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Using nonlinear measures to evaluate postural control in healthy adults during bipedal standing on an unstable surface

Kędziorek Justyna, Błażkiewicz Michalina, Kaczmarczyk Katarzyna

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 1

9--17

EN

This study examined the use of nonlinear measures – sample entropy (SampEn), fractal dimension (FD), and the Lyapunov exponent (LyE) – to evaluate postural control in adults during standing on an unstable surface, with and without visual feedback. Methods: 14 healthy young adults (24.07 ± 7.32 years) completed bipedal standing trials on an unstable-plate Biodex Balance System (BBS) connected to a Vicon system, with eyes open and closed. Each trial lasted 20 sec. Analysis was performed based on the center of mass (CoM), for which the three nonlinear measures were calculated. Results: Excluding visual feedback was found to cause a significant increase in linear and nonlinear parameters. Moreover, SampEn and FD values were found to be significantly higher in the PD direction, compared to AP or ML, whereas LyE values in this direction were minimal. Conclusions: Results show that the three nonlinear measures provide a useful way of evaluating postural control in healthy adults. Moreover, it seems that introducing an unstable surface meant that the projection of the CoM was not perpendicular to the surface, but rather set at a certain continually changing angle, forcing the whole system to adapt to chaotic and unpredictable conditions. Such refined changes in conditions can be evaluated in a precise way only by using nonlinear measures.

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Influence of the base of support widths on postural control and feet loading symmetry during squat – preliminary study

Kędziorek Justyna, Błażkiewicz Michalina

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 2

55--63

EN

The symmetry of feet loading and adequate postural control are crucial aspects of proper squat performance. The study aimed to evaluate the effect of various stance widths during squat on postural control and symmetry of feet loading. Methods: Thirty healthy individuals participated in this study. Each participant performed one type of squat with a narrow stance (NS), hip stance (HS) and wide stance (WS). Results: A significantly higher value of CoP path length, the velocity of sways and Area95 were obtained for the WS squat compared to NS and HS. In addition, the wide feet setting significantly affected not only the feet loading symmetry but also the strategy (high LyE), the amount of irregularities (high SampEn) and the CoP time-series roughness complexity (high FD). It has been shown that as the base of support grew, the asymmetry index grew. Conclusions: The wide squat is less stable, requiring more complex postural control behavior and more flexibility. Performing this squat significantly shifts the pressure to the dominant limb.

3

Joint loads and muscle force distribution during classical and jazz pirouettes

Błażkiewicz Michalina

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 1

3--13

EN

Purpose: The objective of this study was to analyze the muscle force distribution and lower limb joint loading during two types of pirouettes and check which muscle in which pirouette generates the highest force and which joint is the most loaded. Methods: Skilled dancers (n = 16) performed single-turn pirouettes in jazz and classic styles. Kinematic and kinetic data were collected using the Vicon system and Kistler plates. The joint reaction forces and muscle forces were calculated using a musculoskeletal model in the AnyBody Modeling System. Results: No statistically significant differences were found for the duration of the turn in both pirouettes. The range of motion in all joints of supporting leg in sagittal plane and in hip joint in frontal plane for non-supporting leg were significantly higher in classic pirouette. The ankle joint was the most loaded joint in both pirouettes and its maximal value was significantly higher in classic pirouette. The force generated by ankle plantar flexors muscles was significantly greater in the jazz pirouette in turn phase. For the nonsupport limb, external hip rotators generated significantly greater force when performing the classic pirouette. Conclusions: It seems that early stage dancers may start their lessons with jazz pirouettes, where necessary joint mobility is lesser. They also are supposed to increase muscle strength and body awareness with such proceedings. A better awareness of the mechanical loads on the musculoskeletal system which a dancer performing pirouettes faces should have an impact on the way dance classes are conducted and choreographic elements are sequenced.

4

Ocena stabilności posturalnej w funkcji różnego ustawienia stóp na podłożu przy wykorzystaniu miar dynamiki nieliniowej

Kędziorek Justyna, Błażkiewicz Michalina

Aktualne Problemy Biomechaniki

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2020

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z. 19

20--26

PL

Celem pracy była ocena stabilności posturalnej w różnych warunkach podparcia: stanie obunóż, jednonóż i w tandemie przy oczach otwartych. W badaniach wzięła udział grupa trzydziestu trzech zdrowych osób w wieku 21.88 ± 1.65 lat. Badania zostały przeprowadzone przy użyciu platformy AMTI AccuSway (30 sekund – każda próba). Do obliczeń eksportowano położenia środka nacisku stóp na podłoże (CoP) w płaszczyznach x i y. Następnie została policzona długość drogi CoP i współczynniki dynamiki nieliniowej: entropia próbkowa, wymiar fraktalny i wykładnik Lapunowa. Wykazano, że zmniejszenie pola powierzchni podparcia powoduje istotny wzrost współczynnika entropii próbkowej i wymiaru fraktalnego.

EN

The aim of the study was to assess postural stability under different base of support: both foot standing, one-leg standing and tandem with eyes open. A group of thirty-three healthy persons aged 21.88 ± 1.65 years participated in the study. The tests were carried out using the AMTI AccuSway platform. The locations of the center of foot pressure (CoP) in the X and Y planes were exported. Then the CoP path length and nonlinear dynamics coefficients were calculated: sample entropy, fractal dimension and Lapunov exponent. It has been shown that the reduction of the support surface area causes a significant increase in the sample entropy factor and the fractal dimension.

5

Ocena stabilności posturalnej podczas strzelania

Błażkiewicz Michalina, Kędziorek Justyna, Bańkowska Sylwia, Wit Andrzej

Aktualne Problemy Biomechaniki

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2019

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z. 17

5--10

PL

Celem pracy była ocena stabilności posturalnej podczas strzelenia z łuku. W badaniach wzięły udział dwie grupy: zawodowi łucznicy oraz amatorzy, tzn. osoby, które nigdy nie strzelały z łuku. Badania zostały przeprowadzone przy użyciu systemu Vicon i platform Kistler. Do obliczeń zostały eksportowane położenia środka masy ciała. Następnie została policzona długość drogi CoM w przestrzeni 3D oraz współczynniki entropii próbkowej. Wykazano, że długość drogi CoM w przestrzeni 3D jest istotnie (p = 0.0001) dłuższa u łuczników podobnie jak współczynnik entropii próbkowej wzdłuż osi pionowej (p = 0.0117).

EN

The aim of the work was to assess postural stability during archery. Two groups participated in the study: professional archers and amateurs, i.e. people who never shot a bow. The tests were carried out using the Vicon system and Kistler platforms. Body mass center positions were exported to calculations. Next, the CoM distance in 3D space and sample entropy coefficients were calculated. It was shown that the distance of the CoM path in 3D space is significantly (p = 0.0001) longer in archers, similarly as the sample entropy coefficient along the vertical axis (p = 0.0117).

6

Mechanical energy flows between body segments in ballistic track-and-field movements (shot put, discus, javelin) as a performance evaluation method

Błażkiewicz Michalina, Łysoń Barbara, Wit Andrzej

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 1

31--36

EN

Seeking a method to evaluate and monitor the performance of the shot put, discus and javelin throw, we analyzed the transfer of mechanical energy between body segments. Methods: The study was conducted on groups consisting of elite throwers on the Polish National Team for each of the aforementioned sport disciplines. The movements of each throw were recorded using Vicon system and Kistler plates. The power and energy fluctuations were computed for the final acceleration phase of each throw. Results: In all three disciplines studied, we found an average energy loss of 1.63 J/kg generated from shoulder to wrist. The value of generated energy from ankle to torso initially increased in all disciplines, followed by a descent – with the exception of the javelin throw, where there was an average 27% decrease in both hip joints. We found strong correlations between relative amplitude values of energy and the athlete’s personal performance records: –0.8226 (shot put), 0.6008 (discus) and 0.7273 (javelin). Conclusions: Measuring the transfer of mechanical energy between body segments offers a useful method for evaluating the technique of ballistic movements and for monitoring training progress.

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Comparison of muscle activity during hand rim and lever wheelchair propulsion over flat terrain

Błażkiewicz Michalina, Wiszomirska Ida, Fiok Krzysztof, Mróz Anna, Kosmol Andrzej, Mikicin Mirosław, Molik Bartosz, Marszałek Jolanta

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 3

67--74

EN

The aim of this study was to compare the activity of upper limb muscles during hand rim wheelchair propulsion and lever wheelchair propulsion at two different velocity levels. Methods: Twenty male volunteers with physical impairments participated in this study. Their task was to push a lever wheelchair and a hand rim wheelchair on a mechanical wheelchair treadmill for 4 minutes at a speed of 3.5 km/h and 4.5 km/h in a flat race setting (conditions of moving over flat terrain). During these trials, activity of eight muscles of upper limbs were examined using surface electromyography. Results: The range of motion in the elbow joint was significantly higher in lever wheelchair propulsion (59.8 ± 2.43°) than in hand rim wheelchair propulsion (43.9 ± 0.26°). Such values of kinematics resulted in a different activity of muscles. All the muscles were more active during lever wheelchair propulsion at both velocity levels. The only exceptions were extensor and flexor carpi muscles which were more active during hand rim wheelchair propulsion due to the specificity of a grip. In turn, the examined change in the velocity (by 1 km/h) while moving over flat terrain also caused a different EMG timing of muscle activation depending on the type of propulsion. Conclusions: Lever wheelchair propulsion seems to be a good alternative to hand rim wheelchair propulsion owing to a different movement technique and a different EMG timing of muscle activity. Therefore, we believe that lever wheelchair propulsion should serve as supplement to traditional propulsion.