The current study evaluated whether NO synthase (NOS) contributes to cutaneous vasodilation and sweating during prolonged exercise in the heat. In addition, we determined if prolonged exercise-induced increases in reactive oxygen species (ROS) and activation of angiotensin II type 1 receptors (AT1R) impair heat loss responses. On two separate days, eleven young men completed 90-min of continuous cycling at ~600W of metabolic heat production followed by 40-min of recovery in the heat (40ºC). To evaluate the role of excess fluid loss via sweating, participants completed a second session of the same protocol while receiving fluid replacement (FR) determined during the first session (No-FR). Cutaneous vascular conductance (CVC) and local sweat rate (LSR) were measured at four intradermal microdialysis forearm sites perfused with either: (1) lactated Ringer (Control); (2) 10 mM NG-nitro-L-arginine methyl ester (L-NAME, NOS inhibition); (3) 10 mM ascorbate (non-selective anti-oxidant); or (4) 4.34 nM Losartan (AT1R inhibition). Ascorbate treatment increased CVC at 60- and 90-min of exercise versus Control during the FR (P < 0.02), but not the No-FR condition (P > 0.31). CVC was reduced at the L-NAME treated site (P < 0.02), but was not different relative to Control at the Losartan treated site (P > 0.19) irrespective of condition. LSR did not differ between sites or as a function of condition (all P > 0.10). We conclude that NO regulates cutaneous vasodilation but not sweating, irrespective of fluid replacement, and ascorbate sensitive ROS impair cutaneous vasodilation during prolonged exercise in the heat with FR.

Changes in physiological function occurring during a body water deficit may result in significant decrements in performance, cognitive function and fine motor control during exercise. This may be due to the magnitude of the body water deficit. Rehydration strategies are important to prevent these deleterious effects in performance. The purpose of this study was to examine the changes before and after prolonged exercise of an alanine-glutamine dipeptide (AG) on cognitive function and reaction time. Twelve male endurance-trained runners (age: 23.5 [plus or minus] 3.7 y; height: 175.5 [plus or minus] 5.4 cm; weight: 70.7 [plus or minus] 7.6 kg) participated in this study. Participants were asked to run on a treadmill at 70% of their predetermined VO2max for 1 h and then run at 90% of VO2max until volitional exhaustion on four separate days (T1-T4). T1 was a dehydration trial and T2-T4 were all different hydration modalities (electrolyte drink, electrolyte drink with a low dose of AG, electrolyte drink with a high dose of AG, respectively) where the participants drank 250 mL every 15 min. Before and after each hour run, cognitive function and reaction tests were administered. Hopkins Magnitude Based Inferences were used to analyze cognitive function and reaction time data. Results showed that physical reaction time was likely faster for the low dose trial than the high dose trial. Dehydration had a possible negative effect on the number of hits in 60-sec compared to both the low and high dose trials. Comparisons between only the electrolyte drink and the high dose ingestion appeared to be possibly negative. Analysis of lower body quickness indicates that performance in both the low and high dose trials were likely improved (decreased) in comparison to the dehydration trial. Multiple object tracking analysis indicated a possible greater performance for dehydration and low dose compared to only the electrolyte drink, while there was a likely greater performance in multiple object tracking for the high dose trial compared to consumption of the electrolyte drink only. The serial subtraction test was possibly greater in the electrolyte drink trial compared to dehydration. Rehydration with the alanine-glutamine dipeptide during an hour run at a submaximal intensity appears to maintain or enhance subsequent visual reaction time in both upper and lower body activities compared to a no hydration trial. The combination of the alanine-glutamine dipeptide may have enhanced fluid and electrolyte absorption from the gut and possibly into skeletal tissue to maintain neuromuscular performance.

The impact of nutritional intervention on affective states has largely been ignored in the exercise-affect literature. For decades the impact of such interventions on perceptions of exertion has been well documented. However, Hardy and Rejeski (1989) assert that `what' a person feels, as measured by the rating of perceived exertion (RPE) scale, may be very different from `how' they feel, and that on its own the RPE provides limited information about the subjective experiences of individuals during exercise. This thesis describes a series of studies that assess the influence of various fluid ingestion regimes on both `how' and `what' a person feels. Seven studies were undertaken, incorporating a variety of exercise modes, including prolonged running (Study 1,3 & 7), prolonged cycling (Study 2& 4) and prolonged intermittent, high intensity exercise (Study 5,6 & 7). The relationship between fluid ingestion during exercise and affective states during and following exercise proved to be a complex one. The initial investigation (Study 1) showed that the ingestion of water during prolonged running resulted in an overall improvement in valence during the recovery period. A significant increase in activation was also noted in the water trial only, from pre to post exercise. Furthermore, subjective ratings of energy post-exercise were higher in the water trial, compared to the no water trial. In study 2 the beneficial effects observed in study 1 were not so apparent. In this instance the only significant change of interest was in energetic arousal, which was found to be higher 5 min post exercise in the water trial compared to the no water trial. When the ingestion of a CHO solution during exercise was compared to a placebo or flavoured water solution (Studies 3-7) the findings also varied. However, the observation of an enhanced affective profile following CHO ingestion in Study 4 and Study 5 highlights the importance of considering nutritional status and intervention when investigating the exercise-affect relationship. These studies have highlighted some important aspects in our understanding of the exercise-affect relationship alone. Firstly, a robust finding across all the studies was the observation of an almost uniformly positive shift in valence from the final within-exercise assessment to the post exercise assessments. Thus emphasising the dynamic nature of affect and the importance of repeated within exercise assessments. Secondly, moderate intensity exercise of a fixed duration was marked by highly variable inter-individual differences in the response of participants to the valence and activation dimensions. However, exercise to fatigue elicited a homogenous valence response as participants came closer to reaching their exercise capacity.