Greenlee, TA, Greene, DR, Ward, NJ, Reeser, GE, Allen, CM, Baumgartner, NW, Cohen, NJ, Kramer, AF, Hillman, CH, and Barbey, AK. Effectiveness of a 16-week high-intensity cardioresistance training program in adults. J Strength Cond Res 31(9): 2528–2541, 2017—The purpose of this study was to determine the efficacy of a novel, 16-week high-intensity cardioresistance training (HICRT) program on measures of aerobic fitness, agility, aerobic power, muscular endurance, lower-body explosive power, and self-reported activity level. The intervention group (N = 129; 63 f, 24.65 ± 5.55 years) had a baseline V[Combining Dot Above]O2max of 39.83 ± 9.13. These individuals participated in 26, 70-minute exercise sessions, and 4 fitness testing sessions. Participants were matched with a nonexercise control group, paired by sex, age, and baseline V[Combining Dot Above]O2max. Matched controls (N = 129, 63 f, 24.26 ± 5.59 years) had a baseline V[Combining Dot Above]O2max of 39.86 ± 8.59 and completed preintervention and postintervention V[Combining Dot Above]O2max testing only. The results demonstrate that participants in the fitness intervention group significantly increased their V[Combining Dot Above]O2max (2.72 ± 0.31, Mdiff ± SE; p < 0.001) and reported being more physically active (0.42 ± 0.11, Mdiff ± SE; p < 0.001) after the intervention. The matched control group showed no significant pre–post intervention changes. Participants in the fitness intervention showed a significant improvement in 3 of 5 components of the fitness field tests. Specifically, significant improvements were observed for the 1-minute rower (5.32 ± 0.505, Mdiff ± SE; p < 0.001), 1-minute push-up (8.168 ± 0.709, Mdiff ± SE; p < 0.001), and 1.5-mile run tests (1.79 ± 0.169, Mdiff ± SE; p < 0.001). No significant improvements were observed for the shuttle run (p = 0.173) or standing long jump (p = 0.137). These findings demonstrate the efficacy of a novel, HICRT intervention across multiple dimensions of fitness for young- and middle-aged adults. High-intensity cardioresistance training affords flexibility for tailoring to meet desired health and fitness outcomes and makes perceivably daunting high-intensity functional training and multimodal sports training more accessible to general, traditionally nonathletic, populations.