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Themistoklis Tsatalas

UNIVERSITY OF THESSALY, GREECE, DEPARTMENT OF PHYSICAL EDUCATION & SPORT SCIENCE, Post-Doc

Biomechanics +7

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Papers

Development and Usability of a Prototype Upper Extremities Lever-Driven Exercise System

BioMed

The purpose of this paper is to present the design, construction, and technical aspects of a prot... more The purpose of this paper is to present the design, construction, and technical aspects of a prototype upper extremities lever-driven exercise system, called FIT-WHEEL (Functional and Intelligent Training system for WHEELchair users), as well as the preliminary experimental measurements conducted to test the device’s usability in healthy individuals. FIT-WHEEL was developed to provide a training modality that combines the known benefits of eccentric exercise and lever-propelled wheelchairs. Eleven healthy male participants performed, seven days apart, a moderate intensity concentric and eccentric exercise protocol on FIT-WHEEL consisting of 30 trials of both upper extremities at 30% of peak concentric and peak eccentric force, respectively. At the end of each exercise bout, participants completed a number of valid and reliable instruments examining attitudes, intention and enjoyment during concentric or eccentric exercise on the FIT-WHEEL system as well as the usability of the two e...

Portable gait analysis sensor model for Parkinson’s disease

Materials Today: Proceedings

Tibial Rotation Under Combined In Vivo Loading After Single- and Double-Bundle Anterior Cruciate Ligament Reconstruction

Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2011

An Explainable Machine Learning Pipeline for Stroke Prediction on Imbalanced Data

Diagnostics

Stroke is an acute neurological dysfunction attributed to a focal injury of the central nervous s... more Stroke is an acute neurological dysfunction attributed to a focal injury of the central nervous system due to reduced blood flow to the brain. Nowadays, stroke is a global threat associated with premature death and huge economic consequences. Hence, there is an urgency to model the effect of several risk factors on stroke occurrence, and artificial intelligence (AI) seems to be the appropriate tool. In the present study, we aimed to (i) develop reliable machine learning (ML) prediction models for stroke disease; (ii) cope with a typical severe class imbalance problem, which is posed due to the stroke patients’ class being significantly smaller than the healthy class; and (iii) interpret the model output for understanding the decision-making mechanism. The effectiveness of the proposed ML approach was investigated in a comparative analysis with six well-known classifiers with respect to metrics that are related to both generalization capability and prediction accuracy. The best overa...

Leveraging explainable machine learning to identify gait biomechanical parameters associated with anterior cruciate ligament injury

Scientific Reports

Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics d... more Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics during gait. Identifying significant gait changes is important for understanding normal and ACL function and is typically performed by statistical approaches. This paper focuses on the development of an explainable machine learning (ML) empowered methodology to: (i) identify important gait kinematic, kinetic parameters and quantify their contribution in the diagnosis of ACL injury and (ii) investigate the differences in sagittal plane kinematics and kinetics of the gait cycle between ACL deficient, ACL reconstructed and healthy individuals. For this aim, an extensive experimental setup was designed in which three-dimensional ground reaction forces and sagittal plane kinematic as well as kinetic parameters were collected from 151 subjects. The effectiveness of the proposed methodology was evaluated using a comparative analysis with eight well-known classifiers. Support Vector Machines were...

Altered Drop Jump Landing Biomechanics Following Eccentric Exercise-Induced Muscle Damage

Sports, 2021

Limited research exists in the literature regarding the biomechanics of the jump-landing sequence... more Limited research exists in the literature regarding the biomechanics of the jump-landing sequence in individuals that experience symptoms of muscle damage. The present study investigated the effects of knee localized muscle damage on sagittal plane landing biomechanics during drop vertical jump (DVJ). Thirteen regional level athletes performed five sets of 15 maximal eccentric voluntary contractions of the knee extensors of both legs at 60°/s. Pelvic and lower body kinematics and kinetics were measured pre- and 48 h post-eccentric exercise. The examination of muscle damage indicators included isometric torque, muscle soreness, and serum creatine kinase (CK) activity. The results revealed that all indicators changed significantly following eccentric exercise (p < 0.05). Peak knee and hip joint flexion as well as peak anterior pelvic tilt significantly increased, whereas vertical ground reaction force (GRF), internal knee extension moment, and knee joint stiffness significantly dec...

Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks

Applied Sciences

The present study pertains to a key aspect of human-robot collaborative systems which is usually ... more The present study pertains to a key aspect of human-robot collaborative systems which is usually underestimated, namely occupational health prolepsis. The aim of this investigation was to assess the biomechanical effects of manual symmetric load lifting related to a synergistic agricultural task that utilizes an unmanned ground vehicle to undertake the carriage of loads. Towards that goal, kinetic and kinematic data were collected from the lower extremities of thirteen experienced workers, by testing three different deposit heights (70, 80, 90 cm) corresponding to possible adjustments of the available agricultural robot. Moreover, the muscle activation levels of three lower extremity muscles and one trunk muscle were evaluated via a wireless electromyography system. Overall, the experimental findings revealed that the lower examined load height was associated with larger knee flexion moments and hip extension moments. Nevertheless, this height was related to lower activation mainly ...

The acute effects of free-weight and elastic band back squat exercise on subsequent vertical jump performance

Introduction: The back squat exercise is a fundamental exercise for the development of lower limb... more Introduction: The back squat exercise is a fundamental exercise for the development of lower limb strength and power. However, in successful attempts of one repetition maximum (1-RM), the upward barbell movement decelerates for a short period referred to as the “sticking point”. The inclusion of elastic bands (EB) minimises the loading during the early concentric phase, while maintaining average loading throughout the lift may limit the impact of the sticking point and enables the athlete to work more closely to maximal throughout a greater range of the lift. Objective: To examine the inﬂuence of free-weight resistance (FWR) and EB squat exercise following a comprehensive warm-up on subsequent vertical jump (VJ) performance. Hypothesis: The use of EB during squatting following a comprehensive warm-up would:- (a) enhance subsequent VJ performance; (b) alter VJ mechanics; and (c) increase the neuromuscular activity of the lower limb extensor muscles, when compared to FWR. Methods: Fif...

Η επίδραση του μυϊκού τραυματισμού στα εμβιομηχανικά χαρακτηριστικά της βάδισης και του τρεξίματος

Κλινική ανάλυση βάδισης

ΑΣΚΗΣΗ ΚΑΙ ΥΓEΙΑ ΙΙ [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ EΠΙΣΤΗΜΗΣ ΦΥΣΙΚΗΣ ΑΓΩΓΗΣ ΚΑΙ ΑΘΛΗΤΙΣΜΟΥ, ΤΜΗΜΑ... more

Manual for the Physical Evaluation of Special Populations: Laboratory and Field Tests for the Scientific Support of Health Exercise Programs

Variable, but not free-weight, loaded countermovement jump exercise potentiates jump performance following a comprehensive task-specific warm-up

Commercially Available Sensor-based Monitoring and Support Systems in Parkinson's Disease: An Overview

Parkinson's disease is a progressive neurodegenerative disorder correlating with dysfunction ... more Parkinson's disease is a progressive neurodegenerative disorder correlating with dysfunction or deprivation of brains dopaminergic neurons, lack of dopamine, and the formation of abnormal protein particles. There are several clinical tests for detection of Parkinson's disease, but nowadays a demand is rising for an objective assessment of symptoms and health-related outcomes. The rapid development of sensor-based technological devices permits conducting measurements without bias that they are able to be used in scientific research and clinical practice. This paper provides a technical overview of the available commercial wearable systems for monitoring and supporting Parkinson's disease management, taking into account their validity and reliability. The understanding of the current state-of-the-art could help patients and clinicians significantly improve Parkinson's disease management by minimizing health care costs and increasing patient's quality of life.

Upper-Body Posture in Adolescent Pianists: A Cross-Sectional Study

Medical Problems of Performing Artists

AIMS: Although the significance of upper-body posture in relation to piano performance has often ... more AIMS: Although the significance of upper-body posture in relation to piano performance has often been highlighted, the role of experience remains unclear. The aim of this study was to examine selected upper body posture parameters in adolescent piano students of different performance level (beginners vs advanced). METHODS: Thirteen (13) adolescent piano students (14.7±0.5 yrs; 7 beginners and 6 advanced) volunteered. They all performed two specific major scales (G-major and E-major) in five octaves in two predetermined different tempi (slow and fast). An upper body biomechanical model consisting of 27 reflective markers was applied on specific bony landmarks. A 10-T camera Vicon system running Nexus 2 was employed to capture upper body motion—-a) sway of the trunk in relation to the instrument, b) finger/hand sway over the keyboard, c) overall hand movement, and d) spinal angles—-at selected moments of four different performances. RESULTS: Beginners demonstrated more trunk sway than...

The effects of training with high‐speed interval running on muscle performance are modulated by slope

Physiological Reports

We examined changes in selected muscle performance parameters after 8 weeks of interval training ... more We examined changes in selected muscle performance parameters after 8 weeks of interval training using two opposite running inclinations. We hypothesized that the uphill training will affect endurance muscle performance outcomes, whereas the downhill training will affect power muscle performance outcomes. Fourteen physically active volunteers were randomly assigned into either the Uphill group (UG; n = 7; uphill interval running at +10% incline) or the Downhill group (DG; n = 7; downhill interval running at −10% incline) and completed 16 training sessions. Each session consisted of ten 30 s treadmill runs at 90% of maximum aerobic speed (MAS) with a work to rest ratio of 1:2. Vertical jump performance, isometric (MVC) and isokinetic torque of knee extensors and flexors, and fatigue of knee extensors were evaluated pre and post‐training. Moreover, body composition (via bioimpedance) and vastus lateralis muscle architecture (via ultrasonography) were assessed pre and post‐training. Relative lean tissue mass, relative fat mass, and squat jump (cm) significantly (p < .05) changed from baseline values by +4.5 ± 4.0%, −11.5 ± 9.6%, and +9.5 ± 11.7%, respectively, only in the DG. Similarly, DG improved absolute values of knee extension rate of torque development and impulse (p < .05), whereas knee flexion peak torque angle significantly decreased in both groups (p < .05). On the other hand, the UG increased the number of repetitions achieved during the fatigue protocol and total work by 21.2 ± 32.6% and 13.8 ± 21.2%, respectively (p < .05). No differences were found between groups in muscle architecture. Introducing variations in slope during HIIT could be used to induce specific improvements toward muscle endurance or power performance characteristics.

Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up

Scandinavian Journal of Medicine & Science in Sports

The acute effects of an intense stretch-shortening cycle fatigue protocol on the neuromechanical parameters of lower limbs in men and prepubescent boys

Journal of Sports Sciences

ABSTRACT The study examined the differences between boys and adults after an intense stretch-shor... more ABSTRACT The study examined the differences between boys and adults after an intense stretch-shortening cycle fatigue protocol on neuromechanical parameters of the lower limb. Thirteen boys (9–11 years old) and 13 adult men (22–28 years old) were tested for maximal isometric voluntary knee extension torque and drop jump (DJ) performance from 30 cm before and immediately after a fatigue protocol, consisted of 10 × 10 maximum effort vertical jumps. Three-dimensional kinematics, kinetics and electromyographic (EMG) parameters of the lower extremities muscles were recorded during DJs before and after the fatigue test. The results indicated that reduction in maximal isometric torque and jumping performance was significantly higher in adults compared to boys. Vertical ground reaction forces, contact time and maximum knee flexion increased in a greater extend in adults than in boys. In addition, preactivation, EMG agonist activity, knee joint stiffness and stretch reflex decreased more in adults than in boys at all the examined phases of jumping tasks. It is concluded that employed fatigue protocol induced acute reduction in performance and altered motor control during jumping in both age groups. However, the differences in the level of fatigue between the 2 groups could be attributed to neuromuscular, mechanical and kinematic parameters observed between groups.

The Effects of a Stretch-Shortening Cycle Fatigue Protocol on Knee Kinematics During Running in Untrained Children

ABSTRACT

Biomechanics of sit-to-stand transition after muscle damage

The purpose of the study was to examine the effects of exercise-induced muscle damage on the biom... more The purpose of the study was to examine the effects of exercise-induced muscle damage on the biomechanics of the sit-to-stand transition (STST). Seventeen volunteers participated in an intense, eccentric based, muscle damage protocol of knee flexors and extensors via an isokinetic dynamometer. Kinematic and kinetic data were collected using a 10-camera optoelectronic system and a force plate 24h before and 48h after exercise. Statistical analysis showed significant differences in kinematic and kinetic parameters after exercise. Forty-eight hours after exercise, the strategy did change and the knee joint relative effort level increased significantly. Pelvic and hip kinematics, in conjunction with the knee extension joint moment, provided an efficient mechanism to support the participants&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; locomotor system during the STST. These results may be of great significance in designing supportive devices, as well as composing rehabilitation programs for young or elderly individuals, with various musculoskeletal pathologies.

Walking kinematics and kinetics following eccentric exercise-induced muscle damage

Development and Usability of a Prototype Upper Extremities Lever-Driven Exercise System

BioMed

The purpose of this paper is to present the design, construction, and technical aspects of a prot... more The purpose of this paper is to present the design, construction, and technical aspects of a prototype upper extremities lever-driven exercise system, called FIT-WHEEL (Functional and Intelligent Training system for WHEELchair users), as well as the preliminary experimental measurements conducted to test the device’s usability in healthy individuals. FIT-WHEEL was developed to provide a training modality that combines the known benefits of eccentric exercise and lever-propelled wheelchairs. Eleven healthy male participants performed, seven days apart, a moderate intensity concentric and eccentric exercise protocol on FIT-WHEEL consisting of 30 trials of both upper extremities at 30% of peak concentric and peak eccentric force, respectively. At the end of each exercise bout, participants completed a number of valid and reliable instruments examining attitudes, intention and enjoyment during concentric or eccentric exercise on the FIT-WHEEL system as well as the usability of the two e...

Portable gait analysis sensor model for Parkinson’s disease

Materials Today: Proceedings

Tibial Rotation Under Combined In Vivo Loading After Single- and Double-Bundle Anterior Cruciate Ligament Reconstruction

Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2011

An Explainable Machine Learning Pipeline for Stroke Prediction on Imbalanced Data

Diagnostics

Stroke is an acute neurological dysfunction attributed to a focal injury of the central nervous s... more Stroke is an acute neurological dysfunction attributed to a focal injury of the central nervous system due to reduced blood flow to the brain. Nowadays, stroke is a global threat associated with premature death and huge economic consequences. Hence, there is an urgency to model the effect of several risk factors on stroke occurrence, and artificial intelligence (AI) seems to be the appropriate tool. In the present study, we aimed to (i) develop reliable machine learning (ML) prediction models for stroke disease; (ii) cope with a typical severe class imbalance problem, which is posed due to the stroke patients’ class being significantly smaller than the healthy class; and (iii) interpret the model output for understanding the decision-making mechanism. The effectiveness of the proposed ML approach was investigated in a comparative analysis with six well-known classifiers with respect to metrics that are related to both generalization capability and prediction accuracy. The best overa...

Leveraging explainable machine learning to identify gait biomechanical parameters associated with anterior cruciate ligament injury

Scientific Reports

Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics d... more Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics during gait. Identifying significant gait changes is important for understanding normal and ACL function and is typically performed by statistical approaches. This paper focuses on the development of an explainable machine learning (ML) empowered methodology to: (i) identify important gait kinematic, kinetic parameters and quantify their contribution in the diagnosis of ACL injury and (ii) investigate the differences in sagittal plane kinematics and kinetics of the gait cycle between ACL deficient, ACL reconstructed and healthy individuals. For this aim, an extensive experimental setup was designed in which three-dimensional ground reaction forces and sagittal plane kinematic as well as kinetic parameters were collected from 151 subjects. The effectiveness of the proposed methodology was evaluated using a comparative analysis with eight well-known classifiers. Support Vector Machines were...

Altered Drop Jump Landing Biomechanics Following Eccentric Exercise-Induced Muscle Damage

Sports, 2021

Limited research exists in the literature regarding the biomechanics of the jump-landing sequence... more Limited research exists in the literature regarding the biomechanics of the jump-landing sequence in individuals that experience symptoms of muscle damage. The present study investigated the effects of knee localized muscle damage on sagittal plane landing biomechanics during drop vertical jump (DVJ). Thirteen regional level athletes performed five sets of 15 maximal eccentric voluntary contractions of the knee extensors of both legs at 60°/s. Pelvic and lower body kinematics and kinetics were measured pre- and 48 h post-eccentric exercise. The examination of muscle damage indicators included isometric torque, muscle soreness, and serum creatine kinase (CK) activity. The results revealed that all indicators changed significantly following eccentric exercise (p < 0.05). Peak knee and hip joint flexion as well as peak anterior pelvic tilt significantly increased, whereas vertical ground reaction force (GRF), internal knee extension moment, and knee joint stiffness significantly dec...

Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks

Applied Sciences

The present study pertains to a key aspect of human-robot collaborative systems which is usually ... more The present study pertains to a key aspect of human-robot collaborative systems which is usually underestimated, namely occupational health prolepsis. The aim of this investigation was to assess the biomechanical effects of manual symmetric load lifting related to a synergistic agricultural task that utilizes an unmanned ground vehicle to undertake the carriage of loads. Towards that goal, kinetic and kinematic data were collected from the lower extremities of thirteen experienced workers, by testing three different deposit heights (70, 80, 90 cm) corresponding to possible adjustments of the available agricultural robot. Moreover, the muscle activation levels of three lower extremity muscles and one trunk muscle were evaluated via a wireless electromyography system. Overall, the experimental findings revealed that the lower examined load height was associated with larger knee flexion moments and hip extension moments. Nevertheless, this height was related to lower activation mainly ...

The acute effects of free-weight and elastic band back squat exercise on subsequent vertical jump performance

Introduction: The back squat exercise is a fundamental exercise for the development of lower limb... more Introduction: The back squat exercise is a fundamental exercise for the development of lower limb strength and power. However, in successful attempts of one repetition maximum (1-RM), the upward barbell movement decelerates for a short period referred to as the “sticking point”. The inclusion of elastic bands (EB) minimises the loading during the early concentric phase, while maintaining average loading throughout the lift may limit the impact of the sticking point and enables the athlete to work more closely to maximal throughout a greater range of the lift. Objective: To examine the inﬂuence of free-weight resistance (FWR) and EB squat exercise following a comprehensive warm-up on subsequent vertical jump (VJ) performance. Hypothesis: The use of EB during squatting following a comprehensive warm-up would:- (a) enhance subsequent VJ performance; (b) alter VJ mechanics; and (c) increase the neuromuscular activity of the lower limb extensor muscles, when compared to FWR. Methods: Fif...

Η επίδραση του μυϊκού τραυματισμού στα εμβιομηχανικά χαρακτηριστικά της βάδισης και του τρεξίματος

Κλινική ανάλυση βάδισης

ΑΣΚΗΣΗ ΚΑΙ ΥΓEΙΑ ΙΙ [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ EΠΙΣΤΗΜΗΣ ΦΥΣΙΚΗΣ ΑΓΩΓΗΣ ΚΑΙ ΑΘΛΗΤΙΣΜΟΥ, ΤΜΗΜΑ... more

Manual for the Physical Evaluation of Special Populations: Laboratory and Field Tests for the Scientific Support of Health Exercise Programs

Variable, but not free-weight, loaded countermovement jump exercise potentiates jump performance following a comprehensive task-specific warm-up

Commercially Available Sensor-based Monitoring and Support Systems in Parkinson's Disease: An Overview

Parkinson's disease is a progressive neurodegenerative disorder correlating with dysfunction ... more Parkinson's disease is a progressive neurodegenerative disorder correlating with dysfunction or deprivation of brains dopaminergic neurons, lack of dopamine, and the formation of abnormal protein particles. There are several clinical tests for detection of Parkinson's disease, but nowadays a demand is rising for an objective assessment of symptoms and health-related outcomes. The rapid development of sensor-based technological devices permits conducting measurements without bias that they are able to be used in scientific research and clinical practice. This paper provides a technical overview of the available commercial wearable systems for monitoring and supporting Parkinson's disease management, taking into account their validity and reliability. The understanding of the current state-of-the-art could help patients and clinicians significantly improve Parkinson's disease management by minimizing health care costs and increasing patient's quality of life.

Upper-Body Posture in Adolescent Pianists: A Cross-Sectional Study

Medical Problems of Performing Artists

AIMS: Although the significance of upper-body posture in relation to piano performance has often ... more AIMS: Although the significance of upper-body posture in relation to piano performance has often been highlighted, the role of experience remains unclear. The aim of this study was to examine selected upper body posture parameters in adolescent piano students of different performance level (beginners vs advanced). METHODS: Thirteen (13) adolescent piano students (14.7±0.5 yrs; 7 beginners and 6 advanced) volunteered. They all performed two specific major scales (G-major and E-major) in five octaves in two predetermined different tempi (slow and fast). An upper body biomechanical model consisting of 27 reflective markers was applied on specific bony landmarks. A 10-T camera Vicon system running Nexus 2 was employed to capture upper body motion—-a) sway of the trunk in relation to the instrument, b) finger/hand sway over the keyboard, c) overall hand movement, and d) spinal angles—-at selected moments of four different performances. RESULTS: Beginners demonstrated more trunk sway than...

The effects of training with high‐speed interval running on muscle performance are modulated by slope

Physiological Reports

We examined changes in selected muscle performance parameters after 8 weeks of interval training ... more We examined changes in selected muscle performance parameters after 8 weeks of interval training using two opposite running inclinations. We hypothesized that the uphill training will affect endurance muscle performance outcomes, whereas the downhill training will affect power muscle performance outcomes. Fourteen physically active volunteers were randomly assigned into either the Uphill group (UG; n = 7; uphill interval running at +10% incline) or the Downhill group (DG; n = 7; downhill interval running at −10% incline) and completed 16 training sessions. Each session consisted of ten 30 s treadmill runs at 90% of maximum aerobic speed (MAS) with a work to rest ratio of 1:2. Vertical jump performance, isometric (MVC) and isokinetic torque of knee extensors and flexors, and fatigue of knee extensors were evaluated pre and post‐training. Moreover, body composition (via bioimpedance) and vastus lateralis muscle architecture (via ultrasonography) were assessed pre and post‐training. Relative lean tissue mass, relative fat mass, and squat jump (cm) significantly (p < .05) changed from baseline values by +4.5 ± 4.0%, −11.5 ± 9.6%, and +9.5 ± 11.7%, respectively, only in the DG. Similarly, DG improved absolute values of knee extension rate of torque development and impulse (p < .05), whereas knee flexion peak torque angle significantly decreased in both groups (p < .05). On the other hand, the UG increased the number of repetitions achieved during the fatigue protocol and total work by 21.2 ± 32.6% and 13.8 ± 21.2%, respectively (p < .05). No differences were found between groups in muscle architecture. Introducing variations in slope during HIIT could be used to induce specific improvements toward muscle endurance or power performance characteristics.

Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up

Scandinavian Journal of Medicine & Science in Sports

The acute effects of an intense stretch-shortening cycle fatigue protocol on the neuromechanical parameters of lower limbs in men and prepubescent boys

Journal of Sports Sciences

ABSTRACT The study examined the differences between boys and adults after an intense stretch-shor... more ABSTRACT The study examined the differences between boys and adults after an intense stretch-shortening cycle fatigue protocol on neuromechanical parameters of the lower limb. Thirteen boys (9–11 years old) and 13 adult men (22–28 years old) were tested for maximal isometric voluntary knee extension torque and drop jump (DJ) performance from 30 cm before and immediately after a fatigue protocol, consisted of 10 × 10 maximum effort vertical jumps. Three-dimensional kinematics, kinetics and electromyographic (EMG) parameters of the lower extremities muscles were recorded during DJs before and after the fatigue test. The results indicated that reduction in maximal isometric torque and jumping performance was significantly higher in adults compared to boys. Vertical ground reaction forces, contact time and maximum knee flexion increased in a greater extend in adults than in boys. In addition, preactivation, EMG agonist activity, knee joint stiffness and stretch reflex decreased more in adults than in boys at all the examined phases of jumping tasks. It is concluded that employed fatigue protocol induced acute reduction in performance and altered motor control during jumping in both age groups. However, the differences in the level of fatigue between the 2 groups could be attributed to neuromuscular, mechanical and kinematic parameters observed between groups.

The Effects of a Stretch-Shortening Cycle Fatigue Protocol on Knee Kinematics During Running in Untrained Children

ABSTRACT

Biomechanics of sit-to-stand transition after muscle damage

The purpose of the study was to examine the effects of exercise-induced muscle damage on the biom... more The purpose of the study was to examine the effects of exercise-induced muscle damage on the biomechanics of the sit-to-stand transition (STST). Seventeen volunteers participated in an intense, eccentric based, muscle damage protocol of knee flexors and extensors via an isokinetic dynamometer. Kinematic and kinetic data were collected using a 10-camera optoelectronic system and a force plate 24h before and 48h after exercise. Statistical analysis showed significant differences in kinematic and kinetic parameters after exercise. Forty-eight hours after exercise, the strategy did change and the knee joint relative effort level increased significantly. Pelvic and hip kinematics, in conjunction with the knee extension joint moment, provided an efficient mechanism to support the participants&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; locomotor system during the STST. These results may be of great significance in designing supportive devices, as well as composing rehabilitation programs for young or elderly individuals, with various musculoskeletal pathologies.

Walking kinematics and kinetics following eccentric exercise-induced muscle damage