Influence of a Functional Knee Brace and Exercise on Lower Extremity Kinematics During Jogging

ABSTRACT Context: Functional knee braces (FKB) are used prophylactically and in rehabilitation to aide in the functional stability of the knee joint. Objective: To determine if alterations in sagittal plane lower extremity kinematics remain evident throughout a one hour period in healthy individuals. Design: 2X5 repeated measures design. Setting: Biomechanics Laboratory. Subjects: Twenty subjects (14 male and 6 female, mean age 26.5±7 yrs; height 172.4±13 cm; weight 78.6±9 kg), separated into braced (B) and no brace (NB) groups. Intervention: A one-hour exercise program divided into three 20 minute increments. Main Outcome Measures: Synchronized three-dimensional kinematic data were collected at 20-minute increments to assess the effect of the FKB on select lower extremity joint kinematics. Results: Hip, knee and ankle joint position were not significantly affected by time (exercise). However significant decreases in hip (p = .05) and knee flexion (p \u3c .05) were noted in the B group compared to the NB group regardless of time while ankle joint position was unaffected. Conclusions: Hip and knee flexion angles were reduced in the B group compared to the NB group, while ankle joint position was not affected. Wearing a knee brace appears to not only influence knee joint position but also hip joint position. It is possible that repetitive changes to hip joint kinematics may be detrimental to hip and low back function and thus lead to injury

Lower extremity fatigue increases complexity of postural control during a single-legged stance

<p>Abstract</p> <p>Background</p> <p>Non-linear approaches to assessment of postural control can provide insight that compliment linear approaches. Control entropy (CE) is a recently developed statistical tool from non-linear dynamical systems used to assess the complexity of non-stationary signals. We have previously used CE of high resolution accelerometry in running to show decreased complexity with exhaustive exercise. The purpose of this study was to determine if complexity of postural control decreases following fatiguing exercise using CE.</p> <p>Methods</p> <p>Ten subjects (5 M/5 F; 25 ± 3 yr; 169.4 ± 11.7 cm; 79.0 ± 16.9 kg) consented to participation approved by Western Oregon University IRB and completed two trials separated by 2-7 days. Trials consisted of two single-legged balance tests separated by two Wingate anaerobic tests (WAnT; PreFat/PostFat), or rest period (PreRest/PostRest). Balance tests consisted of a series of five single-legged stances, separated by 30 s rest, performed while standing on the dominant leg for 15-s with the participant crossing the arms over the chest and flexing the non-dominant knee to 90 degrees. High resolution accelerometers (HRA) were fixed superficial to L3/L4 at the approximate center of mass (COM). Triaxial signals from the HRA were streamed in real time at 625 Hz. COM accelerations were recorded in g's for vertical (VT), medial/lateral (ML), and anterior/posterior (AP) axes. A newly developed statistic (R-test) was applied to group response shapes generated by Karhunen Loeve (KL) transform modes resulting from Control Entropy (CE) analysis.</p> <p>Results</p> <p>R-tests showed a significant mean vector difference (<it>p </it>< .05) within conditions, between axes in all cases, except PostFat, indicating the shape of the complexity response was different in these cases. R-test between conditions, within axis, differences were only present in PostFat for AP vs. PreFat (<it>p </it>< .05). T-tests showed a significantly higher overall CE PostFat in VT and ML compared to PreFat and PostRest (<it>p </it>< .0001). PostFat CE was also higher than PostRest in AP (<it>p </it>< .0001).</p> <p>Conclusions</p> <p>These data indicate that fatiguing exercise eliminates the differential complexity response between axes, but increases complexity in all axes compared to the non-fatigued condition. This has implications with regard to the effects of fatigue on strategies of the control system to maintain postural control.</p

High Resolution MEMS Accelerometers to Estimate VO2 and Compare Running Mechanics between Highly Trained Inter-Collegiate and Untrained Runners

BACKGROUND: The purposes of this study were to determine the validity and reliability of high resolution accelerometers (HRA) relative to VO(2) and speed, and compare putative differences in HRA signal between trained (T) and untrained (UT) runners during treadmill locomotion. METHODOLOGY: Runners performed 2 incremental VO(2max) trials while wearing HRA. RMS of high frequency signal from three axes (VT, ML, AP) and the Euclidean resultant (RES) were compared to VO(2) to determine validity and reliability. Additionally, axial rms relative to speed, and ratio of axial accelerations to RES were compared between T and UT to determine if differences in running mechanics could be identified between the two groups. PRINCIPAL FINDINGS: Regression of RES was strongly related to VO(2), but T was different than UT (r = 0.96 vs 0.92; p<.001) for walking and running. During walking, only the ratio of ML and AP to RES were different between groups. For running, nearly all acceleration parameters were lower for T than UT, the exception being ratio of VT to RES, which was higher in T than UT. All of these differences during running were despite higher VO(2), O(2) cost, and lower RER in T vs UT, which resulted in no significant difference in energy expenditure between groups. CONCLUSIONS/SIGNFICANCE: These results indicate that HRA can accurately and reliably estimate VO(2) during treadmill locomotion, but differences exist between T and UT that should be considered when estimating energy expenditure. Differences in running mechanics between T and UT were identified, yet the importance of these differences remains to be determined

A comparative analysis of selected ankle orthoses during functional tasks

Les chevillères sont testées lors de sauts en hauteur verticaux, d'inversions, de flexions plantaires et de courses aléatoires. Les résultats démontrent que les chevillères augmentent la protection latérale externe sans restreindre les capacités fonctionnelles

Contributions of lower extremity kinematics to trunk accelerations during moderate treadmill running

Background: Trunk accelerations during running provide useful information about movement economy and injury risk. However, there is a lack of data regarding the key biomechanical contributors to these accelerations. The purpose was to establish the biomechanical variables associated with root mean square (RMS) accelerations of the trunk. Methods: Eighteen healthy males (24.0 ± 4.2 yr; 1.78 ± 0.07 m; 79.7 ± 14.8 kg) performed treadmill running with high resolution accelerometer measurement at the lumbar spine and full-body optical motion capture. We collected 60 sec of data at three speeds (2.22, 2.78, 3.33 m·s ). RMS was calculated for medio-lateral (ML), anterio-posterior (AP), vertical (VT), and the resultant Euclidean scalar (RES) acceleration. From motion capture, we calculated 14 kinematic variables, including mean sagittal plane joint angles at foot contact, mid-stance, and toe-off. Principal components analysis (PCA) was used to form independent components comprised of combinations of the original variables. Stepwise regressions were performed on the original variables and the components to determine contributions to RMS acceleration in each axis. Results: Significant speed effects were found for RMS-accelerations in all axes (p \u3c 0.05). Regressions of the original variables indicated from 4 to 5 variables associated with accelerations in each axis (R = 0.71 to 0.82, p \u3c 0.001). The most prominent contributing variables were associated with the late flight and early stance phase. PCA reduced the data into four components. Component 1 included all hip angles before mid-stance and component 2 was primarily associated with propulsion. Regressions indicated key contributions from components 1 and 2 to ML, VT, and RES acceleration (p \u3c 0.05). Conclusions: The variables with highest contribution were prior to mid-stance and mechanically relate to shock absorption and attenuation of peak forces. Trunk acceleration magnitude is associated with global running variables, ranging from energy expenditure to forces lending to the mechanics of injury. These data begin to delineate running gait events and offer relationships of running mechanics to those structures more proximal in the kinetic chain. These relationships may provide insight for technique modification to maximize running economy or prevent injury. -1

The Influence of Knee and Ankle Bracing on Lower Extremity Kinematics During a Cutting Maneuver

PURPOSE: To determine the effect of four brace conditions on the lower extremity kinematics during a jogging cutting maneuver. METHODS: 18 subjects (9 male and 9 female, age = 22.8±2.0 yrs, ht = 174.7±7.6 cm, wt = 74.9±14.5 kg) participated in this study. Each subject performed 7–10 jogging cutting trials while wearing each of the four brace conditions; ankle brace only (AB), knee brace only (KB), ankle and knee brace together (ABKB) and no brace (NB). Hip and knee sagittal and frontal plane kinematics and ankle sagittal plane kinematics were assessed for each subject during each of the brace conditions. RESULTS: ANOVA (α = .05) revealed that sagittal plane ankle and hip ROM were not influenced by brace condition. Sagittal plane knee ROM was significantly reduced in the KB compared to the NB condition. Frontal plane knee ROM revealed a more varus position during the KB and ABKB conditions compared to the NB and AB conditions. The results also revealed that the hip was significantly more abducted during the KB and ABKB conditions when compared to the AB and NB conditions. CONCLUSIONS: The results indicate that the KB and the ABKB significantly influenced frontal plane hip and knee ROM and sagittal plane knee ROM during a jogging cutting maneuver. These braces may be beneficial in preventing excessive motion at the respective joint however it is important to consider their impact at the hip joint as a result of these bracing techniques. It is possible that these changes in ROM may result in subsequent changes in joint moments and or ground reaction forces

Economy of acceleration for individual axes versus speed in highly trained collegiate (Blue) and untrained (Green) runners during the run stages only.

<p>a) VT b) ML c) AP d) RES. Significant effects for speed in VT and RES (p<.001) and for training present in all axes (p<.001).</p