Diff amounts of static stretching & vertical jumps

[galapogos]

Varying Amounts of Acute Static Stretching and Its Effect on Vertical Jump Performance

Numerous studies have shown that stretching routines can induce strength and force deficits, although the amount of stretching needed to cause these deficits remains unclear. Therefore, the purpose of the study was to examine the relationship between varying amounts of acute static stretching on jumping performance. By systematically increasing the amount of stretching, possible differences in jump height may be discovered, defining a line where acute static stretching becomes detrimental to performance. Ten collegiate athletes and 10 recreational athletes completed 3 different stretching treatments and 1 control treatment on different days in a within-treatment design. Stretching treatments consisted of 2, 4, or 6 sets of stretches, with each stretch held for 15 seconds with a 15-second rest. Stretches were done to the quadriceps, hamstrings, and plantar flexors. Upon arrival, each subject performed a 5-minute warm-up on a stationary upright cycle. After a brief rest period, participants performed 3 trials of a vertical jump test, followed by one of the treatment protocols. After another rest period, a second set of vertical jump trials was performed. Post-6 sets was significantly lower than Pre-6 sets (p ≤ 0.05). Additionally, Post-6 sets was significantly lower than Pre-4 sets, Pre-2 sets, and Pre-control (p ≤ 0.05). No other conditions were significantly different. In conclusion, 6 sets of stretches, or 90 seconds per muscle group, should not be performed before power activities such as jumping where optimal performance is desired.

[hermanchauw]

Why are the stretches 15 seconds each? Why not different multiples of 15 seconds?