Motor strategies for initiating downward-oriented movements during standing in adults

Trunk biomechanical changes between the sit-to-stand and stand-to-sit performed at self-selected and fast speeds in stroke survivors

PURPOSE

To compare the trunk biomechanical characteristics between the sit-to-stand and stand-to-sit performed at self-selected and fast speeds in stroke survivors and healthy-matched controls.

METHODS

Thirty individuals (15 stroke survivors and 15 healthy-matched controls) were included. The following biomechanical characteristics were determined: peak of trunk forward flexion and time until the peak of trunk forward flexion, total duration, phase I (sit-to-stand: time spent from the beginning to seat-off; stand-to-sit: time spent from the beginning to seat-on) and II durations (sit-to-stand: time spent from seat-off to the end of the task; stand-to-sit: time spent from the seat-on to the end of the task). Two-way repeated measures ANOVA was used (α = 5%).

RESULTS

The maximum angle of trunk forward flexion and time spent until the maximum angle of trunk forward flexion in both tasks were significantly higher in stroke survivors. For both groups and speeds, phase I duration and peak of trunk forward flexion of the stand-to-sit were significantly higher than that of the sit-to-stand (11.41≤F ≤ 33.60; 0.001 ≤ p ≤ 0.002) and, phase II duration was significantly higher during the sit-to-stand than that of the stand-to-sit (21.27 ≤ F ≤ 65.10; p ≤ 0.001).

CONCLUSIONS

These results confirm specific trunk biomechanical characteristics between sit-to-stand and stand-to-sit in stroke survivors and healthy-matched controls.

Comparison of the asymmetries in muscle mass, biomechanical property and muscle activation asymmetry of quadriceps femoris between patients with unilateral and bilateral knee osteoarthritis

Background: More and more attention has been paid to the research of muscle mass and muscle quality of quadriceps femoris (QF) in knee osteoarthritis (KOA). This study aimed to explore the asymmetric changes of muscle mass, biomechanical property and muscle activation in the inter-limbs QF of KOA patients, and tried to provide a novel insight for the evaluation, prevention and treatment of KOA. Methods: A total of 56 Participants with unilateral or bilateral KOA were included in this study: 30 patients with unilateral pain and 26 patients with bilateral pain were assigned to the bilateral group (BG) and unilateral group (UG), respectively. The symptom severity of bilateral lower limbs was evaluated by visual analogue scale, and the relatively serious leg (RSL) and relatively moderate leg (RML) were classified. The thickness of rectus femoris (RF), vastus intermedius (VI), vastus medialis (VM) and vastus lateralis (VL) were measured by ultrasound. The Shear wave elastography (SWE) techniqie was used to measure the shear modulus of RF, VM and VL. Surface electromyography (sEMG) was used to assess the root mean square (RMS) of the RF, VM, and VL during straight leg raising in a sitting position and squatting task. We calculated the asymmetry indexes of inter-limbs for the corresponding indices of the measured muscles. Result: Thickness of RF, VI and VL of RSL was lower than those on RML (p < 0.05), and thickness of VM was lower more significant (p < 0.01). Thickness of RF, VI and VL of RSL was also lower than those of RML in BG (p < 0.05), however, there was no significant difference in VM thickness (p > 0.05). There were no significant difference in Asymmetry indexes of all measured muscle thickness between the two groups (p > 0.05). The Shear modulus of RF, VM, and VL in the RML of UG and BG was higher than those in the RSL (p < 0.05). In sitting and straight leg raising task, the RMS of RF, VM and VL in RML were higher than those in RSL, UG and BG both showed this trend (p < 0.05). About squatting task, in UG, the RMS of the three muscles in RML of patients were also higher than those in the RSL (p < 0.05). However, the difference was not significant in BG (p > 0.05). In the straight leg raising task, the asymmetry indexes of RMS in RF, VM, and VL of both the two groups were positively correlated with VAS scores (p < 0.05). Conclusion: The muscle thickness, shear modulus and muscle activation electromyography of QF in RML were higher than those of RSL in unilateral KOA patients. The VM of RML in bilateral KOA patients may show muscle thickness degeneration earlier, which is closer to the VM of RSL. The shear modulus of RF, VM, and VL were higher on the RML side during the single-leg task, but there may be passive compensation for muscle activation in both lower limbs during the bipedal task. In conclusion, there is a general asymmetry of QF muscle mass, biomechanics Characteristic and performance in patients with KOA, which may provide new ideas for the assessment, treatment and rehabilitation of the disease.

Females with knee osteoarthritis use a detrimental knee loading strategy when squatting

BACKGROUND

The purpose of this study was to identify sex differences in lower limb kinematics, kinetics, and muscle activation patterns between individuals with osteoarthritis and healthy controls during a two-legged squat.

METHOD

Thirty OA (15 females) and 30 healthy (15 females) participants performed three 2-legged squats. Sagittal and frontal plane hip, knee, and ankle kinematics and kinetics were calculated. Two-way ANOVAs (Sex X OA Status) were used to characterize differences in squatting strategies between sexes and between those with and without knee OA.

RESULTS

A greater decrease in sagittal hip, knee, and ankle range of motion and knee joint power was observed in the OA participants compared to the healthy controls. Females with OA had significantly reduced hip and knee adduction angles compared to the healthy females and males with OA. Females also had decreased hip power, hip flexion, and hip adduction moments and knee adduction moments compared to their male counterparts, with the greatest deficits observed in the females with OA. Females with OA also had the highest magnitude of muscle activation for the quadriceps, hamstrings, and gastrocnemius throughout the squat, while males with OA showed increased activation of the vastus lateralis and medial gastrocnemius compared to the healthy males.

CONCLUSIONS

OA significantly altered biomechanics and neuromuscular control during the squat, with males employing a hip-dominant strategy, allowing them to achieve a greater lower limb range of motion.

Effects of Squatting Speed and Depth on Lower Extremity Kinematics, Kinetics and Energetics

Squatting has received considerable attention in sports and is commonly utilized in daily activities. Knowledge of the squatting biomechanics in terms of its speed and depth may enhance exercise selection when targeting for sport-specific performance improvement and injury avoidance. Nonetheless, these perspectives have not been consistently reported. Hence, this preliminary study intends to quantify the kinematics, kinetics, and energetics in squat with different depths and speeds among healthy young adults with different physical activity levels; i.e., between active and sedentary groups. Twenty participants were administered to squat at varying depths (deep, normal, and half) and speeds (fast, normal, and slow). Motion-capture system and force plates were employed to acquire motion trajectories and ground reaction force. Joint moment was obtained via inverse dynamics, while power was derived as a product of moment and angular velocity. Higher speeds and deeper squats greatly influence higher joint moments and powers at the hip ([Formula: see text]) and knee ([Formula: see text]) than ankle, signifying these joints as the prime movers with knee as the predominant contributor. These preliminary findings show that the knee-strategy and hip-strategy were employed in compensating speed and depth manipulations during squatting. In certain contexts, appreciating these findings may provide clinically relevant implications, from the performance and injury avoidance viewpoint, which will ameliorate the physical activity level of practitioners.

Hyperalgesia affects muscle activity and knee range of motion during a single-limb mini squat in individuals with knee osteoarthritis: a cross-sectional study

BACKGROUND

The effect of hyperalgesia on functionality remains uncertain for individuals with knee osteoarthritis (KOA). This study aimed examine the clinical measures and hyperalgesia's effect on muscle activity, knee range of motion (ROM) and postural control during the single-leg mini squat (SLMS) in individuals with KOA, determining the correlation between variables.

METHODS

In this cross-sectional study, 60 individuals, 30 healthy (HG, 57.4 ± 6.86 years), and 30 with mild to moderate KOA (KOAG, 59.4 ± 5.46 years) were evaluated by the visual analog scale (VAS), Western Ontario and McMaster Universities Index (WOMAC), and the pressure pain threshold (PPT) in subcutaneous, myotomal, and sclerotomal structures. Muscle activity, knee ROM and postural control were assessed during a SLMS. The analyses were performed in the two phases of the SLMS. Phase 1 - during descending movement (eccentric contraction), Phase 2 - during ascending movement (concentric contraction). Analysis of covariance was applied for each variable separately, using weight as a co-variable. We used Spearman's test for determining the correlation.

RESULTS

There was no difference between groups for age, height, and postural control (p > 0.059), but KOAG presented the highest values for VAS and WOMAC (p = 0.000). In addition, EMG activity was higher in KOAG for gastrocnemius medialis and tibialis anterior muscles during phase 1 (p < 0.027), and for gastrocnemius medialis and gluteus medius muscles during phase 2 (p < 0.007), and reduced values for PPT and knee ROM (p = 0.000). Also, the correlations between PPT with muscle activity and postural control were moderate (rho< 0.482), while strong relationships were observed between some PPT points with VAS and WOMAC (rho> 0.507).

CONCLUSION

Hyperalgesia affects the functionality during a single-limb mini squat. There is an important correlation between hyperalgesia and muscle activity, postural control, and clinical measures in individuals with KOA.

The role of interaction torque and muscle torque in the control of downward squatting

[Purpose] The purposes of this study were first to analyze the multijoint dynamics of downward squatting, and to examine the contribution of interaction torque and muscle torque to net torque, and second, to examine mechanisms of movement control. [Subjects] The subjects were 31 healthy men with a mean age of 21.0 ± 1.2 years (range, 19-24 years). [Methods] Squatting tasks with the trunk in two positions, an erect and anterior tilt position, were performed by the subjects. Net, interaction, muscle, and gravity torque were calculated according to the Lagrange equation using 3D tracking data. [Results] The contribution ratio of interaction torque to net torque was approximately 90%, irrespective of the joint and task. In contrast, muscle torque showed complicated behavior to compensate for gravity torque. A combined muscle and gravity torque profile showed flexion or dorsiflexion immediately after the initiation of the movement, and it later changed to extension or plantar flexion. [Conclusion] The torque that contributes almost exclusively to the net torque was interaction torque. The combination of muscle and gravity torque at the knee joint and the hip joint is important for movement control, independent of the starting position.

Deep flexion activity training in a patient with stroke using task-oriented exercise: a case report

BACKGROUND AND PURPOSE

Many individuals with stroke express desires to resume activities involving deep knee flexion, such as daily living, work-related, and sports activities. However, training methods for improving deep flexion activities have not commonly been reported in the stroke rehabilitation literature. The purpose of this case report is to describe the development of a task-oriented training program and demonstrate its use in improving deep flexion activities in an individual with sub-acute hemiplegia.

CASE DESCRIPTION

The patient was a 55-year-old shoe salesman diagnosed with ischemic stroke 6 weeks before physical therapy evaluation. His primary concerns were functional activities that required deep flexion, such as the inability to squat and to maintain a squatting position in the Eastern toilet and difficulty in performing work-related activities (e.g. fitting shoes for customers while sitting on a low stool).

INTERVENTION

We developed a task-oriented training program that specifically targeted deep flexion activities. The first phase of training consisted primarily of practicing sit-to-stand on a low stool and the second phase consisted of practicing squatting.

OUTCOMES

After 6 weeks of intervention, the patient achieved more than the expected outcome on the Goal Attainment Scale (score = +2) for both primary goals and reported positive changes in social participation, such as visiting his friends and relatives and praying at the temple.

DISCUSSION

The task-oriented deep flexion activity intervention was associated with positive changes in functional activity and social participation in a patient recovering from stroke.

Control of fast squatting movements after stroke

OBJECTIVE

Little is known about how residual motor impairments after stroke affect the motor control of fast movements, particularly those that combine postural control and limb movement. The purpose of this study was to examine the influence of stroke on the motor control of fast squatting movements.

METHODS

Seventeen individuals with hemiparesis and seventeen age- and sex-matched controls performed fast squatting movements. Force platform data, knee acceleration, and electromyographic activity from rectus femoris, biceps femoris, tibialis anterior, soleus, were collected.

RESULTS

Subjects after stroke performed the squats asymmetrically, with reduced velocity and acceleration compared to controls. Subjects with low motor recovery depended on the non-paretic leg to compensate for poor paretic muscle activation whereas subjects with high motor recovery activated muscles in the paretic leg in an adaptive manner, making the movement more symmetrical. Difficulty with postural control was evident by reduced coupling of the timing of the knee movement with the center of pressure excursion.

CONCLUSIONS

Slow performance of squatting movements was accompanied by altered muscle activation, coupled with impaired postural control.

SIGNIFICANCE

Fast squatting movements in standing require appropriate muscle activation and postural control, the latter of which can be measured easily with force platform and accelerometer data.

Squat-to-reach task in older and young adults: kinematic and electromyographic analyses

The purpose of this study was to compare the two-dimensional kinematic and electromyographic (EMG) changes during the squat-to-reach task in older and young adults. Twenty-six older adults and thirty-three young adults were studied. A 16-channel telemetry system was used for recording muscular activity and kinematic data during two trials of a squat-to-reach task. Surface EMG data were recorded on select muscles of the trunk and the lower extremity on the dominant side. An electrogoniometer was fixed over the knee joint, and an inclinometer was fastened on the head and thigh to record kinematic data. The task was split into six movement phases based on the angular displacement and velocities of the knee joint. The mean values of the maximal displacements in the sagittal plane of the head, knee, and thigh were significantly (p<0.05) lower, but those in the frontal plane of the head and thigh were significantly (p<0.05) higher in older adults than in young adults. Thigh muscle activities were significantly (p<0.05) higher in older adults than in young adults throughout the movements. The trunk and leg muscles contracted earlier, but the hip adductors contracted later in older adults compared to young adults (p<0.05). The older adults squatted in a shallow and heel-off posture during forward reaching tasks. Therefore, older adults had increased lateral flexion of the head to compensate for insufficient knee flexion during the squat-to-reach movement and required increased activity of the posture muscles to maintain lateral stability.

Kinematic, kinetic and EMG patterns during downward squatting

The aim of this study was to investigate the kinematic, kinetic, and electromyographic pattern before, during and after downward squatting when the trunk movement is restricted in the sagittal plane. Eight healthy subjects performed downward squatting at two different positions, semisquatting (40 degrees knee flexion) and half squatting (70 degrees knee flexion). Electromyographic responses of the vastus medialis oblique, vastus medialis longus, rectus femoris, vastus lateralis, biceps femoris, semitendineous, gastrocnemius lateralis, and tibialis anterior were recorded. The kinematics of the major joints were reconstructed using an optoelectronic system. The center of pressure (COP) was obtained using data collected from one force plate, and the ankle and knee joint torques were calculated using inverse dynamics. In the upright position there were small changes in the COP and in the knee and ankle joint torques. The tibialis anterior provoked the disruption of this upright position initiating the squat. During the acceleration phase of the squat the COP moved posteriorly, the knee joint torque remained in flexion and there was no measurable muscle activation. As the body went into the deceleration phase, the knee joint torque increased towards extension with major muscle activities being observed in the four heads of the quadriceps. Understanding these kinematic, kinetic and EMG strategies before, during and after the squat is expected to be beneficial to practitioners for utilizing squatting as a task for improving motor function.