If you’re one of the hundreds of thousands of individuals who have adopted High-Intensity Interval Training (HIIT) workouts at home because of their ability to deliver weight loss results quickly, you’ve probably noticed a few other changes too: achy joints, stiffness, pain or strained muscles. While HIIT workouts are great for burning calories and helping you shed pounds quickly, new research suggests that the side effects of such workouts can be detrimental in the long run.