Physiological markers have long been used to monitor physiological state in individual athletes. More recently, heart rate variability (HRV) has become a popular metric to monitor athletes' physiological state over longer periods of time to guide training and detect fatigue. HRV measured immediately prior to shooting has been shown to be a predictor of shooting performance. However, there is a lack of research on how physiological state as measured by HRV in resting states impacts sports shooting performance over longer periods of time. This thesis explored if there was a relationship between HRV and rifle shooting performance through a six-week-long experiment. Ten participants wore wrist sensors that measured HRV during slow wave sleep and performed simulator rifle shooting tasks twice a week to measure shooting performance. The relationship between HRV and shooting performance was analyzed through Pearson’s correlation coefficient, linear regression, and k-means clustering. The results indicated that there was no relationship between HRV and shooting performance in the participants collectively, except for two participants. The thesis contributed to the current knowledge about physiological state and HRV in relation to sports shooting performance. It also gave new insight into how experiments can be designed to study variability of physiological state in relation to shooting performance over longer periods of time.