High Intensity Interval Training (HIIT) Is a workout that switches between intense bursts of activity for fixed periods of less-intense activity or even complete rest. For example, a good beginner workout is running or boxing as fast as you can for 1 minute and then slowing down and walking for 2 minutes. Repeat that 3-minute interval for a few rounds up to 5, It seems too simple to be effective, but it is proven within science.