Sports Medicine Research: In the Lab & In the Field: Effect of Acute Static Stretch on Maximal Muscle Performance (Sports Med Res)


Wednesday, July 20, 2011

Effect of Acute Static Stretch on Maximal Muscle Performance

Effect of Acute Static Stretch on Maximal Muscle Performance: A Systematic Review.

Kay AD, Blazevich AJ. Med Sci Sports Exerc. 2011 Jun 8. [Epub ahead of print]

It is well documented that a warm-up, when preparing for a physical activity or athletic performance, can influence physical performance and risk of injury.  However, pre-exercise routines can include various components (e.g., cardiovascular work, stretching) and can be difficult to figure out which aspects of the warm-up contribute to the benefits. A growing body of literature has indicated that static stretching, a common component of a warm-up routine, may have detrimental effects on muscular performance.  Kay et al performed a comprehensive systematic review of literature to assess the acute effects of static stretching on strength-, power-, and speed-dependent tasks.  The authors also stratified the data according to stretch duration (< 30 s, 30-45 s, 1-2 min, > 2 min).  Out of an initial 4559 potential articles 106 articles were included for review.  55% of the articles reported a significant reduction in strength, power, or speed related tasks while 69% reported no significant reductions.  The conflict in percentages was due to certain studies producing both significant and nonsignificant results concurrently (the authors found 149 findings from the 106 articles).  Closer analysis of the data revealed differences based on the duration of stretch.  When stretch duration was 60 s or longer, significant reductions in muscle performance were reported.  In contrast, a stretch duration of < 45 sec does not result in meaningful reductions in muscle performance.  These findings were consistent regardless of performance task, type of contraction (e.g., isometric, eccentric), or muscle group. However, very few studies assessed changes in maximal eccentric strength and all of these studies used stretch durations >60s. 

This systematic review is interesting because it focused on the acute effects of static stretching and explores potential influential factors (e.g., duration of stretch, contraction type). The lack of data regarding eccentric contractions is interesting and concerning since there is a considerable amount of muscle strain during eccentric loading and these contractions are common in sports. It would be interesting to look at changes in eccentric strength with stretch durations  less than 60s.  Some limitations of the review were a lack of control groups in some studies and possible under-reporting of studies with nonsignificant results. That aside, short duration stretching tends not to result in significant muscular impairments while longer duration stretches do impair performance.  Fortunately, in warm-ups, individuals usually use stretches with shorter durations but longer duration stretches are sometimes used in the clinical setting.  In a clinical setting this review could have implications in terms of the order of activity.  Typically I have patients warm up and stretch prior to exercise and I keep the stretch time to 30 seconds.  Then at the conclusion of the program if joint/muscular stiffness are issues I will address that with low load longer duration stretches.  This pattern of stretching exercises places the long duration stretches at the end of the program so that it cannot negatively impact other exercises. It would be interesting to hear how other clinicians utilize total stretch duration and time with their athletes/patients. This literature review definitely provides some thought provoking data regarding the benefit of static stretching (e.g., increasing range of motion, decreasing musculotendinous stiffness) in relation to injury prevention versus the possible negative effects on muscular performance.  

Written by: Thomas Martin
Reviewed by: Jeffrey Driban

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Chris McKenzie PT, DPT, PES said...

What level of evidence were all these studies you reviewed? Sports require power movements. It does not appear that power, or a time component were looked at in these articles, only strength issues.

Jeffrey B. Driban, PhD, ATC, CSCS said...

Hi Chris: The majority of the studies used a randomized crossover design which meant that the participants and clinicians were not blinded. 32 articles failed to use a proper control group or failed to report reliability analyses. Overall the methodological quality was moderate. When the authors excluded studies with poor methodology they found that this didn't not really influence their results.

Short duration (under 30 s) stretches did not result in reductions in power or speed dependent tasks (e.g., 20 meter spring time, vertical jump) in 9 of of 10 studies. Two studies reported reported improved performance in 5-step jump distance and peak cycling power.

For longer duration stretches (> 60 sec) speed or power were reportedly reduced in ~50% of the 25studies.

When you look at the average reduction in power or speed (across studies) you see almost no change with short duration stretches (0.2% reduction; 4 findings) compared 2.7% or 4.5% reduction with 60 to 120s stretches (23 findings) or >120s stretches (2 findings); respectively. I hope that helps.

Tom Martin said...

Thanks for the comments Chris and Jeff

While nothing will compare to the strength, power and speed components of actual sports participation, I thought this review did a good job of looking thru the literature pertaining to this topic and show some consistent findings.

As for clinical use it will be up to the clinician to evaluate and implement, with their patient/athletic population based on their interpretation of the data/research.

For me it will influence how a implement stretching programs to prevent injury and influence performance prior to athletic activity versus recommending flexibility programs for patient/athletes with flexibility imbalances prior to or cooling down from athletic activity.

Also,just the fact that reductions were found shows there is an area for concern, that clinicians should be aware stretch duration when recommending flexibility exercises prior to muscle performance.

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