I’d guess that most people feel guilty about not stretching enough. Interestingly, health professionals have changed our tune about the importance of stretching. Research over the last 15 years has suggested static stretching is not as beneficial as was once thought. I’ve been having conversations about the reasons to stretch (or not) for at least the last 15 years, but the current science on stretching just isn’t catching on with the general public. So, what do we know?… DOES STRETCHING PREVENT INJURIES?No. There is a lot of evidence that stretching does not reduce the risk of injury. This systematic review and meta-analysis of randomised controlled trials found stretching does not prevent injuries, whether done before or after training. This randomised controlled trial, and this systematic review concluded stretching before exercising only reduces the risk of injury by less than 1%. Therefore, in practical terms the average athlete would need to continuously stretch for 23 years to prevent one injury. Definitely not worth it. DOES STRETCHING HELP MUSCLE SORENESS?No. A systematic review concluded that stretching before or after exercising does not confer protection from muscle soreness (ref). Stretching was found to reduce muscle soreness by a trivially small amount - less than 2%. “Most athletes will consider effects of this magnitude too small to make stretching to prevent later muscle soreness worthwhile.” DOES STRETCHING INCREASE RANGE OF MOVEMENT?No. Stretching for the amount of time that most people hold their stretches, does not make any actual difference to flexibility. The mechanisms of stretching have been extensively studied. There is moderate evidence from a systematic review that stretching can increase flexibility (ref). However, to achieve an actual improvement in muscle compliance we know the total duration of stretching needs to be at least five minutes per muscle group (ref). Therefore to stretch hamstrings, quads, and calves, both left and right, as part of a warm up before sport, it should take at least 30 minutes - which is practically impossible as part of a warm up. We know the one or two, thirty second stretches the majority of athletes would perform during their warm up are just not enough to actually improve flexibility (ref). DOES STRETCHING HELP PERFORMANCE?What people find most surprising about static stretching is it impairs subsequent performance (ref). A substantial body of research has shown that sustained static stretching acutely decreases muscle strength and power (ref). Stretching before an endurance event lowers endurance performance and increases the energy cost of running (ref). Cycling efficiency and time to exhaustion are reduced after static stretching (ref). Pretty much any measure of performance is made worse by stretching. Static stretching impairs:
A comprehensive review (ref) from 2011 concludes: “Based on the majority of the literature, it would seem logical to recommend that prolonged static stretching not be performed prior to a high level or competitive athletic or training performance.” WHAT ABOUT DYNAMIC STRETCHING?Obviously, I’ve been talking about sustained, static stretching. It has been shown that there is no stretch-induced strength loss with dynamic stretching (ref). However, the efficacy of dynamic stretching for increasing flexibility is yet to be determined (ref). SO WHY STRETCH?I do get people to stretch if there’s a specific pathology that needs treating. And you do need to stretch if you need flexibility to achieve certain positions in your sporting performance (hurdlers / gymnasts / divers, etc). SO SHOULD WE STOP STRETCHING?If you’re happy with your stretching routine, keep doing it. If you think it feels good to stretch after exercise then there’s no harm. But I definitely wouldn’t recommend stretching at the expense of other techniques that are proven to aid recovery.  Load Management For Injury PreventionManaging training load is crucial in injury prevention and treatment. A graphic in Tom Goon’s recent blog visualises how training load outweighs all other factors. 
Historically we have advised that training loads shouldn’t increase by more than 10% a week. I’m not sure where this number comes from. I’ve got no problem with it, it seems reasonable, and I’ve quoted it hundreds of times. There’s a 2015 BJSM podcast interview with Tim Gabbett on load management for injury prevention. Specifically Tim talks about this paper:
Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers
- Billy T Hulin, Tim J Gabbett, Peter Blanch, Paul Chapman, David Bailey, John W Orchard, 2013. It is research into fast bowlers, but I think the principles apply just as well to any athlete. The authors measured the acute workload of the last 7 days (and call it “fatigue”) and compare that to the chronic workload of the previous 4 weeks (which they call “fitness”). Measuring Training Load
For runners, if the training is reasonably homogenous, we could most simply measure the workload as the total kms/week.
Or we could be more accurate and account for a mixed training program that may include a variety of hills / sprints / cross training etc, by giving each session a rate of perceived exertion (RPE) out of 10, and multiply that score by the number of training minutes:
Training load = session RPE x duration (minutes)
This is called a Foster’s Score, and provides a simple method for quantifying training loads from a variety of different training modalities.
The research subtracted the current one-week average from the previous 4-week average and called this number the “training-stress balance”. A negative training-stress balance increases the risk of injury by 4 times. So:
[Last 7 days’ session RPE x duration (minutes)] - ([Last 4 weeks’ session RPE x duration (minutes)] / 4) = TRAINING-STRESS BALANCE
Negative balance = 4 times risk of injury
Essentially this formula means you shouldn’t increase your training load by more than 25% a week.
For people that may be more vulnerable to injury I would change the 4-week average to a 6-week average, therefore, bringing the increase in load each week down from 25% to 16%. This more cautious group could include:
Summary of:
FOOTBALL RECOVERY STRATEGIES (Grégory Dupont, Mathieu Nédélec, Alan McCall, Serge Berthoin and Nicola A. Maffiuletti, 2015) Does Fatigue Cause injury?
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