Fábio Barbosa Rodrigues

Local dynamic stability and gait variability during attentional tasks in young adults

Cell phone use while walking may be a cognitive distraction and reduce visual and motor attention. Thus, the aim of this study was to verify the effects of attentional dual-tasks while using a cell phone in different conditions. Stability, regularity, and linear variability of trunk kinematics, and gait spatiotemporal parameters in young adults were measured. Twenty young subjects of both genders were asked to walk on a treadmill for 4min under the following conditions: (a) looking forward at a fixed target 2.5m away (walking); (b) talking on a cell phone with unilateral handling (talking); (c) texting messages on a cell phone with unilateral handling (texting); and (d) looking forward at the aforementioned target while listening to music without handling the phone (listening). Local dynamic stability measured in terms of the largest Lyapunov exponent decreased while handling a cell phone (talking and texting). Gait variability and regularity increased when talking on a cell phone, but no variable changed in the listening condition. Under all dual-task conditions, there were significant increases in stride width and its variability. We conclude that young adults who use a cell phone when walking adapt their gait pattern conservatively, which can be because of increased attentional demand during cell phone use.

Gait stability, variability and complexity on inclined surfaces

This study evaluated the gait stability, variability, and complexity of healthy young adults on inclined surfaces. A total of 49 individuals walked on a treadmill at their preferred speed for 4min at inclinations of 6%, 8%, and 10% in upward (UP) and downward (DOWN) conditions, and in horizontal (0%) condition. Gait variability was assessed using average standard deviation trunk acceleration between strides (VAR), gait stability was assessed using margin of stability (MoS) and maximum Lyapunov exponent (λs), and gait complexity was assessed using sample entropy (SEn). Trunk variability (VAR) increased in the medial-lateral (ML), anterior-posterior, and vertical directions for all inclined conditions. The SEn values indicated that movement complexity decreased almost linearly from DOWN to UP conditions, reflecting changes in gait pattern with longer and slower steps as inclination increased. The DOWN conditions were associated with the highest variability and lowest stability in the MoS ML, but not in λs. Stability was lower in UP conditions, which exhibited the largest λs values. The overall results support the hypothesis that inclined surfaces decrease gait stability and alter gait variability, particularly in UP conditions.

Effects of general fatigue induced by incremental maximal exercise test on gait stability and variability of healthy young subjects

The purpose of this study was to determine whether general fatigue induced by incremental maximal exercise test (IMET) affects gait stability and variability in healthy subjects. Twenty-two young healthy male subjects walked in a treadmill at preferred walking speed for 4min prior (PreT) the test, which was followed by three series of 4min of walking with 4min of rest among them. Gait variability was assessed using walk ratio (WR), calculated as step length normalized by step frequency, root mean square (RMSratio) of trunk acceleration, standard deviation of medial-lateral trunk acceleration between strides (VARML), coefficient of variation of step frequency (SFCV), length (SLCV) and width (SWCV). Gait stability was assessed using margin of stability (MoS) and local dynamic stability (λs). VARML, SFCV, SLCV and SWCV increased after the test indicating an increase in gait variability. MoS decreased and λs increased after the test, indicating a decrease in gait stability. All variables showed a trend to return to PreT values, but the 20-min post-test interval appears not to be enough for a complete recovery. The results showed that general fatigue induced by IMET alters negatively the gait, and an interval of at least 20min should be considered for injury prevention in tasks with similar demands.

A simple, reliable method to determine the mean gait speed using heel markers on a treadmill

Abstract Gait speed is an essential parameter of gait analysis. Our study proposed a simple and accurate method to extract a mean gait speed during walking on a treadmill using only kinematic data from markers placed on the heels of the participants’ feet. This method provided an attractive, simple method that remains resistant to errors in treadmill calibration. In addition, this method required only two markers, since heel markers are essential to gait analysis, and the proposed method is robust enough to differentiate among various gait speeds (mean error <1%).

Use of a backpack alters gait initiation of high school students

We assessed how backpack carriage influences the gait initiation (GI) process in high school students, who extensively use backpacks. GI involves different dynamics from gait itself, while the excessive use of backpacks can result in adverse effects. 117 high school students were evaluated in three experimental conditions: no backpack (NB), bilateral backpack (BB), and unilateral backpack (UB). Two force plates were used to acquire ground reaction forces (GRFs) and moments for each foot separately. Center of pressure (COP) scalar variables were extracted, and statistical parametric mapping analysis was performed over the entire COP/GRFs time series. GI anticipatory postural adjustments (APAs) were reduced and were faster in backpack conditions; medial-lateral COP excursion was smaller in this phase. The uneven distribution of the extra load in the UB condition led to a larger medial-lateral COP shift in the support-foot unloading phase, with a corresponding vertical GRF change that suggests a more pronounced unloading swing foot/loading support foot mechanism. The anterior-posterior GRFs were altered, but the COP was not. A possible explanation for these results may be the forward trunk lean and the center of mass proximity of the base of support boundary, which induced smaller and faster APA, increased swing foot/support foot weight transfer, and increased load transfer to the first step.

Validation of a protocol to evaluate maximal expiratory pressure using a pressure transducer and a signal conditioner

The respiratory muscles can present fatigue and even chronic inability to generate force. So, reliable devices are necessary to their evaluation. The aim of this study is to evaluate the MEP (Maximal Expiratory Pressure) values of individuals between 20 and 25 years old and to validate a protocol using a pressure transducer and a signal conditioner comparing it with the digital manometer. We evaluated the MEP of 10 participants. They remained seated and made six respiratory maneuvers from Total Lung Capacity (TLC) to Residual Volume (RV). The results in the study showed no statistically significant differences when compared to values reported in the literature, and that the pressure transducer provides reliable values for MEP.

Effects of backpack load and positioning on nonlinear gait features in young adults

Abstract Overloaded backpacks can cause changes in posture and gait dynamic balance. Therefore, the aim of this study was to assess gait regularity and local dynamic stability in young adults as they carried a backpack in different positions, and with different loads. Twenty-one healthy young adults participated in the study, carrying a backpack that was loaded with 10 and 20% of their body weight (BW). The participants walked on a level treadmill at their preferred walking speeds for 4 min under different conditions of backpack load and position (i.e. with backpack positioned back bilaterally, back unilaterally, frontally or without a backpack). Results indicate that backpack load and positioning significantly influence gait stability and regularity, with the exception of the 10% BW bilateral back position. Therefore, the recommended safe load for school-age children and adolescents (10% of BW) should also be considered for young adults. Practitioner summary: Increase in load results in changes in posture, muscle activity and gait parameters, so we investigated the gait adaptations related to regularity and stability. Conditions with high backpack loads significantly influenced gait stability and regularity in a position-dependent manner, except for 10% body weight bilateral back position.

Effects of backpack loads and positions on the variability of gait spatiotemporal parameters in young adults

Introduction: People carry backpacks of different weight in different positions every day. The effects of backpack wearing under different loads and positions were assessed according to the gait’s spatiotemporal parameters and their variability in young adults. Methods: Twenty-one subjects performed trials of 4 min in the conditions: control condition with no backpack; bilateral back load consisting of 10% body weight (BW); bilateral back load of 20% BW (B20); unilateral load of 10% BW; unilateral load with 20% BW (U20); bilateral frontal load with 10% BW; bilateral frontal load with 20% BW. Results: Step length (SL) and step frequency (SF) show that frontal conditions differed from others as seen in B20. Gait cycle phases showed an increase in the B20 condition for double stance phase and stance phase, swing phase presented reduction in the B20 condition. There were signi cant main effects in position for SL, SF, and walk ratio, in load only for stride width. The highest variability of spatiotemporal parameters occurred in the U20 condition. All load conditions with 20% BW showed a greater variability when compared to the 10% BW counterpart. Conclusion: We concluded that young adults can cope with up to a 15% BW load under a bilateral back position, but in the frontal position not even a 10% BW load was proven to be a safe limit. 20% BW loads should be avoided in any position. These recommendations may assure increased gait stability, decreased trunk forward lean and decreased muscle activation and fatigue reducing back pain occurrence.

Center of pressure and center of mass behavior during gait initiation on inclined surfaces: A statistical parametric mapping analysis

This study analyzed gait initiation (GI) on inclined surfaces with 68 young adult subjects of both sexes. Ground reaction forces and moments were collected using two AMTI force platforms, of which one was in a horizontal position and the other was inclined by 8% in relation to the horizontal plane. Departing from a standing position, each participant executed three trials in the following conditions: horizontal position (HOR), inclined position at ankle dorsi-flexion (UP), and inclined position at ankle plantar-flexion (DOWN). Statistical parametric mapping analysis was performed over the entire center of pressure (COP) and center of mass (COM) time series. COP excursion did not show significant differences in the medial-lateral (ML) direction in both inclined conditions, but it was greater in the anterior-posterior (AP) direction for both inclined conditions. COP velocities are smaller in discrete portions of GI for the UP and DOWN conditions. COM displacement was greater in the ML direction during anticipatory postural adjustments (APA) in the UP condition, and COM moves faster in the ML direction during APA in the UP condition but slower at the end of GI for both the UP and the DOWN conditions. The COP-COM vector showed a greater angle in the DOWN condition. We observed changes for COP and COM in GI in both the UP and the DOWN conditions, with the latter showing changes for a great extent of the task. Both the UP and the DOWN conditions showed increased COM displacement and velocity. The predominant characteristic during GI on inclined surfaces, including APA, appears to be the displacement of the COM.