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Caffeine is now an unrestricted ergogenic aid for competitive athletes. Previous reviews of caffeine's effects on exercise performance have been limited to qualitative analysis. The purpose of this paper was therefore to quantitatively meta-analyze the effects of caffeine on exercise performance. We identified 90 estimates of performance effects of caffeine in 32 peer-reviewed studies. All estimates were converted to mean power in an equivalent time trial then subjected to a mixed-model meta-analysis. The fixed effects were gender, training status (elite athlete, non-elite athlete, non-athlete), dietary caffeine status (habitual consumer, non-consumer), caffeine abstention period, caffeine dose (mg/kg body mass), type of caffeine (pure or in coffee), delay between ingestion and performance test, duration of test, and presence or absence of fatiguing exercise before the test. The random effects accounted for within- and between-study variance. We found that caffeine enhanced mean power by 2.8% (90% confidence limits ± 1.1%) in male non-elite athletes who are habitual caffeine consumers abstaining from caffeine for 2 d before consuming 6 mg/kg of caffeine capsules 1 h before performing a 30-min time trial without intervening fatiguing exercise. The effects for other athletes and conditions were: females, 3.1% (± 2.7%); elite athletes, 2.9% (± 1.4%); non-athletes, 1.3% (± 1.2%); habitual non-consumers, 4.0% (± 1.4%); 7 d of abstention, 3.4% (± 2.6%); 0.3 mg/kg of caffeine, 1.6% (± 5.3%); caffeinated coffee, 1.0% (± 1.6%); 2-h delay before exercise, 2.9% (± 1.2%); 6-s exercise test, 1.6% (± 1.7%); prior fatiguing exercise, 3.0% (± 1.6%). Each of these effects of caffeine varied typically between studies by ± 1.4% (the between-study random effect; 90% confidence limits ± 0.9 to ± 3.5%). We conclude that caffeine has a greater effect on performance with athletes, with habitual non-consumers of dietary caffeine, when administered as pure caffeine, and in endurance exercise, but there is considerable uncertainty about the magnitude of the effects on individuals. More research is needed to reduce this uncertainty and to determine the performance effects of caffeine with females, following longer periods of dietary abstention, in low doses, and for brief exercise. There has also been no research on effects of caffeine on the repetitive fatiguing exercise typical of team sports.

Response characteristics and tactile coding capacities of single neurons of the dorsal column nuclei (DCN), and the dorsal horn, in particular, neurons of the spinocervical tract (SCT), were investigated in anaesthetized cats. Purely dynamically-sensitive tactile neurons of the DCN could be divided into two classes, one associated with hair follicle afferent (HFA) input, the other with Pacinian corpuscle (PC) input. The HFA-related class was most sensitive to low-frequency (&lt50 Hz) vibration, had phaselocked responses to vibration frequencies up to ~75 Hz and had a graded response output as a function of vibrotactile intensity changes. PC-related neurons had broader vibrotactile sensitivity, extending to ~300 Hz with tightest phaselocking between 50 and 200 Hz. The SCT neurons in the lumbar dorsal horn had tactile receptive fields on the hairy skin of the hindlimb and a very limited capacity to signal, in a graded way, the intensity parameter of the vibrotactile stimulus. Furthermore, because of their inability to respond on a cycle-by-cycle pattern at vibration frequencies above 5-10 Hz, these neurons were unable to provide any useful signal of vibration frequency beyond ~5-10 Hz, in contrast to DCN neurons. In the parallel human psychophysical study, the capacity for vibrotactile frequency detection and discrimination was examined in five subjects in glabrous and hairy skin. The vibrotactile detection threshold values obtained at four standard frequencies of 20, 50, 100 and 200 Hz were markedly higher on the hairy skin than on the glabrous skin. The discrimination task was examined by means of a two-alternative, forced-choice psychophysical procedure. Measures of the discriminable frequency increment (?????) and the Weber Fraction (????? / ??), revealed similar capacities for frequency discrimination at the two different skin sites at the standard frequencies of 20, 100 and 200 Hz, but an equivocal difference at 50 Hz. Cutaneous local anaesthesia in the dorsal forearm produced a marked impairment in vibrotactile detection and discrimination at the low frequencies of 20 and 50 Hz but little effect at higher frequencies, confirming that vibrotactile detection and discrimination in hairy skin depend upon superficial receptors at low vibrotactile frequencies, but depend on deep, probably Pacinian corpuscle receptors for high frequencies.

Recent research has highlighted that information-movement couplings are unique to the constraints of the task, environment and performer. This recent research implies that skills should be developed in practice environments that are reflective of those found in competition. Representative environments should also allow the performer to attune to specifying information essential for success of a skill. However, in water polo, shooting practice is often conducted without the presence of a goalkeeper or defender. The aim of this study was to determine the effect of game-specific task constraints on the ball speed, accuracy and technique of the water polo shot. Ten male competitive level water polo players performed a total of forty shots comprising ten shots in each of four conditions from the 4m-penalty line. Conditions included all combinations of goalkeeper and defender (absent or present). Three Sony mini-digital cameras (50Hz) were placed perpendicular to the movement, giving rear, overhead and a right sagittal view. Ball speed was measured using a Radar-gun (Stalker Pro, USA). For each condition, means and standard deviations were determined for all outcome measures (shooting accuracy and ball speed) and technique variables. A repeated measures ANOVA was used to determine the effect (p<0.05) of the goalkeeper and defender individually as well as in combination on the dependent variables. Cohen's effect sizes were also used to determine the magnitude of the difference between conditions. The presence of a defender resulted in a significant increase in lateral trunk flexion at ball release, decreased the duration of the shot and selected swing sub-phases (i.e. pick-up to top of back swing time) and significantly altered the placement of the ball in the goal. When the goalkeeper only was present, this resulted in decreases in total shot time and pick-up to top of back swing time and significantly altered the placement of the ball in the goal. The presence of the defender and goalkeeper in combination brought about a moderate effect, decreasing the ball speed, significantly decreasing the success of the shots, scores achieved and significantly altering the placement of shots. Forward swing distance and selected swing sub-phases (i.e. total shot time, pick-up to top of back swing time, forward swing start to midway and forward swing start to release) were also significantly decreased in the presence of the defender and goalkeeper. These findings highlight the importance of maintaining appropriate task constraints during water polo shooting practice. In effect the removal of the defender and goalkeeper leads to the development of inappropriate information-movement couplings. Specifically, the presence of the defender and/or goalkeeper lead to reductions in the durations of selected swing sub phases, resulting in changes in the relative coordination and timing of the water polo shot. These findings indicate that in order to facilitate the development of this specific shooting skill, coaches should structure practice to replicate the perceptual information available during competition.

Optimising recovery post-game or post-training could provide a competitive advantage to an athlete, especially if more than one bout of exercise is performed in a day. Active recovery is one common method that is thought to enhance the recovery process. Another recovery method that is gaining popularity is water immersion. The objective of this thesis was to analyse whether these two recovery methods provided greater recovery from explosive exercise than passive recovery. A physiological rationale that may explain the possibility of enhanced recovery with water immersion was initially investigated. The literature surrounding active recovery, water immersion and passive recovery on strength, cycling, running and jumping was then examined. Following these reviews an experimental study was conducted investigating the effects of water immersion, active recovery and passive recovery conducted after repeated bouts of explosive exercise. The rationale for active recovery post-exercise is that during intense exercise, fluid from the blood is forced into the working muscles due to the increase in mean arterial pressure, which increases muscle volume and decreases blood plasma fraction. Active recovery reduces this exercise induced edema and, with an associated increase in blood flow throughout the body, may increase the metabolism of waste substrates produced during exercise. Researchers have observed this increased substrate metabolism with reductions in post-exercise blood lactate accumulation following active recovery. Water immersion would appear to cause a similar physiological response to active recovery without the need to expend extra energy. When a large portion of the body is immersed, hydrostatic pressure acts on the body's fluids within the immersed region. Fluids from the extravascular space move into the vascular system reducing exercise-induced increases in muscular volume and reducing soft tissue inflammation. Additionally, blood volume increases and is redistributed towards the central cavity, which in turn increases cardiac preload, stroke volume, cardiac output, and blood flow throughout the body. Cardiac output increases in relation to the depth of immersion and have been observed to increase by as much as 102% during head-out immersions. These cardiovascular responses occur without any increase in energy expenditure. If extra-intravascular fluid movement is enhanced, then the movement and metabolism of waste substrates could increase. Observations of increased post-exercise blood lactate clearance with water immersion would support this theory. Most methodologies studying the performance benefits of active recovery and water immersion suffer many limitations. These limitations often consist of the experimental time schedule not replicating what is likely to occur in a practical situation, no isolation of water temperature and hydrostatic pressure effects, and lack of a sport-like exercise consisting of repeated expressions of explosive power. Light-intensity active recovery and water immersion do not appear to be detrimental to performance, but neither does there appear to be enough evidence to claim they are beneficial. Effects of active recovery and water immersion would seem to be trivial to small, with any benefits more likely following multiple bouts of high-intensity exercise and recovery or following muscle damaging exercise. There may be a link between blood plasma fraction and performance, however, evidence is inconclusive. Given these issues and limitations the aim of this research was to investigate whether combinations of active recovery, water immersion and passive recovery could maintain peak power and work during subsequent bouts of explosive exercise. We also investigated whether there was any difference in subjects' blood plasma faction and perceived fatigue between the recovery modes. A cross-over experiment was conducted on seven subjects over four weeks. On the same day of each week subjects performed three sessions of maximal jumping, each two hours apart, followed by a different recovery method. Each jump session consisted of three sets of 20 maximal jumps repeated every three seconds, with a minute's rest in-between. Immediately following the jumping subjects performed 10 minutes of either (A) active recovery on a cycle ergometer followed by seated rest, (I) immersion to the gluteal fold in 19°C water followed by seated rest, (AI) active recovery followed by immersion, or (P) seated passive rest. Jumping was conducted on an instrumented supine squat machine that allowed the measurement of total peak power and total work. Pre-jump, post jump and post-recovery blood was taken and the percentage of blood plasma fraction calculated. Perceived leg fatigue was also measured at these times. Observed differences in total peak power and total work between the recovery modes were non-significant. No differences were observed in the change of blood plasma fraction between the recovery modes or perceived fatigue. One reason for any lack of difference between the recovery modes may have been the brevity of the recovery time. Research that has observed significant benefits of active recovery and water immersion compared to passive recovery have used recovery times greater of 15 minutes or more. Additionally, changes in blood plasma fraction between active recovery, water immersion and passive recovery have not been apparent until at least 10 minutes post-recovery in previous research. Alternatively, rather than brevity, it may be that active recovery or water immersion simply does not provide any benefit to performance recovery. Overall there is a meagre amount of research into active recovery, water immersion and passive recovery. Further research that incorporates a variety of exercise and recovery protocols is required.

Sleep loss studies have traditionally focused on cognitive tasks involving alertness, memory, learning and reaction time as well as mood changes and increases in daytime sleepiness. The effects of sleep loss on neuromuscular performance are less well described and understood. Moderate sleep, i.e. loss of a few hours sleep a night, has not been studied with regard to muscular performance. This study examined the effect of moderate sleep loss on sleepiness levels and neuromuscular performance. Nine male subjects (30-50 yr) participated in a cross-over design study and were assessed for sleepiness levels by subjective sleep scales, central nervous system (CNS) arousal by critical flicker fusion (CFF), muscle strength and estimates of submaximal force production for both handgrip and the quadriceps muscle group, and finally fatigue was assessed by repeated maximum voluntary contractions (MVCs) for the quadriceps muscle group. The study was conducted over a five week period and each subject reduced their sleep by 2 hr i.e. from 8 hr to 6 hr for one week. The subjects also completed a daily sleep log that reflected their sleep behavior over the study period. The neuromuscular performance assessments were conducted at the same time of day for each subject to minimise circadian rhythm affects. The results showed with moderate sleep loss, a significant increase in daytime levels of sleepiness as assessed by the Stanford Sleepiness and Epworth Sleepiness scales. There was an increase in negative mood states and a decrease in daily exercise times during the week of moderate sleep loss for those subjects who had normal daily exercise times that exceeded an hour. CFF did not change with moderate sleep loss. There was a 9% decrease in quadriceps maximal force and this was greater than the 2% decrease for handgrip maximal force. The decreases in muscle strength showed greater response from some individuals. Subjects were able to estimate submaximal force production and this estimation did not change with moderate sleep loss. There was no change in the rate of force decline (i.e. fatigue) for repeated MVCs. The conclusions from the study suggest that moderate sleep loss does increase levels of daytime sleepiness and the effect on neuromuscular performance is limited to some effects on maximal force production.

The projects of this thesis examine the complex interaction between isotonic exercise, functional capacity, exercise-induced myocardial ischaemia, severity of regurgitation and left ventricular function in patients with significant chronic mitral regurgitation. The concept of left ventricular contractile reserve, i.e. the ability of the left ventricle to increase its contractility and decrease its end systolic volume with isotonic exercise, is explored. In patients with chronic isolated mitral regurgitation without coronary disease, isotonic exercise was associated with a slight decrease in left ventricular end diastolic volume but a marked decrease in end systolic volume, resulting in a significant increase in the stroke volume and ejection fraction. Early after uncomplicated mitral valve repair surgery, there was a significant decrease in the left ventricular ejection fraction with a proportion of the patients developing left ventricular dysfunction despite a normal pre-operative ejection fraction. When different pre-operative echocardiographic indices of left ventricular function were evaluated for their ability to predict left ventricular function after mitral valve repair, the exercise indices were found to be superior to resting indices. Left ventricular end systolic volume immediately after exercise was found to be the best predictor. The optimal cut-off was at 25 ml/m2, which had a sensitivity and specificity of 83% in predicting early post-operative left ventricular dysfunction. Exercise indices appeared to be superior to resting indices in identifying patients with persistent left ventricular dysfunction &lt1 year after mitral valve repair. The concept of contractile reserve was further examined by estimating the left ventricular stroke work from simplified pressure-volume loops, which were constructed from non-invasively obtained parameters with geometric assumptions. Left ventricular stroke work immediately after exercise, but not at rest, was found to be significantly lower in patients with latent left ventricular dysfunction. Patients without latent ventricular dysfunction had similar increases in stroke work with exercise compared with healthy normal subjects. The ability of the left ventricle to increase its stroke work with exercise, a measure of the contractile reserve, was correlated with the left ventricular ejection fraction after mitral valve repair. A numerical model was constructed using the clinical data as input parameters. The results from the numerical model were similar to that obtained from the clinical study, testifying that the observation made in the clinical study was valid and independent of the geometric assumptions made in constructing the simplified pressure-volume loops. Left ventricular pressure-volume loops under different loading conditions were plotted from simultaneously measured left ventricular pressure and volume to measure the left ventricular end systolic elastance (Ees) and preload recruitable stroke work relationship (MSW). Despite normal or near normal haemodynamics at rest, a significant proportion of the study patients were found to have impaired left ventricular contractility, as measured by Ees, consistent with a state of latent left ventricular dysfunction. Exercise indices of left ventricular function were better correlated with Ees and MSW than resting indices. There were highly significant inverse relationships between end systolic volume index immediately after exercise and Ees and MSW. Moreover, there was a significant powered relationship between MSW and exercise left ventricular ejection fraction. There was no such relationship between Ees or MSW and any of the resting echocardiographic indices of left ventricular function. Furthermore, the optimal diagnostic cut-off level of end systolic volume index after exercise at 25 ml/m2 accurately identified those with impaired left ventricular contractility as defined by an Ees of &gt 2 mmHg/ml. In patients with chronic organic mitral regurgitation with ejection fraction of &lt 50%, objectively measured functional capacity, VO2max, was correlated with exercise cardiac output, patient age and gender but not to the severity of the mitral regurgitation or the resting left ventricular function. The VO2max of these patients were significantly lower than that of age and gender-matched healthy controls despite these patients' relative lack of subjective symptoms. There were significant individual variations in the response of the severity of the mitral regurgitation to isotonic exercise. Patients whose regurgitant stroke volume increased had a lower exercise cardiac output than those whose regurgitant stroke volume decreased. Such variability was also seen with the response of the left ventricular function to exercise. Patients whose left ventricular end systolic volume increased with exercise, i.e. patients with a limited contractile reserve, had a lower exercise cardiac output and lower VO2max than those whose end systolic volume decreased with exercise. The determinants of exercise capacity were then examined in patients with functional mitral regurgitation and left ventricular dysfunction. VO2max of these patients was correlated with exercise cardiac output and exercise left ventricular ejection fraction, a situation similar to that seen in patients with organic mitral regurgitation and normal left ventricular function. Furthermore, indices of left ventricular systolic function at rest and pulsed wave Doppler indices of diastolic function showed no significant correlations with VO2max. The determinants of VO2max remained unchanged in these patients after four weeks of supervised exercise training. The four weeks of exercise training resulted in a significant decrease in left ventricular end systolic volume, a trend towards an increase in left ventricular ejection fraction and some restoration of the contractile reserve. The total exercise time almost doubled. However, this dramatic improvement in total exercise time was accompanied only by non-significant increases in VO2max and left ventricular ejection fraction. Therefore, the benefits of exercise training in these patients may involve more than just central mechanisms. Exercise induced myocardial ischaemia may also contribute to a limited left ventricular contractile reserve in patients with mitral regurgitation. Electrocardiographic changes at rest are commonly seen in patients with mitral regurgitation due to mitral valve prolapse. These resting electrocardiographic changes make exercise electrocardiography uninterpretable for exercise-induced ischaemia. Exercise electrocardiographic changes are also commonly encountered in these patients despite the absence of coronary artery disease and a normal resting electrocardiogram, making exercise electrocardiography unreliable as a non-invasive screening test for coronary artery disease. In these patients, exercise echocardiography was slightly more sensitive but significantly more specific in diagnosing significant coronary artery disease. The overall accuracy and the positive predictive value were significantly higher for exercise echocardiography than for exercise electrocardiography. The &quotcost-effectiveness&quot of different diagnostic strategies for coronary artery disease in patients with mitral valve prolapse was examined based on the results of the clinical study. Strategies involving exercise electrocardiography as part of the screening test were costly and were associated with a high false negative rate. Strategies involving exercise echocardiography were more accurate and less costly but the initial costs of exercise echocardiography for all patients meant that the overall costs were still considerable. Assessing the pre-test probability of coronary artery disease in these patients and using exercise echocardiography as the initial test for patients with at least a moderate pre-test probability of coronary artery disease seemed to result in the best compromise between cost and effectiveness. The studies of this thesis have shown that a limited cardiac contractile reserve is a sign of latent ventricular dysfunction in patients with chronic mitral regurgitation. The presence of a limited contractile reserve can be used to predict left ventricular dysfunction after mitral valve repair. The concept of a limited contractile reserve is further supported by the finding of a limited increase in left ventricular stroke work with exercise from a theoretical as well as a numerical model of left ventricular pressure-volume loops. Exercise echocardiographic indices show better correlations to invasively measured Ees and MSW than resting indices. VO2max in these patients is determined more by their ability to increase their forward cardiac output with exercise and not by the regurgitant volumes. Exercise training in patients with left ventricular dysfunction and functional mitral regurgitation results in some restoration of contractile reserve. Exercise echocardiography is also a reliable and cost-effective test in the non-invasive screening for coronary artery disease in these patients. Based on the results of the studies in the thesis, one can incorporate exercise echocardiography as one of the important assessment tools in the management of patients with significant mitral regurgitation as it allows measurement of left ventricular volumes and assessment of contractile reserve. Further studies are needed to examine whether a policy of monitoring of contractile reserve in these patients to guide therapy and surgical referral will result in a better preservation of long term left ventricular function, an improvement in functional capacity and patient outcome.