Joshua P. Bailey

Muscle activity during backward and forward running with body weight support

We investigated muscle activity during backward (BR) and forward (FR) running with body weight support (BWS). Ten participants completed BR and FR on a lower body positive pressure treadmill while selecting a preferred speed (PS) for different BWS conditions (0%, 20%, 40%, 60%, and 80%BWS). Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA), rating of perceived exertion (RPE), preferred stride frequency (PSF), and PS were measured. Magnitude of muscle activity (BF, TA, and GA), RPE, PSF, and PS were not influenced by the interaction of direction and BWS (P>0.05). BF, TA, and GA were not different between directions (P>0.05) but were different between BWS conditions (P<0.01). RF was influenced by the interaction of direction and BWS (P<0.01). RF, BF, TA, and GA during BR were lower with increasing BWS. RF during BR was 59-86% higher than that of FR within BWS condition. RPE was lower with increasing BWS (P<0.001), regardless of direction of locomotion. PSF was lower and PS was higher during BR and FR with increasing BWS (both P<0.001). PSF during BR was 6-9% higher than that of FR. PS during BR was 24-31% lower than that of FR. These observations demonstrate that a change in BWS influences magnitude of muscle activity, PS, PSF, and RPE for both BR and FR. However, a change in direction of locomotion may not influence magnitude of muscle activity or RPE during running for a given BWS, even though muscle activity pattern, PS, and PSF were different between BR and FR.

Effects of Treadmill Running Velocity on Lower Extremity Coordination Variability in Healthy Runners

With a growing interest in coordination variability and its role in endurance running, it is important to identify the effect of running velocity. The purpose of the current study was to investigate the effect of treadmill running velocity on the coordination and variability of coordination of lower extremity couplings of healthy runners during stance. Fourteen apparently healthy runners ran on a split-belt force instrumented treadmill at five different velocities. Continuous relative phase (CRP) was used to quantify coordination and variability (vCRP) between lower extremity couplings of the right limb (thigh-shank, thigh-foot, shank-foot) during three phases of stance (loading, mid stance, and propulsion). Multiple one-way repeated measure ANOVAs were conducted to identify differences among velocity conditions at each phase and discrete events (initial foot contact, peak knee flexion during stance, and toe-off). Thigh internal/external rotation (IR/ER)-Shank abduction/adduction (AB/AD) coupling was different during the propulsive phase (p = 0.02). Thigh flexion/extension-Shank flexion/extension showed the greatest differences in vCRP across velocity conditions with differences occurring during loading phase, mid stance, propulsive phase, and peak flexion (p < 0.05). Additionally, significant differences were seen in Thigh FL/EX-Shank FL/EX (toe-off, p = 0.01) and Thigh FL/EX-Foot inversion/eversion (IN/EV) (toe-off, p = 0.032). Interestingly, the decreases in vCRP values were accompanied by changes in center of mass vertical motion during stance, but not knee flexion angles. Increases in running velocity led to a more constrained running pattern through a reduction in degrees of freedom.

Implications of Increased Lower Extremity Movement Variability on Fall Susceptibility at Increased Stride Lengths During Locomotion

The purpose of this examination was to explore the effects of stride length (SL) perturbations on walking gait, relative to preferred walking (PW) and running (PR), via lower extremity range of motion (ROM) variability. ROM variability at the hip, knee, and ankle joints, in the sagittal and frontal planes were used in evaluating motor control of gait, where increased gait variability has been previously implicated in fall susceptibly.Nine participants (5 male, 4 female; mean age 23.11±3.55 years, height 1.72±0.18m, mass 72.66±14.37kg) free from previous lower extremity injury were examined. Kinematic data were acquired using a 12-camera system (Vicon MX T40-S; 200Hz). Data filtering and interpolation included a low pass, 4th order, Butterworth filter (15Hz cutoff) and cubic spline. Five gait trials were completed for PW and PR, with subsequent SL manipulations computed as a percentage of leg length (LL). SL perturbations included 60%, 80%, 100%, 120%, and 140% of LL.Kinematic analysis involved one stride (two steps) during each gait trial, assessing ROM at the hip, knee, and ankle from heel contact to toe-off for each limb, in the sagittal and frontal planes. Variability was expressed using coefficient of variation (%). Comparisons were made using 3×7 (joint × stride condition) mixed model ANOVAs, with repeated measures on stride condition (α = 0.05), using SPSS 20.0.Differences in lower extremity ROM variability were detected among stride conditions in the frontal and sagittal planes (F[3.185,76.451] = 3.004, p = .033; F[4.595,110.279] = 2.834, p = .022, respectively). Greater ROM variability was observed at, and in excess of SLs of 100%LL relative to PW in the frontal plane (PW: 9.2±4.2%; 100%LL: 11.8±3.6%, p = .014; 120%LL: 13.5±5.8%, p = .046; 140%LL: 13.8±6.5%, p = .016), and between SLs of 80%LL and 120%LL in the sagittal plane (4.9±3.0%; 7.8±4.7%, p = .046, respectively). From this, PW appeared to occur within SLs of 60%LL to 80%LL, while SLs exceeding 100%LL resulted in increased lower extremity ROM variability. This may have consequences for fall susceptibility at increased stride lengths during walking. PR did not reveal significant variability differences (p>.05) compared to walking conditions in either the sagittal or frontal plane (7.5±5.0%; 12.8±7.7%, respectively), suggesting that running represents a separate, but stable gait pattern. In the sagittal plane, ROM variability was significantly lower at the hip (3.9±1.5%), relative to the ankle (8.4±1.6%, p<.001) and knee joints (7.4±2.6%, p = .001), suggesting that gait control may be more active at the ankle and knee joints. Future investigations should examine kinetic changes in gait when altering stride length.Copyright

Understanding the influence of perceived fatigue on coordination during endurance running

ABSTRACT During the course of a training programme, runners will typically increase running velocity and volume possibly encountering fatigue during a run, which is characterised as a feeling of general tiredness. The purpose of the current study was to identify whether or not level of perceived fatigue affects coordination and coordination variability in healthy runners during the recovery velocity of an endurance interval run. A total of 20 endurance runners completed a 1-hour run that included running velocity intervals at 75% of estimated 10 k race pace (5 minutes) and estimated 10 k race pace (1 minute). After each run, participants completed a fatigue questionnaire and were grouped based on their post-run self-reported perceived fatigue. 3D motion capture data were collected during the run and analysed to generate coordination patterns and variability of the patterns as dependent variables. Multiple mixed model ANOVAs were conducted to test for differences between perceived fatigue groups. Coordination and variability differences were reported in a number of couplings during transition phases (late and early stance) and events (toe-off and foot contact) of the gait cycle. It was concluded that the level of perceived fatigue affected coordination and coordination variability during the recovery velocity of a 1-hour interval run.

A Comprehensive Kinematic Analysis during a 15 Km Submaximal Training Run

Purpose: The purpose of the study was to evaluate kinematics during a 15 km submaximal endurance training run. Methods: Fifteen participants (eight male, seven female; 30.5 ± 8.4 years; 71.8 ± 11 kg; 1.73 ± 0.07 m) currently training for an endurance race completed a 15 km training run (1:24:34 ± 0:10:20 finish times) on an outdoor course. Sagittal plane two-dimensional kinematic data were captured and analyzed for a single stance phase at 0.5 km intervals. All dependent variables (lap times, step length, step frequency, stance time, and joint angles (knee, ankle & hip) at contact and during stance) were calculated every half km and averaged over three km segments. Results: Lap time (p < 0.001) and stance time (p < 0.001) each increased across the duration of the run. Step length decreased (p = 0.020) but there was no change in step frequency (p = 0.087) across time. Knee flexion at foot contact decreased across time (p = 0.041), with no changes in hip (p = 0.916) or ankle (p = 0.591) angles at foot contact. Torso inclination increased across laps (p = 0.001). During stance phase, decreased peak knee flexion (p = 0.041) was the only lower extremity joint angle altered during the run. Conclusion: Runners adjust lower and upper extremity body positions, as well as running gait parameter variables, in response to slower running velocities during the later stages of a submaximal endurance run.