The hands are essential for our ability to complete tasks. Quantifying the many forces acting on the entire hand is important to improve our understanding of hand function and hand-related musculoskeletal disorders. Biomechanical models of the hand used to compute internal tissue loads typically simplify the applied forces into a single point of force applied at the centre of mass of the distal phalanx. Accounting for the distributed loads across the hands and fingers is a needed step in understanding the loads acting on and inside the body. Therefore, the purpose of this thesis was to use a pressure mapping system to examine the effects of distributed loads on net joint moments and muscle activations in the hands during common tasks. Twenty-three right-handed participants completed a series of finger presses, power grips, and pinch tasks. A pressure mapping system measured pressure on 17 regions of the hand. Three- dimensional hand kinematics was collected using a 72-marker setup. Forces were also measured with a six degrees of freedom force transducer to ensure participants matched specified exertion levels. Pressure distribution, kinematics, and kinetics were used to calculate internal net joint moments at the fingers (distal phalangeal flexion, proximal phalangeal flexion, metacarpal flexion, metacarpal abduction) and muscle activations for 22 forearm and hand muscles using an OpenSim model. External loads were represented in three manners: (1) Centre of Mass Model (COM) distributed the forces over segments that contributed to the force production and placed loads at the centre of mass; (2) Centre of Pressure Model (COP) distributed the forces over segments that contributed to the force production and placed loads at the centre of pressure; (3) Single Point Model (SP) placed a single load at the distal phalanx or the centre of mass of the hand. Results of equivalence tests indicate differences in all net joint moments between COM-SP and COP-SP comparisons. There were no differences between COM and COP. COM and COP moments during all tasks were larger in digits with a larger percentage of total force compared to SP. Due to the larger moments in those conditions, COM and COP calculated larger muscle activities compared to SP. Both internal net joint moments and muscle activations were most affected by the pressure distribution and hand posture. Overall, these findings indicate that representing external forces using distributed loads provide increased fidelity of forces at the hand and fingers. Distributed loads provide more information on internal loads of the hand and digits, and in turn, quantify individual differences that can lead to injury in occupational settings. / Thesis / Master of Science in Kinesiology

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Previous research has shown that with advancing age, there are increasing incidences of slip and fall injuries. Understanding mechanisms associated with gait adjustments across a known slippery surface may help in proactively avoiding slips and falls. The primary goal of this study involved examination of gait parameters and muscle activity characteristics of the lower extremities during two different walking conditions. Research has shown that both physical and mental changes accompany the aging process in humans. Moreover, research has shown that emotions and physiological responses are related. A secondary goal of this study was to examine the relationships of fear of falling with gait parameters and muscle activity. This study consisted of exposing 14 younger and 14 older participants to controlled slippery conditions safely, while studying normal and adjusted gait characteristics (friction requirement, heel contact velocity, and step length) and muscle activity characteristics (Integrated EMG). First, a baseline measure was done to study normal gait prior to any exposure to slipping. A second measure was done following a slip from a contaminated floor surface, but before the initiation of a second slip. The results indicate that there were significant gait parameter differences between younger and older participants for both walking conditions. Results also indicate that there were differences in muscle activity between to the two age groups for the adjusted condition. Findings suggest that older individuals require an additional step to properly adjust gait for a contaminated walking surface. / Master of Science

Central nervous system stabilizes body in disturbance by means of anticipatory and compensatory postural adjustments to maintain stable position. Disturbance effects in joint are reduced by activation of agonist and antagonist forearm muscles, the muscles allow consistency by steady posture during shot. Studies showed the importance of posture in the shot, but without focus on the anticipatory and compensatory postural adjustments. The objective of this study was to analyze an electrical activity of archers during the shot an arrow with the bow. Participants consisted of 10 archers of the Brazilian National Team of archery. Electromyography captured electrical activity in 12 muscles. Accelerometer in handle indicated the beginning of the movement. Temporal pattern separated in 500 milliseconds pre and post clicker fall. Protocol started by Maximal Voluntary Isometric Contraction of 12 muscles. Archers release 3 blocks of 6-arrows in warm-up. Archers throw arrows for 12 blocks with 6-arrows with interval of 20 minutes after the block 6. One-way Analysis of Variance and Tukey Test compared temporal pattern. One-way Analysis of Variance with repeated measures compared temporal pattern and 6-arrows. Results showed that all muscles (except m. Lumbar Multifidus) increase in their demand with the proximity of the arrow release. The muscles decreased their activity due to reduced demand in compensatory and modulation phase. Comparison between 12 blocks of 6-arrows showed 3 ways of temporal pattern: 1) muscles affected by phases and muscles affected by all/any phases in the blocks of 6-arrows, 2) muscles affected by phases and muscles unaffected by all/any phases in the blocks of 6-arrows and 3) muscles unaffected by phases and muscles affected by all phases in the blocks of 6-arrows. Muscles were not affected by phases/blocks maintain muscle activity along intervals by similar muscular demand. Cross-correlation between motor muscles showed that forearm muscles obtained inverse relationship between them. Other motor muscles were strong correlation between them. Postural muscles m. Lumbar Multifidus, m. Latissimus Dorsi, m. Upper Trapezius were strong correlation with all postural muscles. Motor and postural muscles showed that m. Triceps Brachii, m. Pectoralis Major Clavicular Head and m. Posterior Deltoid showed strong correlation with all postural muscles. In conclusion, muscle activity increases in anticipatory phase and muscle activity decrease after clicker fall. There are 3 ways to compare phases and blocks: affected by phases and 1) muscles affected/2) muscles unaffected by all/any phases in the blocks of 6-arrows and 3) muscles unaffected by phases and affected by all phase in the blocks of 6-arrows. Correlation in motor muscles showed that forearm muscles obtained inverse relationship between them. Postural muscles m. Lumbar Multifidus, m. Latissimus Dorsi, m. Upper Trapezius were strong correlation with all postural muscles. Motor and postural muscles showed that m. Triceps Brachii, m. Pectoralis Major Clavicular Head and m. Posterior Deltoid showed strong correlation with all postural muscles / O sistema nervoso central estabiliza o corpo na perturbação por meio de ajustes posturais antecipatórios e compensatórios para manter a postura estável. Os efeitos da perturbação na articulação são reduzidos pela ativação dos músculos agonistas e antagonistas do antebraço, os músculos permitem a consistência no tiro pela postura estável. Os estudos mostram a importância da postura no tiro, mas não se concentrarem nos ajustes posturais antecipatórios e compensatórios. O objetivo desse estudo foi analisar a atividade elétrica muscular de arqueiros durante o atirar uma flecha com o arco. Os participantes foram 10 arqueiros da Seleção Brasileira de Tiro com Arco. A eletromiografia captou a atividade elétrica muscular de 12 músculos. O acelerômetro no punho indicou o início do movimento. As fases temporais foram separadas entre 500 milissegundos pré e pós queda do clicker. O protocolo iniciou pela Contração Isométrica Voluntária Máxima dos músculos. Arqueiros lançaram 3 séries de 6 flechas no aquecimento. Arqueiros lançaram 12 séries de 6 flechas com intervalo de 20 minutos após a série 6. Análise de Variância One-way e o Tukey compararam as fases temporais. Análise de Variância One-way com medida repetidas comparou as fases temporais e os blocos de 6 flechas. Os resultados mostraram que todos os músculos (exceção do m. Multifido Lombar) aumentaram a demanda com a proximidade de soltura da flecha. Os músculos diminuem sua atividade pela redução da sua demanda na fase compensatória e de modulação. A comparação entre blocos de 6 flechas mostrou 3 formas do padrão temporal: 1) músculos afetados pelas fases e músculos afetado por todos/alguns fases nos blocos de 6 flechas, 2) músculos afetados pelas fases e músculos não afetados por todos/alguns fases nos blocos de 6 flechas e 3) músculos não afetados pelas fases e músculos afetados por todas as fases nos blocos de 6 flechas. Os músculos não afetados fases pelas fases/blocos mantem a atividade elétrica muscular ao longo dos intervalos pela sustentação da demanda muscular. Correlação cruzada entre os músculos motores mostrou que os músculos do antebraço obtiveram relação inversa entre eles. Outros músculos motores apresentaram alta correlação entre eles. Músculos posturais m. Multifido Lombar, m. Latíssimo do Dorso, m. Trapézio Superior apresentaram alta correlação com todos os músculos posturais. Músculos motores e posturais mostraram que m. Tríceps Braquial, m. Peitoral Maior Clavicular e m. Deltoide Posterior teve alta correlação com todos os músculos posturais. Em conclusão, a atividade elétrica muscular aumenta a demanda na fase antecipatória e diminui na após queda do clicker. Existem 3 caminhos na comparação das fases e os blocos de 6 flechas: afetado pela fase e 1) músculo afetado/2) músculo não afetado por todos/algumas fases nos blocos, 3) músculo não afetado pelas fases e afetado por todos as fases nos blocos. A correlação cruzada entre os músculos motores mostrou que os músculos do antebraço obteram relação inversa entre eles. Músculos posturais m. Multifido Lombar, m. Latissimo do Dorso, m. Trapézio Superior foram altamente correlacionados com todos músculos posturais. Músculos posturais e motores mostraram que m. Triceps Brachial, m. Petoral Maior Clavicular e m. Deltoide Posterior mostraram alta correlação com todos os músculos posturais

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Human locomotion is phenomenon that is extraordinarily complex. It is evident that a complete description of locomotion involves consideration of kinematics, kinetics, and muscle activity of the extremities in all of their various movements. Race walking (RW) is a form of upright locomotion that differs from normal walking and running by its form dictated by the International Amateur Athletics Federation (IAAF). Despite the similarities to both normal walking (NW) and running (RU), RW has not been the subject of equally intensive investigations. This study explores the comprehensive biomechanics of race walking and how it compares to NW and RU. A quantitative approach was used to evaluate kinematic, kinetic and muscle activity variables between race walking and both normal walking and running. A cross-sectional, laboratory design was used on 15 recreationally competitive race walkers to evaluate these variables. Based on the results of this study, RW is an intermediate gait between NW and RU that has characteristics of both gaits, but is still a unique gait in itself. While there are differences between RW and both RU and NW, some of the expected differences between RW and the two gaits did not occur. Significantly greater frontal plane pelvis-trunk joint range of motion and sagittal plane peak hip flexor and extensor moments, hip joint range of motion and rectus femoris muscle activity contribute to the significant differences in both RW and NW, and RW and RU. Significant differences between RW and RU showed that RU requires more contribution from the trunk, pelvis and lower extremities kinematically and kinetically, as well as increased muscle activation, to execute the motion than RW. Conversely, RW requires more contribution from these variables than NW does, but in not as great a capacity as RU compared to RW. In spite of these findings, there were some variables that had no significant differences between RW and RU. This suggests that injuries during RW are similar to those during RU, but may not occur as frequently.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Patellofemoral pain (PFP) is believed to be associated with deficits in coordination between the different heads of the quadriceps muscle; however, considerable debate exists in the literature regarding the presence of such a deficit. Discrepancies between studies may be explained by differences in experimental tasks, such as whether the task is performed with open (OKC) or closed kinetic chain (CKC), or whether the activity is voluntary or triggered. Particular interest has been directed toward the function of the vastus medialis obliquus (VMO), which is a short muscle with limited ability to exert torque across the knee joint, but probably has a particular role in controlling patellofemoral joint position. Another short muscle that may influence knee joint position control is popliteus (POP), which is located in the back of the knee. This thesis investigates task specific activity of quadriceps in CKC versus OKC and studies the relative activity between the four heads of the quadriceps in PFP subjects compared to controls without knee pain in voluntary activity (CKC and OKC) and postural responses to balance perturbations. In addition, this thesis investigates the presumed function of POP for control of joint position in postural tasks in healthy individuals. All subjects were of normal weight and height and between 18 and 40 years. Quadriceps activity was tested for isometric with identical joint configuration in CKC and OKC, and it was performed as a reaction time task. Balance perturbations were elicited by unpredictable anterior and posterior translations of the support surface. Function of POP was investigated in unpredictable support surface translations and in self induced provocations to balance by moving the arms. Muscle activity was recorded with electromyography (EMG). Optic kinematic analysis was used to obtain specific movement responses to perturbations of balance. The quadriceps muscles were activated differently in CKC and OKC. VMO was activated earlier and to a greater degree in CKC. Rectus femoris was activated earlier and to a greater degree in OKC. PFP subjects reacted slower in both CKC and OKC, but there was no difference between groups in the relative activity between the different heads of the quadriceps. In the unpredictable support surface translation in the anterior direction, PFP subjects responded with earlier onset of VMO and with greater trunk and hip flexion in the anterior translation. POP activation in response to support surface translations in both directions occurred before all other muscles measured. In the self-initiated provocations of balance, POP was activated after the initiation of the balance provocation. This thesis concludes that quadriceps activity was task specific. The lack of difference between groups in OKC and CKC, and the difference between groups in postural responses suggest that variations in motor behaviour may occur only in tasks habitually performed. Differences in muscle activation patterns may be related to compensatory strategies to unload the quadriceps muscles and the patellofemoral joint. Furthermore, this thesis suggests that POP muscle may have a particular role in active control of the knee joint.

Headline: Swimming technique of physically disabled swimmers with unilateral above-knee amputation Aim of the Thesis: The aim of this thesis is to describe the intra-individual differences in the swimming technique of unilateral above-knee amputees by measuring the EMG of selected muscle groups. Methods: Surface EMG measurement in combination with using synchronized video recordings. Results: Research of the observed swimmers with unilateral above-knee amputation showed that: when swimming the front crawl, the swimmers unequally balance the intense kick of right and left leg mainly using the abdominal muscles and subsequently also in the electric potential of different sizes in other observed muscles; when swimming the backstroke, the upper body muscles on the side of amputated limb do not show any different activity than the muscles of the opposite side; when swimming the breaststroke, the main propulsion muscle for locomotion through the shoulder girdle - m. latissimus dorsi is activated for a longer period of time on the side of amputated limb; thereby, electrical activity of the selected muscles is not symmetrical in the timeline. Key words: swimming step, swimming, above-knee amputation, electromyography, muscle activity, handicap, EMG.