APML Research Articles

Effects of Functional Fatigue Protocol and Visual Information on Postural Control in Patients with Chronic Ankle Instability

Chronic ankle instability (CAI) patients often exhibit postural control deficits and rely on visual information to maintain static balance to compensate for decreased proprioception. Fatigue impairs neuromuscular control, in addition to postural control, in CAI patients. However, whether functional fatiguing exercises alter postural control and sensory organization strategies during single-leg balance tests in CAI patients remains unclear. This study involved a controlled trial on 28 CAI patients in a laboratory setting. Each participant performed a single-leg balance test with eyes open (EO) and eyes closed (EC) before and after a functional fatigue protocol. Two-way repeated-measures ANOVA evaluated fatigue (pre- vs. post-fatigue) × vision (EO vs. EC) interactions for outcome variables. Additionally, paired-sample t-tests examined differences between two conditions (pre- vs. post-fatigue) for time-to-boundary (TTB) minima (%modulation). We found significant interactions between fatigue and vision conditions in ML and AP TTBmeans and AP TTBsds. %Modulations were significantly decreased after fatigue in AP TTBmean, ML TTBsd, and AP TTBsd. In conclusion, static postural control ability decreased after the functional fatigue protocol with EO, but was unchanged with EC. This suggests that decreased balance ability is more pronounced with EO under fatigue due to less visual dependence. This may increase ankle sprain incidence under fatigue.

Finite Element Analysis and Mechanical Assessment for the Constraint of Total Knee Replacement

The constraint level of TKR is essential for ensuring product performance to prevent knee joint dislocation. Computer modeling and simulation (CM&S) technology is widely used in the medical device industry due to its advantages such as reducing testing time and costs. However, there is a lack of research on the constraint level of TKR according to the size and flexion angle of the femoral component. In this study, the constraint levels of AP draw, ML shear, and rotary laxity were tested according to the size and flexion angle of TKR products using finite element analysis. A TKR model was constructed using a 3D scanner, and a finite element model with mechanical testing and error rates of 2.49% and 3.00% was developed through AP draw testing. In AP draw, as the size of TKR decreases, the constraint level increases by about 3.6%, and rotary laxity also increases by about 1.3%. In all tests, the constraint level increased as the bending angle of the femoral component increased. We found that the curvature and contact area of a TKR influenced the constraint level. Through this study, it is believed that CM&S technolaogy can be widely used in evaluating the unique performance of medical devices.

Effects of Posture and Locomotion Methods on Postural Stability, Cybersickness, and Presence in a Virtual Environment

Virtual reality (VR) users experience unwanted symptoms, such as body imbalance, nausea, dizziness, and loss of presence. This study aims to investigate the effects of posture and locomotion on postural stability, cybersickness, and presence in VR environments. Twenty participants played a VR game under different conditions depending on posture (standing and sitting) and locomotion methods (joystick and teleportation), and seven dependent variables (COM, AP displacement, ML displacement, ASL, PSQ, VRSQ, and SOP) were analyzed to observe postural stability, cybersickness, and presence. The results revealed that postural instability increased when the task was performed in the standing posture with the joystick locomotion method compared to other conditions. The AP displacement, ML displacement, and ASL were lower under teleportation conditions. The PSQ scores indicated that postural stability was better in the sitting posture than in the standing posture. The VRSQ score revealed that the sitting with teleportation condition had less cybersickness than the other conditions. The SOP score was the highest in the standing posture with the teleportation condition. This study concludes that a sitting posture with teleportation locomotion can be considered when designing games in which users actively interact with virtual movements.

Does Nordic Walking technique influence the ground reaction forces?

BackgroundNordic Walking (NW) practice has increased during the last decade, generating great benefits related to the reduction of ground reaction forces (GRF). However, there is still limited evidence regarding how the NW technique could affect GRF. Research questionTo analyze the effect of the speed and the differences in ground reaction forces (GRF) between NW with Diagonal technique (DT) versus Alpha technique (AT) and compare them with normal walking (W) Methods29 male physically active sport science students were randomly assigned to one of the training groups: AT (n = 15) or DT (n = 14). After 5 technique familiarization sessions, participants performed 5 experimental trials on a walkway for both NW and W at two different walking speeds, previously randomized. A two-way repeated measures ANOVA analysis was carried out to find differences between speeds (preferred, fast) and gait (NW, W) as within-subject factors and NW techniques (DT vs AT) as between-subject factor. ResultsDuring NW, both technique groups (AT, DT) showed an increase in GRF variables compared to W, such as in stance time (2.9 % mean increment, p < 0.01, ES = 0.3; 95 %IC[−0.027, −0.008]), vertical force impact or vertical heel strike variables (4.9 % mean increment, p < 0.01, ES = 0.4; 95 %IC[0.101, 0.036]; 7.3 % mean increment, p < 0.01, ES = 0.8; 95 %IC[−0.133, −0.081] respectively). Moreover, AT group experienced significant lower forces at vertical force at midstance (10.1 % mean descent, p = 0.036, ES = 0.3; 95 %IC[−0.083, −0.009]) and higher forces at AP propulsive forces (23.7 % mean increment, p < 0.001, ES = 0.6; 95 %IC[0.078, 0.202) and ML max force (14.0 % mean increment, p = 0.045, ES = 0.3; 95 %IC[0.002, 0.026]) compared to DT group. Walking speed was significantly higher during NW (Preferred: 1.89 ± 0.18 m/s; Fast: 2.17 ± 0.21 m/s) compared to W (Preferred: 1.76 ± 0.15 m/s; Fast: 2.04 ± 0.19 m/s) in both speed conditions. SignificanceNW favours an increase in GRF and speed in comparison with Walking, independently of the technique, with no evidence that justifies the use of one technique or another.

Walking With Horizontal Head Turns Is Impaired in Persons With Early-Stage Multiple Sclerosis Showing Normal Locomotion.

BackgroundTurning the head while walking (an action often required during daily living) is particularly challenging to maintain balance. It can therefore potentially reveal subtle impairments in early-stage people with multiple sclerosis who still show normal locomotion (NW-PwMS). This would help in identifying those subjects who can benefit from early preventive exercise aimed at slowing the MS-related functional decline.ObjectivesTo analyze if the assessment of walking with horizontal head turns (WHHT) through inertial sensors can discriminate between healthy subjects (HS) and NW-PwMS and between NW-PwMS subgroups. To assess if the discriminant ability of the instrumented WHHT is higher compared to clinical scores. To assess the concurrent validity of the sensor-based metrics.MethodsIn this multicenter study, 40 HS and 59 NW-PwMS [Expanded Disability Status Scale (EDSS) ≤ 2.5, disease duration ≤ 5 years] were tested. Participants executed Item-6 of the Fullerton Advanced Balance scale-short (FAB-s) wearing three inertial sensors on the trunk and ankles. The item required to horizontally turn the head at a beat of the metronome (100 bpm) while walking. Signals of the sensors were processed to compute spatiotemporal, regularity, symmetry, dynamic stability, and trunk sway metrics descriptive of WHHT.ResultsMediolateral regularity, anteroposterior symmetry, and mediolateral stability were reduced in NW-PwMS vs. HS (p ≤ 0.001), and showed moderate discriminant ability (area under the receiver operator characteristic curve [AUC]: 0.71–0.73). AP symmetry and ML stability were reduced (p ≤ 0.026) in EDSS: 2–2.5 vs. EDSS: 0–1.5 subgroup (AUC: 0.69–0.70). The number of NW-PwMS showing at least one abnormal instrumented metric (68%) was larger (p ≤ 0.002) than the number of participants showing abnormal FAB-s-Item6 (32%) and FAB-s clinical scores (39%). EDSS: 2–2.5 subgroup included more individuals showing abnormal instrumented metrics (86%) compared to EDSS: 0–1.5 subgroup (57%). The instrumented metrics significantly correlated with FAB-s-Item6 and FAB-s scores (|Spearman's rs| ≥ 0.37, p < 0.001), thus demonstrating their concurrent validity.ConclusionThe instrumented assessment of WHHT provided valid objective metrics that discriminated, with higher sensitivity than clinical scores, between HS and NW-PwMS and between EDSS subgroups. The method is a promising tool to complement clinical evaluation, and reveal subclinical impairments in persons who can benefit from early preventive rehabilitative interventions.

Dynamic stability during gait in idiopathic normal pressure hydrocephalus and Parkinson's disease.

To clarify a characteristic of dynamic stability during gait in idiopathic normal pressure hydrocephalus (iNPH) and Parkinson's disease (PD), and to explore the association between dynamic stability and disease severity in each disease. The 5-m gait of 36 iNPH (precerebrospinal fluid drainage), 20 PD (medicated state), and 25 healthy controls (HC) were evaluated using three-dimensional motion analysis. Ambulatory dynamic stability was defined as the ability to maintain the extrapolated center of mass within the base of support at heel contact, with the distance between the two referred to as the margin of stability (MOS). Anteroposterior direction (AP) MOS was significantly larger in the iNPH and PD groups than in the HC group; no significant difference was found between the iNPH and PD groups. Mediolateral direction (ML) MOS was significantly larger in the iNPH and PD groups than in the HC group and significantly larger in the iNPH group than in the PD group. In the iNPH group, the disease severity was positively correlated with only ML MOS. In the PD group, the disease severity was positively correlated with the AP MOS and ML MOS. Dynamic stability in iNPH increases in AP and ML, and it may be associated with not only iNPH-associated gait disturbance but also with a voluntarily cautious gait strategy. Dynamic stability in PD only increased in AP, and this may be associated with PD symptoms. These findings will help physicians understand the difference in pathological gait including dynamic stability between patients with iNPH and PD.

Effect of varying Number of Spacing between Antenna Elements, Snapshots, SNR on AP ML, AP-SSF and ESPRIT Algorithm

The direction of arrival estimation is the main key problem in array signal processing. In this paper, the alternating projection maximum Likelihood (AP-ML), Alternating projection sub space framework (APSSF) and ESPRIT algorithm are studied. The simulation is performed in MATLAB for single and multiple sources. The effect of the varying number of spacing between antenna elements, number of snapshots and SNR are studied. The performance comparison shows that ESPRIT algorithm performs better as compared to the AP-ML and AP-SSF. Key-Words: - AP-ML, AP-SSF, Direction of Arrival, ESPRIT, Snapshots, SNR

The effects of exergaming on pain, postural control, technology acceptance and flow experience in older people with chronic musculoskeletal pain: a randomised controlled trial

BackgroundOlder people with chronic musculoskeletal pain are at risk of falls. This study aimed to investigate the effects of exergaming on pain and postural control in older people with chronic musculoskeletal pain. Secondary outcomes were technology acceptance, flow experience, perceived physical exertion, expended mental effort and heart rate.MethodsFifty four older adults (age: 71 ± 5 years) with chronic musculoskeletal pain were randomised into 2 groups. Group 1 received exergaming training using the Interactive Rehabilitation and Exercise System (IREX®). Group 2 undertook traditional gym-based exercise (TGB). Both groups completed twice weekly 40-min exercise sessions for 6 weeks. Perceived pain was measured using a numeric pain rating scale and the Multidimensional Affect and Pain Survey questionnaire. Postural control was measured as sway using a Kistler™ force platform. Technology acceptance was measured with the Unified Theory of Acceptance and Use of Technology questionnaire and flow experience with the Flow State Scale. Physiological measures of perceived physical exertion, expended mental effort and heart rate were recorded during all sessions.ResultsThe exergaming group demonstrated significant reductions in pain intensity and thermal pain including a near significant approach in physical engagement in comparison to TGB group. Although no intervention effects on postural control were found, the exergaming group showed significant improvements in three sway measures (AP SD, ML SD and AP range) over time whereas significant improvements in ML range were found in the TGB group. Relating to technology acceptance, significant intervention effects on social influence and behavioural intention were found in the TGB group instead, although both groups demonstrated increases of acceptance over time. Regarding flow experience, concentration at task was significantly influenced in the TGB group and significant increases in flow variables over time were observed in both groups. Significant increases over time in perceived physical exertion and expended mental effort were found in both groups.ConclusionOur findings support the potential of exergaming to alleviate pain and improve balance in older people with chronic musculoskeletal pain. Both forms of exercise are acceptable, intrinsically motivating and show evidence of benefit to older people with chronic musculoskeletal pain.Trial registrationClinicalTrials.gov Identifier: NCT04029285 (retrospectively registered, July 23, 2019)

Flowcytometric Evaluation and Morphological and Cytochemical correlation of 150 cases of Acute Leukemia

Background : Immunophenotyping by flowcytometry is well conceived & fundamental tool to diagnose & subtype hematological malignancy, especially acute leukemia. By detecting various antigens presenting in various parts of cell, it is possible to know cell lineage & immaturity of the cell or group of cells. Apart from diagnostic importance, this specialized tool is also useful in prediction of prognosis & detection of minimal residual disease. Now, immunophenotyping can diagnose and type also those acute leukemias where morphology and cytochemistry fail. Aim : Study of Immunophenotypic patterns and their correlation with morphology and cytochemistry in North Indian Population. Materials and methods : Short clinical details and complete blood count of 150 patients were noted in the department of hematology of tertiary health centre. Sample of each patient was processed as per protocol and run on FACS CALIBUR OF BD BIOSCIENCES, USA . Dot plot data of each patient was analyzed and result was released. Results: AML, B-ALL and T-ALL comprised 38%, 49%, and 13% of all cases. Almost all blasts were expressing dimCD45 with no significant differences between the subtypes. CD34 have different expressions in AML subtypes, usually negative in APML. Aberrant expression of CD7 and CD19 were expressed in 5% and 3.4%of all cases of AML respectively. In 40% cases, morphology and Cytochemical studies clinched the diagnosis. 60% cases essentially needed Flowcytometric evaluation for diagnosis and subtyping of acute leukemias. Conclusion: Flowcytometric analysis of the patterns and intensity of antigen expression in blasts improved the diagnosis of AML and ALL in our centre. All cases do not require Immunophenotyping for diagnosis. Simultaneous use of conventional morphology, cytochemistry and flowcytometry reduce diagnostic cost of acute leukemia. Immunophenotyping results of our acute leukemia patients were comparable to international published studies.

Effects of window size on ankle joint stiffness calculation during quiet standing: How the rule changes the result

Measuring ankle joint stiffness (AJS) during quiet standing QS using an inverted pendulum model typically involves a single calculation covering the entire period of QS. This study compared AJS using the same 20.0s set of QS postural sway data but employing seven different calculation windows (0.25s, 0.5s, 1.0s, 2.0s, 5.0s, 10.0s and 20.0s). AJS was calculated for both anterio-posterior AP and medio-lateral ML directions of sway. Postural sway data from 19 subjects were used to calculate mean±SD and time-normalized AJS over the same 20s period of QS. Statistical power of this study was 0.99. The AJS had ICCs ranging from 0.47 to 0.85 with coefficient of variations ranging from 11.1% to 31.8%. There were significant differences in AJS between window sizes (P<0.0001) for both directions of sway. Specifically, AJS calculated by 1.0s windows was significantly larger (P<0.01) than others, except 0.5s, while the AJS of the largest two windows 10.0s and 20.0s were significantly smaller (P<0.01) than all others in both directions of sway. In conclusion, it is recommended that 1.0s windows be used to calculate AJS and that stiffness analyzed as a continuous signal offers a more complete picture of how AJS behaves during QS.

Effects of ankle and hip muscle fatigue on postural sway and attentional demands during unipedal stance

The effect of muscle fatigue on quiet standing is equivocal, including its duration/recovery and whether it leads to an increase in attentional demands. The purpose of this study was to assess the effects of ankle and hip muscle fatigue on postural sway and simple reaction time during a unipedal task. Two groups of 14 young adults (mean age=22.50±3.23) had to stand on their dominant leg for 30-s trials before and after fatigue of hip or ankle flexors and extensors. Half of the unipedal trials were performed in a dual-task condition where subjects, in addition to standing, had to respond verbally to an auditory stimulus. Sway area, and sway variability and velocity in the AP and ML planes were calculated using center of pressure data obtained from a force platform. Voice reaction time was recorded seated and during the dual-task condition to assess attentional demands. A main effect of fatigue was found for AP sway variability (p=0.027), AP sway velocity (p=0.017) and ML sway velocity (p=0.004). Both groups showed increased sway velocity in both directions and in reaction time during the dual-task condition (p<0.001), but reaction time did not increase with fatigue. A group by fatigue interaction was found significant for ML sway velocity (p=0.043). Results suggest that hip and ankle fatigue affected postural control in the fatigued plane (AP) but only hip fatigue affected postural control in the non-fatigued plane (ML sway velocity). However, fatigue did not lead to an increase in attentional demands and increased AP and ML sway velocity had recovered within 30min.

Test–retest reliabty of center of pressure measures of postural stability during quiet standing in a group with musculoskeletal disorders consisting of low back pain, anterior cruciate ligament injury and functional ankle instability

Reliability is a population-specific property, but to the authors’ knowledge there has been no study to determine the test–retest reliability of the postural stability measures such as center of pressure (COP) measures in the population of patients with musculoskeletal disorders (MSDs), while their clinical applications have been presented in literature. So, 33 patients with low back pain (LBP), anterior cruciate ligament (ACL) injury and functional ankle instability (FAI) randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. COP data were used to calculate standard deviation of amplitude, standard deviation of velocity, phase plane portrait, mean total velocity and area (95% confidence ellipse). Relative reliability of these measures was assessed using intraclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM) and coefficient of variation (CV). Also, minimal metrically detectable change (MMDC) was calculated to quantify intervention effects. Among different COP parameters, mean total velocity in all conditions of postural difficulty showed high to very high reliability, with ICC range of 0.74–0.91, SEM range of 0.09–0.40 cm/s, CV range of 5.31–8.29% and MMDC range of 0.19–0.79 cm/s. Phase plane portrait in anteroposterior–mediolateral (AP–ML) and ML direction were other best parameters with respect to the level of reliability. Mean total velocity and phase plane portrait parameters are suggested as good candidates to use for quantification and assessment of balance performance and identifying those with MSDs.