Purpose: This is the first study done to determine the efficacy of 10-weeks of Nexersys training on improving cardiovascular fitness (CF) and body composition (BC). Nexersys is an "exergaming" system that combines mixed martial arts, high-intensity interval training and core work into an interactive unit with a monitor and 7-strike pads. Participants were provided a Nexersys unit in their homes to complete 10-weeks of training 3 to 4 times a week progressing from 5, 3-min rounds with a minute rest to 15 rounds at the end of 10-weeks. Participants were tested on 3 separate occasions, prior to beginning training (0wk), at 5-weeks (5wk) and 10-weeks (10wk). Body mass (BM), percent body fat (%BF), fat mass (FM) and lean mass (LM) were assessed using dual-energy X-ray absorptiometry (DEXA). CF was assessed during a 10-round Nexersys bout (NB) and a VO2max treadmill (VO2max) test. CF during NB and VO2max treadmill test was assessed by using regression analysis to determine the estimated average heart rate for a range of VO2 10-25 ml/kg/min (HRN) and 10-30 ml/kg/min (HRV) respectively. Results and Conclusion: Relative to starting values, BM did not change (79.8 ± 7.9 to 79.7 ± 7.5 kg). %BF and FM decreased from starting values (36.0 ± 3.4% to 34.1 ± 5.3%, p=0.003 and 30.0 ± 4.9 kg to 28.4 ± 4.6 kg, p=0.045, respectively). LM increased from starting values (46.7 ± 3.5kg to 48.4 ± 3.6kg, p=0.001). HRN and HRV decreased from starting (148 ± 2.7 to 140.8 ± 1.9 bpm, p=0.003 and 148 ± 1.8 to 140.1 ± 1.8 bpm, p=0.003, respectively). VO2max trended to increase but did not reach statistical significance (33.9 ± 1.7 to 36.3 ± 1.7 ml/kg/min, p=0.054). These findings suggest 10-weeks of Nexersys training improves body composition both by increasing LM and decreasing BF with no change in BM. CF improved at submaximal intensities. / text