The article I am critiquing is “The Effect of Static, Ballistic, and Proprioceptive Neuromuscular Facilitation Stretching on Vertical Jump Performance” in The Journal of Strength and Conditioning Research: Vol. 21, No. 1, pp. 223–226. Prior to reading this article, I had originally been taught in my personal training course that static and even ballistic stretching could be detrimental to subsequent power and strength movements. This seemed to be true from personal experience when I was shot putting, jumping, or lifting heavy weights. During our Essentials of Strength and Conditioning class last semester, the book published with NSCA approval claimed that stretching prior to a strength or power movement could actually increase strength and power levels and therefore performance. This seemed feasible only if ballistic stretching was done because it more closely mimics the movement that will be performed.
In this article, 18 collegiate males were tested to determine the effects of static, ballistic, and proprioceptive neuromuscular facilitation (PNF) stretching on their vertical jump measurements. Their measurements were taken prior to stretching and then after different time intervals after stretching had occurred. Measurements compared statistically showed a 4-5% decrease in vertical jump after static and PNF stretching, and a 2-3% drop in vertical jump height after ballistic stretching. Both of these decreases were relatively consistent until about 15 minutes beyond the time of stretching, then there was no statistically significant difference after this point. The study concluded that static and PNF stretching was not a good idea prior to a strength or power movement. They attribute the decrease in vertical jump performance from a decrease in stiffness in the musculotendinous unit.
I am not an expert by any means but I agree with this study for the most part. I understand the fact that strength and power will be diminished if musculotendinous units are too tight or there is significant deficits of joint range of motion. For most individuals though, adequate range of motion and musculotendinous junctions should be sufficient for an exercise such as the vertical jump, as long as this tightness does not get in the way of the movement. The only criticism I have for this article is that the sample size could have been bigger ideally and the athletic experiences of the subjects is not given. I wonder what their athletic backgrounds were and if college or elite athletes would have the same results. It would also be interesting to see if female subjects would have the same results if tested in this fashion. After reading this article I am more confident that ballistic stretching or very minimal overall stretching is the way to go prior to a power movement (a specific warmup is always warranted though of course).