Riegler, M, Stotz, G, Fitzgerald, K, Munoz, CK, Lewis, J, Ring, S, and Astorino, TA. Acute responses to the 7-minute workout. J Strength Cond Res 31(9): 2572-2578, 2017-A popular smartphone application called the 7-Minute Workout (7Min) claims to be scientifically proven to promote weight loss and improve cardiovascular function. The application has 10 million downloads and has been reviewed by 350,000 users. However, changes in metabolic and perceptual variables in response to 7Min are unknown. Our study compared acute responses between 7Min and a time-matched session of cycling-based high-intensity interval exercise (HIIE). Fourteen active men and women (age and V[Combining Dot Above]O2max = 25.4 ± 8.3 years and 40.5 ± 6.4 ml·kg·min) initially underwent V[Combining Dot Above]O2max testing. During 2 subsequent sessions separated by ≥48 hours, they completed 7Min or HIIE. During exercise, oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), blood lactate concentration (BLa), and rating of perceived exertion were measured. Peak V[Combining Dot Above]O2 was higher (p < 0.001) in HIIE vs. 7Min, and HIIE yielded greater (p < 0.001) mean V[Combining Dot Above]O2 (1.83 ± 0.41 L·min vs. 1.44 ± 0.32 L·min) and HR (159.0 ± 10.7 b·min vs. 140.7 ± 18.3 b·min, p < 0.001) vs. 7Min. Blood lactate concentration increased (p < 0.001) during exercise but was similar between bouts (p = 0.07). Rating of perceived exertion was higher (p = 0.008) in response to HIIE vs. 7Min. Although 7Min yields lower peak V[Combining Dot Above]O2 and HR than HIIE, it is characterized by bursts approaching 90 %HRmax and causes significant BLa accumulation, representing vigorous exercise. Nevertheless, 7Min is on the low end of the intensity spectrum, which questions whether it represents true HIIE and will confer similar benefits if performed long term.