Keywords: PNF (proprioceptive neuromuscular facilitation) – stretching technique used commonly to enhance passive and active range of motion. The mechanism behind PNF: autogenic inhibition reflex, this is a sudden relaxation of muscle upon development of high tension, self induced feedback lengthening reaction that protects against muscle tears, golgi tendon organs (GTO) are the receptors for this reflex.
Golgi tendon organs: sensory receptor organ that is at the origins and insertion points of skeletal muscle and is responsible for sensing changes in muscle tension. The GTO generates sensory feedback when a muscle is lengthened or shortened, the GTO will send greater sensory feedback when lengthened at a high rate.
I want to discuss the value of the double bounce back squat. This is an exercise that I love to use for numerous reasons. I believe it has a very positive impact on flexibility, trunk stability and core strength, all while doing a great job awakening the central nervous system.
When watching elite weightlifting, many athletes unknowingly utilize a double bounce particularly on heavy cleans. I believe it is important to recognize the mechanisms behind the double bounce. Why do athletes use it when they rarely will train the double bounce? It is an innate reaction their body discovers to improve their position when exiting the deep catch position. When they hit the second bounce, it is a form of PNF. In fact, the GTO sends signals to the spine to recruit even more high threshold motor units than they did on the first bounce. These extra MU’s improve the speed out of the hole and in turn make it easier to stand up with the clean. It forces the athlete to hit a deeper, more stretched position which requires the incredible excitement from the central nervous system to get out of that position. This will also leave a neurological imprint on the nervous system that the athlete can handle a heavy load in a deeper position, thus improving flexibility and technique.
What about the knees? Obviously, the knee aspect needs to be addressed on an individual basis. Past knee injuries or outside stress from other activities may lead further distress on the knee joint. With that being said, deep squats utilizing a double bounce will result in greater activation of leg muscles when compared with shallow or 90 degree squats. It is also known that squatting past 90 degrees does not increase shear force on the knee joint because science has shown us that in both 90 degree squats and deep squats, the maximum shear force on the knee joint is found around 90 degrees. When it comes to knee health, there are many things that need to be factored. Sitting for extended periods of time will tend to be the most detrimental activity for the knee joint and the lower back. This is because the hamstrings tend to shut off from extended periods of sitting and flexibility is loss as is proper posture. It as been shown that sitting throughout the day can have a very negative impact on posture which in turn can lead to poor squat technique.
What to do in training. Using training modalities such as PNF, double bounces, pause squats, fast eccentrics, slow eccentrics and plyometrics all utilize the same mechanisms to increase muscle activation and motor unit recruitment. Be sure to program these methods properly and monitor any potential contraindications an athlete may have to deal with when squatting with full range of motion.
Do I have my athlete’s always double bounce? No, we simply use it as a tool when trying to correct positions or trying to drastically increase leg strength in certain portions of the lifts.