In the debate of steady state cardio vs. high intensity interval training (HIIT) I am torn. I hedge my bets by doing both; mainly because mountain bike riding and RPM are HIIT and road riding is more steady state cardio. But fence sitters tend to annoy binary thinkers so my lack of endorsement or a condemnation for one doesn’t sit well with many people. The long and the short of it is that the body will adapt to whatever you throw at it so you need to keep changing things up to make sure you are getting the full benefit from exercise.
But the evidence for in support of HIIT is starting to grow. Short Bursts Of Exercise May Fend Off Disease by the Globe And Mails Paul Taylor reports on a study that tested the impact of HIIT on insulin sensitivity.
The body releases insulin in response to an elevated blood sugar level and this hormone will help facilitate the transport of sugar into the body tissue (fat cells when the muscles do not need it or into the muscles when their levels are diminished. With people who have normal insulin sensitivity, the amount the body releases is appropriate and blood sugar returns to normal levels quickly. However, obese people and type II diabetics are not as sensitive to insulin so their blood sugar levels do not drop as quickly as they should so the body releases more insulin. Blood glucose in high levels is very damaging to the body so being insulin resistant is a long term health risk.
The study revealed that 4 blocks of 30 second intervals of high intensity effort followed by 4 minutes rest was enough to improve insulin sensitivity by 23% in health but sedentary males. These improvements were seen after two weeks of 2-3 sessions per week. The reason for the improvement is that the efforts were high enough to spend most of the stored glycogen in the muscles therefore increasing the need to sugar transfer into the muscles.
The author of the article draws some conclusions about HIIT being better than traditional gym work for lowering heart disease risk that may not be accurate given that insulin resistance is only one of the factors associated with heart disease. The conclusion also fails to consider the positive cardiovascular impact of longer duration exercise.
However, this study is good news for the pro HIIT crowd and anyone who has only less than 60 minutes to workout per week. And it’s more evidence for my belief that intensity is the key component to any exercise routine.