Sleep quality appears to be an important variable for recovery and training adaptation of competitive athletes, with reduced sleep quality having negative effects on performance and wellness. Overtraining (OT) caused by an imbalance between training load and recovery has been suggested to reduce sleep quality(1). Little is known about the relationship between training and sleep quality amongst mixed martial arts (MMA) competitors. As a multi-discipline combat sport, training volume and intensity is thought to be high in this population, though this has not been adequately quantified in the literature. The aim of this study was to measure the training load of MMA participants and assess the affects of these loads on sleep quality. n = 6 human MMA participants (age = 20.5±3.6; mass = 71.3±4.4 kg; stature = 169.8±8.9 cm) took part in this study with institutional ethical approval for 8 consecutive weeks. Participant’s daily mean training load (sessional rating of perceived exertion, strain and monotony) was recorded after every training session(2). At the end of each day participants recorded soreness using a 10cm visual analogue scale for the following body regions: head and neck; shoulders and arms; upper torso; lower torso; legs. Fatigue score was measured via short questionnaire of fatigue at the end of each day(3). Sleep quality was recorded via Pittsburgh Sleep Quality Index (PSQI) at the start of each week(4). Relationships between variables were assessed using Bayesian Kendall’s Tau coefficient (BF10). To determine which model of variables most likely affect PSQI, Bayesian multiple regression (BF10) was performed. Moderate or better correlations with moderate or better BF10 are reported(5). All analyses were completed in JASP 0.10.2. The following variables were found to be moderately correlated: daily mean load-lower torso (T = .304, BF10 = 34); strain-lower torso (T = .305, BF10 = 36); strain-legs (T = .316, BF10 = 50); fatigue score-upper torso (T = .331, BF10 = 81); fatigue score-PSQI (T = .315, BF10 = 49); lower torso-PSQI (T = .326, BF10 = 69). Bayesian multiple regression found the strongest model to predict PSQI to be strain + fatigue score (adjusted R2 = .471, BF10 = 67), which provided the following predictive equation: predicted PSQI = 1.532 + (8.279e-4*strain) + (0.131*fatigue score). Increased strain caused by an unbalanced training load in MMA is related to increased soreness which leads to increased feelings of fatigue. Soreness appears to mainly affect the lower torso and legs. These issues appear to combine to reduce sleep quality amongst this population. This in turn may negatively affect the recovery of MMA competitors and contribute to the potential onset of OT. These findings may be used to assist coaches plan appropriate recovery after high load sessions to prevent OT and optimise training adaptation.