The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knee... more The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Signif-icant differences (p 0.05) in peak knee extension and flexion torques, hamstring/quad-riceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identi-fied. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninv...
Journal of Theoretical and Applied Mechanics, 2004
The study of spatial human movements requires the development and use of a three-dimensional mode... more The study of spatial human movements requires the development and use of a three-dimensional model. The model proposed here has 44 degrees-of-freedom and it is described using natural coordinates, which do not require an explicit definition of rotation coordinates. The biomechanical model consists of 16 anatomical segments composed of 33 rigid bodies. Joint actuators are introduced into equations of motion of the multibody model by means of kinematic driver constraints in order to reflect the effect of the muscle forces about each anatomical joint. After associating a Lagrange multiplier to each joint actuator, the torques that represent muscle forces become coupled with the biomechanical model through the Jacobian matrix of the underlying multibody system. The developed model is applied to identify net torques and reaction forces at the anatomical joints in application cases that include the take-off to aerial trajectories and standing backwards somersault.
PURPOSE The identification of activation, synchronization and work of individual muscles in the s... more PURPOSE The identification of activation, synchronization and work of individual muscles in the subsequent stages of lifting weights is interesting for researchers and trainers. Unfortunately, the existing methods of research do not provide such possibilities. Such information could be gathered from infrared measurements as they are non-invasive and can be carried out without the direct involvement of the weightlifter. The purpose of the study was to analyse temperature changes in the shoulder girdle in the first phase of the snatch in weightlifting. METHODS The study involved 11 weightlifters who competed in two weight categories, 94 and 105 kg, during the World University Championships in 2018. The performance of the snatch was recorded using a thermographic camera in three consecutive attempts. We analysed the temperature changes in the left and right shoulder girdles in the two initial stages of the snatch. Statistical analysis of empirical data was performed using linear mixed ...
The assumption that optimization results depend on coordinate system selected to describe a biome... more The assumption that optimization results depend on coordinate system selected to describe a biomechanical model is tested by comparing two solutions obtained with generalized and natural coordinate systems. A 5-degrees of freedom planar musculoskeletal model actuated by 9 Hill-type musculotendon units was created to simulate lifting a leg up. Each individual muscle force was discretized into a set of independent design variables, and an inverse dynamic parameter optimization method was used in the computations. The optimal time characteristics of the predicted muscle forces for both solutions are presented. Some remarks concerning the efficiency of natural coordinates for solving optimal control problems are also included.
The research work aimed to identify and analyse reactions in the joints of the lower limb as well... more The research work aimed to identify and analyse reactions in the joints of the lower limb as well as in the intervertebral joints of the lumbar spine when lifting weights and making a squat. The determination of loads of the skeletal-muscular system involved the performance of simulations in the AnyBody software programme. Input data used in the research-related tests came from the tests concerning the kinematics of weightlifting by a weightlifter. The use of mathematical modelling and static optimisation methods made it possible to identify resultant responses in the joints in individual positions of a squat made under various external loads. The highest resultant responses in all of the joints subjected to analysis were identified at an angle of \(135^{\circ }\) in knee joints. As a result, it is important to pay attention during training not to stop moving during an exercise at the above-named angle.
PURPOSE The state of athletes' muscles is not constant, but it differs depending on the stage... more PURPOSE The state of athletes' muscles is not constant, but it differs depending on the stage of sports training, which is associated with different degrees of muscle fatigue. There is thus a need to find a non-invasive and simple method to assess muscle fatigue. The aim of the study was to determine the relationship between muscle fatigue due to physical effort and changes in skin temperature, measured using a thermographic camera. METHODS The study involved 12 volleyball players. The participants were to maintain 70% of peak torque in the joint for as long as possible. We measured peak torque and the time of maintaining 70% of its value (tlim) as well as continuously recording skin temperature and electromyographic (EMG) signals in the region of the belly of the rectus femoris. The measurements were taken twice: before and after a series of squats. RESULTS The study found that tlim decreased when isometric contraction was per- formed after physical effort. Pre- and post-exerci...
The primary aim of the current study was to determine the time curves of changes in the record sc... more The primary aim of the current study was to determine the time curves of changes in the record scores in the snatch and its variations during a two-year training cycle in young weightlifters. This study also aimed at assessing the ratios between these scores and at predicting the snatch record scores at the end of the subsequent annual training macrocycle. The final purpose was to compare the record scores with the isometric peak torque values of the trunk and knee extensors. The study involved 16 weightlifters who were tested seven times at three-month intervals. The overall mean ratios of the record scores in the hang snatch to those in the snatch and the record scores in the hang power snatch to those in the snatch were approximately constant and amounted to 0.95 and 0.79, respectively. The overall mean ratio between the scores in the power snatch to those in the snatch was approximately 0.88. Statistically significant differences (p < 0.05) between the individual time trajectories of record scores in the snatch and its derivatives were identified in two consecutive annual training macrocycles. The error in predicting record results at the end of the following annual training macrocycle was 6.7 ± 4.7% or 8.1 ± 3.4% depending on the way the measurement data were modeled. The results of the study also indicate that the measurements of the isometric peak torque of the trunk extensors performed in laboratory conditions can be useful in diagnosing the strength capacity of young weightlifters.
Introduction. The aim of the study was to determine the changes in the peak torque of the knee ex... more Introduction. The aim of the study was to determine the changes in the peak torque of the knee extensors and flexors of the dominant lower limb, the shoulder internal and external rotators of the dominant upper limb, and the shoulder extensors and flexors of the dominant upper limb as well as the changes in jump height in volleyball players during the annual training macrocycle. Material and methods. The study involved 13 volleyball players from a Polish second-league team. The measurements were performed five times: before the preparation period (T1), at the beginning of the competitive season (T2), in the middle (T3) and at the end of the first competition period (T4), and after the competitive season (T5). The torque of the knee muscles and shoulder rotators was measured in isokinetic conditions, and the torque of the shoulder extensors and flexors was assessed in isometric conditions. Jumping ability was tested using a piezoelectric platform. Results. We observed statistically s...
International Journal of Structural Stability and Dynamics
The aim of this paper is to present the results of an assessment of internal loads in the joints ... more The aim of this paper is to present the results of an assessment of internal loads in the joints of the lower limbs during the snatch performed by young weightlifters. A planar model of a weightlifter composed of 7 rigid segments (the lower trunk, thighs, lower legs and feet) connected by six hinge joints was used in the computations. The dynamic equations of the motion of the model were obtained using a projective technique. Kinematic data were recorded by a Vicon system with a sampling frequency of 200 Hz. The ground reactions were measured independently for the left and right limbs on two force platforms. The inverse dynamics problem was solved to assess the internal loads (the muscle forces and joint reactions) in the lower limbs. Relatively high differences in the reactions in the joints and muscle forces in the left and right lower extremities were identified. The obtained results also reveal that the snatch, a lift which tends to be geometrically symmetrical in the sagittal p...
The purpose of the current study was to assess the effectiveness of rehabilitation in patients af... more The purpose of the current study was to assess the effectiveness of rehabilitation in patients after anterior cruciate ligament reconstruction (ACLR) using a wavelet analysis of the torque-time curve patterns of the extensors of the affected knee. The analysis aimed at the quantitative evaluation of irregularities in these torque-time patterns. The study involved a group of 22 men who had had ACL reconstruction. The torque-time characteristics were recorded 3, 6 and 12 months after the surgery by an isokinetic dynamometer. They were then examined using the orthogonal Daubechies 4 (Db 4) and biorthogonal Bior 3.1 wavelets. A statistical analysis of the results revealed significant differences in values of the high-frequency energy stored in the details of the signal from the dynamometer between the first and last measurements, both for the Db 4 ( p ≤ 0.023) and Bior 3.1 ( p ≤ 0.01) wavelets. These differences were found in 73% of patients whose curve patterns were analysed using the ...
Introduction. The aim of the current study was to examine the relationship between knee and elbow... more Introduction. The aim of the current study was to examine the relationship between knee and elbow isometric muscle torque values and the results obtained in special and specific exercises in young weightlifters. Material and methods. The study involved eight young weightlifters (age: 19.9 ± 4.3 years; height: 176.8 ± 10.6 cm; weight: 69.0 ± 19.7 kg - pretest, 70.9 ± 21.6 - posttest). Their performance put them in the second and third top classes of weightlifters their age according to the Polish norms for weightlifting (the so-called ‘national class’ and ‘first class’ in the Polish system, which are lower than the ‘international class’). The differences between the values obtained in the first measurement of torque performed at the beginning of the preparation period and those obtained at the beginning of the immediate pre-competition period were compared with the differences in the maximal load lifted in special and specific exercises. Results. The training that the weightlifters u...
The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knee... more The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Significant differences (p 0.05) in peak knee extension and flexion torques, hamstring/quadriceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identified. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninvolved knee joint. The results helped to evaluate the progress of the rehabilitation and to implement necessary modifications optimizing the rehabilitation training program. The results of the study may also be used as referential data for physically active males of similar age.
Introduction. The aim of the study was to determine the torque of the knee extensors and flexors ... more Introduction. The aim of the study was to determine the torque of the knee extensors and flexors of the lead lower limb, the torque of the shoulder extensors and flexors of the dominant upper limb, and the torque generated by the muscles of the kinematic chain going from the trail lower limb to the hand of the dominant limb in male handball players during the annual training macrocycle. Changes in jump height and throwing velocity were also investigated. Material and methods. The study involved 13 handball players from a Polish second-league team. The measurements were performed four times: at the beginning of the preparation period, at the beginning of the season, at the end of the first part of the season, and at the end of the second part of the season. Torque was measured in isokinetic and isometric conditions. Jumping ability was tested using a piezoelectric platform, and throwing velocity was measured with a speed radar gun. Results. The study found statistically significant d...
Acta of bioengineering and biomechanics / Wrocław University of Technology, 2008
The assumption that optimization results depend on coordinate system selected to describe a biome... more The assumption that optimization results depend on coordinate system selected to describe a biomechanical model is tested by comparing two solutions obtained with generalized and natural coordinate systems. A 5-degrees of freedom planar musculoskeletal model actuated by 9 Hill-type musculotendon units was created to simulate lifting a leg up. Each individual muscle force was discretized into a set of independent design variables, and an inverse dynamic parameter optimization method was used in the computations. The optimal time characteristics of the predicted muscle forces for both solutions are presented. Some remarks concerning the efficiency of natural coordinates for solving optimal control problems are also included.
The paper analyzes the use of natural coordinates in modeling and simulation of musculoskeletal m... more The paper analyzes the use of natural coordinates in modeling and simulation of musculoskeletal models of the human body. A biomechanical model of the lower extremity of the human body was constructed for the analysis. It consists of three anatomical segments described by eight natural coordinates located at the joints. The developed model was applied to solve three classic dynamics problems of human motion: inverse dynamics, direct dynamics, and static optimization. The analysis covers the raising of a leg together with; the time characteristics of the resultant net torques at the basic joints of the leg (inverse dynamics), the time histories of natural coordinates and their velocities (direct dynamics) as well as the time-varying muscle force patterns (static optimization). In order to check the numerical efficiency of modeling in the natural coordinates' environment the results were compared with the ones received through generalized coordinates. Some conclusions drawn from this comparison and final remarks referring to the biomechanical identification of the analyzed motor task were included in the paper. r
The study of spatial human movements requires the development and use of a three-dimensional mode... more The study of spatial human movements requires the development and use of a three-dimensional model. The model proposed here has 44 degrees-of-freedom and it is described using natural coordinates, which do not require an explicit definition of rotation coordinates. The biomechanical model con-sists of 16 anatomical segments composed of 33 rigid bodies. Joint actuators are introduced into equations of motion of the multibody model by means of kinematic driver constraints in order to reflect the effect of the muscle forces about each anatomical joint. After associating a Lagrange multiplier to each joint actuator, the torques that represent muscle forces become coupled with the biomechanical model through the Jacobian matrix of the underlying mul-tibody system. The developed model is applied to identify net torques and reaction forces at the anatomical joints in application cases that include the take-off to aerial trajectories and standing backwards somersault.
This study presents an inverse dynamic parametric optimization method for solving optimal control... more This study presents an inverse dynamic parametric optimization method for solving optimal control problems involving planar biomechanical linkages. Two biomechanical models of the human lower leg have been defined in generalized and natural coordinates to validate the method in different modeling conditions. Both models are composed of three anatomical segments representing the thigh, shank and foot. The configuration of the models is described by five generalized, and eight natural coordinates. After solving the inverse dynamic problem, a parametric optimization was applied to find the optimal control. The optimization criterion was to minimize the performance time of a karate kick. The velocities were chosen as state variables. The starting and final configuration of the leg, which formed the boundary conditions of the movement, were in accordance with video recordings. A sequential quadratic programming method (SQP) was used in the computations. The optimal time characteristics o...
The Journal of sports medicine and physical fitness, 2012
The purpose of this study was to examine how focusing attention during nine weeks of plyometric t... more The purpose of this study was to examine how focusing attention during nine weeks of plyometric training influence jumping performance. It was hypothesized that participants utilizing an external focus of attention during practice would produce greater improvements in jumping behavior compared to participants practicing in the internal and control conditions. Thirty-six untrained but physically active male college students were randomly assigned to 1 of 3 plyometric groups with a different focus of attention: external (EXF; N.=12), internal (INF; N.=12), and control (CON; N.=12). All participants subsequently participated in the same an 9-week periodized training program. Standing long jump (SLJ), countermovement jump (CMJ) and drop jump (DJ) were tested pre- and posttraining intervention. The EXF group exhibited greater improvement (P<0.05) in jumping distance for SLJ and height for CMJ than both the INF and CON groups, while the enhancement in jumping height for DJ was not supe...
Introduction. The number of arthroscopic reconstructions of the anterior cruciate ligament (ACL) ... more Introduction. The number of arthroscopic reconstructions of the anterior cruciate ligament (ACL) has been increasing not only among competitive athletes, but also among recreational athletes. The monitoring of the rehabilitation process in order to determine a safe time to return to the pre-injury activity is thus of great practical importance. The aim of this paper is to analyse the changes in selected biomechanical variables which occur after the therapeutic training following an anterior cruciate ligament reconstruction. Materials and methods. Twenty nine males (age 27.3 ± 5.7 years) after the anterior cruciate ligament reconstruction participated in the study. A quadruple-stranded semitendinosus/gracilis graft was used for the reconstruction. The biomechanical evaluation of the rehabilitation process was provided by an isokinetic dynamometer Biodex System Pro-3 working at speeds of 60 deg/s and 180 deg/s during testing the knee extensor and flexor muscles. In the case of an injured limb, the absolute peak torque, relative peak torque, average power and hamstring/quadriceps (H/Q) ratio were determined. In addition, the values of flexor and extensor torques for healthy and injured limbs were compared. The study was carried out in four stages: before the surgery, three, six and twelve months after the surgery. Results and analyses. The results showed significant differences in each value between various stages of the biomechanical rehabilitation process of the knee. The applied therapeutic training influenced significantly the changes in the values of the tested variables. The results have confirmed that the biomechanical measurements can be treated as a supplementation to the clinical evaluation of the patient after ACL reconstruction. They may also be used for the optimisation of the therapeutic training.
The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knee... more The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Signif-icant differences (p 0.05) in peak knee extension and flexion torques, hamstring/quad-riceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identi-fied. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninv...
Journal of Theoretical and Applied Mechanics, 2004
The study of spatial human movements requires the development and use of a three-dimensional mode... more The study of spatial human movements requires the development and use of a three-dimensional model. The model proposed here has 44 degrees-of-freedom and it is described using natural coordinates, which do not require an explicit definition of rotation coordinates. The biomechanical model consists of 16 anatomical segments composed of 33 rigid bodies. Joint actuators are introduced into equations of motion of the multibody model by means of kinematic driver constraints in order to reflect the effect of the muscle forces about each anatomical joint. After associating a Lagrange multiplier to each joint actuator, the torques that represent muscle forces become coupled with the biomechanical model through the Jacobian matrix of the underlying multibody system. The developed model is applied to identify net torques and reaction forces at the anatomical joints in application cases that include the take-off to aerial trajectories and standing backwards somersault.
PURPOSE The identification of activation, synchronization and work of individual muscles in the s... more PURPOSE The identification of activation, synchronization and work of individual muscles in the subsequent stages of lifting weights is interesting for researchers and trainers. Unfortunately, the existing methods of research do not provide such possibilities. Such information could be gathered from infrared measurements as they are non-invasive and can be carried out without the direct involvement of the weightlifter. The purpose of the study was to analyse temperature changes in the shoulder girdle in the first phase of the snatch in weightlifting. METHODS The study involved 11 weightlifters who competed in two weight categories, 94 and 105 kg, during the World University Championships in 2018. The performance of the snatch was recorded using a thermographic camera in three consecutive attempts. We analysed the temperature changes in the left and right shoulder girdles in the two initial stages of the snatch. Statistical analysis of empirical data was performed using linear mixed ...
The assumption that optimization results depend on coordinate system selected to describe a biome... more The assumption that optimization results depend on coordinate system selected to describe a biomechanical model is tested by comparing two solutions obtained with generalized and natural coordinate systems. A 5-degrees of freedom planar musculoskeletal model actuated by 9 Hill-type musculotendon units was created to simulate lifting a leg up. Each individual muscle force was discretized into a set of independent design variables, and an inverse dynamic parameter optimization method was used in the computations. The optimal time characteristics of the predicted muscle forces for both solutions are presented. Some remarks concerning the efficiency of natural coordinates for solving optimal control problems are also included.
The research work aimed to identify and analyse reactions in the joints of the lower limb as well... more The research work aimed to identify and analyse reactions in the joints of the lower limb as well as in the intervertebral joints of the lumbar spine when lifting weights and making a squat. The determination of loads of the skeletal-muscular system involved the performance of simulations in the AnyBody software programme. Input data used in the research-related tests came from the tests concerning the kinematics of weightlifting by a weightlifter. The use of mathematical modelling and static optimisation methods made it possible to identify resultant responses in the joints in individual positions of a squat made under various external loads. The highest resultant responses in all of the joints subjected to analysis were identified at an angle of \(135^{\circ }\) in knee joints. As a result, it is important to pay attention during training not to stop moving during an exercise at the above-named angle.
PURPOSE The state of athletes' muscles is not constant, but it differs depending on the stage... more PURPOSE The state of athletes' muscles is not constant, but it differs depending on the stage of sports training, which is associated with different degrees of muscle fatigue. There is thus a need to find a non-invasive and simple method to assess muscle fatigue. The aim of the study was to determine the relationship between muscle fatigue due to physical effort and changes in skin temperature, measured using a thermographic camera. METHODS The study involved 12 volleyball players. The participants were to maintain 70% of peak torque in the joint for as long as possible. We measured peak torque and the time of maintaining 70% of its value (tlim) as well as continuously recording skin temperature and electromyographic (EMG) signals in the region of the belly of the rectus femoris. The measurements were taken twice: before and after a series of squats. RESULTS The study found that tlim decreased when isometric contraction was per- formed after physical effort. Pre- and post-exerci...
The primary aim of the current study was to determine the time curves of changes in the record sc... more The primary aim of the current study was to determine the time curves of changes in the record scores in the snatch and its variations during a two-year training cycle in young weightlifters. This study also aimed at assessing the ratios between these scores and at predicting the snatch record scores at the end of the subsequent annual training macrocycle. The final purpose was to compare the record scores with the isometric peak torque values of the trunk and knee extensors. The study involved 16 weightlifters who were tested seven times at three-month intervals. The overall mean ratios of the record scores in the hang snatch to those in the snatch and the record scores in the hang power snatch to those in the snatch were approximately constant and amounted to 0.95 and 0.79, respectively. The overall mean ratio between the scores in the power snatch to those in the snatch was approximately 0.88. Statistically significant differences (p < 0.05) between the individual time trajectories of record scores in the snatch and its derivatives were identified in two consecutive annual training macrocycles. The error in predicting record results at the end of the following annual training macrocycle was 6.7 ± 4.7% or 8.1 ± 3.4% depending on the way the measurement data were modeled. The results of the study also indicate that the measurements of the isometric peak torque of the trunk extensors performed in laboratory conditions can be useful in diagnosing the strength capacity of young weightlifters.
Introduction. The aim of the study was to determine the changes in the peak torque of the knee ex... more Introduction. The aim of the study was to determine the changes in the peak torque of the knee extensors and flexors of the dominant lower limb, the shoulder internal and external rotators of the dominant upper limb, and the shoulder extensors and flexors of the dominant upper limb as well as the changes in jump height in volleyball players during the annual training macrocycle. Material and methods. The study involved 13 volleyball players from a Polish second-league team. The measurements were performed five times: before the preparation period (T1), at the beginning of the competitive season (T2), in the middle (T3) and at the end of the first competition period (T4), and after the competitive season (T5). The torque of the knee muscles and shoulder rotators was measured in isokinetic conditions, and the torque of the shoulder extensors and flexors was assessed in isometric conditions. Jumping ability was tested using a piezoelectric platform. Results. We observed statistically s...
International Journal of Structural Stability and Dynamics
The aim of this paper is to present the results of an assessment of internal loads in the joints ... more The aim of this paper is to present the results of an assessment of internal loads in the joints of the lower limbs during the snatch performed by young weightlifters. A planar model of a weightlifter composed of 7 rigid segments (the lower trunk, thighs, lower legs and feet) connected by six hinge joints was used in the computations. The dynamic equations of the motion of the model were obtained using a projective technique. Kinematic data were recorded by a Vicon system with a sampling frequency of 200 Hz. The ground reactions were measured independently for the left and right limbs on two force platforms. The inverse dynamics problem was solved to assess the internal loads (the muscle forces and joint reactions) in the lower limbs. Relatively high differences in the reactions in the joints and muscle forces in the left and right lower extremities were identified. The obtained results also reveal that the snatch, a lift which tends to be geometrically symmetrical in the sagittal p...
The purpose of the current study was to assess the effectiveness of rehabilitation in patients af... more The purpose of the current study was to assess the effectiveness of rehabilitation in patients after anterior cruciate ligament reconstruction (ACLR) using a wavelet analysis of the torque-time curve patterns of the extensors of the affected knee. The analysis aimed at the quantitative evaluation of irregularities in these torque-time patterns. The study involved a group of 22 men who had had ACL reconstruction. The torque-time characteristics were recorded 3, 6 and 12 months after the surgery by an isokinetic dynamometer. They were then examined using the orthogonal Daubechies 4 (Db 4) and biorthogonal Bior 3.1 wavelets. A statistical analysis of the results revealed significant differences in values of the high-frequency energy stored in the details of the signal from the dynamometer between the first and last measurements, both for the Db 4 ( p ≤ 0.023) and Bior 3.1 ( p ≤ 0.01) wavelets. These differences were found in 73% of patients whose curve patterns were analysed using the ...
Introduction. The aim of the current study was to examine the relationship between knee and elbow... more Introduction. The aim of the current study was to examine the relationship between knee and elbow isometric muscle torque values and the results obtained in special and specific exercises in young weightlifters. Material and methods. The study involved eight young weightlifters (age: 19.9 ± 4.3 years; height: 176.8 ± 10.6 cm; weight: 69.0 ± 19.7 kg - pretest, 70.9 ± 21.6 - posttest). Their performance put them in the second and third top classes of weightlifters their age according to the Polish norms for weightlifting (the so-called ‘national class’ and ‘first class’ in the Polish system, which are lower than the ‘international class’). The differences between the values obtained in the first measurement of torque performed at the beginning of the preparation period and those obtained at the beginning of the immediate pre-competition period were compared with the differences in the maximal load lifted in special and specific exercises. Results. The training that the weightlifters u...
The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knee... more The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Significant differences (p 0.05) in peak knee extension and flexion torques, hamstring/quadriceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identified. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninvolved knee joint. The results helped to evaluate the progress of the rehabilitation and to implement necessary modifications optimizing the rehabilitation training program. The results of the study may also be used as referential data for physically active males of similar age.
Introduction. The aim of the study was to determine the torque of the knee extensors and flexors ... more Introduction. The aim of the study was to determine the torque of the knee extensors and flexors of the lead lower limb, the torque of the shoulder extensors and flexors of the dominant upper limb, and the torque generated by the muscles of the kinematic chain going from the trail lower limb to the hand of the dominant limb in male handball players during the annual training macrocycle. Changes in jump height and throwing velocity were also investigated. Material and methods. The study involved 13 handball players from a Polish second-league team. The measurements were performed four times: at the beginning of the preparation period, at the beginning of the season, at the end of the first part of the season, and at the end of the second part of the season. Torque was measured in isokinetic and isometric conditions. Jumping ability was tested using a piezoelectric platform, and throwing velocity was measured with a speed radar gun. Results. The study found statistically significant d...
Acta of bioengineering and biomechanics / Wrocław University of Technology, 2008
The assumption that optimization results depend on coordinate system selected to describe a biome... more The assumption that optimization results depend on coordinate system selected to describe a biomechanical model is tested by comparing two solutions obtained with generalized and natural coordinate systems. A 5-degrees of freedom planar musculoskeletal model actuated by 9 Hill-type musculotendon units was created to simulate lifting a leg up. Each individual muscle force was discretized into a set of independent design variables, and an inverse dynamic parameter optimization method was used in the computations. The optimal time characteristics of the predicted muscle forces for both solutions are presented. Some remarks concerning the efficiency of natural coordinates for solving optimal control problems are also included.
The paper analyzes the use of natural coordinates in modeling and simulation of musculoskeletal m... more The paper analyzes the use of natural coordinates in modeling and simulation of musculoskeletal models of the human body. A biomechanical model of the lower extremity of the human body was constructed for the analysis. It consists of three anatomical segments described by eight natural coordinates located at the joints. The developed model was applied to solve three classic dynamics problems of human motion: inverse dynamics, direct dynamics, and static optimization. The analysis covers the raising of a leg together with; the time characteristics of the resultant net torques at the basic joints of the leg (inverse dynamics), the time histories of natural coordinates and their velocities (direct dynamics) as well as the time-varying muscle force patterns (static optimization). In order to check the numerical efficiency of modeling in the natural coordinates' environment the results were compared with the ones received through generalized coordinates. Some conclusions drawn from this comparison and final remarks referring to the biomechanical identification of the analyzed motor task were included in the paper. r
The study of spatial human movements requires the development and use of a three-dimensional mode... more The study of spatial human movements requires the development and use of a three-dimensional model. The model proposed here has 44 degrees-of-freedom and it is described using natural coordinates, which do not require an explicit definition of rotation coordinates. The biomechanical model con-sists of 16 anatomical segments composed of 33 rigid bodies. Joint actuators are introduced into equations of motion of the multibody model by means of kinematic driver constraints in order to reflect the effect of the muscle forces about each anatomical joint. After associating a Lagrange multiplier to each joint actuator, the torques that represent muscle forces become coupled with the biomechanical model through the Jacobian matrix of the underlying mul-tibody system. The developed model is applied to identify net torques and reaction forces at the anatomical joints in application cases that include the take-off to aerial trajectories and standing backwards somersault.
This study presents an inverse dynamic parametric optimization method for solving optimal control... more This study presents an inverse dynamic parametric optimization method for solving optimal control problems involving planar biomechanical linkages. Two biomechanical models of the human lower leg have been defined in generalized and natural coordinates to validate the method in different modeling conditions. Both models are composed of three anatomical segments representing the thigh, shank and foot. The configuration of the models is described by five generalized, and eight natural coordinates. After solving the inverse dynamic problem, a parametric optimization was applied to find the optimal control. The optimization criterion was to minimize the performance time of a karate kick. The velocities were chosen as state variables. The starting and final configuration of the leg, which formed the boundary conditions of the movement, were in accordance with video recordings. A sequential quadratic programming method (SQP) was used in the computations. The optimal time characteristics o...
The Journal of sports medicine and physical fitness, 2012
The purpose of this study was to examine how focusing attention during nine weeks of plyometric t... more The purpose of this study was to examine how focusing attention during nine weeks of plyometric training influence jumping performance. It was hypothesized that participants utilizing an external focus of attention during practice would produce greater improvements in jumping behavior compared to participants practicing in the internal and control conditions. Thirty-six untrained but physically active male college students were randomly assigned to 1 of 3 plyometric groups with a different focus of attention: external (EXF; N.=12), internal (INF; N.=12), and control (CON; N.=12). All participants subsequently participated in the same an 9-week periodized training program. Standing long jump (SLJ), countermovement jump (CMJ) and drop jump (DJ) were tested pre- and posttraining intervention. The EXF group exhibited greater improvement (P<0.05) in jumping distance for SLJ and height for CMJ than both the INF and CON groups, while the enhancement in jumping height for DJ was not supe...
Introduction. The number of arthroscopic reconstructions of the anterior cruciate ligament (ACL) ... more Introduction. The number of arthroscopic reconstructions of the anterior cruciate ligament (ACL) has been increasing not only among competitive athletes, but also among recreational athletes. The monitoring of the rehabilitation process in order to determine a safe time to return to the pre-injury activity is thus of great practical importance. The aim of this paper is to analyse the changes in selected biomechanical variables which occur after the therapeutic training following an anterior cruciate ligament reconstruction. Materials and methods. Twenty nine males (age 27.3 ± 5.7 years) after the anterior cruciate ligament reconstruction participated in the study. A quadruple-stranded semitendinosus/gracilis graft was used for the reconstruction. The biomechanical evaluation of the rehabilitation process was provided by an isokinetic dynamometer Biodex System Pro-3 working at speeds of 60 deg/s and 180 deg/s during testing the knee extensor and flexor muscles. In the case of an injured limb, the absolute peak torque, relative peak torque, average power and hamstring/quadriceps (H/Q) ratio were determined. In addition, the values of flexor and extensor torques for healthy and injured limbs were compared. The study was carried out in four stages: before the surgery, three, six and twelve months after the surgery. Results and analyses. The results showed significant differences in each value between various stages of the biomechanical rehabilitation process of the knee. The applied therapeutic training influenced significantly the changes in the values of the tested variables. The results have confirmed that the biomechanical measurements can be treated as a supplementation to the clinical evaluation of the patient after ACL reconstruction. They may also be used for the optimisation of the therapeutic training.
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Papers by Adam Czaplicki