This article reports the findings on the effect an individual’s chronotype has on their diurnal performance and exertion variation, in aerobic exercise. Additionally, the relationship between personality and chronotype is discussed in detail, including the potential for personality to be a predictor of chronotype. The participants (n=16), were female and all regular, active sportswomen. For measuring personality, the BFI-44 was completed, while to test for chronotype, the rMEQ-5 was utilised and participants were categorised into ‘Owls’, ‘Larks’, or ‘Neutrals’. A 12-minute cooper run was completed once at 8am and again at 8pm the following day, where distance travelled was measured. This study found a strong positive, significant, correlation between rMEQ-5 score and the difference in am-pm distance run (r = -0.780, p < 0.05) and also found a moderately positive, significant, correlation between rMEQ-5 score and the difference am-pm RPE score (r = 0.572, p < 0.05). These results are in support of previous research. Regarding personality and chronotype, one significant relationship was found between Openness and Larks (t(10) = 2.582, p < 0.05). The other personality factors found trends, none of which were statistically significant: Neuroticism and Extraversion towards Owls, Agreeableness and Conscientiousness towards Larks. These results add to an already contrasting results field but are attributed to the participants being competitive athletes, and women. The logistic regression of the BFI predicating rMEQ-5 score, showed a strong positive, but non-significant correlation (r = 0.773 (r2 = 0.597, SE = 4.525), p > 0.05). Showing the need for further research in this area, to also cover a wider demographic.