Effects of secondary warm up following stretching

Evidence suggests that static stretching inhibits muscular power. However, research does not reflect practice whereby individuals follow up stretching with secondary activity. This study investigated muscular power following stretching, and after a second bout of activity. Participants (n = 13) completed 3 randomized testing sessions which included a 5 min warm-up, followed by a vertical jump (VJ) on a force platform; an intervention (static stretching, dynamic, or control), followed by a second VJ. Participants then completed a series of movements, followed by a VJ, up to 60 min post activity. Immediately following the intervention, there was a 10.7% difference in VJ between static and dynamic stretching. The second warm up bout increased VJ height following the dynamic intervention, whereas the static stretching condition did not show any  differences. The novel finding from this study demonstrates a second exercise bout does not reverse the effects of static stretching and is still detrimental to VJ.

Warming up and stretching for athletes : A meta-analysis of the research literature from 2000 to 2006 in light of current athletic practice

This review presents the methods used to investigate the effects of various stretching protocols on muscular force and performance, in light of current individual and elite athlete stretching practices in their warm-up routines. A meta-analysis of peer-reviewed articles between the years of 2000 and 2007 revealed the majority of studies support the notion that static stretching is detrimental to muscular force and performance. However, the meta-analysis also revealed that the protocols used do not necessarily match current practice with many elite athletes. This article proposes, based on the mismatch between research and practice, that further studies must address this issue in further exploring the role of stretching in pre-training and competition warm-up routines.

Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics

The current literature recommends dynamic rather than static stretching for the athletic warm-up. Dynamic stretching and various conditioning stimuli are used to induce potentiation in subsequent athletic performance. However, it is unknown as to which type of activity in conjunction with dynamic stretching within a warm-up provides the optimal potentiation of vertical jump performance. It was the objective of the study to examine the possible potentiating effect of various types of conditioning stimuli with dynamic stretching. Twenty athletes participated in 6 protocols. All the experimental protocols included 10 minutes of dynamic stretching. After the dynamic stretching, the subjects performed a (a) concentric (DS/CON): 3 sets of 3 repetition maximum deadlift exercise; (b) isometric (DS/ISOM): 3 sets of 3-second maximum voluntary contraction back squats; (c) plyometric (DS/PLYO): 3 sets of 3 tuck jumps; (d) eccentric (DS/ECC): 3 modified drop jumps; (e) dynamic stretching only (DS), and (f) control protocol (CON). Before the intervention and at recovery periods of 15 seconds, 4, 8, 12, 16, and 20 minutes, the participants performed 1-2 maximal countermovement jumps. The DS and DS/CON protocols generally had a 95-99% likelihood of exceeding the smallest worthwhile change for vertical jump height, peak power, velocity and force. However, the addition of the deadlift to the DS did not augment the potentiating effect. Time-to-peak potentiation was variable between individuals but was most consistent between 3 and 5 minutes. Thus, the volume and the intensity associated with 10 minutes of dynamic stretching were sufficient to provide the potentiation of vertical jump characteristics. Additional conditioning activities may promote fatigue processes, which do not permit further potentiation.

Online stretching of directly electrospun nanofiber yarns

Nanofiber yarns are important building blocks for making three-dimensional nanostructures, e.g. through a knitting or weaving process, with better mechanical properties than nanofiber nonwovens and well-controlled fibrous construction. However, it still remains challenging to produce quality nanofiber yarns in a sufficient rate. In this study, we have proven that online stretching during electrospinning of nanofiber yarns can considerably improve fiber alignment and molecular orientation within the yarn and increase yarn tensile strength, but reduce fiber/yarn diameters. By compensating twist during online stretching, the device can prepare nanofiber yarns with different stretch levels, but maintaining the same twist multiplier. This allows us to examine the effect of stretching on fiber and yarn morphology. It was interesting to find that on increasing the stretching ratio from 0% to 95%, the yarn diameter reduced from 135.1 ± 20.3 μm to 46.2 ± 10.2 μm, and the fiber diameter reduced from 998 ± 141 nm to 631 ± 98 nm, whereas the yarn tensile strength increased from 48.2 ± 5.6 MPa to 127.7 ± 5.4 MPa. Such an advanced yarn electrospinning technique can produce nanofiber yarn with an overall yarn production rate as high as 10 m min−1. This may be useful for production of nanofiber yarns for various applications.