Stretching & Flexibility
Static stretching pre-exercise Static stretching & vertical jump
Should we perform static stretches before activity?
Why do we perform static stretches before exercise? Well, maybe because it's tradition! The two most common reasons for pre-activity static stretching are that it improves performance and reduces injury risk but there is no credible research to support these theories! In fact, the majority of recent research finds the opposite and concludes that static stretching may hinder performance and increase injury risk.
Static stretching pre-activity can decrease performance by up to 30% in activities that require strength, power and speed and this detrimental effect may last for up to 60 minutes. Possible reasons for this include changes in reflex sensitivity, muscle & tendon stiffness and/or neuromuscular activation. Some studies have suggested that the effect of static stretching may be influenced by the speed of the following activity but more research needs to be carried out before drawing any firm conclusions.
Cold muscles are more susceptible to injury so we perform warm ups but should static stretching form part of this practise? Current thinking suggests not! The theory is that tight muscles/tendons are more likely to suffer injuries as there are less 'stretchable' so stretching them will reduce injury risk. Once again, good research does not support this theory with studies unable to link pre-exercise static stretching with injury rates. However, flexibility itself may be linked to injury risk so there is a case for flexibility training at other times.
General consensus is that pre-activity static stretching does not improve performance or reduce injury risk. Although poor flexibility and range of motion may hinder performance and increase injury risk, static stretching should not be performed pre-activity. Instead, dynamic, sports-specific movements should be carried out as part of a warm up and static stretching should be performed afterwards as part of the cool down or as a separate training session.
Effects of static stretching on vertical jump performance
To stretch before exercise or not to stretch? If yes, what kind of stretching? These are questions which are still hotly debated but more evidence is emerging which points towards static stretching being detrimental to subsequent performance. This study looked at the effects of static stretching on jump performance (Brandenburg et al. (2007) Time Courses of Changes in Vertical-Jumping Ability After Static Stretching. International Journal of Sports Physiology and Performance, 2007;2:170-81) and it also monitored the time course of any stretch-induced changes.
16 subjects took part in the experiment and they each completed 2 testing sessions consisting of a warm-up, a jump assessment, lower body static stretching (3 stretches, 3 x 30s holds) OR rest and further jump assessments at 3, 6, 12 & 24 minutes. Results showed that static stretching and rest caused a decline in post-trial jump height - average jump height reduced by 1.4cm and 1.6cm respectively. In addition, the reductions in performance remained for 24 minutes. The researchers concluded that static stretching and rest result in similar reductions in jump performance and this suggests that anyone preparing for explosive lower body activities should avoid inactivity and static stretching after their warm up.
Effect of stretch duration on ROM
The time for which we should hold stretches is another area which is debated and this study looked at the effect of 4 different stretch durations on range of movement (ROM) at the knee (Ford et al. (2005) The Effect of 4 Different Durations of Stretch Hamstring Stretching on Passive Knee-Extension Range of Motion in Healthy Subjects. Journal of Sport Rehabilitation, 2005;14:95-107). 35 subjects took part in the study all of whom had at least a 20 degree loss of knee extension ROM. The subjects followed a 5 week programme of daily stretching which required them to perform a static hamstring stretch daily holding it for either 30, 60, 90 or 120 seconds.
The results showed that the hamstring stretch was effective in improving knee extension ROM regardless of stretch duration. Importantly, no difference in improvement existed between the 4 stretch duration groups indicating that stretch duration had no effect on improvements in ROM. This data suggests that holding static stretching for more than 30 seconds will not result in any further benefits in ROM.