Research has consistently shown that high intensity interval training (HIIT) is not only time-efficient but also very effective in improving health and fitness. The duration used for some of the early HIIT research may have utilized brief work periods (like 20 seconds) but the intensity level used to get results was extremely high (i.e. 170% VO2 max).
In 2010 Martin Gibala, PhD and colleagues from McMaster University took HIIT research to the next level, showing significant results could be obtained by using a lower intensity during the interval stages. His group used a protocol that involved 8-12 one-minute sprints on a bike with 75 seconds of recovery in between the sprints, 3 times week for 2 weeks. The intensity used during each work stage was about 100% of peak power output (an average output of about 350 Watts).
The “secret” to why HIIT is so effective is unclear. However, the study by Gibala and co-workers also provides insight into the molecular signals that regulate muscle adaptation to interval training.
It appears that HIIT stimulates many of the same cellular pathways that are responsible for the beneficial effects we associate with endurance training.
The great thing about a well-designed HIIT training session is that it can be fast but yet effective in producing health benefits. Here are a few examples of HIIT that I used in a recent workout. This template can be adapted for your needs depending on your fitness level and goals. The first interval example was performed on a stationary cycle using a 1:3 work-to-rest ratio while the second example was performed on an erg (Concept 2 rowing machine) using a 1:2 work-to-rest ratio. Try this type of protocol using other modalities that may fit your needs like running or other cardio equipment like an elliptical machine or treadmill.
The key take away is that the duration should be short and the intensity should be high. Use this type of HIIT protocol 1-3 times a week. The higher the intensity, the higher the excess-post oxygen consumption (epoc). EPOC is a “measurably increased rate of oxygen intake following strenuous activity intended to erase the body’s oxygen deficit.” In recovery, oxygen is used in the processes that restore your body to a resting state. It is possible to expend a few hundred extra calories (depending on body weight and intensity of the workout) over the course of 24 hours or more following strenuous exercise.
Example of HIIT Bike Protocol
20 seconds of all-out work (300-700 Watts) >100 rpm
1:00 recovery (<50 rpm)
Repeat x 3 then cool-down
Example of HIIT Rowing Protocol
2:00 Easy Rowing (damping set at 4-5, 20-25 spm)
30 seconds of all out work (damping set at 4-5 and >30 spm)
Repeat x 3 and cool-down
Jonathan P Little, Adeel S Safdar, Geoffrey P Wilkin, Mark a Tarnopolsky, and Martin J Gibala (2010). A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. The Journal of Physiology, DOI: 10.1113/jphysiol.2009.181743