Exercise-induced pain (EIP) is a natural consequence of exercising intensely, and results due to an accumulation of endogenous algesic substances, an increase in muscular pressure and muscular distortion or tissue damage. However, the presence of EIP may have negative consequences for exercise and endurance performance, brought about by the physiological and/or psychological effect of pain. EIP has not been widely addressed in sport and exercise science research, and much of the contemporary literature has ignored its potential role in endurance exercise performance, despite the wide acknowledgement it gains in interviews with athletes, coaches, exercise scientists and health and fitness practitioners. Therefore, more empirical research needs to be completed that explores the role of EIP in endurance performance, and the physiological and/or psychological contribution it may make to fatigue and work rate regulation. Therefore, the main purpose of this thesis was to examine the effect of EIP on endurance exercise performance, and identify strategies to mitigate its impact in various endurance exercise tasks. Consequently, this thesis consists of 5 experimental studies, as outlined below. The 1st experimental study (Chapter 3) assessed the relationship between traditional experimental measures of pain (the cold pressor test (CPT) and algometry), EIP tolerance and participants' performance of a 10 mile (16.1 km) cycling time trial. The primary finding was that no correlation was found between experimental pain measures and TT performance (mean pain in CPT; R = 0.222; time lasted in the CPT; R = -0.292; PPT; R = -0.016). However, there was a significant correlation between EIP tolerance and TT performance (R = -0.83, P 0.05). The ANOVA also revealed a significant main effect of condition for exercise-induced pain during the TTE test (P = 0.035). No significant changes in rating of perceived exertion (RPE) were found between the three conditions (P > 0.05). A 3 x 8 (condition x iso-time) ANOVA revealed a significant interaction effect for exercise-induced pain over time between conditions during the TTE test with lower pain intensity in the TENS and IFC conditions (F (3.4, 58.4) = 3.671, P = 0.013). No interaction and main effects for RPE were found between the three conditions (P > 0.05). For the MVC, paired-sample t-tests demonstrated that MVC was significantly reduced following the TTE in the Sham (t (17) = 9.069, P 0.05). No significant differences in mean RPE were found between conditions during the TT (P > 0.05). Interestingly, this study also showed that TENS elicits an analgesic effect on EIP and improves the TT performance, whereas IFC technique does not elicit any reduction of EIP and consequently has no effect on whole-body endurance performance. This experiment demonstrated the first time that TENS intervention significantly improved completion time of the cycling TT, and that this was attained by the cyclists sustaining a greater power output (PO), heart rate (HR) and blood lactate (B[La]). Regardless of the increased physiological stress and metabolic rate induced by the higher PO, participants perceived EIP in the TENS strategy alongside in the absence of a difference in RPE between conditions. The improvement in dynamic endurance was probably the result of reduction in EIP for a given load. This is the first experiment showing that a TENS intervention can be used to elicit this analgesia to EIP, and suggests that there may be scope for TENS to be used during exercise in those where EIP negatively effects their engagement in physical activity. The final experiment in this thesis (Chapter 7) examined the effect of mood and emotional state on EIP and endurance performance. The use of painful images prior to endurance cycling performance was used to negatively affect mood, which was hypothesised to increase EIP. The primary finding was that the ANOVA revealed a significant difference in completion time between conditions (F (2, 40) = 8.480, P = 0.001). Pairwise comparisons revealed that participants performed a significantly faster TT (P = 0.003) in the pleasant condition (29 min 38 s ± 4 min 35 s) and the neutral condition (29 min 39 s ± 3 min 34 s) compared to the painful condition (30 min 19 s ± 5 min 7 s). There were no significant differences between the neutral condition and the pleasant (P = 1.000). The ANOVA also revealed a significant difference in PO (F (2, 40) = 6.318, P = 0.004), mean HR ((F (2, 40) = 4.502, P = 0.017) and mean B[La] (F (2, 40) = 5.724, P = 0.007) between conditions during ?the TT cycling performance, but no significant effect of condition for mean RPE or EIP (P > 0.05). In the FP, a ?significant main effect of condition for EIP (F (2, 40) = 4.363, P = 0.019), but no difference for RPE, HR or B[La]. This experiment demonstrated the first time that painful images negatively affect mood and elicit a compassionate hyperalgesia response to exercise. The results demonstrate that an increased pain sensation during exercise (induced via compassional hyperalgesia) can decrease TT performance, and highlights there is an emotional element to the processing of EIP that can be influenced by compassional hyperalgesia. This is probably the consequence of 'top-down' processing increasing the pain sensation elicited by a given 'bottom-up' stimulus. These results highlight the importance of maintaining a positive mood and emotional state prior to and during exercise. The experimental studies performed as part of this thesis provides unique empirical evidence to advance scientific knowledge and understanding of the phenomenon of EIP. This thesis provides further new insights into how different interventions both alleviate and exacerbate EIP, which subsequently influences endurance exercise performance. Furthermore, considering the lack of knowledge regarding the testing and role of EIP in exercise, this thesis contributes to and enhances scientific understanding for how to test for and control these variables
