Limb immobilization is a commonly used therapeutic intervention during periods of recovery from injury. To improve rehabilitation outcomes, interventions that curtail the severe decrements in muscular size and strength that occur during immobilization are critically needed. The purpose of this study was to assess the effects of two distinct interventions during one week of knee-joint immobilization on muscular size, strength, and neuromuscular function. Thirty-nine healthy, college-aged adults (21 males and 18 females) participated in this study. Participants were randomized into one of four groups: immobilization only (n = 9) , immobilization + action observation/mental imagery (AOMI) (n = 10), immobilization + neuromuscular electrical stimulation (NMES) (n = 12), or a control group (n =8). The AOMI group performed daily video observation and mental imagery training of leg extensions. The NMES group performed twice daily sessions of vastus lateralis (VL) and rectus femoris (RF) stimulation at increasing intensities. Muscular size, muscular strength, and neuromuscular function were measured before and after the immobilization period. The results of multiple analyses of covariance (ANCOVAs) indicated that neither AOMI nor NMES significantly mitigated disuse-induced deficits. However, based on percent differences in outcomes between groups, AOMI may hold promise as an effective method of maintaining greater levels of strength during periods of immobilization, as ANCOVA adjusted posttest means indicated 10.7% greater MVC peak torque for the AOMI group versus the immobilization group, as well as 18.2% and 9.6% greater concentric isokinetic peak torque at 30°/s and 180°/s, respectively. Additionally, when examining within group changes, AOMI resulted in increased concentric isokinetic peak torque at 30°/s by 7.2%. Given the daily video/imagery content of the AOMI group, successful AOMI interventions are likely highly specific, and may be modulated by increased corticospinal excitability. These findings may have clinically significant implications for those undergoing periods of prescribed immobilization.

Background Cycling is a popular recreational and competitive form of physical activity and method of transport. Cycling is broadly categorised as road cycling or mountain biking, and each form presents unique challenges and has different skill requirements. While cycling, in general, provides many benefits to both physical health and social behaviours, there are legitimate concerns about injuries related to both road and mountain cycling. Most of the available research presents the injury incidence in commuter or road cycling, with an apparent lack of evidence in mountain biking. The van Mechelen model of injury prevention outlines four stages in injury prevention research; the first stage investigates the extent of the injury and provides the basis on which the remaining stages depend. Based on the van Mechelen conceptual model, the broad aim of this thesis was to investigate acute injury epidemiology in mountain biking and the factors affecting bicycle control and falling. Investigations We performed a systematic review of the incidence of injury in mountain biking. Acute injury incidence ranged from 4% to 71% in cross-country mountain bike races. The causal indicators of bicycle control may include balance, agility and visual perception. In a pilot study, we developed novel tests to assess static bicycle balance and bicycle agility as measures of bicycle control. In the following study, we developed additional dynamic bicycle balance with four increasingly difficult levels. In this study, twenty-nine participants attended three days of repeated testing for reliability assessments of these tests. Participants also completed an outdoor downhill run. Performance in the balance tests were compared to performance in the outdoor downhill test to assess their ecological validity. All tests were assessed for reliability using typical error of measurement, standardised typical error, intraclass correlation coefficients, limits of agreement, effect sizes and repeated measures ANOVA's (with post hoc testing) analyses. The novel bicycle balance and agility were significantly associated with the performance in the outdoor downhill run (r=-0.51 to 0.78; p=0.01 to 0.0001). Cognitive and physical fatigue are factors that may contribute to loss of control of the bicycle. In our final study, we aimed to assess the effect of these factors on the performance in the novel tests. Rate of perceived exertion was significantly increased for all tests following physical fatigue (Cliff's d effect size= 0.27-0.40; p=0.001 to 0.037), but balance and agility performance were not affected. Cognitive fatigue had no effect on balance and agility performance. The fatigue induced in these protocols was insufficient to change performance in the bicycle-specific balance and agility tests. This indicates that either the fatigue protocols did not sufficiently replicate the fatigue experienced in mountain biking or that the tests are too blunt to be affected by the magnitude of fatigue in these protocols. Conclusion The overall incidence of injury in mountain biking is difficult to determine due to different injury definitions in the research. However, the available data clearly indicates an area of concern in sports and exercise medicine. We developed novel tests to assess the skill components of balance and agility on a mountain bike. The novel bicycle-specific tests are robust assessments of mountain biking performance and can be applied in clinical and research environments to determine bicycle control. Cognitive and physical fatigue did not affect performance on these novel tests. Based on the overall findings of our studies, we recommend that further research is conducted on the epidemiology of mountain biking injuries. The effect of fatigue on the novel tests needs to be investigated further using a combination of physical and cognitive fatigue.

The purpose of this thesis is to investigate the relationship between Omega-3 Fatty Acid supplementation and recovery from resistance training. Omega-3 Fatty Acids are a type of polyunsaturated fatty acid that is commonly found in marine sources. Omega-3 Fatty Acids are widely known for offering cardiovascular health benefits and for their anti-inflammatory properties, but their role in resistance training recovery is a relatively novel area of research. This review was conducted by qualitatively analyzing a collection of studies that have been published on the relationship between Omega-3 Fatty Acid supplementation and recovery from resistance training in either resistance-trained or untrained young adults between the ages of 18 and 40 years. Several statistically significant (p

Advances in surface electromyographic (sEMG) signal decomposition algorithms have allowed for a richer understanding of motor unit behavior during voluntary contractions. However, this technology has primarily been applied to conditions in which muscle length remains constant (isometric contractions) and force is low. It is unclear if previous findings obtained during isometric contractions are applicable to dynamic, real-world movements, particularly when examined across days. We sought to determine the reliability of firing rates from the biceps brachii during the concentric (lifting) and eccentric (lowering) phases of one-repetition maximum (1RM) curls using a novel sEMG signal decomposition algorithm. Fourteen resistance trained adults (six males, eight females) participated in three laboratory visits, during which 1RM strength for the barbell curl exercise was assessed while sEMG signals were recorded from the biceps brachii. The motor unit mean firing rate (pulses per second [pps]) versus action potential amplitude (millivolts [mV]) relationship was quantified, and linear regression was used to determine the slopes and y-intercepts. The slopes during both the concentric and eccentric phases demonstrated intraclass correlation coefficients (model 3,1) ≥ 0.861, standard errors of measurement ~26.5%, and minimal differences needed to be considered real ~34.5 (pps/mV). The y-intercepts displayed intraclass correlation coefficients ≥ 0.375, standard errors of measurement ≥ 10.0%, and minimal differences needed to be considered real ≥ 7.8 (pps). For both the slopes and y-intercepts, there were no significant differences across days (p > .05) and small effect sizes were observed (ƞp2 < 0.01). In summary, motor unit data from the biceps brachii obtained during high-force, dynamic contractions across multiple days appears to demonstrate sufficient reliability to track neuromuscular adaptations.

Muscle strength declines ~3% per year after the age of 70, leading to functional impairments and the loss of independence. Resistance training guidelines for older adults are typically based on free-weight and machine exercises, which may be inaccessible and lack carryover to activities of daily living. The present study tested the hypothesis that resistance training adaptations are task specific in older adults. Thirty older adults (8 males, 22 females; mean age = 71 years) were randomly assigned to participate in 6 weeks of supervised, high-intensity resistance training (twice per week) utilizing free-weight and machine exercises (traditional) versus functional activities that were overloaded with a weighted vest (functional). Participants were thoroughly familiarized with the exercises and testing prior to beginning the study. Major outcome measures included assessments of functional performance, five-repetition maximum strength, isometric knee extensor force, and quadriceps muscle mass and muscle quality. Physical activity and nutrition were monitored. The study results demonstrate that the magnitude of improvement within a given outcome was largely dependent on group assignment, with greater improvements in gait speed and the timed-up-and-go in the functional group, but 2-3x greater five-repetition maximum strength improvements for the trap bar deadlift, leg press, and leg extension exercises following traditional resistance training. Both groups showed improvements in isometric knee extensor force and muscle size, suggesting that some aspects of the observed adaptations were generic, rather than specific. Importantly, accelerometer data revealed an increase of time spent in moderate-to-vigorous activities outside of the laboratory. Overall, these novel findings suggest that, among older adults, 1) resistance training adaptations exhibit a high degree of task specificity and 2) significant improvements in functional outcomes can be achieved with the simple use of a weighted vest.

Ninety percent of all low back pain cases are classified as non-specific low back pain (NSLBP). NSLBP stands as the leading cause of disability and premature retirement worldwide. It is crucial to intervene between the ages of 18-45 years old as NSLBP prevalence increases with age. Providing patients with innovative feasible methods to undertake rehabilitation can enhance their exercise literacy. This 6-week randomized controlled trial evaluated outcomes of pain, disability, adherence, compliance, and lateral abdominal wall muscle thickness between a gamified exercise group and an at-home exercise packet group. Forty participants were allocated into a gamified group or a packet group. Participants completed a 6 week at-home exercise protocol that included the seven core exercises. Weekly hold times were collected with electronic surveys. The gamified group received a leaderboard of the hold times each week. The first visit, 3-week survey, and last visit included questionnaire completion regarding the outcomes. The first and last visit included dynamic ultrasound to measure the lateral abdominal wall during exercise static and starting positions. Disability was significantly lower at 6 weeks compared to baseline in both groups. No significant findings between groups or within groups were found regarding adherence. At 6 weeks, the packet group had a higher % thickness change in the right internal oblique during two exercises compared to the gamified group. The packet group had a higher % thickness change in the left internal oblique during the foot-elevated side plank and dead bug. Disability was significantly decreased in both groups from baseline to 6 weeks. Participants had decreased fear-avoidance beliefs at the end of 6 weeks, suggesting an increased willingness to engage in activity and exercise. The gamified group did not have greater exercise adherence, although they did have 12% higher compliance. Internal oblique % thickness had the greatest change of muscles.

The relationships between hyperthermia, dehydration and oxidative stress have been thoroughly studied separately within the literature both in vitro and in vivo. However, no in vivo attempts have been made to manipulate the hydration status of individuals to investigate the resulting changes in oxidative and cellular stress during and after exercise in hyperthermic conditions and what effect these changes may have on exercise performance. The purpose of the first experiment was to investigate the effects of exercise-induced dehydration with and without hyperthermia on oxidative stress. Seven healthy male trained cyclists (mean ± SD) age: 36 ± 6 yrs, height: 177.4 ± 6.5 cm, weight: 72.8 ± 7.0 kg, and power output (PO) at lactate threshold (LT): 199.3 ± 19.0 Watts (W) completed 90 min cycling exercise at 95% LT followed by a 5 km time trial (TT) in four conditions: 1) euhydration in a warm environment (EU-W, control), 2) dehydration in a warm environment (DE-W), 3) euhydration in a thermoneutral environment (EU-T), and 4) dehydration in a thermoneutral environment (DE-T) (W: 33.9 ± 0.9°C; T: 23.0 ± 1.0°C). Whole blood oxidised glutathione (GSSG) increased significantly post exercise in dehydration trials only (DE-W: p < 0.01, DE-T: p = 0.03), and while not significant, whole blood total glutathione (TGSH) and plasma thiobarbituric acid reactive substances (TBARS) tended to increase post exercise in dehydration trials (p = 0.08 for both). Intracellular monocyte heat shock protein 72 (HSP72) concentration was increased (p = 0.01) while intracellular lymphocyte HSP32 concentration was decreased for all trials (p = 0.02). Exercise-induced dehydration led to an increase in GSSG concentration while maintenance of euhydration attenuated these increases regardless of environmental condition. Additionally, evidence of increased cellular stress (measured via HSP) was found during all trials independent of body mass loss and environment. Finally, total distance covered during 90 min and PO during both 90 min and 5 km TT performance were reduced during only the DE-W trial, likely a result of combined cellular stress, hyperthermia and dehydration. These findings highlight the importance of fluid consumption during exercise to attenuate thermal and oxidative stress during prolonged exercise in the heat. The purpose of the second experiment was to investigate the effect of prolonged exercise-induced dehydration with and without hyperthermia on cellular and oxidative stress markers in untrained individuals, to serve as a comparison to the results of the first experimental chapter. Seven untrained male university students (mean ± SD) age: 21 ± 3 yrs, height: 181.1 ± 9.2 cm, weight: 76.8 ± 8.8 kg, and PO at LT 100.0 ± 13.0 W, who were unacclimatised to heat, participated in this study. Subjects completed the same experimental protocol as outlined in experimental chapter one, in warm (33.9 ± 1.0°C) and thermoneutral (22.9 ± 1.0°C) environments. Whole blood GSSG increased an average of 32% (p < 0.01) as a result of prolonged exercise, however unlike the trained subjects of experiment one, there was no effect of body mass loss on GSSG (p = 0.63). Similarly, intracellular monocyte HSP72 concentration increased 14% (p < 0.01) as a result of prolonged cycling regardless of body mass loss and environmental heat stress, analogous to subjects in experiment one. While there were no significant changes as a result of hydration or environment, a relationship was found between GSSG concentration and body mass loss (r2 = 0.5, p = 0.05), while HSP72 was correlated with body temperature and levels of heat storage (r2 = 0.5, p = 0.01). Similar to the trained individuals in experiment one, PO during the 90 min (7%, p < 0.01) and TT (14%, p < 0.01) were decreased while thermoregulation was impaired during DE-W only. These results demonstrate the increased level of stress in untrained subjects as a result of exercise and highlight the importance of participation in recommended physical activity to aid in positive cellular adaptations leading to superior antioxidant defences to aid in disease prevention. In light of the findings from the first experimental chapter that dehydration can significantly influence oxidative stress in trained subjects, the purpose of the third experimental chapter was to compare pre-exercise hyperhydration with plain water (W) or water with glycerol (G) to no hyperhydration (C) on markers of oxidative stress prior to and after a 90 min TT. Seven trained male cyclists and triathletes (age: 28 ± 8 yrs, height: 178.4 ± 7.8 cm, and mass: 73.2 ± 9.6 kg) covered as much distance as possible during a 90 min cycle after G, W or C. Blood was collected pre ingestion (PRE), post ingestion/pre exercise (PI), immediately post exercise (PE) and 1 hour post exercise (1HR) and analysed for whole blood TGSH, GSSG, and plasma levels of lipid hydroperoxides (LOOH) and protein carbonyls (PC). TGSH concentration increased post exercise in W and C (p < 0.01) while PC concentration increased post exercise during C only (p = 0.03). Additionally, GSSG concentration was greater PI and PE in C compared to G (p = 0.05, and p < 0.01, respectively), likely due to the inferior amount of fluid retained during C compared to the G and W trials. Therefore, it appears that both pre exercise hyperhydration with ad libitum fluid ingestion during exercise is sufficient to attenuate rises in exercise-induced oxidative stress. The novel findings presented in this thesis indicate fluid ingestion plays a vital role in providing cellular protection from oxidative stress. These results suggest that individuals participating in prolonged exercise should consume adequate fluid during exercise to avoid dehydration, matching fluid intake with body mass loss. Additionally, individuals who wish to hyperhydrate prior to exercise may enhance their ability to delay dehydration and thus enhance their cellular protection from oxidative stress.

Hamstring strains are one of the primary injuries within modern soccer match-play. The injury is well recognised by medical personnel, coaches and athletes as a major concern causing significant financial costs and lost time from training and matches. The temporal pattern of hamstring injury incidence during matches has shown almost half of all injuries to occur during the latter stages of each half, thus suggesting fatigue as an important contributing factor for injury. This thesis comprises four experimental chapters that examine the effect of multidirectional soccer-specific fatigue on the primary aetiological risk factors and mechanism of injury. This was then used to create and evaluate an injury prevention programme aimed at reducing the risk of hamstring strains in soccer.

The central nervous system is highly sensitive to reductions in oxygen availability but the neurophysiological responses in healthy human lowlanders are not well understood. In severe hypoxia, whole-body exercise tolerance is impaired and neuromuscular fatigue, defined as any exercise-induced reduction in the ability of a muscle to generate force or power, reversible by rest, may be largely due to cerebral perturbations. The primary aim of this thesis was to determine the mechanisms of exercise-induced neuromuscular fatigue and the related neurophysiological responses to acute, chronic and intermittent severe hypoxia in healthy humans. In acute severe hypoxia (AH), exercise tolerance was, in part, mediated by a hypoxia-sensitive source of central fatigue, measured as a decrease in voluntary activation (VA) of the knee extensors (Study 1 – 4). This coincided with a significant challenge to systemic (arterial oxygen saturation [SpO2] ≈ 70%, Study 1 - 4) and cerebral oxygen availability at end-exercise (Study 3 - 4). The rate of development of peripheral locomotor muscle fatigue was blunted at task failure in AH in comparison to normoxia (Study 1 – 2). Corticospinal excitability and the neuromuscular mechanisms of fatigue were measured after a prolonged (two-week) exposure to high altitude in Study 3 (5260 m above sea level, Mount Chacaltaya, Bolivia). This was the first study to show that acclimatisation to chronic severe hypoxia (CH) alleviates the development of supraspinal fatigue induced by whole-body exercise in AH. This occurred in parallel to an improved cerebral oxygen delivery and cerebral oxygenation. Interestingly, the neurophysiological responses at rest in CH were characterised by an increased corticospinal and muscle membrane excitability. The peripheral contribution to neuromuscular fatigue was not attenuated following acclimatisation to high altitude. In study 4, a two-week protocol of intermittent hypoxia (IH) attenuated exercise-induced supraspinal fatigue measured in AH and substantially improved constant-power cycling in severe hypoxia. Total haemoglobin mass was unaltered by IH, but arterial oxygen content was improved due to an increase in SpO2, secondary to an enhanced ventilatory response to exercise. Peripheral locomotor muscle fatigue was lower following IH, which may be related to exercise training in hypoxia. Although corticospinal excitability was unchanged following a single 2-h exposure to severe hypoxia, repeated exposures of IH resulted in a transient increase in motor cortex excitability without changes in intracortical inhibition. (Study 5). In conclusion, in acute severe hypoxia, whole-body exercise tolerance is impaired through oxygensensitive mechanisms which exacerbate central fatigue. The acute response can be alleviated following both chronic and intermittent severe hypoxia.

The capability to perform your best is an important aspect in the sport of soccer. The relationship between anthropometric measures to vertical jump height among NCAA Division I Women’s soccer players is a subject lacking sufficient scientific research. Purpose: To analyze this relationship, body mass and %body fat was correlated with un-weighted countermovement jump height to determine the strength of this relationship in NCAA DI female soccer players. Methods: Data from an ongoing athlete monitoring program from fourteen NCAA D1 female soccer players in the year 2007 was analyzed. Air Displacement Plethysmography (ADP) via a BOD POD (Life Measurement, Inc., Concord, CA) measured body composition. Height and weight were measured using BOD POD Scale (Life Measurement Inc., Concord, CA) and a stadiometer (Detecto Scale Program, Webb City, MO). To measure the strength characteristics, a Countermovement Jump was utilized. Those jumps were measured using force plates (Rice Lake Weighing Systems, Rice Lake, WI). Results: There was an inverse and moderate correlation (r = -0.371) between 0kg CMJ and %BF, and an inverse and trivial correlation (r = -0.034) between the 0kg CMJ and BM. Conclusion: The relationship between %BF and jump height has a larger impact on this particular group compared to the BM relationship with jump height, but they both however play a significant role in DI women’s soccer.