Step Descent Research Articles

Muscle activity during multi-step descent

BackgroundPrevious step studies have shown mechanical variances across steps in descent; however, muscle activity differences have not been examined across steps in a staircase. The purpose of this study was to quantify differences in muscle activity during step descent between step strategies (step-over-step and step-match) and across steps. MethodsTwenty-five individuals descended a seven-step staircase at self-selected pace (rise: 15.5 cm) in both descent types. Muscle activity was recorded with bipolar electrodes placed on the right tibialis anterior, peroneals, medial gastrocnemius, rectus femoris, and biceps femoris. Two-way Repeated Measures ANOVA tests were conducted for co-activation (ankle: tibialis anterior/medial gastrocnemius; knee: rectus femoris/biceps femoris) and integrated EMG in the lead and trail limbs. ResultsResults showed muscle activity is dependent on the step number for both descent strategies. ConclusionsBetween strategies, lead limb step-match co-activation began the staircase high then decreased for both ankle and knee, while step-over-step activity was the opposite. Trail limb co-activation was more similar beginning high for both joints in step-over-step and the knee in step-match. Across steps, this study supports previous findings of differences between entry and exit steps compared to middle stairs. Additionally, differences were found between mid-staircase steps. These differences in both descent strategies counters previous assumptions of ‘steady-state’ step descent, which may have implications for individuals dealing with lower extremity musculoskeletal issues. Patients may benefit by training on their most encountered staircase length, and researchers must recognize the challenge of generalizing across step studies of varying step number.

Design and analysis of extrusion die for T-shaped sheet materials

Abstract The study explores plastic deformation behavior of T-shaped plates using DEFORM™ 3D, a perfect plastic finite element analysis software that considers T-shaped and double T-shaped extrusion dies as rigid bodies and compares effective strain, effective stress, blank temperature, die wear and temperature conditions. Moreover, the study employed the machine learning step descent method to predict effective stress and effective strain. Furthermore, the Pearson product difference correlation was utilized to examine the relationship between effective stress, effective strain, and temperature in T-shaped extrusion. Lastly, META analysis was conducted to synthesize statistical data on effective stress and temperature from various research.

The influence of women’s age and fall history on foot and lower limb kinematics during transition step descent

Falls are a major public health concern, with older women being at the greatest risk to experience a fall. Step descent increases the likelihood of a fall injury, yet the influence of age and fall history on lower extremity kinematics have not been extensively studied. The purpose of this study was to examine lower extremity and foot kinematics of women with and without a fall history during single step descent. Hip, knee, and foot kinematics of young women (n = 15, age = 22.6 ± 3.2 years), older women with no recent falls (n = 15, age = 71.6 ± 4.4 years), and older women with a fall history (n = 15, age = 71.5 ± 5.0 years) as they descended a 17 cm step were examined. Differences in initial contact angles and ROM during landing were examined with between group MANOVA tests. Distal foot initial contact angles were not significant between groups. For range of motion, both older groups went through greater hip extension (p = 0.003, partial η2 = 0.25), but less hip adduction (p = 0.002, partial η2 = 0.27) and less lateral midfoot dorsiflexion (p = 0.001, partial η2 = 0.28) than the younger women. The older fall group had reduced knee flexion (p = 0.004, partial η2 = 0.23) than the younger group, and the older non-fallers slightly plantarflexed at the medial midfoot (p = 0.005, partial η2 = 0.23) while the young women dorsiflexed. Thelanding phase ROMdifferences exhibited by the older adult groupsmayincrease the likelihood of a misstep, which may result in a fall.

Surface electromyography and kinetics during step descent in individuals with low-level chronic or recurrent low back pain and lumbar instability

Background: Most biomechanical studies in populations with low back pain have examined level gait or stationary tasks. This study investigates step negotiation in a subgroup of individuals with low back pain. Methods: Surface electromyography and kinetic data were collected in 22 subjects. Results: Vertical ground reaction force rise-time was slower in participants with low back pain when leading with the left leg and they had delayed muscle onsets of the right gluteus medius, left rectus abdominis with left stepping, right lumbar erector spinae with right stepping but earlier onset with left stepping. EMG activations were higher in the participants with low back pain in the right lumbar erector spinae, right gluteus medius, and left gluteus medius in both left and right steps. Conclusion: The results of this study show that the participants with low back pain have higher muscle activity levels, delayed muscle onsets, and slower weight acceptance.

The Effect of Age and Fall History on Lower Extremity Neuromuscular Function During Descent of a Single Transition Step.

Despite the higher injury rate of falls on steps versus level ground, few studies have examined the influence of age and fall history on step descent. The purpose of this study was to determine the lead and trail limb neuromuscular function (peak joint moments and powers, electromyographic activity) differences between young females (n = 15) and older females with (n = 15) and without (n = 15) a fall history while descending a single step. Trail limb moments and powers did not differ between groups. Lead limb sagittal plane powers at the hip and knee were greater in the young adults. Electromyographic co-activation levels (knee and ankle) were not significantly different between groups. However, peroneal activation was greater in the older groups, which may have assisted in stabilizing the ankle joint in lieu of increased co-activation at the ankle. These results demonstrate consideration of step descent is important in working with older women at risk of falls.

Comparison and Improvement of 3D-Multilateration for Solving Simultaneous Localization of Drones and UWB Anchors

Drone fleets have attracted a lot of attention from the research community in recent years. One of the biggest challenges in deploying such systems is localization. While GNSS localization systems can only be effective in open outdoor environments, new solutions based on radio sensors (e.g., ultra-wideband) are increasingly being used for localization in various situations and environments. However, self-localization without prior knowledge of anchor positions remains an open problem, which, for example, makes it impossible to track a moving target. In this article, we provide a comparison of different variants of gradient descent-based algorithms, with a new improved variant, for solving the localization problem using relative distance measurements and multilateration. Extensive simulation results are provided, varying the number of neighboring nodes for multilateration, algorithm initialization, and cost functions, in addition to accounting for node positioning errors and ultra-wideband sensor noise. They help set the adequate rate for fixed step descent when used and produce a damping effect in the variable step rate, which will otherwise diverge. In particular, we consider three scenarios: (i) self-localization of anchors; (ii) tracking moving targets using ultra-wideband range sensors; and (iii) simultaneously estimating unknown positions of ultra-wideband anchors and mobile agents (drones). The latter shows a great improvement in localization accuracy.

WAVE communication based on improved NLMS adaptive filtering delay compensation method*

In order to improve the signal quality of the Wireless Access Vehicle Environment (WAVE), in this paper, the dynamic step factor is introduced into the Normalized Least Mean Square (NLMS) algorithm based on multi-step step descent, so that the algorithm has a wide dynamic adaptive range. And an improved NLMS adaptive filtering method is proposed to reduce the noise of the communication signal of the WAVE system. At the same time, by introducing the unit delay operator z −Δ of the adaptive FIR filter and the transmission delay t p of the WAVE system, a delay compensation function is constructed to solve the delay problem in the signal transmission and processing process of the WAVE system and meet the real-time requirement of the system. In this paper, the above method is simulated and tested under typical working conditions of the Cooperative Adaptive Cruise Control (CACC) system. Experimental results show that the NLMS adaptive filtering method can effectively reduce the error between the acquired signal and the expected signal and make the signal waveform smoother by introducing the dynamic step factor. By introducing the filtering delay compensation function into the signal filtering results, it can effectively reduce the adverse effects of the delay problem caused by signal transmission and signal processing on the desired target signal.

An Adaptive Model Predictive Control System for Virtual Coupling in Metros

Virtual coupling (VC) is an emerging concept and hot research topic in railways, especially for metro systems. Several unit trains in VC drive with a desired minimum distance, and they, as a whole, are regarded as a single train. In this work, a distributed adaptive model predictive control (AMPC) system is proposed to coordinate the driving of each unit train in VC. To obtain the accurate parameters of train dynamics model in a time varying environment, an estimator of the train dynamics model is designed for each AMPC controller. A variable step descent algorithm along the negative gradient direction is adopted for each estimator, which steers the estimated values of the parameters to real ones. Simulations are conducted and the results are compared with both nominal model predictive control system and AMPC system with fixed steps in the literature. Our proposed AMPC system with variable step (AMPCVS) has better performances than other two systems. Results indicate that there is an improvement of the proposed AMPC system with variable steps system when compared with other two existed systems. A running process of VC in a whole inter-station is also simulated here. Experimental results show that the trains track the desired objective well.

Lead limb loading during a single-step descent in persons with and without a transtibial amputation in the trailing limb

BackgroundDecreased mechanical work done by the trailing limb when descending a single-step could affect load development and increase injury risk on the leading limb. This study assessed the effect of trailing limb mechanics on the development of lead limb load during a step descent by examining individuals with unilateral transtibial amputations who are known to exhibit reduced work in the prosthetic limb. MethodsEight amputees and 10 able-bodied controls walked 5 m along the length of a raised platform, descended a single-step of 14 cm height, and continued walking. The intact limb of amputees led during descent. Kinematic and kinetic data were recorded using integrated motion capture and force platform system. Lead limb loading was assessed through vertical ground reaction force, and knee moments and joint reaction forces. Sagittal-plane joint work was calculated for the ankle, knee, and hip in both limbs. FindingsNo differences were found in lead limb loading despite differences in trail limb mechanics evidenced by amputees performing 58% less total work by the trailing (prosthetic) limb to lower the centre of mass (P = 0.004) and 111% less for propulsion (P < 0.001). Amputees descended the step significantly slower (P = 0.003) and performed significantly greater lead limb ankle work (P = 0.017). After accounting for speed differences, initial loading at the knee was significantly higher in the lead limb of amputees versus controls. InterpretationIncreasing lead limb work and reducing forward velocity may be effective compensatory strategies to limit lead limb loading during a step descent, in response to reduced trailing limb work.

Knee biomechanics while navigating steps in participants with anterior cruciate ligament reconstruction, between 2 and 10 years following surgery

ObjectiveTo compare knee angles and moments between the injured and contralateral knee in participants with anterior cruciate ligament reconstruction, and compared with uninjured controls while navigating steps. DesignCross-sectional study. SettingUniversity laboratory-based study. ParticipantsTwenty-five participants (30.8 ± 9.7 years; 13 women) with anterior cruciate ligament reconstruction (2–10 years post-surgery), and 24 controls (31.0 ± 10 years, 13 women). Main outcome measuresThree-dimensional motion analysis was used to record peak knee angles and external moments during step ascent and descent in three planes, along with spatiotemporal variables. ResultsDuring step ascent, the reconstructed knee exhibited significantly: (1) lower peak flexion angles compared to the controls (P = 0.005); (2) lower flexion moments (P < 0.001) compared to contralateral side and controls. No significant differences were found in the frontal and transverse planes between groups and sides. During step descent, no significant differences in angles and moments were found. ConclusionsSide-to-side asymmetries and lower knee flexion angles and external knee flexion moments were evident in participants with anterior cruciate ligament reconstruction and compared to controls. These findings suggest that incomplete recovery and compensatory or protective changes in neuromuscular control and joint function may persist 2–10 years post-surgery.

Step descent strategy is altered bilaterally despite unilateral muscle strength impairment after total knee arthroplasty.

Muscle weakness and difficulty descending stairs are common after unilateral total knee arthroplasty (TKA), but the relationship between each is unclear. The purpose of this study was to compare lower extremity muscle strength, lower extremity support moments during step descent, and assess relationships between each. The study included 40 subjects (20 post-TKA, 20 control). Knee extensor, hip abductor, and hip external rotator strength were measured and biomechanical analyses of step descent performed. Patients with TKA were assessed 3 and 6months post-surgery. At 3 and 6months post-TKA, operated limb hip external rotator and knee extensor strength were impaired compared to the non-operated limb (p < 0.01); however, no between-limb differences were observed during step descent. Compared to the control group, hip external rotator and knee extensor strength, total lower extremity support moment, and knee support moment during step descent were impaired post-TKA (p < 0.05). At 6months post-TKA, knee extensor and hip external rotator strength correlated with total support moment during step descent (rs = 0.40, 0.41, p < 0.02). Hip abductor and external rotator strength negatively correlated with knee support moment during step descent (rs = - 0.35, - 0.39, p < 0.03). Persistent operative limb knee extensor and hip external rotator muscle weakness are noted following unilateral TKA. Despite unilateral weakness, bilateral alterations in step descent strategy occur following TKA. Patients with TKA utilize hip musculature to reduce knee muscle demand during step descent, possibly contributing to limitations in long-term step descent performance.

Reliability of skin-markers based measures of medial longitudinal arch angle

Medial wedged foot orthoses are frequently prescribed to reduce retropatellar stress in patients with patellofemoral pain (PFP) by controlling calcaneal eversion and internal rotation of the tibia. During activities of daily living, the highest patella loads occur during stair descent, but the effect of foot orthoses during stair descent remains unclear.The purpose of this study was to compare the kinematics, kinetics and muscle activation during a step descent task in healthy volunteers using three designs of foot orthoses (insoles).Sixteen healthy subjects with a mean age of 25.7 years, BMI of 23.3, and +5 Foot Posture Index were recruited. Subjects performed a step down task from 20 cm using a 5o rearfoot medial wedge (R), a 5o rearfoot and forefoot medial wedge (R/F), and a control flat insole (C).Significant improvements in control were seen in the R and R/F insoles over the C insole in the foot and at the ankle and hip kinematics. The R and R/F insoles increased the knee adduction moments, but reduced knee internal rotation moment compared to the C insole. Abductor hallucis (AH) activity was reduced with both insoles, whereas tibialis anterior (TA) activity was reduced with the R insole only.Foot orthoses can change joint mechanics in the foot and lower limbs providing greater stability and less work done by AH and TA muscles. This data supports the use of foot orthoses to provide functional benefits during step descent, which may benefit patients with PFP.

Influence and benefits of foot orthoses on kinematics, kinetics and muscle activation during step descent task

BackgroundMedial wedged foot orthoses are frequently prescribed to reduce retropatellar stress in patients with patellofemoral pain (PFP) by controlling calcaneal eversion and internal rotation of the tibia. During activities of daily living, the highest patella loads occur during stair descent, but the effect of foot orthoses during stair descent remains unclear. Research questionThe purpose of this study was to compare the kinematics, kinetics and muscle activation during a step descent task in healthy volunteers using three designs of foot orthoses (insoles). MethodsSixteen healthy subjects with a mean age of 25.7 years, BMI of 23.3, and +5 Foot Posture Index were recruited. Subjects performed a step down task from 20 cm using a 5o rearfoot medial wedge (R), a 5o rearfoot and forefoot medial wedge (R/F), and a control flat insole (C). ResultsSignificant improvements in control were seen in the R and R/F insoles over the C insole in the foot and at the ankle and hip kinematics. The R and R/F insoles increased the knee adduction moments, but reduced knee internal rotation moment compared to the C insole. Abductor hallucis (AH) activity was reduced with both insoles, whereas tibialis anterior (TA) activity was reduced with the R insole only. SignificanceFoot orthoses can change joint mechanics in the foot and lower limbs providing greater stability and less work done by AH and TA muscles. This data supports the use of foot orthoses to provide functional benefits during step descent, which may benefit patients with PFP.

Lower extremity muscle activity during descent from varying step heights

During step descent, lower extremity musculature is critical for positioning the foot and ankle for initial contact and stabilizing the structures following contact. Although continuous stair descent has been extensively examined, curb/single transition steps where many injuries occur requires further study. The purpose of this study was to identify the influence of landing strategy and step height on lower extremity muscle activity of uninjured individuals during transition step descent. Twenty-two participants walked along a level walkway, stepped down a single step (heights: 5-cm, 15-cm, 25-cm) landed with the heel or forefoot, and continued walking. Muscle activity of the leading leg’s peroneals, tibialis anterior, and medial gastrocnemius were recorded 200 ms before and after initial contact. Two-way Repeated Measures ANOVAs within the three step heights and two landing strategies were run for both the pre- and post-contact periods. Step height by landing strategy interactions existed during the pre-contact periods for all three muscles. During the post-contact period, all muscle activity increased with each step height increment. Additionally, the medial gastrocnemius and tibialis anterior demonstrated significant landing strategy differences. This study highlights the importance of considering both landing strategy and step height when designing or interpreting investigations of transition step negotiation.

The effects of three quarter and full length foot orthoses on knee mechanics in healthy subjects and patellofemoral pain patients when walking and descending stairs

BackgroundAn increased load of the patellofemoral joint is often attributed to foot function in patients with patellofemoral pain. Foot orthoses are commonly prescribed for this condition; however the mechanisms by which they work are poorly understood. The aim of this study was to investigate the kinematics and kinetics of the knee between patellofemoral pain patients and a group of healthy subjects when using a standardised foot orthosis prescription during walking and step descent. MethodFifteen healthy subjects and fifteen patients diagnosed with PFP with a foot posture index greater than 6, had foot orthoses moulded to their feet. They were asked to walk at a self-selected pace and complete a 20 cm step descent using customised orthoses with ¾ and full length wedges. Kinematic and Kinetic data were collected and modelled using Calibrated Anatomical System Technique. ResultsSignificant differences were seen in both the kinematics and kinetics between the healthy group and the PFP patients at the knee. A significant reduction in the knee coronal plane moment was found during the forward continuum phase of step descent when wearing the foot orthoses; this was attributed to a change in the ground reaction force as there were no changes reported in the kinematics of the knee with the orthoses. ConclusionsThis study identified potentially clinically important differences in the knee mechanics between the PFP patients and the healthy group during walking and step descent. The foot orthoses reduced the coronal plane knee moment in the PFP patients to a value similar to that of the healthy subjects with no intervention.

Trunk movement compensations and corresponding core muscle demand during step ambulation in people with unilateral transtibial amputation

The objective of this investigation was to identify demands from core muscles that corresponded with trunk movement compensations during bilateral step ambulation in people with unilateral transtibial amputation (TTA). Trunk rotational angular momentum (RAM) was measured using motion capture and bilateral surface EMG was measured from four bilateral core muscles during step ascent and descent tasks in people with TTA and healthy controls. During step ascent, the TTA group generated larger mediolateral (P = 0.01) and axial (P = 0.01) trunk RAM toward the leading limb when stepping onto the intact limb than the control group, which corresponded with high demand from the bilateral erector spinae and oblique muscles. During step descent, the TTA group generated larger trunk RAM in the sagittal (P < 0.01), frontal (P < 0.01), and transverse planes (P = 0.01) than the control group, which was an effect of falling onto the intact limb. To maintain balance and arrest trunk RAM, core muscle demand was larger throughout the loading period of step descent in the TTA group. However, asymmetric trunk movement compensations did not correspond to asymmetric core muscle demand during either task, indicating a difference in motor control compensations dependent on the leading limb.

Assessment of Knee Kinematics in Older Adults Using High-Speed Stereo Radiography.

Quantification of knee motion is essential for assessment of pathologic joint function, such as tracking osteoarthritis progression and evaluating outcomes after conservative or surgical treatment, including total knee arthroplasty. Our purpose was to establish a useful baseline for the kinematic envelope of knee motion in healthy older adults performing movements of daily living. A high-speed stereo radiography system was used to measure the three-dimensional tibiofemoral kinematics of eight healthy people over 55 yr of age (4 women/4 men; age, 61.7 ± 5.4 yr; body mass, 74.6 ± 7.7 kg; body mass index, 26.7 ± 4.4 kg·m; height, 168.2 ± 13.7 cm) during seated knee extension, level walking, pivoting, and step descent. Internal-external and varus-valgus rotation and anterior-posterior range of motion through stance in normal walking averaged 3.6° ± 1.1°, 2.3° ± 0.6°, and 3.4 ± 1.57 mm, respectively. Average range of motion across subjects was greater during the step-down in both internal-external rotation (average, 6.5° ± 3.1°) and anterior-posterior translation (average, 4.5 ± 1.1). Average internal-external range of motion increased to 13.5° ± 3.6° during pivoting. Range of motion of the knee in varus-valgus rotation was nearly the same for each subject across activities, rarely exceeding 6°. Pivoting and step descending during walking had greater internal-external rotation and anterior-posterior translation than normal gait. Internal-external rotation and anterior-posterior translation were shown to have greater activity dependence, whereas varus-valgus rotation was consistent across activities. These results were similar to prior measurements in younger cohorts, though a trend toward reduced range of motion in the older adults was observed.

Biomechanical compensations of the trunk and lower extremities during stepping tasks after unilateral transtibial amputation

BackgroundLower extremity movement compensations following transtibial amputation are well-documented and are likely influenced by trunk posture and movement. However, the biomechanical compensations of the trunk and lower extremities, especially during high-demand tasks such as step ascent and descent, remain unclear. MethodsKinematic and kinetic data were collected during step ascent and descent tasks for three groups of individuals: diabetic/transtibial amputation, diabetic, and healthy. An ANCOVA was used to compare peak trunk, hip and knee joint angles and moments in the sagittal and frontal planes between groups. Paired t-tests were used to compare peak joint angles and moments between amputated and intact limbs of the diabetic/transtibial amputation group. FindingsDuring step ascent and descent, the transtibial amputation group exhibited greater trunk forward flexion and lateral flexion compared to the other two groups (P<0.016), which resulted in greater low back moments and asymmetric loading patterns in the lower extremity joints. The diabetic group exhibited similar knee joint loading patterns compared to the amputation group (P<0.016), during step descent. InterpretationThis study highlights the biomechanical compensations of the trunk and lower extremities in individuals with dysvascular transtibial amputation, by identifying low back, hip, and knee joint moment patterns unique to transtibial amputation during stepping tasks. In addition, the results suggest that some movement compensations may be confounded by the presence of diabetes and precede limb amputation. The increased and asymmetrical loading patterns identified may predispose individuals with transtibial amputation to the development of secondary pain conditions, such as low back pain or osteoarthritis.

Trunk kinetic effort during step ascent and descent in patients with transtibial amputation using angular momentum separation

BackgroundPatients with transtibial amputation adopt trunk movement compensations that alter effort and increase the risk of developing low back pain. However, the effort required to achieve high-demand tasks, such as step ascent and descent, remains unknown. MethodsKinematics were collected during bilateral step ascent and descent tasks from two groups: 1) seven patients with unilateral transtibial amputation and 2) seven healthy control subjects. Trunk kinetic effort was quantified using translational and rotational segmental moments (time rate of change of segmental angular momentum). Peak moments during the loading period were compared across limbs and across groups. FindingsDuring step ascent, patients with transtibial amputation generated larger sagittal trunk translational moments when leading with the amputated limb compared to the intact limb (P=0.01). The amputation group also generated larger trunk rotational moments in the frontal and transverse planes when leading with either limb compared to the healthy group (P=0.01, P<0.01, respectively). During step descent, the amputation group generated larger trunk translational and rotational moments in all three planes when leading with the intact limb compared to the healthy group (P<0.017). InterpretationThis investigation identifies how differing trunk movement compensations, identified using the separation of angular momentum, require higher kinetic effort during stepping tasks in patients with transtibial amputation compared to healthy individuals. Compensations that produce identified increased and asymmetric trunk segmental moments, may increase the risk of the development of low back pain in patients with amputation.

Timed mobility: description of measurement, performance, and dimensionality among older adults

Purpose: To describe the measurement, performance, and dimensionality of five timed mobility activities completed by older adults.Materials and methods: Cross-sectional observational study using correlational and factor analysis to examine the dimensionality of five timed mobility activities performed by 189 older adults in an outpatient setting.Results: The times to complete supine-to-sit, five repetition sit-to-stand, 8 m comfortable gait, four step ascent, and four step descent were correlated significantly with one another (r = 0.294–0.827, p < 0.001). The times were also internally consistent (α = 0.71) and loaded highly on a single factor (0.587–0.888).Conclusion: The timed measurements of this study were easily obtained. They can be viewed as unidimensional and representative of a single construct of the international classification of functioning, disability, and health -timed mobility.Implications for rehabilitationFor patients who are independent in mobility, timing offers a means of differentiating the performance of individual patients.As the times to complete five mobility activities are interrelated, mobility is supported as a rehabilitation construct and patients who are faster at one activity should be expected to be faster at another.