Acta of bioengineering and biomechanics最新文献

Purpose: Rowing engages large muscle groups and electromyography (EMG) analysis is used to assess athletes' condition and refine sports technique. The aim of the experiment was to evaluate the muscle activation level during different phases of the rowing cycle on an ergometer.

Methods: In a study involving one professional and five amateurs, the mean EMG amplitudes from the quadriceps, gastrocnemius, biceps and triceps brachii were analyzed during different phases of rowing. A comparison was made between the degree of muscle engagement during the exercise between the professional and inexperienced individuals as well as among the different individuals during recordings obtained at different rowing speeds. The correlation coefficient between the values recorded using a strain gauge and the EMG amplitude recorded from the surface of the biceps and triceps brachii muscles was evaluated.

Results: The muscle activation pattern during rowing has a predictable character. A difference in the muscle activation pattern during rowing between the professionals and amateurs was observed. The EMG signal is correlated with the force recorded by the resistive strain gauge only in the experienced rower at stroke rates 20 and 25 [1/min].

Conclusions: Electromyographic analysis can be useful for assessing the correctness of rowing techniques. The activation pattern of muscles during rowing has a predictable nature. The force generated by the participants increases with an increase in rowing frequency.

Purpose: Children with cerebral palsy have limitations in utilizing neural information to perform smooth movement and maintain balance during walking. This study aimed to develop a wearable sensor that tracks balance continuously and provides haptic biofeedback to its user through real-time vibration stimulus to assist patients with balance and postural control impairments such as cerebral palsy.

Methods: Twelve children with cerebral palsy and 12 age-matched typically developed children used the sensor during walking at a self- -selected speed. The lower extremity joint kinematics, center of mass, and spatial-temporal parameters were recorded with Xsens MVN during "with" and "without" biofeedback conditions.

Results: The sensor did not disturb healthy gait. Pearson correlation coefficient and Root Mean Square Error techniques showed that biofeedback regulated the gait parameters and trunk stability of the CP group. The extended stance percentage (without BF: 73.91% ± 10.42, with BF: 63.53% ± 2.99), step width (without BF: 0.20 m ± 0.05, with BF: 0.18 m ± 0.07), and step time (without BF: 1.55 s ± 1.07, with BF: 0.73 s ± 0.14) parameters decreased. Similarly, cadence and walking speed increased.

Conclusions: Obtained results indicated that this wearable sensor can be integrated into the physical therapy and rehabilitation process of children with balance and postural control impairments to improve motor learning and balance control. The present findings contribute to a better understanding of the adaptation of innovative engineering applications with rehabilitation processes, which, in turn, could assist patients with balance impairments and facilitate their integration into society.

Purpose: The purpose of the study was to try to determine the factors that differentiate the height, weight, BMI and age of high-level handball players participating in the Tokyo 2020 Olympic Games.

Methods: The study included handball players participating in the Tokyo 2020 Olympic Games. The study material consisted of data on athletes' body height, body weight, age and BMI. The collected study material was analyzed about the position of the game, quarter and semester of the birth, continental location of the country and geographical region. In parametric distribution, Student's t-test and ANOVA were used. In non-parametric variables, the Mann-Whitney U-test and the Kruskal-Wallis test were used.

Results: The highest average heights, weights and BMIs were found in players playing in the pivot position, while the lowest were found in wing players. Interactions were shown within the body weight and BMI of the athletes. Players from Europe have the highest weight and BMI in the second semester of birth, while other players' highest results were in the first semester.

Conclusions: The factors that most strongly differentiate body height, body weight, and BMI are playing positions. Factors that differentiate height and weight are the continental location and region of the country represented.

Purpose: Tendons adapt to loads affecting them by changing tendons' mechanical and morphological properties. The aim of the study was to investigate the influence of involvement in sport activities in the form of CrossFit training by individuals of different age upon the mechanical properties of Achilles tendon.

Methods: 231 people participated in the study. One group consisted of subjects who trained CrossFit as amateurs, the other group comprised subjects who were not physically active. Achilles tendon was studied for various positions of the ankle joint: 0° DF/PF, 10° DF, 20° DF, 20° PF and 40° PF. The following mechanical and viscoelastic tendon properties were measured using MyotonPRO: frequency [Hz], stiffness [N/m], decrement [log], relaxation time [ms] and creep [De]. The results have been compared in reference to physical activity, BMI, age and length of training history.

Results: Both the tension and stiffness increased with degree of Achilles tendon stretching and decreased as it contracted. Higher values have been noted in the group of people in training and with higher BMI values. The elasticity of Achilles tendon decreased with plantar flexion increase. Lower elasticity has been recorded in the group in training and with higher BMI. No significant influence of age and length of training history upon the parameters achieved has been noted.

Conclusions: The specificity of CrossFit training and accompanying mechanical load result in development of adaptation changes in Achilles tendon, in the form of its higher tone/tension and stiffness, as well as lower elasticity.

Purpose: This paper examines the biomechanical mechanism behind the effect of the invisible aligner technique on tooth movement processes.

Methods: To compare the effects of different target positions on tooth movement and the periodontal ligament (PDL), two kinds of aligners were designed to provide displacements of 0.2 mm (Model A) and 0.3 mm (Model B). Different displacements of the maxillary second molar were simulated using the finite element (FE) method.

Results: The results of numerical simulations showed that the maximum stress was in the PDL of the distal surface and the palatal surface. The stress of the PDL in Model B was larger than Model A, with the displacement of the second molar 0.027 mm in Model A, by 44.9% lesser than that in Model B.

Conclusions: The aligner that provided a displacement of 0.2 mm was more suitable for pushing the second molar backward in the initial stage. During the tooth movement processes, the displacement of the crown was larger than that of the root and the displacement decreased gradually from the crown to the root. In addition, the displacement and rotation of teeth during orthodontic treatment were measured and analysed.

Purpose: Basketball jump shot success is determined mainly by the height, velocity and angle of ball release. To achieve a successful shot, these variables need to be adjusted according to the player's position on the court. This study aimed to identify the changes in kinematics variables of the basketball jump shot with an increasing shooting distance performed by players with varying skill levels.

Methods: Seventeen male subjects, divided into experienced (N = 9), and non-experienced (N = 8) players, performed three successful jump shots from the free-throw line (4.23 m) and the 3-point line (6.75 m). All attempts were recorded at 120 Hz with a camera perpendicularly to the sagittal plane, and the kinematics variables were calculated using Tracker software.

Results: The increase in shooting distance shows a decrease in height and angle of ball release. In contrast, the velocity of ball release increased for both groups at longer distances. Experienced players presented a higher mean value of the height of ball release in both distances, which allowed for a lower velocity of ball release.

Conclusions: The most meaningful improvement for players training the jump shot technique is to increase the release height of the ball, jumping higher and shooting the ball near the peak of the jump.

Purpose: This paper presents tribological and rheological analysis results of artificial synovial fluid base solutions. Special attention was paid to polyacrylamide preparations with different molecular weights and concentrations.

Methods: Tribological tests were conducted using the Al2O3-CoCrMo friction pair in the presence of investigated lubricants. Confocal microscopy was used to analyze and assess of volume, depth, and width of wear traces. Moreover, the viscosity and viscoelasticity tests of analyzed solutions were carried out. The rheological measurements were focused on the oscillatory tests, which allowed us to determine the elasticity modulus (G') and viscosity (G″).

Results: Viscoelastic nature of the tested preparations depends on the strain rate. It has been shown that elastic properties dominate at higher frequencies. The molecular weight of the polymer has a particular influence on these properties. The most promising results were obtained for 6% and 8 % high molecular weight polyacrylamide compositions.

Conclusions: However, all tested polyacrylamide solutions show better rheological and tribological characteristics than commercial preparation based on hyaluronic acid.