According to McMullen, an app can certainly be as effective as in-class training, but as with any fitness program, consistency is very important. "Effectiveness is an elusive measurement because it's specific to individual goals, but consistency is always the biggest contributor to success," McMullen explained. It's also worth noting that you may need to work around an injury or movement limitation from time to time, which may be harder to do with an app. Physical trainers can help you plan for these situations and adjust your workouts in real time, whereas an app may not provide as many options for workout modifications. McMullen suggests searching for apps that can help you adapt the workouts to your physical needs.