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Dear Alissa,

Almost. In the unlikely event that you can achieve your target heart rate in 2 minutes, keep it up for 6 and cool for 2, and do this four times daily you could almost equal the 40 minute efforts. There are two types of muscle fibers, slow-twitch and fast twitch. You would be using mostly fast-twitch with your four times daily program. The slow-twitch or endurance fibers would best respond to the longer effort.

George Dixon MD