The word "negative" often implies pessimism and gloom. In the gym, however, performing "negatives" or eccentric reps yields positive sports performance-enhancing, muscle-building and injury-preventive results! Mark Coberley, Iowa State University's Associate Athletic Director for Sports Medicine, told Athletic Business that "eccentric exercise is being pushed quite a bit in both the strength and conditioning world and the sports medicine world because of its importance in injury prevention and also performance." He adds that many non-contact ACL injuries, for instance, are deceleration-related injuries (meaning they occur during the eccentric movement), and the goal therefore is to prevent injury during deceleration. Athletes and non-athletes commonly focus on how much weight they can explosively push, press, pull or squat during the muscle-shortening phase of each exercise (which is known as the concentric portion of the movement) and minimize the equally significant muscle-lengthening phase (which is known as the eccentric portion) of the movement. Think of it like this: The eccentric portion of a Barbell Squat is you lowering into the squat position, while the concentric portion of a Barbell Squat is you exploding from that squatted position into a standing position. While explosive concentric movements definitely improve strength and power, simply slowing down your average eccentric rep tempo can have great benefits. Not only is it in many cases safer, as a slower eccentric can help eliminate the poor technique that contributes to joint and muscle injuries, but it can also mean more productive and intense reps and ultimately greater muscle growth. Enhanced power and flexibility are also two known benefits of eccentric-focused training. And emphasizing slower muscle-lengthening eccentric rep tempo in the weight room may also mimic protective benefits on the field, court or ice where gradually decreasing the muscle-lengthening eccentric deceleration speed (instead of abrupt stops) may indeed help decreasesports-related injuries. A University of California-Berkeley Wellness letter states there's evidence eccentric training may help tendon injuries (such as chronic tendinitis) heal more effectively than standard treatment practices.