Introduction: The role of muscle forces in determining bone micro-architecture and strength in children is poorly understood as limited evidence relies on surrogate measures of muscle force such as muscle size. The objective of this thesis was to explore the role of muscle area, peak forces from neuromuscular performance tests and physical activity in determining bone properties at the radius and tibia in children. Methods: 37 boys and 42 girls (mean age 10.5; SD 1.6y) had their dominant forearm and lower leg imaged using peripheral quantitative computed tomography (pQCT) and high resolution pQCT (HR-pQCT). Bone mass, density, area and estimated strength were assessed. Muscle area was determined from the pQCT scans and grip strength measured via a handheld dynamometer. Peak force from a single maximal push-up performed on force platforms and the number of standard push-ups completed in a single attempt were recorded. Countermovement and standing long jump maximal forces were recorded, impulse and power were calculated, and average standing long jump distance was measured. Physical activity was measured using the Physical Activity Questionnaire for Children. Sex, maturation (estimated age from peak height velocity), weight and limb length (ulna and tibia) were controlled in the linear regression models. Variance predicted (R2) by models using muscle area, neuromuscular performance measures as independent predictors (squared partial r) of bone properties are reported. Results: Grip strength and muscle area independently predicted 14-18% of the variance in bone area at the distal radius and 9-22% of the variance in bone strength at the distal and shaft sites of radius. Peak push-up force predicted 10% of the variance in trabecular number at the distal radius. Muscle area independently predicted 5-28% and countermovement and standing long jump forces and impulses predicted 6-10% of the variance in bone area, cortical content or density at the tibia shaft. Standing long jump power predicted 5-8% of the variance in bone area and cortical density at the tibia shaft. Physical activity predicted 9% of the variance in trabecular number at the distal tibia. Discussion: Thesis findings support the use of muscle area as a surrogate for muscle forces and identified neuromuscular performance measures that will guide targeted exercise interventions aiming to optimize bone strength development in children.

Whole body vibration (WBV) is a mode of exercise by which an individual stands on a vibration platform that may be oscillating and therefore creating vertical displacement which affects gravitational forces acting upon the whole body. Manipulations of platform amplitude or frequency can affect the rate of change of the WBV (i.e. acceleration) acting upon an individual. The specific influences of frequency or amplitude, however, are unknown. The aim of the study, therefore, was two fold; (1) to identify chronic WBV effects of neuromuscular performance within a community dwelling older adult sample, and; (2) to identify WBV methods that would elicit chronic neuromuscular performance changes within such a sample. The study incorporated a randomised controlled experimental design to examine the aim. Seventy-three community dwelling older adults freely consented to the requirements of the study (mean age = 72.0 years). Neuromuscular performance was quantified with the 5-Chair Stands test, the Timed Up and Go (TUG) test and the Tinetti test. Health Related Quality of Life (HRQOL) was qualified with the SF-36 Health Survey. A six week WBV intervention significantly changed the quantifiers of neuromuscular performance in a community dwelling older adult sample. The WBV intervention significantly reduced time taken to complete the 5-Chair Stands test (p <.05) and the TUG test (p <.05). The six week WBV intervention significantly improved Tinetti test scores (p <.05). The six week WBV intervention significantly improved all components of HRQOL. For the 5-Chair Stands test, a three WBV sessions per week intervention elicited significantly larger (p <.05) neuromuscular performance gains than a two WBV sessions per week intervention in the target sample. For the TUG test, a three WBV sessions per week intervention elicited significantly larger (p <.05) neuromuscular performance gains than a zero and one WBV session per week intervention in the target sample. A significant difference (p <.05) was found between pre-test and post-test Tinetti test scores for all WBV intervention groups. There was an insignificant difference (p >.05) found within the control group of community dwelling older adults for the Tinetti test. Detraining effects were observed three weeks after the cessation of the six week WBV intervention for the three WBV sessions per week group. Neuromuscular performance reduced after the detraining period. Vibration platform dynamics (manipulated frequency and controlled amplitude) showed that gravitational forces created by the WBV were safe since no injuries were associated with the intervention and since participant compliance was 100% during the six week WBV intervention. The methods of this study showed a chronic WBV intervention to be a safe and easily administered exercise to improve neuromuscular performance and HRQOL of a community dwelling older adult sample. Specifically, WBV could be used as a safe and effective tool to improve aspects of normal daily function such as body balance and gait speed.

The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of countermovement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 ± 0.06 ng·ml-1 and 6.49 ± 0.37 ng·ml-1; p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70).

Thesis Title: Enhancing rehabilitation following anterior cruciate ligament reconstruction. Context: Physical training with a neuromuscular focus has been shown to reduce anterior cruciate ligament (ACL) injury. However, ACL injury remains prevalent and often leads to joint instability, which requires surgical reconstruction. Following reconstructive surgery, a minimum of 6 months supervised rehabilitation is recommended with associated with financial cost implications to the National Health Service (NHS), the patient and society. Traditionally rehabilitation is offered in a concurrent format, whereby strength and cardio-vascular endurance exercises are performed in the same session. However, accumulating evidence from healthy populations, suggests that the development of strength might be attenuated by cardio-vascular endurance conditioning performed in close temporal proximity. This thesis comprises an entirely novel investigation of potential attenuation of strength gains in rehabilitating clinical populations that is associated with temporal incompatibility of physiological conditioning stimuli. No study has previously investigated this phenomenon, whether it might compromise the efficacy of treatment or recovery, or its potential influence on objectively-measured and patients’ perception of functional, musculoskeletal and neuromuscular performance capabilities. Objectives: The purpose of this thesis was to assess the effects of reconstruction surgery and 24 weeks of non-concurrent strength and endurance rehabilitation (with 48 week post-operative follow-up) on (a) subjective (IKDC; KOOS; PP [Chapter 4]) and objective measures of function (HOP [Chapter 5]) (primary outcome measures for this thesis), and (b) objective measures of musculoskeletal (ATFD) and neuromuscular performance (PF, EMD, RFD, SMP [Chapter 5]) (secondary outcome measures), in patients with anterior cruciate ligament deficiency. The secondary aim was to evaluate the relationships amongst a subjective outcome of function (IKDC), an objective outcome of function (HOP), and the secondary objective outcomes of musculoskeletal (ATFD) and neuromuscular (PF, RFD, EMD, SMP) performance at pre-surgery and at 24 weeks post-surgery (Chapter 6). Setting: Orthopaedic Hospital NHS Foundation Trust. Design: Prospective random-allocation to group trial involving iso-volume rehabilitative intervention versus contemporary practice, using contralateral limb assessment and clinico-social approbation controls. The design compared the effects of experimental post-surgical rehabilitation comprising non-concurrent strength and endurance conditioning with two conditions of control reflecting contemporary clinical practice (matched versus minimal assessment interaction). Participants: Eighty two patients (69♂, 13♀, age: 35.4 ± 8.6 yr; time from injury to surgery 9.4 ± 6.9 months [mean ± SD]) electing to undergo unilateral ACL reconstructive surgery (semitendinosus and gracilis graft [n = 57]; central third, bone-patella tendon-bone graft [n = 25]); were allocated to groups (2:2:1 purposive sampling ratio, respectively). Nineteen patients were lost to follow-up. Intervention: A standardised traditional concurrent (CON) ACL rehabilitation programme acted as the control versus an experimental non-concurrent (NCON) ACL rehabilitation programme that involved separation of strength and cardio-vascular endurance conditioning. An additional control group (Limited testing CON) matched the CON group rehabilitation applied within contemporary clinical practice. Outcome Measures: Chapter 4: The self-perceived primary outcome measures of function IKDC, KOOS and PP were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and 48 weeks post-operative for the Limited testing CON group. Chapter 5: The primary objective outcome of function was HOP; the secondary outcomes were ATFD, PF, RFD, EMD and SMP associated with the knee extensors and flexors of the injured and non-injured legs. These objective outcomes were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and at 48 weeks post-operative only for the Limited testing CON group. Chapter 6 Self-perceived (IKDC) subjective knee evaluation and the objective outcome of function (HOP), and selected objective outcomes of musculoskeletal and neuromuscular performance including ATFD, PF, RFD, EMD and SMP of the knee extensors and flexors of the injured and non-injured legs where applicable; measured at pre-surgery and at 24 weeks post-surgery were analysed for association, using Pearson product-moment correlation coefficients. A priori alpha levels were set at p<0.05. Results: Chapter 4: Factorial analyses of variance (ANOVAs) with repeated-measures investigating the primary aim showed significant group (NCON; CON) by test occasion (pre-surgery, 6, 12. 24 and 48 weeks post-surgery) interactions for self-perceived outcomes of function IKDC, KOOS and PP confirmed increased clinical effectiveness of NCON conditioning (F(2.0, 82.9)GG = 4.0 p<0.05, F(2.2, 134.7)GG = 5.5 p<0.001, F(1.9, 121.4)GG = 14.6 p<0.001, respectively) and the group mean peak relative difference in improvement for NCON was ~5.9% - 12.7% superior to CON. The greatest interaction effect was found to occur between pre-surgery and the 12 weeks post-operative test occasion for IKDC and KOOS, and between pre-surgery and the 24 week test occasion for PP. Patterns of improvements in self-perceived fitness over time were represented by a relative effect size range of 0.71 to 1.92. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery vs. 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 5: Factorial analyses of variance (ANOVAs) with repeated-measures showed significant group (NCON; CON) by leg (injured/non-injured) by test occasion (pre-surgery, 6, 12, 24 and 48 weeks post-surgery) interactions of the objective measure of function (HOP) together with the secondary outcomes of ATFD, PF, RFD, EMD and SMP. Similar responses were noted for the knee extensors and flexors of the injured and non-injured legs (F(2.1, 248) GG = 4.5 to 6.6; p<0.01) and confirmed increased clinical effectiveness of NCON conditioning (range ~4.7% - 15.3% [10.8%]) better than CON between 12 and 48 weeks. Patterns of improvements in physical fitness capabilities over time were represented by a relative effect size range of 1.92 to 2.89. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery versus 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 6: Two-tailed probabilities were used due to the exploratory nature of this study. A limited number of weak to moderate statistically significant correlations were confirmed (ranging from r = 0.262 – 0.404; p<0.05; n=48 [amalgamated NCON and CON groups] ) between IKDC and most notably, the neuromuscular performance outcome of EMD. Conclusion: Overall, the patterning and extent of changes amongst self-perceived, functional, musculoskeletal and neuromuscular performance scores offer support for the efficacy of using non-concurrent strength and endurance conditioning to enhance post-surgery rehabilitation. The limited robustness of relationships amongst the validated and frequently-used self-perceived outcome of function [IKDC], and objectively-measured outcomes of function and musculoskeletal and neuromuscular performance suggested that each might properly reflect an important but separate aspect of clinical response and should be deployed to detect change.

The purpose of the study was to examine changes in cardiovascular function and neuromuscular performance of primary grade girls after a six-week treatment program. The Kraus-Weber Tests and modified Harvard Step Test were administered to sixty-seven subjects before and after the treatment program, which consisted of exercises and running for the experimental group and sedentary games for the control group. None of the significant differences in recovery heart rate or the Kraus-Weber tests could be attributed to the treatment program. The length of training program was apparently not enough to detect change in fitness level of the subjects. A need exists for exercise tests that are more meaningful and more easily administered.

Caffeine is often used in a variety of forms to enhance athletic performance; however, research regarding caffeine’s effects on strength and power in female athletes is lacking. Therefore, the purpose of this study was to analyze the acute effects of caffeine anhydrous (6 mg/kg of body mass) on jumping performance and maximal strength in female collegiate athletes. Eleven athletes (19.7 ± 0.9 yrs; 166.4 ± 10.2 cm, 67.7 ± 9.4 kg) performed two testing sessions separated by one week, and randomly received caffeine or placebo using a double-blind approach. Heart rate, blood pressure, and tympanic temperature were recorded before athletes received each condition, following 60 min of quiet sitting, and directly after performance testing. Athletes were assessed on unweighted and weighted squat jump height (SJH0, SJH20) and countermovement jump height (CMJH0, CMJH20), isometric mid-thigh pull peak force (IPF), and rate of force development from 0–200 ms (RFD200). Resting systolic blood pressure was significantly greater following caffeine administration compared to a placebo (p = 0.017). There were small, significant differences in SJH0 (p = 0.035, g = 0.35), SJH20 (p = 0.002, g = 0.49), CMJH0 (p = 0.015, g = 0.19), and CMJH20 (p < 0.001, g = 0.37) in favor of caffeine over placebo. However, there was no significant difference in IPF (p = 0.369, g = 0.12) and RFD200 (p = 0.235, g = 0.32) between conditions. Therefore, caffeine appears to enhance jumping performance, but not maximal strength in female collegiate athletes.

The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of counter-movement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 ± 0.06 ng·ml−1 and 6.49 ± 0.37 ng·ml−1; p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70).