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Ratios of torques of antagonist muscle groups in female soccer players

Struzik A., Siemieński A., Bober T., Pietraszewski B.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 1

153--158

EN

An increase in the value of the hamstring-to-quadriceps (H/Q) ratio with an increase in angular velocity may effectively prevent injuries of the back of the thigh. Previous studies have found that the conventional H/Q ratio was unaltered along with an increasing angular velocity in females. Therefore, this study aimed to investigate the relationships between the conventional H/Q ratio and angular velocity in a group of female soccer players. Methods: The study was carried out on a group of 16 female soccer players (age: 20.7 ± 3.9 years, body height: 166.1 ± 5.8 cm, body mass: 58.4 ± 6.2 kg, training experience: 8.8 ± 4.1 years). Measurements of peak torque of extensors and flexors of the knee joint under static conditions and under isokinetic conditions (at angular velocities of 30°/s, 60°/s, 90°/s and 120°/s) were carried out using a Biodex dynamometer. Results: There was a statistically significant increase in the conventional H/Q ratio with an increase in angular velocity. These differences occurred between measurements at angular velocities of 0°/s and 30°/s, and 30°/s and 60°/s. Conclusions: As previously found for males, an increase in conventional H/Q ratio with increased angular velocity was also present in this group of female players. This phenomenon should reduce the number of injuries of the muscles of back of the thigh. Coaches should pay attention to increasing the level of strength in the group of knee joint flexor muscles so as to make the value of the H/Q ratio appropriately high and increasing with increasing angular velocity.

2

Lower extremity power in female soccer athletes : a pre-season and in-season comparison

Pietraszewski B., Siemieński A., Bober T., Struzik A., Rutkowska-Kucharska A., Nosal J., Rokita A.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 3

129--135

EN

Purpose: Lower extremity power is an important physical capacity of a soccer athlete. Power represents, and can be modified by, the training of strength and speed. Pre-season and in-season training differs in the relative emphasis on these two quantities. It is nevertheless desirable that the mechanical power remain the same or become higher during the in-season period. The purpose of this study was to identify changes in quantities related to “explosive strength” and to check whether, in collegiate female soccer players, pre- and inseason lower extremity power will remain unaltered. Methods: Twenty collegiate female soccer players, representing all field positions, participated. Lower extremity power was assessed by a series of drop jumps executed from four different heights (15, 30, 45, and 60 cm). Mechanical power was calculated using subject’s mass, jump height, and acceleration due to gravity. This value was further normalized by body mass of each athlete to obtain the relative (or normalized) mechanical power. Results: The normalized lower extremity mechanical power was highest when landing from the 30 cm height for both pre- and inseason periods. However, contrary to expectations, it turned out lower during the in-season than during the pre-season test, even though no significant differences were found between the corresponding jump heights. Conclusions: It is concluded that altered, perhaps inadequate, training strategies were employed during the in-season period. Besides, advantages of adding the relative mechanical power as a season readiness indicator are underlined compared with relying on the jump height alone.

3

Integral method (IM) as a quantitative and objective method to supplement the GMFCS classification of gait in children with cerebral palsy (CP)

Dziuba A., Bober T., Kobel-Buys K., Stempień M.

Acta of Bioengineering and Biomechanics

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2013

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Vol. 15, no. 2

105--111

EN

Gait analysis is an objective tool for the clinical assessment of locomotor activity in children with cerebral palsy (CP). Correct diagnosis and properly planned rehabilitation are necessary for enhanced motor functions in persons suffering from cerebral palsy. Orthoses, orthopedic operations, medications and physiotherapy are the most common treatments. However, there is still a lack of objective methods for assessing motor behavior and monitoring the progress of recovery. The aim of the study was to use the ground reaction force patterns generated during walking to create the Integral Method (IM), which could become an objective tool that could supplement the functional classification of CP children based on the Gross Motor Function Classification System (GMFCS). A total of 15 healthy children and 34 children with CP who walk independently participated in the study. A Kistler force plate and GRFintegral software were used. Of the 34 measurements based on the IM for CP children, 17 matched the level assigned by the GMFCS, 2 children were assigned a higher level, and 15 were assigned a lower level. Pearson’s correlation coefficient between the IM and the GMFCS was moderate (r = 0.61, p ≤ 0.01). Asymmetry was found in 11 cases. The IM supplements the GMFCS and is an objective and quantitative assessment of motor abilities. The method allows for the detection of asymmetry, diagnosis of the improvement of gait pattern and assessment of foot support technique. With the appropriate software, the IM provides pediatricians, neurologists, orthopedists, surgeons and physiotherapists with a simple and fast way to assess gait.

4

EMG frequency during isometric, submaximal activity : a statistical model for biceps brachii

Solnik S., De Vita P., Grzegorczyk K., Koziatek A., Bober T.

Acta of Bioengineering and Biomechanics

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2010

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Vol. 12, no. 3

21-28

EN

The purpose of this study was to develop a statistical model to describe the electromyography (EMG) signal frequency changes during a submaximal isometric contraction. Thirty subjects performed a 30-second isometric contraction of the biceps brachii muscle at 80% of the maximal voluntary isometric force. Surface EMG electrodes recorded electrical activity of the biceps brachii. Zero-Crossing-Rate was calculated to identify EMG frequency shifts. The mean frequencies for every one-second period were used to calculate a linear relationship between frequency and time. A significant relationship ( p < 0.05) between slope and initial frequency value was identified. The model described EMG frequency changes during submaximal effort of biceps brachii up to 15 seconds. The prediction error was 9.8%. Modifying this equation to initial values of frequency of each participant decreased prediction error to 7.2%. These results demonstrate that despite individual differences between subjects it is possible to derive single equation that describes EMG alterations during submaximal, isometric contractions across a homogeneous group of people.

5

Gait characteristics following Achilles tendon elongation: the foot rocker perspective

Bober T., Dziuba A., Kobel-Buys K., Kulig K.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 1

37-42

EN

The action of three functional rockers, namely the heel, ankle and forefoot rocker, assist the progression of the leg over the supporting foot. The purpose of this case series was to analyze the occurrence of foot rockers during gait in three children with cerebral palsy (CP) who had undergone the tendo-Achilles lengthening (TAL), procedure followed by a clinic- or home-based intervention and in one child with CP without history of surgery. Self-selected gait was video-recorded in a laboratory during six testing sessions at half-year intervals rendering a 3 year period of observation. One child had pre- and post-surgical gait data and the other two had post surgical data only. Sagittal plane knee angular velocity, as well as foot to ground positions, and foot rocker occurrence were analyzed. In a child with history of CP, and without history of surgery, mean angular velocities of the 1st, 2nd and 3rd foot rocker were 3.7, 0.57 and 6.67 rad/s, respectively, and the step length and cadence were normal. In children who underwent TAL the 1st and 2nd rocker was absent, as the initial contact of the foot with the ground was either with foot-flat or forefoot. The mean velocity of the 3rd rocker in children who underwent TAL was lower by approximately 50–80% than that of the nonsurgical case. Furthermore, the characteristic pattern of the knee joint to foot–floor position during gait was not observed in these cases. Foot rocker analysis identified children with abnormal gait characteristics. Following surgery these gait characteristics remained abnormal.

6

Predictive torque equations for joints of the extremities

Bober T., Kulig K., Burnfield J. M., Pietraszewski B.

Acta of Bioengineering and Biomechanics

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2002

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Vol. 4, nr 2

49-60

EN

The purpose of this study was to develop regression equations predicting torque output throughout the range of motion for the human elbow, shoulder, knee, and hip. Twenty-two healthy males participated. Torque values throughout the sagittal plane range of motion (i.e., flexion and extension) of the right elbow, shoulder, knee and hip were recorded (isokinetic dynamometer, 1 rad/sec) and expressed as a percentage of the peak torque produced for each motion. For each joint tested, regression equations based on ensemble-averaged, normalized torque data were calculated to predict the relative torque throughout the investigated range of motion when torque in one angular position was known. Shoulder flexion was best described by a second-order polynomial, while shoulder extension, elbow and knee flexion and extension, and hip flexion were described best by third-order polynomials. Hip extension was best described by a fourth-order polynomial. The regression multiple R2 values ranged between 0.998 and 1.000. These regression equations can be used to predict the expected torque anywhere in the sagittal plane range of motion based on knowledge of a torque recorded at another joint angle for the elbow, shoulder, knee, or hip joint. These equations can be used in the clinical setting when a direct examination of strength capability is not possible due to limitations in equipment or due to the presence of pain within the arc of motion.