For years track and field athletes have worn spiked shoes to enhance performance. This study was conducted to determine the effect of track spikes on hip, knee, and ankle peak joint moments (PJM) in collegiate and elite athletes while running. To measure differences in joint moments, ten intercollegiate and post graduate male distance runners from Brigham Young University ran at a four-minute-mile pace (6.7 m/s) across a force plate synched with infrared cameras tracking body positioning in each shoe condition. Repeated measures ANOVA (p < 0.05) revealed no significant peak joint differences between running shoes and track spikes. The minimum hip and peak knee PJM approached significance (F = 3.221, P = 0.116 and F = 2.875, P = 0.134 respectively). The high variability of joint moments between trials made it difficult to detect differences between conditions. The variability may be explained by any number of factors including: biomechanical differences in running form, running at high speeds, type of subjects, and potentially other factors.

The purpose of this study was to measure the change in joint energy of the hip,knee and ankle of the right and left leg, in the sagittal plane during the delivery phase of the rotational shot put. We hypothesized that (1) throwers who produced a greater total hip energy change would have greater horizontal displacement and (2) throwers who produced a higher ratio of hip energy, in each leg independently, would produce greater horizontal displacement. Subjects (n = 8) must have been right-handed, collegiate or post collegiate level throwers trained in the rotational technique. Vicon Nexus System (Denver, CO, USA) used six MX13+, two F20, two T20 cameras recorded at 240 Hz, and the body Plug-in Gait model to track the body position during each trial. Two AMTI force plates (OR-6, Watertown, MA, USA) were used for collecting ground reaction force data at 960 Hz. A linear regression analysis was performed to determine a relationship between total hip energy change and horizontal displacement. A mixed model regression was used to determine any correlation between horizontal distance and left and right energy change ratios. Athletes who produced a greater total hip energy change had the greatest horizontal displacement (p = .022). Also throwers who produced a higher ratio of left hip energy change to total left leg energy produced the greatest horizontal displacement (p = .02). The ratio of right hip energy change to right leg energy change was found to not be significant to horizontal displacement (p = .955). We feel the findings on the left leg energy change are an attempt by the athlete to both accelerate the shot put as well as stop the rotational progression to allow the athlete to complete a fair throw. The athlete extending both the right and the left hip rapidly during the delivery phase can help explain the combined right and left hip energy change. This action accelerates the ball in a proximal-distal sequence, which allows athletes to reach high final shot put velocities. The higher the final velocity on the shot put positively correlates with the horizontal displacement.

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

Parkinson's disease (PD) is a neurological condition that can lead to changes to gait and postural stability of people with this condition. Tai Chi (TC) has been recommended for the management of PD by improving muscle strength, balance, and coordination. However, biomechanics research in TC for PD is lacking. This thesis investigated the effects of a biomechanical-based TC intervention program for people in the early-stage of PD by realizing three specific research objectives: 1) to develop a biomechanical-based TC intervention program for PD; 2) to examine the effects of a 12-week TC intervention on gait and postural stability in people with PD, by pre-test and post-test biomechanical analysis of obstacle crossing; 3) to explore the neuromuscular effects of TC intervention on gait and postural stability by analyzing the electromyography (EMG) activity of the lower limb muscles during obstacle crossing. Seven typical TC movements were selected, including Starting Form, Hero Touch Sky, Push Hand Back, Brush Knee and Twist Step, Repulse Monkey, Wave-hand in Cloud, and Lateral Forward Step to develop the TC intervention program. The joint angles, joint moment, and EMG signals of lower limbs muscles were analyzed during performance of the selected TC movements by an experienced TC master aged 38 years. Results showed that the selected TC movements are characterized by multidirectional movements, greater joint movement angles of the lower limb, and more active muscle activity than walking. The TC intervention program was formed based on the biomechanics analysis of the seven TC movements. The program consisted of 5-10 min warm up, 40 minutes of core activities, and 5 min cool down. To examine the effects of a biomechanical-based TC intervention program on gait and postural stability and to explore the neuromuscular effects of TC intervention on the lower limb muscles in people with PD, fifteen individuals in the early stage of PD (n = 15, Hoehn and Yahr stages 1 to 2; age 72.0 ± 6.9) participated in a 12-week online TC intervention, and 15 age- and sex-matched healthy participants (n = 15) served as control. The 3D motion data of the lower limb and EMG signals from the rectus femoris, adductor longus, tibialis anterior, semitendinosus, gluteus medius, tensor fasciae latae, and medial and lateral gastrocnemius muscles were collected during obstacle crossing from both groups using Vicon motion analysis system before intervention in both groups and after TC intervention in the TC group. Obstacle crossing was used to challenge the participants' gait and postural stability. Gait was assessed by measuring the temporospatial parameters such as crossing stride length, crossing step length, and crossing speed. Postural stability was assessed by measuring toe and clearance distance, pre- and post-horizontal distance, displacement and velocity of center of mass (COM), and COM-center of pressure (COP) separation. To examine the neuromuscular activity of the lower limbs following TC training, the ratio of the peak EMG, the integrated EMG (iEMG), and the ratio of the peak EMG and iEMG antagonistic pairs of the leading and trailing limb were examined during obstacle crossing and walking. In addition, the timed up-and-go test (TUG) and single-leg stance with eyes open and closed were tested. VICON Nexus, custom MATLAB scripts, and SPSS software (version 20) were used to analyze the data. Analysis of the PD participants' obstacle crossing performance revealed that they had significantly slower gait speed, smaller hip flexion angles, and larger knee adduction angles of the trailing limb, significantly larger mediolateral (ML) COM displacement and COM-COP separation distance, and significantly higher peak EMG ratios of the adductor longus, gluteus medius, and tensor fasciae latae (p < 0.05) than the healthy participants. Following the 12-week TC intervention, the PD participants had significantly increased crossing stride length, significantly decreased ML COM-COP separation (p < 0.05) and significantly increased AP COM displacement (p < 0.05), and increased EMG activity of the tibialis anterior in the leading and trailing limbs during obstacle crossing, whereas the activity of the gluteus medius and adductor longus in the leading limb decreased (p < 0.05). Moreover, the significant differences in the EMG of the gluteus medius and tensor fasciae latae muscles between PD and healthy participants found in pre-test were no longer present. After the TC intervention, the PD participants significantly improved their performance on the TUG test (p = 0.002). Therefore, people with early-stage PD presented changed gait and postural stability as well as changed neuromuscular activity of the lower limb. The 12-week online biomechanical-based TC intervention improved their gait and postural stability, particularly dynamic postural stability as measured by the COM-COP separation in people with early-stage PD. Compared to walking, performing the TC movements involved larger changes in the lower limb angles, range of motion, and higher muscle activity, particularly in the hip abductors and adductors. These characteristics of the TC movements could provide training to strengthen the muscles and improve the range of motion of the lower limbs. The gait and postural stability improvements following TC intervention are consistent with the neuromuscular activity changes in gluteus medius, tensor fasciae latae, and adductor longus muscles, indicating the mechanisms of TC training. The 12-week online biomechanical-based TC intervention program helped to decrease the ML COM-COP separation distance and could be used for the management of PD in the early stages of this condition.

No description available.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / People who have suffered stroke often have difficulty during walking. One of the reasons is hemiplegia, which is the main motor impairment caused by stroke. Hemiplegia generates asymmeries in limb control that often can result in compensation and overload in one of the hemisphere, leaving individuals susceptible to joint moments and/or exaggerated in both affected and unaffected limbs. The objective of this study was to analyze joint mechanics during hemiplegic gait, post-stroke. The sample was composed of 28 hemiplegic subjects and 22 subjects without hemiplegia. Kinetic and kinematic gait magnitudes were obtained for subsequent calculation of joint moments via inverse dynamics method. The hemiplegic individuals were divided into two groups: fast group and slow group, according to their self selected speed adopted during the data collection, and subjects without hemiplegia took part of the third group. Comparisons were conducted between groups and between the affected and unaffected members in the hemiplegic group. The results showed similar joint moments patterns between hemiplegic individuals and subjects without hemiplegia. Nevertheless, a higher number of differences were found in joint moments between groups and it became more evident at the beginning of the stance phase. Few differences were found on comparisons between the affected and unaffected limbs within the hemiplegic group. We concluded that people who have suffered strokes are susceptible to changes in joint moments, being more evident in hemiplegic individuals who adopted a faster walking speed. It occurs because the walking speed is an intervening factor for the calculation of joint moments. / Pessoas que sofreram Acidente Vascular Encefálico (AVE) frequentemente apresentam dificuldade durante a marcha. Um dos motivos para tal é a hemiplegia, que é o principal comprometimento motor ocasionado pelo AVE. A hemiplegia gera assimetrias corporais que muitas vezes podem resultar em compensações e sobrecargas em um dos hemicorpos, deixando os indivíduos suscetíveis a momentos articulares desproporcionais e/ou exagerados nos membros afetado e não afetado. O objetivo deste estudo foi analisar a mecânica articular durante a marcha de hemiplégicos, pós-AVE. A amostra foi composta por 28 sujeitos hemiplégicos e 22 sujeitos sem hemiplegia. Foram obtidas grandezas cinéticas e cinemáticas da marcha para posterior cálculo dos momentos articulares utilizando o método de dinâmica inversa. Os indivíduos hemiplégicos foram divididos em dois grupos: grupo rápido e grupo lento, de acordo com a velocidade autosselecionada adotada, e os sujeitos sem hemiplegia constituíram o terceiro grupo. As comparações foram realizadas entre os três grupos e entre os membros afetado e não afetado do grupo hemiplégico. Os resultados mostraram curvas de momentos articulares similares para indivíduos hemiplégicos e sujeitos sem hemiplegia. Ainda assim, um maior número de diferenças foi encontrado nos momentos articulares entre grupos e estas se fizeram mais presentes no início da fase de apoio. Nas comparações entre os membros hemiplégico e não hemiplégico poucas diferenças foram encontradas. Conclui-se que pessoas que sofreram AVE estão suscetíveis a alterações nos momentos articulares, sendo estas alterações mais evidentes no grupo hemiplégico que adotou uma velocidade de caminhada mais rápida. Isso ocorre porque a velocidade de caminhada é um fator interveniente para o cálculo dos momentos articulares.

Background: Joint stability has been experimentally and clinically linked to mechanisms of knee injury and joint degeneration. The only dynamic, and perhaps most important, regulators of knee joint stability are contributions from muscular contractions. In participants with unstable knees, such as anterior cruciate ligament (ACL) injured, a range of neuromuscular adaptations has been observed including quadriceps weakness and increased co-activation of adjacent musculature. This co-activation is seen as a compensation strategy to increase joint stability. In fact, despite increased co-activation, instability persists and it remains unknown whether observed adaptations are the result of injury induced quadriceps weakness or the mechanical instability itself. Furthermore, there exists conflicting evidence on how and which of the neuromuscular adaptations actually improve and/or reduce knee joint stability. Purpose: The overall aim of this thesis is therefore to elucidate the role of injury and muscle weakness on muscular contributions to knee joint stability by addressing two main objectives: (1) to further our understanding of individual muscle contribution to internal knee joint moments; and (2) to investigate neuromuscular adaptations, and their effects on knee joint moments, caused by either ACL injury and experimental voluntary quadriceps inhibition (induced by pain). Methods: The relationship between individual muscle activation and internal net joint moments was quantified using partial least squares regression models. To limit the biomechanical contributions to force production, surface electromyography (EMG) and kinetic data was elicited during a weight-bearing isometric force matching task. A cross-sectional study design determined differences in individual EMG-moment relationships between ACL deficient and healthy controls (CON) groups. A crossover placebo controlled study design determined these differences in healthy participants with and without induced quadriceps muscle pain. Injections of hypertonic saline (5.8%) to the vastus medialis induced muscle pain. Isotonic saline (0.9%) acted as control. Effect of muscle pain on muscle synergies recruited for the force matching task, lunging and squatting tasks was also evaluated. Synergies were extracted using a concatenated non-negative matrix factorization framework. Results/Discussion: In CON, significant relationships of the rectus femoris and tensor fascia latae to knee extension and hip flexion; hamstrings to hip extension and knee flexion; and gastrocnemius and hamstrings to knee rotation were identified. Vastii activation was independent of moment generation, suggesting mono-articular vastii activate to produce compressive forces, essentially bracing the knee, so that bi-articular muscles crossing the hip can generate moments for the purpose of sagittal plane movement. Hip ab/adductor muscles modulate frontal plane moments, while hamstrings and gastrocnemius support the knee against externally applied rotational moments. Compared to CON, ACL had 1) stronger relationships between rectus femoris and knee extension, semitendinosus and knee flexion, and gastrocnemius and knee flexion moments; and 2) weaker relationships between biceps femoris and knee flexion, gastrocnemius and external knee rotation, and gluteus medius and hip abduction moments. Since the knee injury mechanism, is associated with shallow knee flexion angles, valgus alignment and rotation, adaptations after ACL injury are suggested to improve sagittal plane stability, but reduce frontal and rotational plane stability. During muscle pain, EMG-moment relationships of 1) semitendinosus and knee flexor moments were stronger compared to no pain, while 2) rectus femoris and tensor fascia latae to knee extension moments and 3) semitendinosus and lateral gastrocnemius to knee internal rotation moments were reduced. Results support the theory that adaptations to quadriceps pain reduces knee extensor demand to protect the joint and prevent further pain; however, changes in non-painful muscles reduce rotational plane stability. Individual muscle synergies were identified for each moment type: flexion and extension moments were respectively accompanied by dominant hamstring and quadriceps muscle synergies while co-activation was observed in muscle synergies associated with abduction and rotational moments. Effect of muscle pain was not evident on muscle synergies recruited for the force matching task. This may be due to low loading demands and/or a subject-specific redistribution of muscle activation. Similarly, muscle pain did not affect synergy composition in lunging and squatting tasks. Rather, activation of the extensor dominant muscle synergy and knee joint dynamics were reduced, supporting the notion that adaptive response to pain is to reduce the load and risk of further pain and/or injury. Conclusion: This thesis evaluated the interrelationship between muscle activation and internal joint moments and the effect of ACL injury and muscle pain on this relationship. Findings indicate muscle activation is not always dependent on its anatomical orientation as previous works suggest, but rather on its role in maintaining knee joint stability especially in the frontal and transverse loading planes. In tasks that are dominated by sagittal plane loads, hamstring and quadriceps will differentially activate. However, when the knee is required to resist externally applied rotational and abduction loads, strategies of global co-activation were identified. Contributions from muscles crossing the knee for supporting against knee adduction loads were not apparent. Alternatively hip abductors were deemed more important regulators of knee abduction loads. Both muscle pain and ACL groups demonstrated changes in muscle activation that reduced rotational stability. Since frontal plane EMG-moment changes were not present during muscle pain, reduced relationships between hip muscles and abduction moments may be chronic adaptions by ACL that facilitate instability. Findings provide valuable insight into the roles muscles play in maintaining knee joint stability. Rehabilitative/ preventative exercise interventions should focus on neuromuscular training during tasks that elicit rotational and frontal loads (i.e. side cuts, pivoting maneuvers) as well as maintaining hamstring balance, hip abductor and plantarflexor muscle strength in populations with knee pathologies and quadriceps muscle weakness.

During human walk, we balance internal muscle forces and external forces outside of the body, while trying to minimize physiological energetic expenditure and mechanical loading on the body. The biomechanics of walking can be affected by various factors, including body size. In individuals with greater body size, the ground reaction force increases, so it is expected that joint moment of the lower limb in individuals with greater body size should increases. However, this relationship is not always true - as documented by previous studies, larger individuals use moderating mechanisms in the form of postural adjustment of the lower limb which decreases the load on joints during walking. The aim of this diploma thesis is to investigate the effect of body size and posture on the biomechanics of walking in the stance phase of walking, and to verify the presence of moderating mechanisms. We obtained kinematic and kinetic data from nineteen probands. The data was collected during three types of walking - during normal walking, walking with extended knees and crouched walking. We used Visual3D software to calculate angles in joints and joints moments of the lower limb. The independent effect of body mass, lower limb length measured in Visual3D, lower limb length measured anthropometrically, biiliac...

Formål: Formålet med studiet er at undersøge hvordan løb med en dagligdagsprotese og en løbespecifikprotese påvirker kinetik i nedre ekstremiteter hos mennesker med en transtibial-amputation.   Metode: Kinetisk data blev indsamlet ved løbetests, med begge proteser, med et motion capture system og kraftplader i et klinisk ganganalyse lab i Göteborg, Sverige. Deltagere(n=2) udførte løbetests i selvvalgt hastighed, iført refleksive markører. Vertikal GRF, fod progressions vinkel, adducerende/abducerende hofte- og knæmoment udvalgt til videre databehandling.   Resultat: Forskelle i hofte- og knæ adduktions moment og fod progressions vinkel blev observeret mellem de to protesetyper. Momenterne var mindre, når deltagerne løb med den løbespecifikke protese. Forskelle på den amputerede side og den kontralaterale side noteredes ved alle parametre uanset protesetype. Den kontralaterale side havde forøgede værdier sammenlignet med den amputerede side.   Konklusion: Grundet forsøgets størrelse kan vi ikke konkludere, at individer med unilateral amputation i nedre ekstremitet absorberer belastning bedre, når de løber med en løbespecifikprotese fremfor en dagligdagsprotese. / Aim: The aim of this study was to investigate how running with a daily-use prosthesis and a running specific prosthesis affects kinetics in the lower extremities when it comes to people with a transtibial amputation.   Method: Kinetic data was collected through running tests, using both type of prosthesis, with a motion capture system and force plates in a clinical gait lab in Gothenburg, Sweden. Participants (n=2) executed the running tests in a self-selected speed, while wearing reflective markers. Vertical ground reaction force, foot progression angle, hip- and knee moment were selected for data processing.   Results: Differences in hip- and knee adduction moment and foot progression angle were observed between the two types of prostheses. Moments were smaller when participants ran with running-specific prosthesis. Dissimilarity for the amputated side and the contralateral side were noted for all parameters regardless of type of prosthesis. The contralateral side had increased values compared to the amputated side.     Conclusion: Because of the sample size we cannot conclude that individuals with a unilateral lower body amputation absorb load more efficiently when running with a running-specific prosthesis rather than a daily-use prosthesis.