This thesis includes one qualitative literature review and five empirical studies examining aspects of a) the relationship between bone mass and physical activity in children aged 8-11 years using pedometry and accelerometry, and b) the variability and reliability of the RT3 accelerometer as a means of assessing physical activity patterns in children. Previous research has shown a positive relationship between physical activity and bone mineral density in children. However, study design appears to be confounded by the accuracy of measures of physical activity limiting conclusions that can be drawn. Prior to our investigation research investigating the relationship between bone mass and habitual physical activity measured by objective means in children is scarce, and no study had evaluated the technical performance of the R T3 accelerometer; a small lightweight triaxial accelerometer. To examine the relationship between bone mass, physical activity and calcium intake methodology included; the objective assessment of habitual physical activity initially by pedometry and finally by accelerometry; dietary analysis of calcium intake; and dual energy X-ray absorptiometry measured bone area, mineral content and density of the whole body and proximal femur. To examine the variability and reliability of the RT3 accelerometer methodology included; the assessment of intraand inter-monitor variability by vibration assessment at increasing Hz levels; intermonitor reliability and variability by inducing a variety of human motions in a laboratory based environment; and epoch selection was assessed comparing the 60 to one second time sampling modes using children in a field setting. The main findings were: a) steps per day, assessed by pedometry, explained a significant proportion of the variance in bone mass at the hip in children; b) the RT3 triaxial accelerometer was reliable across trials, although the anterioposterior vector recorded counts consistently higher than the mediolateral and vertical vectors; c) interunit variability of the RT3 was evident, particularly as activity intensity increased; d) use of the 60 second epoch setting may lead to inaccuracies when assessing activity of a vigorous intensity and above; and e) vigorous physical activity, assessed by the RT3 accelerometer, and calcium intake have an interactive effect on bone mass in children, whereby bone mineral content is only high when both vigorous activity and calcium intake are high. In conclusion, this thesis has highlighted quality control procedures that need to be in place when using the RT3 accelerometer and presented evidence for a synergistic action of vigorous physical activity and calcium intake on bone mass in children.

Research in this thesis has examined the acute and chronic effects of exercise on hunger, energy intake and expenditure. Cross-sectional studies examined the effect of 60 min of moderate-intensity cycling on immediate and subsequent three day energy intake and expenditure in active and inactive men (study one) and women not using hormonal contraceptives (study two) and taking oral contraceptives (study three). Study four examined the effects of 12 weeks of moderate-intensity aerobic exercise on 7-day free-living energy intake and expenditure. A total of 47 men (mean ± SD; age 23.8 ± 4.2 y; body mass index 24.2 ± 3.0 kg-m'2) and 52 women (22.7 ± 3.4 y; 22.1 ± 2.1 kg-m'2)were recruited into four studies. In study one, 60 min of moderate-intensity (50% of maximum oxygen uptake) cycling did not have an effect on hunger or ad libitum lunch energy intake (p > 0.05) but induced an acute (within the experimental day, p = 0.024, d = 0.56) and delayed (third day after the experimental day,/ > = 0.024, < i= 0.80) increase in free-living energy intake in active and inactive participants, respectively with no compensatory changes in freeliving energy expenditure (p > 0.05). Similarly, studies two and three demonstrated that an acute bout of moderate-intensity aerobic exercise does not increase hunger or ad libitum lunch energy intake in active and inactive women {p > 0.05). In study two there were no exercise-induced compensatory responses in free-living energy intake {p > 0.05) whereas in study three, the inactive group decreased their daily energy intake on the first day after the exercise experimental day compared with control (p = 0.002, d = -0.89). No compensatory changes in daily physical activity energy expenditure were observed in these studies (p > 0.05). In study four 12 weeks of moderate-intensity aerobic exercise did not induce changes to weekly free-living energy intake and expenditure (p > 0.05) despite the high inter-individual variability in changes in body composition. Additionally, inactive participants are not able to independently maintain their physical activity behaviour after the end of a supervised exercise intervention. Overall, this research shows that an acute bout of moderate-intensity aerobic exercise did not affect hunger irrespective of sex or habitual physical activity, however the use of oral contraceptives may have heightened appetite in women. Active men were able to compensate for the acute exercise-induced energy deficit by increasing their energy intake quicker (within the experimental day) than inactive men (third day after the experimental day). In women, no clear relationship was apparent. Moreover, an acute bout of exercise did not elicit compensatory changes in physical activity in men and women. These findings enhance the knowledge of how an acute bout of exercise affects immediate and subsequent energy intake and expenditure in active and inactive men and women but more work is needed to confirm and explore the potential causal mechanisms.

INTRODUCTION: Abnormal kinematic coupling between the foot and lower limb has been associated with chronic overuse injuries of the lower extremity during running. However, the normal coupling relationship between the two segments remains unclear. The equivocal findings in the literature may be due to previous studies concentrating on determining coupling at discrete instances only, along with the failure to include the midtarsal joint in coupling analyses. By including motion across the midtarsal joint and measures of continuous coupling, this research aimed to gain a more complete understanding of the relationship between foot and lower limb kinematics during gait. METHODS: Following the development of a multi-segment foot model, in-vitro and invivo studies were conducted to assess the validity and reliability of determining foot and lower limb segmental kinematics during gait. Three experiments were then undertaken to assess the rigidity of the kinematic coupling between the forefoot, rearfoot and shank by manipulating step width, running speed, foot strike pattern and mode of gait (run versus walk). Kinematic coupling was assessed by determining how well matched the angular displacements of two adjacent segments (e. g rearfoot eversion/inversion with shank intemal/external rotation) were in both spatial and temporal terms using both discrete point and cross correlation analyses. RESULTS: Although the in-vitro study suggested care should be taken when interpreting data obtained from skin mounted markers the modelling and analysis approach used in-vivo was found to have good within- and between-day reliability. In all conditions it was evident that following touchdown, the shank internally rotated, the rearfoot everted and the forefoot dorsiflexed and abducted. This was followed by the reversal of the segmental angular displacements starting with that of the shank, followed by the rearfoot and then the forefoot. During running, coupling between rearfoot eversion/inversion and shank internal/external rotation was consistently high (r > 0.92) regardless of step width, speed or foot strike pattern. In walking, however, this coupling value was low (r = 0.49). Rearfoot eversion/inversion was also highly coupled with both forefoot dorsiflexion/plantarflexion and abduction/adduction in running and walking. However, there was little evidence of any coupling between rearfoot eversion/inversion and forefoot eversion/inversion. CONCLUSION: The consistently high kinematic coupling between the rearfoot and shank during running suggests a robust coupling mechanism that is able to withstand changes in the loading of the subtalar joint. However, lower coupling between these two segments in walking, implies that the relationship is not entirely rigid and some degree of elasticity exists at the subtalar joint. Strong coupling of forefoot sagittal and transverse plane motions with rearfoot frontal plane motion during running and walking suggests the two segments are linked via the action of the midtarsal joint. From the timings of discrete kinematic events it appeared that shank external rotation was driving rearfoot inversion and that this in turn was causing the forefoot to plantarflex and abduct. This implies that a kinetic chain exists with proximal segments driving motion of the distal segments during propulsion. IMPLICATIONS: If the proximal segments drive the motion of the foot then injuries associated with excessive or prolonged pronation should not only be treated using orthoses, but also by using interventions to modify the kinematics of the joints proximal to the ankle-joint-complex. Future work should determine the effects of muscle stiffness on subtalar joint kinematics since this may have important implications in terms of lower extremity injuries.

No description available.

Current techniques of rearfoot alignment measurement have been reviewed and a new clinical technique of rearfoot measurement in weight bearing stance has been developed. This technique was validated by radiographic and cadaveric anthropometric studies. The relationship between a central heel bisection line and the underlying bone structure was investigated, and showed that the heel bisection line was coincident with the centre of the x-ray image of the calcaneus at its upper margin, but appeared to be skewed to the lateral side of the image of calcaneus (to 40% of its width) at its lower margin. A cadaveric study confirmed that this appearance arose as a result of a calcaneal tubercle that is larger medially than it is laterally. Reliability of rearfoot measurement was investigated and showed good repeatability (within the 0.5" resolution of the instrument) when made by an experienced podiatrist, with intratester repeatability of 0.93 and 0.95.

A successful golf swing is dependent on the performance of a complex sequential action. This movement involves the feet, knees, rotation of the hips and trunk, which result in a transmission of forces and torques between the feet/shoes and the ground (Williams and Sih, 1998). The aim of this thesis was to investigate golf shoe interface aspects relevant to the golf swing process. One flat-soled, one traditional and three alternative spiked golf shoe sole interfaces were evaluated. Using a mechanical traction-testing device, specific linear forces and rotational torques were applied to the forefoot and whole-foot of the five different golf shoe sole interface designs on a grass covered force platform. Greater linear and rotational ground action forces were identified within the traditional sole (whole-foot limiting friction 1.01) and alternative sole conditions (whole-foot limiting friction Blue 1.00, Red 1.02, Yellow 1.01) when compared to a flat-soled shoe (whole-foot limiting friction 0.88). The traditional shoe was also identified to frequently produce greater friction (forefoot limiting friction 0.97) in comparison to the alternative shoe soles (forefoot limiting friction Blue 0.92, Red 0.91, Yellow 0.91). Due to the mechanical nature of the study it was important to gain an understanding of how the golf shoe sole interface interacted with the ground and if between-shoe differences were repeated when subjected to dynamic human movement during the golf swing. Dynamic analysis of the five soles identified two between shoe-sole differences (P = <.OS); Driver back foot Tz range (BW.m) (Traditional shoe (IS.98 ± 1.11) was significantly different to the Blue alternative (12.77 ± .83) and flat-soled shoe (12.73 ± .8S)); and 7iron front foot, Mz maximum time (s) (Flat-soled shoe (1.39 ± .02) was significantly different to Blue (1.72 ± .03) Red (1.71 ± .03) and Yellow (1.72 ± .04) alternative spiked shoes). The low handicap group (0-7) produced significantly slower weight transfer times (s) when compared to the medium (8-14) and high (15+) groups within all club conditions (3iron Low 0.73 ± .03, Medium 0.43 ± .02 and High 0.41 ± .02; 7iron Low 0.76 ± .01 Medium 0.S4 ± .01 and High 0.54 ± .01; Driver Low 0.70 ± .01, Medium 0.48 ± .01 and High 0.43 ± .01). However, no significant differences in forces or torques were identified between handicap groups. The findings contradict the previous mechanical testing results concluding mechanical traction tests are not an appropriate test of between shoe differences when relating the findings to the golf swing. The differences in forces created between the shoe and ground identified between the mechanical and dynamic studies was a result of the adaptation by the golfer to the footwear condition. Dynamic in-shoe pressure analysis identified regional pressures created between the golfer and shoe throughout the swing process. The highest peak pressures (N/cm2 ) were associated with the lateral regions of the front-foot from the point of ball impact (Front foot Traditional (R5) 114.33 ± 6.29 N/cm2 Back foot Traditional (R5) 7.18 ± 1.07 N/cm2) supporting previous kinematic and ground action force findings. The traditional spiked shoe produced greater in-shoe pressures within the front foot lateral mid-foot region however all sole conditions provided significantly higher pressures within specific in-shoe regions at different stages of the swing process. The comparable between shoe findings support the previous dynamic findings. The thesis enhanced current understanding of between shoe-ground and shoe-golfer interactions. Different demands were placed on the front and back shoes during the golf swing highlighting the need for asymmetrical shoe sole designs. Limited differences were identified between the different shoe sole interface designs, concluding that golf shoe interface designs are not effective for the demands of the golf swing, subsequently shoe outsole modifications were suggested.

Flatwater sprint kayaking performance can be assessed through the analyses of average boat velocity a paddler can produce, which has been shown to be directly linked to the levels of force production. Furthermore kayaking has been the subject of substantial level of investigation, within which research has identified that the evolution of equipment and resultantly technique has a direct effect on performance. The focus of the previous research has revolved around the upper limbs, with the trunk and lower limbs viewed as an inconsequential base around which the upper limbs move. Therefore the current thesis attempts to identify the application of the entire body during kayak paddling and clarify the importance of trunk and leg contributions to performance. A notational analysis of technique was conducted comparing novice, national and international level paddlers. International paddlers displayed significantly (P < 0.05) lower race and stroke times, as a result of significantly higher stroke rates. In addition aspects of technique were ranked from zero to five from which international paddlers displayed significantly (P < 0.05) greater trunk rotation, leg motion, stroke width, and forward reach. These findings were supplemented by the international paddlers entering the paddle significantly closer to the centre line of the kayak, while holding a fixed forward lean position of the trunk. These findings provide important factors within technique that can be identified visually; however further investigation was required to identify their importance in the development of force and kayak velocity. Consequently the development of an on-water analysis system was required to ensure a comprehensive analysis of technique. This was conducted through the combination of kinetic, 3-demensional kinematic, electromyographic and electrogoniometric analysis methods, using subjects (n = 8) with international experience. Subjects were prepared with passive surface electrodes and joint markers, and completed the testing protocol following completion of informed consent and a medical questionnaire. Statistical analysis identified that a moderate positive significant predictive relationship (R1= 0.529, P<0.05) existed between peak force and mean velocity during the left paddle stroke. Separating the trunk into thoracic and lumbar regions revealed a significant negative predictive relationship (P < 0.05) between velocity and range of lumbar spine rotation. Further significant (P < 0.05) findings were identified between activation levels of the rectus abdominus, external obliques and the production of force and velocity. The combination of these findings indicated that the lower trunk acted as a strong stable base against which force was produced increasing average kayak velocity. The activation of the left rectus femoris displayed significant relationships (P < 0.05) with force and velocity during both left and right strokes; indicating that the legs act as braces against which the force is transferred to the kayak. These findings reinforced those identified during the notational analysis, indicating that the legs and trunk play a fundamental role within the development of kayak velocity and therefore performance. It is therefore important that paddlers ensure that the musculature of the trunk and legs are used during performance and that the vital axial rotations occurring in the spine are produced in the thoracic region.

The main aim of this study is to use electromyography to study muscle activation during natural, unrestrained movements. At total of fifty-seven male volunteers participated in the experiments. There were three main studies: vertical jumping, kicking a tethered football and isokinetic dynamometry. These experiments were designed to investigate the hamstrings activity during high-velocity knee extension movements in an attempt to relate the magnitude of hamstrings co-activation and the timing of hamstrings activity to the speed or power of the movements. It is clear that there is substantial co-activation of the three muscles in hamstrings and vastus lateralis in all three studies. Co-activation is present in almost all volunteers even in the slowest speed and lowest power movements studied. Co-activation has been reported by others during single knee extension movements on isokinetic dynamometers. This thesis reports for the first time that the extent of co-activation changes during repeated movements. Co-activation occurs during unrestrained vertical jumps across the whole range from the lowest power jumps in which the volunteer barely leaves the ground to maximum power jumps. In addition, it is commonly observed even in professional football players capable of producing very fast knee extensions during powerful kicks. The duration of co-activation of hamstrings during kicking was significantly shorter in the highly trained 15-year-old footballers that in their 11-year-old counterparts or in untrained adults. It is possible that this reflects changes in the way their kicking movements have developed with prolonged training. This is the first study of age related changes in co-activation. Interestingly, there is anecdotal evidence from the club coaches that injuries are far more frequent in the 15 year olds than in the younger teams. It may be that the increase in speed of movement achieved by reducing co-activation, places the limb at more risk.

The foot forms the dynamic base upon which a sprinter functions. The actions that occur within the foot are of critical importance to the task of sprint running, since they influence the functional mechanisms of the entire body and especially the lower extremity. The aim of this research was to evaluate how foot function may contribute to sprinting performance and the interaction between the mechanical properties of sprinting footwear and performance, with a focus on the role of the metatarsophalangeal joint (MPJ). Currently, little is known about the effect of footwear upon the normal biomechanical function of the MPJ during sprinting, as this joint has often been neglected in previous biomechanical studies of lower limb energetics. A series of empirical and theoretical investigations were therefore undertaken to advance the understanding in this area. The initial study revealed the importance of two important methodological issues on the analysis of MPJ function during sprinting. Appropriate MPJ axes representation and appropriate data processing procedures are vital to ensure the accurate assessment of joint kinetics. Empirical investigations on eight trained sprinters performing maximal sprint trials, both in barefoot and sprint spike conditions determined normal patterns of foot behaviour and the role of the MPJ during sprinting. Several aspects of foot function, including kinematic, kinetic and pressure characteristics, were determined. Sprint spikes reduced MPJ range of motion and dorsiflexion velocity but increased total energy generated during the push-off phase, biomechanical measures which may be linked to sprinting performance. To investigate whether manipulations in the mechanical properties of sprinting footwear may influence sprinting performance and MPJ function, sprint spikes with insoles of varying stiffness's were manufactured and mechanically tested. For a group of sprinters increasing the sprint spike stiffness did not elicit an improved sprinting performance. Due to the high variability between athletes and highly individualised responses to perturbations in footwear a single- subject analyses was undertaken. This study demonstrated that individual sprinting performance may be improved by implementation of relevant shoe mechanical characteristics. Whilst varying the mechanical characteristics of sprint spikes clearly showed controlling influences over the natural motion of the MPJ, the relatively minimal effect on the resultant MPJ energetics, potentially suggests that sprint spikes do not minimise energy loss during sprinting. The combined empirical and theoretical understanding therefore highlighted several aspects of MPJ function which could be altered by footwear in an attempt to improve sprint running performance.

Clinical decisions based on gait data obtained by optoelectronic motion capturing require profound knowledge about the repeatability of the used measurement systems and methods. The purpose of this study was to evaluate the effects of inconsistent anthropometric measurements on joint kinematics calculated with the Plug-in Gait model. Therefore, a sensitivity study was conducted to ascertain how joint kinematics output is affected to different anthropometric data input. One previously examined gait session of a healthy male subject and his anthropometric data that were assessed by two experienced examiners served as a basis for this analytical evaluation. This sensitivity study yielded a maximum difference in joint kinematics by the two sets of anthropometrics of up to 1.2°. In conclusion, this study has shown that the reliability of subjects’ anthropometrics assessed by experienced examiners has no considerable effects on joint kinematics.