Begin slowly. "HIIT training is a tremendous technique to train and generates amazing outcomes for the majority of individuals who utilize it in terms of cardio improvements, weight and fat reduction, and general increases in overall fitness and health," adds Matt. He also notes that while many people over 40 need more intense exercise, this type of training is perfect for those looking to start exercising more safely or recover from injuries or surgery. Don't worry about going too hard either. "It's important to push yourself but you don't want to hurt yourself," advises Matt. He goes on to say that if you feel like you are going to pass out or suffer some other kind of serious injury, stop immediately. Trust your body and take care of itself first before continuing with your workout. And finally, have fun! "At the end of the day, exercise is an enjoyable experience; therefore, you should look forward to doing it instead of seeing it as a burden," he says. If you're not having fun then you should probably consider changing something about your routine. But if you're still enjoying yourself even after working up a sweat for 30 minutes straight, then you know it's the right choice for you. The most important thing is to listen to your body and try not to overdo it.