Masaya Anan

Do patients with knee osteoarthritis perform sit-to-stand motion efficiently?

The sit-to-stand motion (STS) is a frequently executed activity that is affected by weakness in the quadriceps femoris muscle and knee joint pain in patients with knee osteoarthritis (OA). We investigated whether patients with knee OA can efficiently perform STS through mechanical energy transfer assessments. Participants were 20 women with knee OA and 17 age-matched asymptomatic controls. The center of mass (COM), segment angles, joint moments, and powers during STS were measured. The negative mechanical work in the proximal portion of the shank, negative mean powers in the distal portion of the pelvis and proximal portion of the shank, and the positive mean power in the proximal and distal portions of the thigh were significantly lower in the knee OA group than in the control group. Patients with knee OA primarily performed thoracic forward lean movement, shifting their COM closer to the base of support provided by the feet alone, in an attempt to achieve stability at and after buttocks-off. However, control ability, which generates and absorbs kinetic energy quickly, was not enhanced in these patients, and their motion was unable to increase absorption of the mechanical energy in hip extensors and reduce the load on knee extensors. Furthermore, STS in patients with knee OA had reduced energy absorption in the knee extensors from the shank forward lean movement after buttocks-off, had reduced knee extensor efficiency, and made greater use of physiological energy. These findings suggest that, from the standpoint of mechanical energy transfer, patients with knee OA do not perform STS efficiently.

Biomechanics of rising from a chair and walking in pregnant women.

The present study aimed to assess the changes in the pattern of rising from a chair and walking forward as pregnancy progressed. Twelve pregnant women and 10 nulliparous women were included in this study. Participants were videotaped with a digital video camera in the sagittal plane, and the coordinates of the markers attached to the subjects were identified using image analysis software. The peak trunk-flexion angle in pregnant women during rising was smaller, but the hip-extension angle during the stance phase was larger than in controls. Also, the peak horizontal and vertical velocities of the center of mass were lower, and appeared earlier, in pregnant women than in controls. During rising, pregnant women dampened the propulsion attributable to increased uterus volume, and they enhanced the forward propulsion at gait initiation. To ensure safe motion, pregnant women should not initiate gait until reaching a stable standing position after rising.

Foot alignments influence the effect of knee adduction moment with lateral wedge insoles during gait.

Lateral wedge insoles (LWIs) reduce the peak external knee adduction moment (KAM). However, the efficacy of LWIs is limited in certain individuals for whom they fail to decrease KAM. Possible explanations for a lack of desired LWI response are variations in foot alignments. The purpose of this study was to evaluate whether the immediate biomechanical effects of LWIs depend on individual foot alignments during gait. Fifteen healthy adults participated in this study. Their feet were categorized as normal, pronated, and supinated using the foot posture index. All subjects were subsequently requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record the kinematic and kinetic data, included peak KAM, KAM impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm (KLA). Furthermore, lower limb frontal plane kinematic parameters at the rear foot, ankle, knee, and hip were evaluated. Among all feet, there was no significant difference in the peak KAM and KAAI between the conditions. In contrast, the peak KAM was significantly reduced under the LWI condition relative to the barefoot condition in the normal foot group. Reductions in the peak KAM were correlated with a more lateral center of pressure and reduced KLA. In addition, a reduced KLA was correlated with decreased hip adduction. LWIs significantly reduced the peak KAM in normal feet, indicating that biomechanical effects of LWIs vary between individual foot alignments. Our findings suggest that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with knee osteoarthritis.

Biomechanical effects of lateral and medial wedge insoles on unilateral weight bearing

[Purpose] Lateral wedge insoles reduce the peak external knee adduction moment and are advocated for patients with knee osteoarthritis. However, some patients demonstrate adverse biomechanical effects with treatment. In this study, we examined the immediate effects of lateral and medial wedge insoles under unilateral weight bearing. [Subjects and Methods] Thirty healthy young adults participated in this study. The subjects were assessed by using the foot posture index, and were divided into three groups: normal foot, pronated foot, and supinated foot groups. The knee adduction moment and knee-ground reaction force lever arm under the studied conditions were measured by using a three-dimensional motion capture system and force plates. [Results] In the normal and pronated groups, the change in knee adduction moment significantly decreased under the lateral wedge insole condition compared with the medial wedge insole condition. In the normal group, the change in the knee-ground reaction force lever arm also significantly decreased under the lateral wedge insole condition than under the medial wedge insole condition. [Conclusion] Lateral wedge insoles significantly reduced the knee adduction moment and knee-ground reaction force lever arm during unilateral weight bearing in subjects with normal feet, and the biomechanical effects varied according to individual foot alignment.

Estimation of inertial parameters of the lower trunk in pregnant Japanese women: A longitudinal comparative study and application to motion analysis.

We aimed to quantify the inertial parameters of the lower trunk segment in pregnant Japanese women and compare kinetic data during tasks calculated with parameters estimated in this study to data calculated with standard parameters. Eight pregnant women and seven nulliparous women participated. Twenty-four infrared reflective markers were attached to the lower trunk, and the standing position was captured by eight infrared cameras. The lower trunk was divided into parts, and inertial parameters were calculated. Pregnant women performed a movement task that involved standing from a chair, picking up plates, and walking forward after turning to the right. Kinetic analysis was performed using standard inertial parameters and the newly calculated parameters. There were more significant differences between methods in the kinetic data at the latter stages of pregnancy. The inertial parameters calculated in this study should be used to ensure the validity of biomechanical studies of pregnant Japanese women.

Influences of trunk flexion on mechanical energy flow in the lower extremities during gait

[Purpose] The time-series waveforms of mechanical energy generation, absorption, and transfer through the joints indicate how movements are produced and controlled. Previous studies have used these waveforms to evaluate and describe the efficiency of human movements. The purpose of this study was to examine the influence of trunk flexion on mechanical energy flow in the lower extremities during gait. [Subjects and Methods] The subjects were 8 healthy young males (mean age, 21.8 ± 1.3 years, mean height, 170.5 ± 6.8 cm, and mean weight, 60.2 ± 6.8 kg). Subjects walked at a self-selected gait speed under 2 conditions: normal gait (condition N), and gait with trunk flexion formed with a brace to simulate spinal curvature (condition TF). The data collected from initial contact to the mid-stance of gait was analyzed. [Results] There were no significant differences between the 2 conditions in the mechanical energy flow in the knee joint and negative mechanical work in the knee joint. However, the positive mechanical work of the knee joint under condition TF was significantly less than that under condition N. [Conclusion] Trunk flexion led to knee flexion in a standing posture. Thus, a strategy of moving of center of mass upward by knee extension using less mechanical energy was selected during gait in the trunk flexed posture.

The effects of altering attentional demands of gait control on the variability of temporal and kinematic parameters

The purpose of this study was to investigate the effects of cognitive and visuomotor tasks on gait control in terms of the magnitude and temporal structure of the variability in stride time and lower-limb kinematics measured using inertial sensors. Fourteen healthy young subjects walked on a treadmill for 15min at a self-selected gait speed in the three conditions: normal walking without a concurrent task; walking while performing a cognitive task; and walking while performing a visuomotor task. The time series data of stride time and peak shank angular velocity were generated from acceleration and angular velocity data recorded from both shanks. The mean, coefficient of variation, and fractal scaling exponent α of the time series of these variables and the standard deviation of shank angular velocity over the entire stride cycle were calculated. The cognitive task had an effect on long-range correlations in stride time but not on lower-limb kinematics. The temporal structure of variability in stride time became more random in the cognitive task. The visuomotor task had an effect on lower-limb kinematics. Subjects controlled their swing limb with greater variability and had a more complex adaptive lower-limb movement pattern in the visuomotor task. The effects of the dual tasks on gait control were different for stride time and lower-limb kinematics. These findings suggest that the temporal structure of variability and lower-limb kinematics are useful parameters to detect a change in gait pattern and provide further insight into gait control.

Relationships Between Trunk Movement Patterns During Lifting Tasks Compared With Unloaded Extension From a Flexed Posture

Objectives The purpose of this study was to investigate between movement patterns of trunk extension from full unloaded flexion and lifting techniques, which could provide valuable information to physical therapists, doctors of chiropractic, and other manual therapists. Methods A within‐participant study design was used. Whole‐body kinematic and kinetic data during lifting and full trunk flexion were collected from 16 healthy male participants using a 3‐dimensional motion analysis system (Vicon Motion Systems). To evaluate the relationships of joint movement between lifting and full trunk flexion, Pearson correlation coefficients were calculated. Results There was no significant correlation between the amount of change in the lumbar extension angle during the first half of the lifting trials and lumbar movement during unloaded trunk flexion and extension. However, the amount of change in the lumbar extension angle during lifting was significantly negatively correlated with hip movement during unloaded trunk flexion and extension (P < .05). Conclusions The findings that the maximum hip flexion angle during full trunk flexion had a greater influence on kinematics of lumbar–hip complex during lifting provides new insight into human movement during lifting. All study participants were healthy men; thus, findings are limited to this group.

Dynamic Frequency Analyses of Lower Extremity Muscles during Sit-To-Stand Motion for the Patients with Knee Osteoarthritis

Objective Muscle activities during the sit-to-stand motion (STS) are characterized by coordinated movements between hip extensors and knee extensors. However, previous reports regarding the STS and lower extremity muscle activities have focused on some quantitative assessment, but little qualitative research. This study aimed to examine the muscle activities of the lower extremity both quantitatively and qualitatively. Methods Study participants included 13 patients with knee osteoarthritis (knee OA) and 11 age-matched asymptomatic controls. The task was STS from a chair with a height-adjustable seat. EMG activities were acquired using surface electromyogram. The root mean square signals normalized as a percentage of maximum voluntary isometric contraction values (RMS%MVC) and the mean power frequency (MPF) were calculated. Results During STS, knee OA patients had increased RMS%MVC of the vastus medialis and raised MPF of the rectus femoris before buttocks-off. Conclusion These findings suggest that STS of knee OA patients not only increased relative muscle activity of the vastus medialis, but also enlisted the rectus femoris in knee extension to improve muscle contraction force by activating more type II fibers to accomplish buttocks-off.