There has been an abundance of research over the past few decades that has consistently demonstrated the benefits of interval-based training. Interval training (aka HIT or HIIT) involves intense bouts of work followed by brief recovery periods that are repeated for a desired amount of time. Most of the research has focused on the effects of workloads using ratios of 1:1 or 2:1 or greater. The interval durations typically range from 15 seconds of work to 2.5 minutes and the intensity (workload) used has been in most cases extremely high (upwards of 170% of VO2 Max). A study (published in the Journal of Strength and Conditioning Research 25(4):1104-1112, 2011) that caught my attention, because of the manageable workload (80% of VO2 max), looked at trying to improve aerobic capacity using a group of college students. This particular study involved college-aged men using a cycle that included six 90-second bouts of work followed by 180-second recovery periods (a 1:2 work/rest ratio). The protocol was performed 3x/week (M-W-F) for a total of 27 minutes of actual work using, as mentioned, 80% of subjects VO2 max.
How can this benefit you?
A similar protocol can be used by you for your cardio routine that you are currently doing in the gym or at home. You might venture to try a similar protocol on a treadmill, elliptical, rowing machine, bike or even take it to the pool.
Following an efficient 5-8 minute warm-up, try power walking, running, rowing, swimming or pedaling on a bike for 90 seconds at about 80% of your max heart rate and then recover for 180 seconds going at a slower pace. Repeat this sequence 6 times for a total of 9 minutes and then cool down for the same amount of time that you warmed-up. Try this 1-2 times a week on the same piece of equipment or mix it up using different equipment.
You could also use a Polar heart rate device to monitor your heart rate and look at the delta between peak HR and recovery.
If you were wondering how well the test subjects did in this particular study utilizing just 27 minutes a week of interval-based exercise…well their VO2 Max increased by 11% and work output increased by 4.3% in just 6 weeks!