Kinetic and 3D Kinematic analysis of netball movements: with and without prophylactic knee bracing

Patellofemoral pain is one of the most common musculoskeletal pain conditions, with a multifactorial aetiology. It is reported that young females are at high risk of developing patellofemoral pain. During dynamic, fast-paced games athletes are exposed to high ground reaction forces, contributing to lower body injury occurrence during landing and high patellofemoral loads. Knee braces, such as knee sleeves, are commonly used for patellofemoral pain; however the underlying mechanisms on the patellofemoral joint remain unclear. An increase in understanding of joint mechanics during sporting and functional tasks could help our understanding of injury mechanisms and preventative interventions. The aim is to identify any changes in the kinetics and kinematics of the tibiofemoral joint and the patellofemoral loading experienced in healthy subjects during a range of functional movements with and without a prophylactic knee sleeve

Noncontact injuries in Scottish hockey: A study of epidemiology, current practice and a preventative measure

Introduction: There is limited evidence on noncontact injury epidemiology, current warm-up practice and exercise interventions used to reduce injuries in hockey. Therefore, the aims of this thesis are to investigate (1) noncontact injuries, (2) current warm-up practice and (3) the effects of a novel warm-up on female sub-elite hockey players in Scotland. Methodology: Study 1 was an online injury survey on 317 hockey players focussing on noncontact injuries. Study 2 was an observational study that investigated the current warm-up practices of 17 hockey teams. Study 3 was a controlled study that used 40 female hockey players and explored the effects of an 8-week hockey-specific neuromuscular training programme (NMTP) on electromyography, kinematics and kinetics during a sagittal plane hop, hop and twist and unanticipated sidecut. Results: Study 1 showed that the most common injuries were affecting the knee and hamstrings (0.89 and 0.69/1000 hours respectively) with no timeloss (31.4%) or mild to moderate injuries (30.3%) and usually occurred during sidecutting, sudden acceleration and landing (19.6%, 13.8% and 12.9% respectively). The injuries were more frequently occurring to females than males 4.73 vs 3.47/1000 hours. Study 2 revealed a warm-up time of 20 minutes including pulse raiser, activate and mobilise and potentiate elements. The occurrence of static stretching was greater (41.2%) than neuromuscular training (11.7%). Study 3 showed some significant increases in muscle activation for Gastrocnemius, Quadriceps and Gluteals both pre-and post-landing, with greater increases in the intervention group. There were significant reductions in maximum knee abduction, excursion and the rate of force development following 8-weeks of neuromuscular training. There were no significant differences in performance. Conclusion: Noncontact hockey injury epidemiology requires further research and the current provision of warm-ups should be evidence-based. A novel hockey-specific NMTP can elicit some significant changes in muscle activity, kinematics and kinetics that may reduce the risk of noncontact injuries

The relationship between stiffness, asymmetries and change of direction speed

A thesis submitted to the University of Bedfordshire, in fulfilment of the requirements for the degree of Doctor of PhilosophyChange of direction speed (CODS) is an important determinant of performance in many sports. Greater stiffness of the lower limb should be beneficial to CODS, but this had not been well investigated. The purpose of this thesis was to establish the relationship between vertical stiffness, vertical stiffness asymmetries and CODS, with a view to augmenting CODS performance. The pilot study and studies 1-2 sought to determine the most reliable and ecologically valid method to assess stiffness in athletes required to perform changes of direction. The pilot study reported that the use of ultrasonography to determine Achilles tendon stiffness did not demonstrate appropriate reliability for inclusion in subsequent studies. Coefficients of variation (CVs) in excess of 27% were reported during an isometric plantar flexion task. Study 1 reported that CVs for vertical stiffness were lower when assessed during unilateral drop jumping (~7%) than during bilateral drop jumping (~12%) or bilateral hopping (~14%). Study 2 reported that the expression of vertical stiffness (P = 0.033) and vertical stiffness symmetry angle (P = 0.006) was significantly different across three performance tasks: unilateral drop jumping, bilateral drop jumping and bilateral hopping. Asymmetry percentages between compliant and stiff limbs were 5.6% (P < 0.001; d: 0.22), 23.3% (P = 0.001; d = 0.86) and 12.4% (P = 0.001; d = 0.39), respectively. Given the findings of studies 1 and 2, this thesis demonstrated the reliability and validity of a novel method by which to assess vertical stiffness - the unilateral drop jump. This task was used in subsequent studies to measure vertical stiffness. Study 3 sought to determine if vertical stiffness and vertical stiffness asymmetries influenced CODS performance determined during a 90o cutting task. Multiple regression analyses reported that mean vertical stiffness and asymmetry in jump height explained 63% (r2 = 0.63; P = 0.001) of CODS performance. Study 3 was the first investigation to demonstrate the importance of vertical stiffness to CODS performance. Study 4 sought to determine if acute exercise interventions designed to augment vertical stiffness would improve CODS. Unilateral and bilateral ‘stiffness’ interventions were evaluated against a control condition. CODS performances following the unilateral intervention were significantly faster than control (1.7%; P= 0.011; d = -1.08), but not significantly faster than the bilateral intervention (1.0% faster; P = 0.14; d = -0.59). Versus control, vertical stiffness was 14% greater (P = 0.049; d = 0.39) following the unilateral intervention. Study 4 demonstrated that a novel unilateral ‘stiffness’ intervention improved vertical stiffness and CODS performance. This highlights that the potential applicability of unilateral stiffness interventions in the pre-performance preparation of athletes

Acute effects of stretching on athletic performance : the ability of some exercises in compensating stretching-related performance deficits

The purpose of the dissertation was to investigate the acute effects of stretching on various athletic performances, and how to quickly compensate the expected stretching-related performance-deficits following static stretching. A number of recent studies researched the acute effects of static stretching on athletic performance were reviewed and analyzed in the theoretical part of the dissertation. The reviewed studies were di-vided into two groups: studies which reported negative effects (49 studies), and studies which reported equivocal effects (39 studies). The practical part of the dissertation consists of three studies with 67 participants (sport students at the Saarland Univer-sity). A repeated measures within-subject design was applied in the three studies. First study: Purpose: This study aimed to investigate the acute effects of hamstring static and dy-namic stretching on peak isokinetic concentric torque at a low velocity, the knee angle, at which this peak torque occur, and the hip flexion range of motion. Methods: 17 sport students participated in this study. Measurement of concentric isokinetic knee flexion peak torque including the angle at peak torque, as well as the hip flexion range of motion were performed before and immediately following four conditions. Subjects attended a total of four testing ses-sions (A, B, C and D) so that the order of the conditions assignment was randomized per person (within-subject design). The four conditions were: (A) hamstring static stretching (three sets of four stretches with 30 seconds holding the stretch). (B) ham-string dynamic stretching (three sets of four stretches with 12-14 repetitions). Condi-tion (C) and (D) consisted of ten minutes passive sitting and were set as control condi-tions. The difference between (C) and (D) was that in (C) both force and flexibility tests were performed, whereas in (D) merely the isokinetic test was performed. Results: Repeated measures analyses of variance showed no significant differences between the four protocols regarding the peak torque and the angle at peak torque (p=0.474, F= 0.85) and (p=0.59, F= 0.63), respectively. On the other hand, hamstring static and dynamic stretching resulted a significantly greater hip flexion range of mo-tion (p=0.009, F=8.6, ES= 0.37) and (p=0.000, F=33.7, ES=0.55), respectively, when compared to the control condition (C). There was no significant deference between static and dynamic stretching in enhancing the range of motion. Conclusion: Hamstring static and dynamic stretching enhanced the hip flexion range of motion with neither impairment nor facilitation in isokinetic concentric knee flexion force at low velocity. Second study: Purpose: The aim of the second investigation was to find out which procedure - with or without a prior stretch- would best suit in warm-up program to prepare the athlete for the following training or competition, and which procedure would best suit in re-storing the expected reduction of performance following a stretch. Methods: 20 sport students performed triple-hop test on eight separate days before and after completing eight different warm-up protocols in a randomized order. The eight warm-up protocols were: a. 3x10 consecutive maximum vertical jumps (JU), b. 3x8 dynamic half-squats (SQ) with 50% of body weight, c. 3x10 seconds isometric-squats (ISO) by knee angle 120° with 50% of body weight, d. 3 minutes rest with no activity (REST), e. 2 sets of 4 passive static stretching exercises (SS) with a 30 seconds hold followed by 3x10 maximum vertical jumps (SS+JU), f. (SS + SQ), g. (SS + ISO), h. (SS + REST). In the last four conditions the triple-hop test was performed before and immediately after stretching and once again after the second treatment. Results: Jump performance following (JU) was significantly better than following SS+JU (F= 7.2, p=0.015, ES=0.12), and following (SQ) and (ISO) were better than following (SS+SQ) and (SS+ISO), respectively, but not significantly. There was no significant difference between the (JU), (SQ), (ISO) and (REST) protocols. There was no significant difference between the (SS+JU), (SS+SQ), (SS+ISO) and (SS+REST) protocols. The half squat exercise showed significant improvements of 5 % (F=18.5, p=0.0004, ES=0.23) in horizontal jump distance which was decreased following static stretching as compared to the condition SS+REST, whereas the improvements in jump performance following the (JU) or (ISO) exercises by 3.7 % and 3.8 %, respectively tended to be significant (p=0.064 and p=0.052). Conclusion: The implication of a static stretching program in the warming-up phase seemed to be not suitable, especially if the subsequent performances require a high level of power and reactive force production with a rapid stretch shortening cycle. When static stretching combines with dynamic squats with moderate loads, decrements in jump performance may be compensated. Third study: Purpose: The third investigation aimed to examine if the expected decrement in jump performance following static stretching could be compensated using weighted jumps with a light load, and if changes may occur in muscles activity (IEMG). Methods: 30 sport students performed in two separate days countermovement jumps prior to static stretching, immediately after static stretching, and once again after weighted jumps (experimental condition), or before and after rest-ing times which matched the duration of static stretching and weighted jumps (control condition). Jump height, time of force plate contact, peak force and muscle activity of four muscles were measured during the countermovement jump. Results: Jump height was significantly decreased by 5.3 % (p=0.000) following static stretching (immediately after stretching and before the weighted jumps). There was a significant increase (p=0.000) in jump height by 6.9 % following weighted jumps (per-formance decrement was significantly overcompensated). There were no significant changes in muscles activities between the two conditions across the three test times in all four muscles. Conclusion: The decreased performance due to static stretching can be compensated using a suitable procedure such as weighted jumps with a light load (30 % of 1-RM). Even more, the combination of static stretching exercises followed by weighted jumps resulted overall in a significant improvement in the jump height by 1.6 %.Die vorliegende wissenschaftliche Arbeit setzt sich mit den kurzfristigen Effekten des Dehnens auf die sportliche Leistungsfähigkeit auseinander sowie mit der Frage, wie man die erwarteten Leistungseinbußen nach statischem Dehnen möglichst schnell kompensieren kann. Innerhalb des theoretischen Teils der Dissertation wurden aktuelle wissenschaftliche Studien zu den kurzfristigen Effekten des Dehnens auf unterschiedliche Aspekte der sportlichen Leistungsfähigkeit analysiert und zusammengefasst. Anschließend wurden die ausgewählten Studien in folgende zwei Gruppen unterteilt: Studien, die negative Effekte (49 Studien) und Studien, die keine Effekte registriert haben (39 Studien). Der praktische Teil der Dissertation besteht aus drei Untersuchungen mit insgesamt 67 Probanden (Sportstudenten der Universität des Saarlandes). Innerhalb der drei Untersuchungen wurden jeweils wiederholte Messungen (within-subject) durchgeführt. Untersuchung 1 Ziel: Untersuchung der kurzfristigen Effekte des statischen und dynamischen Dehnens der ischiocrurale Muskulatur auf die maximale konzentrische isokinetische Kraft in einer langsamen Winkelgeschwindigkeit, auf den Kniewinkel, bei dem sich die maximale Kraft entfaltet und auf das Bewegungsausmaß der Hüft-Flexion. Methoden: 17 Sportstudenten nahmen an dieser Studie teil. Die Messungen der maximalen konzentrischen isokinetischen Kraft des Kniewinkels, bei dem sich die maximale Kraft entfaltet und das Bewegungsausmaß der Hüft-Flexion wurden vor und unmittelbar nach vier unterschiedlichen Bedingungen durchgeführt. Die Probanden absolvierten, die im Folgenden dargestellten vier Test-Durchgänge (A, B, C und D) in einer randomisierten Reihenfolge (pro Person). (A) Statisches Dehnen der ischiocrurale Muskulatur (3 Sätze x 4 Übungen für 30 Sekunden). (B) Dynamisches Dehnen der ischiocrurale Muskulatur (12-14 Wiederholungen, 3 Sätze x 4 Übungen). (C) und (D) wurden als Kontrollbedingungen gesetzt. In diesen beiden Test-Durchgängen mussten die Probanden für zehn Minuten einfach passiv sitzen. Der Unterschied zwischen beiden Kontrollbedingungen war, dass in (C) Kraft- und Flexibilitätsmessungen durchgeführt während in (D) nur mit Kraftmessungen gearbeitet wurde. Ergebnisse: Die Varianzanalyse mit Messwiederholung zeigte keine signifikante Unterschiede zwischen den vier Test-Durchgängen hinsichtlich der maximalen Kraft und des Kniewinkels, bei dem sich die maximale Kraft entfaltet (p=0.474, F= 0.85) und (p=0.59, F= 0.63). Andererseits gab es eine signifikante Vergrößerung des Bewegungsausmaßes bei der Hüft-Flexion nach dem statischen und dynamischen Dehnen der ischiocrurale Muskulatur (p=0.009, F=8.6, ES= 0.37) und (p=0.000, F=33.7, ES=0.55) im Vergleich zu der Kontrollbedingung (C). Es gab keinen signifikanten Unterschied zwischen dem statischen und dynamischen Dehnen hinsichtlich der Vergrößerung des Bewegungsausmaßes bei der Hüft-Flexion. Fazit: Statisches und dynamisches Dehnen der ischiocrurale Muskulatur vergrößert das Bewegungsausmaß der Hüft-Flexion bei gleichzeitig unveränderter maximaler konzentrischer isokinetischer Kraft in einer langsamen Winkelgeschwindigkeit. Untersuchung 2 Ziel: Das Ziel der Untersuchung bestand darin, herauszufinden welche Übungen - mit oder ohne Dehnen – sich in der Aufwärmphase von Athleten am besten zur Vorbereitung auf das anschließende Training oder einen Wettkampf eignen und welche Übungen die erwarteten Leistungseinbußen nach dem statischen Dehnen kompensieren können. Methoden: 20 Sportstudenten führten Dreier-Hop-Tests an acht separaten Terminen, vor und nach acht verschiedenen Übungssequenzen, in einer randomisierten Reihenfolge durch. Die acht Übungssequenzen waren: (A) 3x10 aufeinanderfolgende maximale Sprünge (JU). (B) 3x8 dynamische Halb-Squats (SQ) mit 50% des Körpergewichts. (C) 3x10 Sekunden isometrische Squats (ISO) bei einem Kniewinkel von 120° mit 50% des Körpergewichts. (D) 3 Minuten Pause (REST). (E) 2 Sätze x 4 passive statische Dehnübungen (SS) gefolgt von 3x10 aufeinanderfolgenden maximalen Sprünge (SS+JU). (F) SS+SQ. (G) SS+ISO. (H) SS+REST. In den letzten vier Übungssequenzen wurde der Dreier-Hop-Test vor dem Dehnen, unmittelbar nach dem Dehnen und nach dem zweiten Treatment durchgeführt. Ergebnisse: Die Sprungleistung war nach JU signifikant besser als nach SS+JU (F= 7.2, p=0.015, ES=0.12), und nach SQ und ISO tendenziell besser als nach SS+SQ und SS+ISO. Es gab keine signifikanten Unterschiede zwischen den JU, SQ, ISO und REST Übungssequenzen sowie zwischen den SS+JU, SS+SQ, SS+ISO und den SS+REST Einheiten. Die dynamischen Halb-Squats (SQ) konnten die verminderte Sprungleistung nach dem Dehnen, im Vergleich zu der Kontrollbedingung SS+REST, kompensieren (5%, F=18.5, p=0.0004, ES=0.23) während die maximalen Sprünge JU und die isometrischen Squats ISO diese reduzierte Sprungleistung nur tendenziell (p=0.064 und p=0.052) kompensierten. Fazit: Statisches Dehnen scheint in der Aufwärmphase ungünstig zu sein, insbesondere wenn die folgenden Leistungen ein hohes Maß an Schnell- und Reaktivkraft im schnellen Dehnungs-Verkürzungs-Zyklus fordern. Eine Leistungsverschlechterung nach dem statischen Dehnen könnte kompensiert werden, wenn auf die Dehnübungen dynamische Halb-Squats folgen. Untersuchung 3: Ziel: Die Untersuchung beschäftigt sich mit der Frage, ob dehnbedingte Einbußen der Sprungleistung durch die Durchführung von „Weighted Jumps“ mit leichtem Gewicht kompensiert werden können und inwiefern es diesbezüglich zu Veränderungen der Muskelaktivität kommt. Methoden: 30 Sportstudenten führten den Countermovement Jump-Test an zwei separaten Terminen vor, unmittelbar nach dem Dehnen und nach den Weighted Jumps durch (Experimentalbedingung) bzw. vor und nach entsprechenden Pausen (Kontrollbedingung). Gemessen wurden die Sprunghöhe, die Kontaktzeit, die maximale Sprungkraft und die Muskelaktivität von vier Muskeln während der CMJ. Ergebnisse: Das statische Dehnen führte zu einer signifikanten Verschlechterung der Sprungleistung von 5,3% (p=0.000) (unmittelbar nach dem Dehnen und vor der Durchführung der Weighted Jumps). Es kam zu einer signifikanten Verbesserung der Sprungleistung von 6,9% (p=0.000) nach den Weighted Jumps (Leistungseinbußen wurden signifikant überkompensiert). Die Muskelaktivitäten der vier abgeleiteten Muskeln zeigten keine signifikanten Veränderungen. Fazit: Die dehnbedingten Einbußen der Sprungleistung lassen sich durch die Durchführung der Weighted Jumps (mit 30% der 1-RM) kompensieren. Des Weiteren resultierte die Kombination von Dehnübungen und Weighted Jumps in einer signifikanten Verbesserung der Sprungleistung von 1,6%

Quantification of eccentric load using accelerometer imbedded in GPS

Global positioning system (GPS) with a triaxial accelerometer is widely used to monitor movements of athletes in games and training, and “body load” (BL) representing the accumulation of the rate of changes in three planes of movements is obtained to determine the training load of a session. Deceleration, change of directions and stopping require eccentric contractions of leg muscles, potentially causing muscle damage and affecting athletic performance. Thus, it is important to monitor eccentric loading in games and training. A variable known as “eccentric index” (EI) purports to be a better representation of eccentric loading than BL. However, it is not known whether BL or EI accurately represents eccentric loading. The present study compared BL and EI during a drill consisting of several movements requiring eccentric contractions of leg muscles (Study 1), and monitored BL and EI over four training sessions of football (soccer) together with changes in maximal voluntary contraction (MVC) strength of the knee extensors and muscle soreness of the thigh muscles before and after each training session (Study 2). In Study 1, 11 university students performed a drill consisting of 3 segments separated by 2 vertical jumps (segment 1: 70 m, segment 2: 50 m, segment 3: 60 m) with several movements including half turns (approximately 45°), 90° and 180° turns and a stop for a total distance of 180 m. All subjects performed the drill at 30%, 60% and 100% of their perceived maximal velocity, 2 trials for each velocity with a 5-min rest between trials. The same trials were repeated on two different days separated by at least 2 days. The time to complete the drill was measured by timing gates, and the time to complete each segment and entire distance, BL (GPSports, Australia) and EI (Athletic Data Innovations, Australia) of each segment were calculated from the GPS/accelerometer data using a specific software. One-way ANOVA compared the three velocities and three segments for the time, BL and EI, and a Pearson product-moment correlation was used to examine the relationships between them. The time to complete the drill was 102.9 ± 15.2 s for 30%, 56.3 ± 5.6 s for 60%, and 42.6 ± 3.1 s for maximum (100%) velocity, with each significantly different from the others (p In Study 2, 6 state league level outfield football (soccer) players were monitored for 4 training sessions, each lasting for 90-120 minutes. BL and EI were calculated as per Study 1 and MVC strength and muscle soreness were assessed before and 1 day after each training session. BL and EI were similar across the 4 sessions; however a large variability in the EI was evident among the players. It was found that a high EI player had a high total mechanical work (total accumulation of changes of directions, accelerations and decelerations). No significant correlation was found between BL and EI, indicating that BL and EI showed different aspects of the movements. No significant changes in MVC strength and muscle soreness were observed after any training session, suggesting that muscle damage was not induced, because of the protective effect conferred by regular training. From the two studies, it was concluded that EI was a better marker to quantify eccentric load than BL, however it is still unclear how accurately EI represents actual muscle damage of leg muscles, which warrants further studie

To do or not to do (exercise) : physical activity in the lives of people with cerebral palsy

We examined the lives of adults with cerebral palsy who had minimal involvement in physical activity (Judy, aged 60; Alana, aged 29), who were involved in physical activity (Amy, aged 25; Ben, aged, 30), or who had minimal involvement in physical activity and who then participated in physical activity (David, aged 27; Tim, aged, 24). After receiving ethical approval, a life-history research approach (Denzin, 1989: Interpretive biography. Newbury Park, CA: Sage) was used, with the participants&rsquo; stories being interpreted using primarily psychodynamic theory (Freud, Erikson, Adler, Basch) to gain insight into their meaning and experiences of physical activity. Judy and Alana had similar childhood experiences, which included: performing difficult, and sometimes painful, physiotherapy; wearing callipers to assist their walking; lacking competence at physical activity; and being socially isolated from their classmates. These aspects of their life histories seemed to contribute to their subsequent avoidance of physical activity and early onset of functional decline.Amy and Ben had negative experiences with physical activity as children (similar to Judy and Alana), but were involved in, and valued, physical activity as adults. Physical activity was a means of displaying competence, delaying further functional loss, and becoming socially connected.David and Tim lost the ability to walk in early adolescence. The minimal physical activity in which they engaged during their adult lives was directed towards trying to walk again. Walking seemed to be intimately connected with psychosocial growth. David&rsquo;s weight-training programme seemed to provide him with another avenue for self-improvement towards his goal of attracting a life partner. Tim&rsquo;s warm-water aerobic programme provided him with an opportunity to develop competence at swimming and at walking, and to enhance his self-esteem for these activities.Involvement in physical activity may be important for people with cerebral palsy in their endeavours to successfully face the various psychosocial challenges throughout life. Implications of this research include: parents and teachers of children with cerebral palsy should provide support for their involvement in physical activity; physiotherapists should try to reduce the pain and increase the perceived relevancy of the treatments they deliver to young people with cerebral palsy; and psychologists should be aware of some of the difficulties people with cerebral palsy face and how they may manifest in adults with the condition.<br /