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How Long to Stretch

If you are involved in a stretching program you are probably wondering how long to stretch. If you take the time to stretch will it make a difference? Research into the subject has shown variable results which depend on age, activity level, previous injuries, etc. Books and websites that tell us how long to hold a stretch give us different answers. So, when it comes to learning the best time to stretch I hope to shed some light onto the latest literature.

How Long to Stretch - what does the research say?
What Factors Influence the Ability to Stretch?
Viscoelasticity of Muscles
Kids - What's the Best Time to Stretch?
Stretching Seniors -How long?
How does How Long You Stretch Affect Active Range of Motion?
How many repetitions?
how long to stretch

How Long to Stretch - what does the research say?

Results  of long term studies with healthy humans between the age 21 and 39 have shown that after 6 weeks, the people who stretch thirty seconds per muscle every day were able to increase their mobility more than the people that stretched fifteen seconds per muscle per day. (1) Changes in mobility amongst those that stretched for fifteen seconds per muscle per day were statistically insignificant. People that stretched sixty seconds per muscle per day increased their range of motion but not significantly more than those that held their stretches for thirty seconds.

Other studies have shown that people can increase their range of motion using only 15 second stretches while others gain very little increased mobility with even 45 second stretches. How long to stretch appears to vary depending on which muscle groups are being stretched.

What Factors Influence the Ability to Stretch.

Factors that influence the ability to stretch the connective tissues in a muscle are as follows:
  • muscle fatigue
  • the presence of scar tissue
  • muscle temperature
  • activity prior to the stretch
  • collagen/elastic content (varies with age)
  • hydration/dehydration
  • medical conditions (diabetes, connective tissue disorders, smoking)

Viscoelasticity of Muscles

Viscoelasticity is the physical property of a substance that is both viscous and elastic. Elasticity in a rubber band is reflected  by its ability to bounce back to its original length after it has been stretched or deformed.  Viscosity is the resistance measured in a substance to deformation by a stress and is a reflection of internal friction amongst its molecules.

Muscles contain both of these properties which influence how long to stretch a muscle. The more elastic elements of a muscle will behave like a rubber band.  It will lengthen and then upon release return to its original length. This is not dependent on time. The flow of a viscous muscle however (like cold motor oil, or honey) is dependent on time.  Therefore, the length of a muscle will increase with time if it is held stretched to a particular length. When this force is taken away, the muscle will return slowly to its original length. This physical property is different from the physical property of plasticity in which the new length would be maintained.

Patients are prescribed stretches to increase their range of motion in the short term or the long term. There is research to support the use of one fifteen to thirty second stretch per muscle group for most people, but some patients or particular muscle groups may need  a longer duration of stretch or more than one repetition. The immediate effects of stretching are the result of  a reduction in viscoelasticity and an analgesic effect (tolerance to stretch).  In rabbit tendons that were stretched for thirty seconds, increased range of motion was due to viscoelasticity until the fourth repetition. In humans, hamstring muscles displayed decreased stiffness after five repetitions. It has been found that amongst other muscle groups in humans that range of motion increases did not depend on time when 15, 45, and 120 second stretches were compared. It is also true that stretching in some muscle groups are more limited by pain.

Long term studies amongst humans show that a hamstring stretch lasting thirty seconds once a day resulted in the same change in flexibility as three stretches of thirty seconds duration. (1)
When stretching over the long term (ie weeks) viscoelasticity is constant  and the improved range of motion can be attributed to increased tolerance to stretch (tolerance to discomfort).   This literature supports the general use of thirty second stretches for most groups of healthy individuals. This recommendation is like the recommended daily allowance for vitamin intake. It's a general guideline for a healthy population for how long to stretch.

Muscle fatigue changes viscoelasticity,  as do injuries, tears, scar tissue, and atrophy. So if you have any injuries you must seek professional advice as to how long to stretch a muscle. For more information on muscle physiology click here.

Kids - How Long to Stretch

A study done amongst a relatively small sample size of thirteen healthy 13-15 year olds examined the effect of four different stretching protocols. (3) All protocols lasted 60 seconds:
  1. one stretch of 60 seconds duration
  2. two stretches of 30 second duration
  3. four stretches of 15 second duration
  4. 12 stretches of five second duration
Measurements were made of hip flexion, extension, abduction, knee flexion and ankle dorsiflexion.

Results showed that there were no significant differences between the stretching protocols. One 60 second stretch was as effective as 12 five second, four 15 second, or two 30 second stretches. If you have a child in this age group asking how long to stretch, generally, 15-30 seconds is adequate, provided there are no injuries or underlying conditions.

Stretching Seniors -How long to stretch?

A study published in Physical Therapy in 2001 amongst 60  healthy individuals (mean age 84.7, SD=5.6)  with tight hamstrings compared stretches for the hamstrings held for 15, 30 and 60 seconds over a period of 6 weeks(4)

These results  indicate that a stretch of sixty seconds was more effective than one of thirty seconds within this group of older individuals. Previous studies with a younger populations suggest that a sixty second stretch was just as effective as a thirty second stretch. In this study a sixty second stretch repeated four times, once a day, five times per week for 6 weeks improved hamstring flexibility in people over 70 better than those that stretched 15, or 30 seconds. In this group, improvements in range were also seen in those stretching 15 seconds and 30 seconds. In other words a short stretch is better than no stretch, but 60 seconds is optimal.  This study also showed that stretching must be continued if the benefits of stretching are to be maintained over time.

For more on stretching exercises for seniors click here.

How does How Long You Stretch Affect Active Range of Motion?

A study published in the British Journal of Sports Medicine investigated the effects of stretching for different durations on active range of motion and passive range of motion of the lower extremity over five weeks of training. (5) 24 active 19 to 21 year olds were divided into three groups:
  1. one group stretched 5 seconds, 9 times
  2. the second group stretched 15 seconds, 3 times
  3. the third group didn't stretch
Active and passive range of motion was measured before and after the training program.
Results were as follows:
  • Significant improvements were seen in both of the stretching groups.
  • There was no difference in range of motion in the control group.
  • The five and 15 second group showed no difference when passive range of motion was measured.
  • The 15 second stretch group showed significant improvement over the five second group when measuring active range of motion.
Hence, when looking to find out how long to stretch, the longer stretch resulted in greater active range of motion, but if looking to increase passive range only, five seconds is fine.

How many repetitions

Repeated stretching in one session of static stretching has been looked at in animal studies. (6) 80% of the changes in a muscle length with stretching occurred with the first four repetitions. Most of the lengthening resulting from the first stretch

 
   
References
1.  Bandy WD, Irion JM, Briggler M: The effect of time and frequency of static stretching on flexibility of the hamstring muscles. Phys Ther 1997;77(10):1090-1096
2.  Madding SW, Wong JG, Hallum A, et al: Effect of duration of passive stretch on hip abduction range of motion. J Orthop Sports Phys Ther 1987;8:409-416
3.  T. Ioannis, G. Christos, Z. Nikolaos, V. Aikaterini, V. Efstratios The Effect of Stretching Duration on the Flexibility of Lower Extremities in Junior Soccer Players.
Aristotle University of Thessaloniki Department of Physical Education and Sports Sciences Thessaloniki, Greece Physical Training Sept 2005.
4.  Feland JB, Myrer JW, Schelthies SS, Fellingham GW, Measom GW. The effect of duration of stretching of the hamstring muscle group for increasing range of motion in people aged 65 years or older. Phys Ther 2001;81:1110-1117.
5.  Jennifer M Roberts, Karen Wilson Jennifer M Roberts, Karen Wilson  Effect of stretching duration on active and passive
range of motion in the lower extremity. How long to stretch.Br J Sports Med 1999;33:259–263
6.  DC Taylor , JD Dalton, AV Seaber, WE garrett Viscoelastic properties of muscle-tendon units. The biomechanical effets of stretching. Am J Sports Med, 18(3),300-309.