronal, and transverse planes, and contrasted using paired t-tests. Of the analysed parameters hip flexion at footstrike and ankle excursion to peak angle were found to be significantly reduced during treadmill running by 12° (p = 0.001) and 6.6° (p = 0.010), respectively. Treadmill running was found to be associated with significantly greater peak ankle eversion (by 6.3°, p = 0.006). It was concluded that the mechanics of treadmill running cannot be generalized to overground running.     

Neuromuscular variables affecting the magnitude of force loss after eccentric exercise

The aim of this study was to examine neuromuscular variables contributing to differences in force loss after participants were exposed to the same relative bout of eccentric exercise. Thirty-six males performed 50 maximal eccentric contractions of the elbow flexors and were stratified into high responders (n?=?10) and low responders (n?=?10) based on force loss 36 h after exercise. Maximal voluntary isometric contractions (MVCs) and electromyography (EMG) were measured at baseline and 36 h after exercise. During eccentric exercise, mean peak torque, mean end-range torque from the final 25% of each trial and total angular impulse were computed over 25 contractions in each of two bouts. The slope of the change in these values for each 25 eccentric contractions was calculated for each participant using linear regression. At baseline, MVC was not different between groups (low responders: 97.0?±?9.6 N?·?m; high responders: 82.7?±?6.4 N?·?m; P?=?0.08). High responders demonstrated a 68% (range 62-78%) reduction in MVC and low responders a 39% (29-48%) reduction after exercise. Peak torque, end-range torque and total angular impulse were 13%, 40% and 33% higher, respectively, in the low than in the high responders (peak torque: P?=?0.0002; end-range torque: P?<?0.0001; total angular impulse: P?<?0.001). The rate of decline in peak torque slope was greater in high than in low responders (P?=?0.044). In conclusion, lower peak torque, end-range torque and total angular impulse during eccentric contractions and a greater peak torque slope may identify high responders to eccentric exercise.