Short, fast workouts can be done even if you feel you “don’t have any speed.” They are also different than traditional speed workouts of 200s, 400s and 800s. These workouts are ultra-short intervals designed to simply get your legs turning over faster and make you aware of your true speed.
A proper warmup is very important before one of these types of workouts. Typically, tight hamstrings are the most venerable to injury. Each workout should be proceeded by at least a 10-minute warmup and some light dynamic stretching, such as leg swings. Your first few intervals should be used to just turn your legs over. Toward the end of the workout, when you are fully warmed up, you can start going for faster times.
The distances are short in order to take out a huge part of the endurance factor. Often even 200m or 400m repeats done in traditional speed workouts are way too long to really develop speed and good mechanics. Very short distances allow you to go fast and recover quickly. Running these workouts is not about running all out the entire time. Focus on just turning your legs over and having smooth mechanics. You want to have a good turnover rate, but also try to open up your stride a bit by running with a higher knee lift and a bigger arm swing.