I always here from clients that stretching is not their favorite part of working out, but doing flexibility work is just as important for your fitness as strength and cardio work.
Including some stretching exercises into your workout schedule will help you improve flexibility, reduce tightness, and most importantly, make your workouts more efficient and safe.
When we do a lot of work that contracts the muscles (shortening them) such as hiit training and weight training with never stretching (lengthening) your muscles, they will end up imbalanced. Imbalances in the body increase your risk for injury because they can cause some muscles and joints to overcompensate for other ones that are too tight to engage properly. This leads to strains and discomfort.
Stretching also increases our ROM (range of motion) which helps us to do our other workout properly. For example, increasing range of motion in our hips will allow us to move deeper into a squat, which in turn will make the squat more effective.
So include routines such as this one a couple times a week into your weekand watch all your other workouts become more effective!