A variety of behavioural tests were used to examine both sensory and motor function of freely behaving unilaterally spinal cord-injured and uninjured rats. The first experiment was designed to determine whether sensory and motor differences existed between uninjured Fischer, Lewis, Long-Evans, Sprague-Dawley and Wistar rats using endpoint, quantitative kinematic, and kinetic measurements. The second experiment examined differences in sensorimotor responses to cervical spinal cord hemisection in Lewis, Long-Evans and Wistar rats. For the third experiment, reflex and locomotor abilities of unilateral cervical or thoracic spinal cord hemisected Long-Evans rats were determined using endpoint, semi-quantitative kinematic, and kinetic measurements. The fourth experiment was designed to investigate the importance of the rubrospinal tract and ascending dorsal column pathways to overground locomotion. This experiment was conducted to help explain the behavioural observations made following cervical spinal cord hemisection. Furthermore, this experiment examined the effects of combined unilateral rubrospinal and dorsal column injury on overground locomotion using endpoint and kinetic measurements. Finally, the fifth experiment set out to investigate the contribution of tracts running in the ventrolateral spinal cord on overground locomotion in freely behaving Long-Evans rats. These animals were assessed using endpoint and kinetic measurements. The results of these studies revealed that motor and sensory functions are not similar for all uninjured strains of rats. Specifically, Fischer rats tend to have considerable differences in their morphological features and sensorimotor abilities compared to the other strains examined. Results from the other experiments indicate that adult freely behaving female rats develop a characteristic gait when pathways important for locomotion are injured unilaterally, regardless of strain. The rubrospinal tract and ascending dorsal column pathways appear to be important for both skilled and flat-ground locomotion as well as forelimb use while rearing. Pathways traveling within the ventrolateral pathway, however, are not necessary or sufficient for locomotion or limb useage while rearing when injured by themselves. Animals with ventrolateral spinal funiculus injuries regain normal forelimb use and skilled locomotor abilities. Injury to the ventrolateral spinal funiculus, however, results in mild (compared to rubrospinal and dorsal column injured animals) yet long-lasting locomotor changes based on ground reaction force determination. These findings are in agreement with the current opinion that there is a substantial amount of functional redundancy of pathways traveling in the ventral and ventrolateral funiculi.

A variety of behavioural tests were used to examine both sensory and motor function of freely behaving unilaterally spinal cord-injured and uninjured rats. The first experiment was designed to determine whether sensory and motor differences existed between uninjured Fischer, Lewis, Long-Evans, Sprague-Dawley and Wistar rats using endpoint, quantitative kinematic, and kinetic measurements. The second experiment examined differences in sensorimotor responses to cervical spinal cord hemisection in Lewis, Long-Evans and Wistar rats. For the third experiment, reflex and locomotor abilities of unilateral cervical or thoracic spinal cord hemisected Long-Evans rats were determined using endpoint, semi-quantitative kinematic, and kinetic measurements. The fourth experiment was designed to investigate the importance of the rubrospinal tract and ascending dorsal column pathways to overground locomotion. This experiment was conducted to help explain the behavioural observations made following cervical spinal cord hemisection. Furthermore, this experiment examined the effects of combined unilateral rubrospinal and dorsal column injury on overground locomotion using endpoint and kinetic measurements. Finally, the fifth experiment set out to investigate the contribution of tracts running in the ventrolateral spinal cord on overground locomotion in freely behaving Long-Evans rats. These animals were assessed using endpoint and kinetic measurements. The results of these studies revealed that motor and sensory functions are not similar for all uninjured strains of rats. Specifically, Fischer rats tend to have considerable differences in their morphological features and sensorimotor abilities compared to the other strains examined. Results from the other experiments indicate that adult freely behaving female rats develop a characteristic gait when pathways important for locomotion are injured unilaterally, regardless of strain. The rubrospinal tract and ascending dorsal column pathways appear to be important for both skilled and flat-ground locomotion as well as forelimb use while rearing. Pathways traveling within the ventrolateral pathway, however, are not necessary or sufficient for locomotion or limb useage while rearing when injured by themselves. Animals with ventrolateral spinal funiculus injuries regain normal forelimb use and skilled locomotor abilities. Injury to the ventrolateral spinal funiculus, however, results in mild (compared to rubrospinal and dorsal column injured animals) yet long-lasting locomotor changes based on ground reaction force determination. These findings are in agreement with the current opinion that there is a substantial amount of functional redundancy of pathways traveling in the ventral and ventrolateral funiculi.

Introduction: Irish dance has evolved to become more athletically demanding, thus making the art form very hard on dancers' bodies. Irish dancers must land from difficult moves without letting their knees bend or heels touch the ground, causing large amounts of force to be absorbed by the body. Past studies have found dancers landing with a range of 4.5–6 times body weight, potentially causing high amounts of overuse injury. The majority of injuries incurred by Irish dancers are due to overuse (79.6%). The landings that occur in Irish dance have been minimally evaluated in current literature. Obtaining values of vertical ground reaction forces (GRFs) produced by Irish dancers will assist in understanding the causes of overuse injuries, fill significant gaps in the current literature, and identify which Irish dance moves should be used less frequently to possibly reduce the chance for overuse injury. Purpose: To determine vertical GRFs produced by female Irish dancers in hard and soft shoes during common movements. The purpose of this study was to determine peak force, rise rate of force, and impulse in selected Irish hard shoe and soft shoe dance movements. Materials and Methods: Sixteen female Irish dancers between 14 and 25 years of age were recruited from the 3 highest competitive levels. Each performed a warm-up, reviewed 8 common Irish dance moves, and then performed each move 3 times upon a force plate. Four moves each were performed in soft and hard shoes. GRFs were measured using a 3-dimensional force plate running at 1000 Hz. Peak force, rise rate, and vertical impulse were all calculated. It was hypothesized that the 8 moves would produce different GRFs. Results: Peak forces normalized by each dancer's body weight were significantly different across moves (F = 65.4, p < 0.01; F = 65.0, p < 0.01; and F = 67.4, p < 0.01 respectively). Years of experience was not correlated with peak force, rise rate, or impulse (p < 0.40). Conclusion: There is a large range in peak forces created by Irish dancers. Moves that have high average peak forces may have a higher risk in causing overuse injuries. All dancers should take care to limit the use of these moves in their choreography to prevent such injury.

Gait biomechanics of forty male subjects was evaluated at normal and fast walking speeds. The forty subjects composed four groups based on their body mass index, with ten subjects in each of the groups: underweight, normal weight, overweight and obese. To our knowledge this is the first comprehensive 3-dimensional kinetic and kinematic gait analysis of all four groups based on body mass index. The obese subjects walked with significantly slower gait speed by taking shorter steps and strides, while having significantly higher step widths and longer gait cycle times than the other subjects. The obese subjects spent significantly less time in single support and more time in double support than their non-obese counterparts. These adjustments in temporal characteristics for the obese participants may be as a result of the gait compensation for the additional body weight in order to give them the most efficient, stable and balanced walking ability. Body mass index affected significantly the forces and moments at the ankle, knee and hip in the medial-lateral plane while speed effects were more prominent in the sagittal and transverse planes. These results suggest that an increase in the body weight would affect the gait stability while increasing the speed will affect the gait progression. Contrary to most researchers beliefs that an increase of the body weight would increase the forces and moments of the knee in all three planes, this study was able to prove that the actual forces and moments in the medial-lateral plane for the knee joint decrease while the ones in the sagittal plane increase. On the other hand, the hip joint in the medial-lateral plane displays the highest forces and moment for the obese subjects. These results are indicative of a gait compensation related to increasing body weight in the medial-lateral compartment of the lower extremity joints. Recommendations for further studies and follow up experiments are enclosed.

Tree-planters are likely to suffer from musculoskeletal injuries during their short work season. The objective of this research is to identify the biomechanical mechanisms that contribute to these injuries with an overall goal of reducing injury frequency and severity. Pre- and post-season discomfort questionnaires were administered to workers in two tree-planting camps to identify areas of the body most prone to injury. Musculoskeletal pain and discomfort were significantly higher post season. Greatest pain and discomfort were reported in the feet, wrists and back, while the highest frequency of pain was reported in the back. Upper body and trunk postures were recorded during the tree-planting task in the field using digital video and inclinometers. Results indicated that deep trunk flexion occurred over 2600 times per day and workers spent at least half of their workday in trunk flexion greater than 45 degrees. Although results provide useful insight into injury mechanisms, postural data were two dimensional. Inertial motion sensors were used in a second field study the following season to examine differences in three-dimensional upper limb and trunk relative joint angles during commonly used tree seedling unloading methods. Results showed trunk rotation up to 50 degrees combined with deep trunk flexion during parts of the task. Trunk flexion and rotation were significantly less when the tree seedling load was distributed asymmetrically as compared to symmetrically. Joint reaction forces in the lower body and trunk during the same unloading methods was examined during a simulated planting task in a lab environment. Greatest joint reaction forces and non-neutral postures occurred when the tree was inserted into the ground. Right-loaded planting bags resulted in more substantial differences in posture and joint reaction forces than either left-loaded or even-loaded bags. Axial forces were greater in the right leg than the left throughout the task, regardless of loading condition. In conclusion, underlying biomechanical mechanisms for injury during tree-planting seem to be a combination of awkward postures (particularly the trunk), repetitive motions, and carrying of heavy loads. Different seedling unloading strategies did not result in substantial overall differences in posture or joint reaction forces. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2010-04-14 10:02:32.385

Tai Chi Chuan, Tai Chi (TC) in short, is a popular form of Chinese martial arts which have been practised by millions of people and provides various health benefits, such as improving balance control, strengthening leg muscles, reducing fear of falling, enhancing flexibility and many more. The American Geriatrics Society and the British Geriatrics Society have recommended TC as a suitable exercise for preventing falls of older people. However, it is not clear which TC components are the most effective for balance improvement. In addition, it is also unknown what differences in biomechanics aspects are between non-TC participants and experienced TC practitioners. This thesis aims to provide new knowledge and understanding of the kinetics and kinematics characteristics of two most frequently presented TC foot movements: push-hand and Tai Chi gait (TCG), through a comparative experimental study on the ground reaction forces (GRFs) and plantar pressure distribution on both feet induced by TC and non-TC participants. Three hypotheses were proposed for facilitating this research. The characteristics of foot/leg movements in each of the simplified 24-form TC are investigated and each form is classified into one of four types. Two most frequently presented foot movements, push-hand and TCG foot movements, were identified, which are embedded in 18 of the 24 forms. This forms a basis for further biomechanics study. Ten male TC and ten male non-TC participants attended the experiments while performing push-hand, with and without an opponent, and TCG. The GRFs in the three perpendicular directions and plantar pressure distribution were measured simultaneously through using two force platforms and an insole system. A video recording system was also used to capture the movements of selected points on the subjects. The kinematics data were used to identify the critical positions that divide the leg stance phases of TCG.The characteristics of the foot forces during the two fundamental foot movements were examined and revealed. The differences and similarities on the GRFs and plantar pressure distribution generated by the two groups of participants were assessed and identified. The similarities show that the non-TC participants are able to achieve similar characteristics of foot forces as the TC participants do. The differences show that the TC participants have better control of their body movement, generating larger GRFs during push-hand and smaller GRFs during TCG in the two horizontal directions. These reflect the TC participants’ ability developed by practising TC for several years which cannot be achieved by the non-TC participants during the tests. It is also demonstrated that push-hand generates the lowest vertical foot forces among those generated by other possible human movements, such as TCG and walking.

To measure the differences in ground reaction forces between running shoes, racing flats, and distance spikes, twenty intercollegiate distance runners ran across a force plate at 6.7m/s (for males) and 5.74m/s (for females) in each of the three types of shoes. In order to control for differences in foot strike, only subjects who had a heel strike were included in the data analysis (N=16). Repeated-measures ANOVA and Tukey's post-hoc test (p<0.05) revealed loading rate and impact peak to be significantly increased in the flats and spikes compared to running shoes. Stiffness in spikes was significantly higher than in running shoes. Stance time in spikes and flats was decreased. These results can be used to better inform competitive runners, coaches, and trainers of the risks and performance benefits when determining the frequency and duration of the use of competitive footwear in training.

Infants explore environments through repetitive movements which are constrained or facilitated by the environmental context. The current studies analyzed how typically developing infants bounced in four environments that differed by system natural frequency. Four pre-walking infants (age 9.7 months ±1.8) were placed in four spring conditions with natural spring frequencies of 0.9, 1.15, 1.27 and 1.56 Hz. All infants bounced above the natural spring frequency in all conditions suggesting that they do not solely behave like a mass-spring system. Two patterns of bouncing adaptations were identified. Three infants regulated bounce frequency, while one infant regulated the percentage of time on the ground. When infants matched their bounce frequency to the natural frequency, trunk vertical displacement and joint ranges of motion decreased across conditions and demonstrated a shift from non-spring like to circular spring-like phase planes. Moderate to high correlations were found for inter- and intra-limb coordination. Conversely, when an infant regulated time on the ground, trunk vertical displacement and joint ranges of motion remained the same across conditions and inter- and intra-limb correlations were low to moderate. Phase planes remained circular spring-like for this infant. Asymmetrical loading patterns and decreasing vertical ground reaction forces were found in all infants suggesting that a timing component is always regulated. The difference in bouncing pattern may be indicative of different bouncing skill level.

The adaptation of inverse dynamics was performed to quantitatively examine the subtle locomotor changes, previously undetectable, in rodent locomotion following nervous system injury. The first experiment performed an injury with known effects, a unilateral lesion of the medial and lateral branches of the left tibial nerve of Long-Evans rats, and measured the resulting data via inverse dynamics. Special effort was made to account for skin movement artefacts using a global optimization method for marker digitization. The second experiment attempted to apply this technique to Long-Evans rats with spinal hemisections at spinal level T-10. After the peripheral nerve injury to the tibial nerve branches, the main findings were that ankle joint still produces an extensor moment and positive power without the active contraction of the gastrocnemius m. It is possible that this phenomenon is due to passive contractile elements of the muscle and tendon. In addition, the knee and hip of the lesion leg stiffen, resulting in substantial reductions in moment generation and nearly total losses of both negative and positive power production. There were also compensations made by the opposite hindlimb and contralateral forelimb. The spinal cord hemisection produced subtle, complicated intra and interlimb changes in both joint moment and joint power analysis that could not be seen by looking at joint angles alone.

Infants explore environments through repetitive movements which are constrained or facilitated by the environmental context. The current studies analyzed how typically developing infants bounced in four environments that differed by system natural frequency. Four pre-walking infants (age 9.7 months ±1.8) were placed in four spring conditions with natural spring frequencies of 0.9, 1.15, 1.27 and 1.56 Hz. All infants bounced above the natural spring frequency in all conditions suggesting that they do not solely behave like a mass-spring system. Two patterns of bouncing adaptations were identified. Three infants regulated bounce frequency, while one infant regulated the percentage of time on the ground. When infants matched their bounce frequency to the natural frequency, trunk vertical displacement and joint ranges of motion decreased across conditions and demonstrated a shift from non-spring like to circular spring-like phase planes. Moderate to high correlations were found for inter- and intra-limb coordination. Conversely, when an infant regulated time on the ground, trunk vertical displacement and joint ranges of motion remained the same across conditions and inter- and intra-limb correlations were low to moderate. Phase planes remained circular spring-like for this infant. Asymmetrical loading patterns and decreasing vertical ground reaction forces were found in all infants suggesting that a timing component is always regulated. The difference in bouncing pattern may be indicative of different bouncing skill level.