Q. Is a 15-minute session on the stationary bike twice a day as good as 30 minutes at once?
A. Jennifer Sacheck, PhD, an associate professor at Tufts' Friedman School who specializes in physical activity research, says: "The current Physical Activity Guidelines for Americans recommend that you accumulate 150 minutes of moderate-to-vigorous physical activity per week, ideally in bouts of 10 minutes or longer. So, either longer or shorter sessions on your exercise bike can be beneficial. If you work at a higher intensity during 15-minute bouts and a slower intensity during the 30-minute bouts, they may end up having nearly equal physiological benefits. The higher intensities can boost your fitness level while the longer durations at a lower intensity can boost overall endurance.
"As for your exercise mindset, if you only have time for 15 minutes, that is certainly better than zero minutes! And, if it is easier to motivate yourself to get on the bike if you know you will only be on it for 15 minutes, go for it. Oftentimes, once you get started and get warmed up, you will feel great and end up staying on longer."