There are three types of Les Mills Grit classes in the series: Cardio, Plyo, and Strength. Each one is its own 30 minute complete workout.
Grit is a high intensity interval training workout, using slow and fast twitch muscle fibers to burn fat and activate pushing your body beyond its limits.
Our traditional 50-60 minute workouts keep us at an aerobic phase, pacing ourselves to keep on going. Grit is entirely the opposite of this mentality, where we are meant to get our bodies to the anaerobic phase, which can only be sustained for short bursts. The point of this type of workout is to get to failure, fatigue, and stop. We want to use so much energy we are forced to stop. We recover for a short amount of time and repeat the phase all over again.
“Here’s a brief overview of the science behind HIIT. Muscle contractions require energy known as adenosine triphosphate (ATP). ATP can be produced one of two ways: either with oxygen from the aerobic pathways or without oxygen from the anaerobic pathways. The aerobic pathways are efficient when muscles need a consistent amount of force over an extended period of time like when walking, cycling or jogging. The anaerobic pathways produce ATP up to six times quicker and are used when muscles need energy immediately to generate high amounts of force for activities like sprinting or heavy weight lifting. In general, the anaerobic pathways can produce enough ATP to fuel approximately 15-90 seconds of work, the higher the intensity-the faster the supply of ATP is depleted. Once anaerobic contractions have exhausted the immediate source of ATP the aerobic system kicks in to help refuel the muscles.
It’s important to note that the human body uses approximately five calories of energy to consume a liter of oxygen to fuel muscle activity; the higher the intensity – the more oxygen used and the more calories burned. In general, HIIT works by exhausting the ATP available in the anaerobic pathways during the work interval and then relying on the aerobic pathways to refuel the ATP during the active recovery interval. Here’s one cool feature of HIIT – not only will you burn calories during the high intensity portion, but you will also burn calories during the lower intensity recovery as your body uses oxygen to restore the ATP which will fuel the next phase of anaerobic conditioning.
A second feature of HIIT is that it supports muscle growth. Adults lose lean muscle mass during the aging process and exercise which promotes muscle growth can actually provide an anti-aging effect. If you’ve done HIIT then you know that burning you feel in your muscles? It’s the waste produce (think exhaust) of muscle contraction and includes lactic acid and hydrogen ions technically referred to as acidosis. As your fitness levels improve, then your muscles increase their tolerance and ability to deal with this waste. The really cool thing is that the exercise intensity which increases acidosis also stimulates production of the hormones – Testosterone (T), Growth Hormone (GH) and Insulin-like Growth Factor (IGF-1) which can help you increase your lean muscle mass and retain a more youthful appearance.
The final, and best, benefit of HIIT is that your body continues to burn calories once the workout is over thanks to a physiological feature known as Excess Post-Exercise Oxygen Consumption (EPOC). During the period after HIIT EPOC means the body continues to uses oxygen at the rate of five calories a liter to perform the following functions: restore ATP used during the workout, work with protein to repair damaged muscle tissue and restore body temperature to normal resting levels. The higher the intensity of the HIIT intervals, the longer the EPOC effect and the more calories you’ll burn after the workout” (Les Mills program description).
So basically, what you can achieve in a 60+ minute workout you can achieve calorie wise in a 30 minute workout, because your body will continue to burn calories and fat as it tries to bring itself back to its resting state.
So if you like to push the limits, challenge yourself, limited on time, or want to just experience something different, then this workout is for you!