The primary difference between HIIT and SIT are timing (duration of the work effort and rest intervals) and intensity (how hard you push yourself during the work effort).

• Sprint Interval Training (S.I.T) is done with a 110% supramaximal effort for the interval.

• The interval is 30 seconds or less with variable recovery. The recovery can be as little as 30 seconds or as much as 3-4 minutes.

• The goal of the recovery is to completely recover to be able to hit the supramaximal intensity again.

• Because these are so hard, usually only 2 or 3 efforts are achievable at the beginning of this kind of training. As you get more trained, 8 -10 efforts is ideal.

• H.I.I.T is High Intensity Interval Training that is done with 80-95% effort training intervals. The shorter the interval the higher percentage.

• The H.I.I.T intervals are 45 seconds to 4 minutes with variable recovery in between. There is usually a 1:1 work to rest ratio because the intervals are not supramaximal.

• The usual goal of H.I.I.T is to tap into VO2/sustainable anaerobic efforts for metabolic conditioning.

As you reach your postmenopausal years, SIT increases lean muscle mass and reduces fat mass in a relatively short period of time. It helps burn belly fat, improves insulin sensitivity, and lowers blood sugar levels. This kind of training can also ‘make you smarter’ because it triggers an increase in chemical messengers in the brain to improve cognition and working memory.

HIIT provides a metabolic stimulus to trigger performance-boosting body composition changes - specifically beneficial for women who are either perimenopausal and postmenopausal. Since SIT is technically a form of HIIT, you will also get similar benefits as SIT, but SIT will achieve those benefits at a higher degree due to the more intense stimulus.

Although it is a continuum, conceptually Sprint Interval Training (SIT) is all about supra-maximal efforts for 30 seconds or less and an active resting interval that is about 5 times longer than the intense interval. High Intensity Interval Training (HIIT) is a 80-90% effort for 1-4 minutes with equal work rest periods (i.e. 1-4 minutes rest). I hope that helps you understand the differences so you can tailor your training to your needs.