Gustavo Leporace

Classification of gait kinematics of anterior cruciate ligament reconstructed subjects using principal component analysis and regressions modelling

The aim of this study was to compare the knee kinematics of anterior cruciate ligament reconstructed (ACL-R) and healthy subjects (CG) during gait and classify the status of normality. Ten healthy and six ACL-R subjects had their gait analyzed at 60 fps. 3D knee angles were calculated and inserted into three separate matrices used to perform the principal component (PC) analysis. The scores of PCs retained in each analysis were used to calculate the standard distances (SD) of each participant in relation to the center of the CG. The PC scores of the three planes were used in a logistic regression to define normality. In the sagittal plane there was no difference between groups. In the frontal and transverse planes ACL-R subjects showed higher SD values than CG. PCs identified that ACL-R subjects showed increased adduction, internal and external rotation. All these subjects had their gait classified as abnormal by logistic regression. Therefore, in the studied ACL-R subjects the gait pattern did not return to normal levels after surgery. This may lead to degenerative injuries, as osteoarthritis, in the future.

What is the best questiOnnaire fOr mOnitOring the physical characteristics Of patients With knee OsteOarthritis in the brazilian pOpulatiOn

Objective: To measure the validity and reliability of the WOMAC, IKDC and Lysholm questionnaires among patients with knee osteoarthritis and determine the influence of age on their scores. Method: Fifty-seven patients diagnosed with primary osteoarthritis of the knee answered the SF-36, WOMAC, IKDC and Lysholm questionnaires. Validity was tested by measuring the correlation (Pearson’s correlation coefficient, “r”) between the questionnaires. Internal consistency was measured using Cronbach’s α and concordance was measured through the Altman-Bland graphical representations and survival concordance. To determine the influence of age on the results, we correlated this variable with the scores from the three knee questionnaires using Pearson’s coefficient of determination (“r2”). Results: IKDC (0.62) and WOMAC (0642) showed moderate to strong correlations in relation to the summarized physical capacity score of the SF-36, while Lysholm showed moderate correlations (0.555). The Cronbach α values for IKDC, WOMAC and Lysholm were 0.811, 0.959 and 0.734, respectively. Despite the strong correlations between IKDC and WOMAC (0.843), Lysholm and WOMAC (0.759) and IKDC and Lysholm (0.858), the Bland-Altman graphical representations and survival concordance showed that the concordance between the three questionnaires was low. IKDC, Lysholm and WOMAC showed coefficients of determination (r2) with age of 0.004, 0.010 and 0.043, respectively. Conclusion: Age was not found to be a limiting factor for the use of any of the questionnaires applied in this study. The concordance tests and correlations with the physical components of SF-36 suggest that WOMAC is more appropriate for assessing physical capacities and limitations relating to physical traits, while IKDC seems more appropriate for assessing the functional limitations relating to pain.

Differences in time-frequency representation of lower limbs myoelectric activity during single and double leg landing in male athletes

This study compared the instantaneous median frequency (IMF) obtained by means of a Choi-Williams transform of an electromyogram of the lower-limb muscles during single-leg (SL) and double-leg (DL) landings performed by fifteen male athletes. The IMF values of the rectus femoris (RF), biceps femoris (BF) and hip adductors (HA) were compared between two landing tasks, within each landing, and before and after ground contact (GC). The IMF values of the RF did not change between landings in contrast to those of the BF, which presented from 20- to 40-ms higher SL values before GC and from 40 to 60 ms after GC. HA presented higher SL values during the 40-60 ms range before GC. Within each landing, the RF IMF decreased from 40 ms to 60 ms after GC in the SL. Similar results were found for the HA IMF, which decreased from 40ms to 80 ms after GC. The BF IMF showed no significant change. These results suggest muscle recruitment related to anterior cruciate ligament protection since the IMF values of the RF decreased in the SL, whereas the BF IMF increased. Results for the HA showed the importance of hip muscles in stabilizing the core region, allowing the activation of distal muscles with greater safety.

Ativação muscular do quadril e do joelho em duas aterrissagens realizadas por atletas do sexo masculino

OBJECTIVE: To compare the myoelectric activity before and after ground contact between single leg (SL) and double leg (DL) landings in male athletes. PARTICIPANTS: Fifteen male volleyball athletes without signs and symptoms of lesions in the lower extremities, with a minimum of three years experience in the sport (13 ± 1 years, 1.70 ± 0.12 m, 60 ± 12 kg). MEASUREMENTS: Participants performed two vertical jumps, landing unilaterally and bilaterally. The myoelectric activity of the rectus femoris (RF), biceps femoris (BF), hip adductors (HA) and the BF/RF ratio were compared between the two landings and between the phases characterized by 100ms before (PRE) and after 100 ms (POST) ground contact using ANOVA two-way test with post hoc test of Bonferroni (α = 5%). RESULTS: In both landings activation of RF was higher in the POST in relation to the PRE (p <0.0001). Comparing the landings in the same phase statistical differences (p = 0.2212) were not found. Although the BF did not present significant differences between the PRE and POST in each landing (p = 0.2321), its activation was higher in SL (p = 0.0051). The HA showed greater activation in the POST during the SL (p = 0.0013), however there were no differences when comparing the two landings (p = 0.9233). The BF/RF ratio was higher in both landings during PRE (p = 0.0012). Nevertheless, no differences between the landings (p = 0.7037) were found. CONCLUSION: The results suggest that each muscle has a different role during landing tasks in men. While RF has the main function to decelerate the knee and the downward movement, characterized by increased activation in the POST, BF seems to attenuate the loads on the knee in activities of higher impact, staying more active throughout the cycle in the SL. The increased activation of HA after ground contact in the SL highlights the importance of core region in stabilizing the pelvis in situations of great instability. Further studies are needed to determine the effects of muscle activation at the imposition of mechanical load on the knee that are potentially harmful to male athletes.

Prediction of 3D ground reaction forces during gait based on accelerometer data

Introduction: The aim of this study was to predict 3D ground reaction force signals based on accelerometer data during gait, using a feed-forward neural network (MLP). Methods: Seventeen healthy subjects were instructed to walk at a self-selected speed with a 3D accelerometer attached to the distal and anterior part of the shank. A force plate was embedded into the middle of the walkway. MLP neural networks with one hidden layer and three output layers were selected to simulate the anteroposterior (AP), vertical (Vert) and mediolateral (ML) ground reaction forces (GRF). The input layer was composed of fourteen inputs obtained from accelerometer signals, selected based on previous studies. Principal component analysis (PCA) was used to compare the simulated and collected curves. The Pearson correlation coefficient and the mean absolute deviation (MAD) between signals were calculated. Results: PCA identified small, but significant differences between collected and simulated signals in the loading response phases of AP and ML GRF, while Vert did not show differences. The correlation between the simulated and collected signals was high (AP: 0.97; Vert: 0.98; ML: 0.80). MAD was 1.8%BW for AP, 4.5%BW for Vert and 1.4%BW for ML. Conclusion: This study confirmed that multilayer perceptron neural network can predict the highly non-linear relationship of shank acceleration parameters and ground reaction forces, as well as other studies have done using plantar pressure devices. The greater advantages of this device are the low cost and the possibility of use outside the laboratory environment.

USE OF SPATIOTEMPORAL GAIT PARAMETERS TO DETERMINE RETURN TO SPORTS AFTER ACL RECONSTRUCTION

Objective : To compare gait spatiotemporal parameters of healthy and ACL reconstructed subjects in order to classify the status of gait normality. Methods : Fourteen healthy subjects and eight patients submitted to ACL reconstruction walked along a walkway while the lower limbs movement was captured by an infrared camera system. The frames where the initial contact and toe-off took place were determined and the following dependent variables, which were compared between groups through the Mann-Whitney test (a=0.05) were calculated: percentage of time in initial double stance, percentage of time in single stance, percentage of time in terminal double stance, stride length and gait velocity. Initially, all variables were compared between groups using a Mann-Whitney test. A logistic regression was applied, including all dependent variables, to create a model that could differentiate healthy and ACL reconstructed subjects. Results : ACL reconstructed group showed no differences in any spatiotemporal parameter of gait (p > 0.05) in relation to the control group, although the angular kinematic differences of the knee remained altered, as evidenced in a study with a similar sample. Conclusion : The regression classified all subjects as healthy, including the ACL reconstructed group, suggesting the spatiotemporal variables should not be used as the sole criterion of return to sports activities at the same level as prior to injury. Level of Evidence III, Case Control Study.

KNEE SYNERGISM DURING GAIT REMAIN ALTERED ONE YEAR AFTER ACL RECONSTRUCTION

ABSTRACT Objective: To compare the activation of the vastus lateralis (VL) and biceps femoris (BF) muscles during gait, as well VL/BF muscular co-contraction (MCC) between healthy (CG) and anterior cruciate ligament reconstructed (ACL-R) subjects. Methods: Nineteen subjects, ten controls and nine ACL-R patients had a VL and BF electromyogram (EMG) captured to calculate the MCC ratio. A Principal Component (PC) Analysis was applied to reduce the dimensionality effect of each of the MCC, VL and BF curves for both healthy and ACL reconstructed groups. The PC scores were used to calculate the standard distance (SD). SD values were employed in order to compare each dependent variable (MCC, VL and BF) between the two groups using unpaired t-test. Results: ACL-R group presented a lower VL activation at the beginning and at the end of the gait cycle, as compared to the control group. However, no difference was found for BF or VL/BF MCC. Conclusion: The gait analysis of ACL reconstructed patients demonstrated a persistent deficit in VL activation when compared to the control group, even one year after surgery. Level of Evidence III. Case Control Study

Residual analysis of ground reaction forces simulation during gait using neural networks with different configurations.

The aim of the study was to analyze and compare the residuals obtained from ground reaction force (GRF) models developed using two different neural network configurations (one network with three outputs; and three networks with one output each), based on accelerometer data. Seventeen healthy subjects walked along a walkway, with a force plate embedded, with a three dimensional accelerometer attached to the shank. Multilayer perceptron networks (MLP) models were developed with the 3D accelerometer data as inputs to predict the GRF. The residuals of these models were evaluated graphically and numerically to verify the fitting. A visual analysis of the simulated signals suggests the model was able to adequately predict the GRF. The errors and correlations found in the MLP models for the 3D GRF is at least similar to other studies, although some of them showed higher errors. There was not difference between the two MLP configurations. However, despite the high correlation coefficient and closeness to a normal probability distribution, the residual analysis still presented a higher kurtosis and skewness, suggesting that the inclusion of other variables and the increase of the validation sample size could increase the fitting of the simulation.

Motor coordination during gait after anterior cruciate ligament injury: a systematic review of the literature☆

To investigate the state of art about motor coordination during gait in patients with anterior cruciate ligament (ACL) injury. Searches were carried out, limited from 1980 to 2010, in various databases with keywords related to motor coordination, gait and ACL injury. From the analysis of titles and applying the inclusion/exclusion criteria 24 studies were initially selected and, after reading the abstract, eight studies remained in the final analysis. ACL deficient patients tend to have a more rigid and less variable gait, while injured patients with ACL reconstruction have less rigid and more variable gait with respect to healthy individuals. The overall results suggest the existence of differences in motor coordination between the segments with intact and those with injured knee, regardless of ligament reconstruction. ACL injured patients present aspects related to the impairment of the capability to adapt the gait pattern to different environmental conditions, possibly leading to premature knee degeneration. However, the techniques used for biomechanical gait data processing are limited with respect to obtaining information that leads to the development of intervention strategies aimed at the rehabilitation of that injury, since it is not possible to identify the location within the gait cycle where the differences could be explained.

Influence of a preventive training program on the lower limbs kinematics and vertical jump height of male volleyball athletes

Background The effectiveness of preventive training programs (PTP) aiming at changing the biomechanical behaviour related to anterior cruciate ligament injuries is subject to pre-existing risk. However, these assumptions are based on studies in females. Moreover, it is unclear what influence this training has on performance of young male athletes. Objective To examine the influence of a PTP on changes in kinematics during landings and in maximum vertical jump height (VJH) in males. Design 6 weeks prospective exercise intervention. Setting Young male volleyball athletes. Participants 15 male volleyball athletes (13±0.7 years, 1.70±0.12 m, 60±12 kg). Interventions PTP consisting of plyometric, balance and core stability exercises three times per week for 6 weeks. Bilateral vertical jumps with double leg (DL) and single leg (SL) landings were performed to measure the effects of training. Main outcome measurements Kinematics of knee and hip before and after training and VJH attained during both tasks after training. The hypothesis was that the PTP would produce improvements in VJH, but would not generate great changes in biomechanical behaviour. Results The only change revealed for the SL was the longest duration of landing (p=0.0273), while in the DL was the largest angular displacement of the knee (p=0.0371). The training did not significantly alter the VJH in the SL (diff: 2.7 cm, p=0.3054) or DL condition (diff: 3.5 cm, p=0.3635). Conclusion Despite the alterations in the kinematics behaviour, the changes observed are specific for each landing task, which highlights the importance of the principle of specificity. Despite the absence of significant increases in the VJH after training, the absolute differences pre to post training showed an increase consistent with other studies that compared the results with control groups. The present study showed that short time PTP in low-risk populations, although generating little influence on the kinematics, are capable of enhancing performance.