Why Stretch?

What does the research say?

“This article will hopefully assist you in saving time, increase and improve your outcome measures and increase the efficiency and effectiveness of your workouts

The Longevity Blog   •   April 6th, 2020

For my friends, family, and followers

One of the most common and misleading pieces of information “make sure you stretch after your workout! It helps with recovery” is under the ironing board in this review of the literature.

Time to lead you on the path of evidence-based and proven (or at least statistically significant) exercise advice.

Why Stretch?

What Does The Research Say?

K ey Takeaways:

Current research suggests: 
All types of stretching before and/or after exercise does not assist with recovery
Static stretching before exercise does not reduce injury risk but dynamic stretching may provide some benefit
⬆️ All stretching increases Joint Range of Motion (ROM) with static stretching providing the most benefits
Static stretching before exercise decrease performance
Static stretching post-exercise increases muscle soreness/DOMS acutely but not chronically
Firstly lets define STRETCHING

Weerapong et al. (2004) does it exceptionally defining it by the movement applied by an external and/or internal force in order to increase muscle flexibility and/or joint range of motion (ROM).

Secondly let us differentiate between FLEXIBILITY and STIFFNESS

  • Flexibility is a term used to describe the muscles associated with a particular joints and it’s range of motion (i.e. if the joint is limited in it’s ROM it could be suggested that the muscle in question is lacking flexibility).
  • Stiffness is a term used to describe a muscles compliance to stretch. Often a ‘hard’ or ‘tight’ sensation is used to subjectively define a feeling of a muscle that is less compliant to stretch.
  • Passive Stiffness is the muscles ability to lengthen at rest 
  • It is important to mention another aspect of these are the muscle/tendon stiffness and compliance

Lastly these definitions are all not completely separate from each other but rather it is a scale and should not be kept separated from each other.

Stretching Post-Exercise

Does stretching after exercise assist in recovery?

A systematic review of 99 studies with 1188 subjects by (Dupuy et al., 2018) found that when comparing the following recovery techniques:
  • Active Recovery (AR)
  • Stretching
  • Massage
  • Massage + Stretching
  • Electrostimulation
  • Ecompression Garments (CG)
  • Immersion
  • Contrast Water Therapy (CWT)
  • Cryotherapy
  • Hyperbaric Therapy
Massage seemed to be the most effective method for reducing Delayed Onset Muscle Soreness (DOMS) and perceived fatigue with AR, CG, immersion, CWT and Cryotherapy also showing small benefits. 
 
No benefit from stretching was observed.
 
It is interesting this has been a common recommendation because for some time stretching has not been recommended after exercise (Herbert and Gabriel, 2002; Herbert et al., 2011) and has been suggested to even increase DOMS (Smith et al., 1993).

Is there a difference between Static, Ballistic & Proprioceptive Neuromuscular Facilitation (PNF) stretching on muscle soreness/DOMS?

Diving in further…
Smith et al. (1993) found that for a person that is new to exercises:
  • Both static and ballistic stretching post-execise induce significant increases in DOMS and the associated Creatine Kinase (which is the inflammatory molecules released in response to muscle damage leading to DOMS. 
  • Static stretching after produce significantly more DOMS than ballistic stretching. 
  • McGrath et al., (2014) found consistent results of previous research demonstrating post-exercise static stretching and PNF stretching also does not prevent DOMS.

What about Stretching Before Exercise?

Does stretching before exercise reduce muscle soreness/DOMS?

Answer:
Short-term – Stretching before an exercise session does not reduce muscle soreness/DOMS from that session!
Long-term – Stretching increases muscle flexibility and reduces muscle stiffness which is suggested to be a preventative measure of muscle soreness/DOMS
The Evidence:
Several studies (High et al., 1989Johansson et al., 1999Rodenburg et al., 1994Wessel & Wan, 1994) and a meta-analysis by Herbert & Gabriel, (2002) failed to find stretching as a protective effects on eccentric exercise-induced muscle damage leading to muscle soreness and DOMS.
However…
Muscle stiffness and its clinical correlate, static flexibility, are risk factors for more severe symptoms of muscle damage after eccentric exercise (McHugh et al., 1999).
McHugh et al. (1999) reported that the subjects whose hamstrings were more compliant had significantly less symptoms of muscle damage after eccentric exercise of the knee flexors than those who had stiff hamstrings.
Chen et al. (2011) also noted that eccentric exercise-induced muscle damage, soreness/DOMS can be reduced with long-term flexibility training. Long-term flexibility training may reduce muscle stiffness and/or increase muscle flexibility, therefore acting as a preventative measure of muscle soreness/DOMS.

Does Stretching Decrease Performance?

Answer:
Static stretching has been documented to have negative effects on strength, speed, or power performance.
However, a more recent study concludedstatic or dynamic stretching are unlikely to affect sprint running, jumping, or change of direction performance.
The Evidence:
Fletcher & Anness. (2007) looked at the performance of 18 professional sprinters after different warm-up routines and concluded that in a warm-up passive static stretching in a decreases sprint performance.
It has also been documented that static stretching has even negative effects on strength, speed, or power performance (Fletcher & Anness, 2007; Herda et al., 2008; Samuel et al., 2008). 
Herda et al. (2008) reviewed the effect of static or dynamic stretching on 14 males and their isometric and dynamic hamstring strength. It was concluded that dynamic stretching may be less detrimental to muscle strength than static stretching for the hamstrings.
However, a more recent study by Blazevich et al. (2018) looked at the performance of 20 participants after either static stretching or dynamic stretching and found no effect of muscle stretching was observed on physical function compared with no stretching, and therefore concluded these types of stretching are unlikely to affect sprint running, jumping, or change of direction performance.
Because of the mixed results, it would be better to use dynamic stretching before activity as this has been consistently supported by the literature.
Does Stretching Decrease Injury Risk?
Answer:
Stretching before exercise does not reduce injury risk.
The Evidence:
Pre-exercise static stretching has been advocated to be beneficial for prevention of soft tissue (e.g., muscle, tendon, ligament) injuries (Cheung et al., 2003Connolly et al., 2003). 
 
However, a meta-analysis by Herbert & Gabriel, (2002) pooled estimates from two studies and found that stretching decreased the risk of injury by 5% was statistically non-significant.
 
A meta-analysis by Weerapong et al. (2004) reported there is limited scientific data to support the suggested benefits of stretching to reduce injury risk.
Conclusion:
The ideal flexibility (joint ROM), muscle and tendon stiffness for the performance of each sport, activity or human movement is different. 
 
A compliant muscle (one that is able to lengthen) might be beneficial to eccentric contraction while a stiffer muscle might be more suitable for concentric and isometric contractions. 
The real question is: 
Does flexibility help to reduce the rate of injury? 
 
It seems that most of the research in leaning towards not supporting this.
Most activities human requires repetitive movement in normal ROMs. Therefore increasing ROMn, is not necessary and may in fact lead to an increase in risk of injury.
 
Weerapong et al. (2004) mentions reducing resistance during repetitive movement might be more beneficial in terms of increasing quality of movement and reducing the risk of overuse injury.
 
When looking at a movement that does not require compliant muscle/tendons (ie, the movements and power generation are within the ROM in question and are not challenging the ROM) do we actually need to stretch them? 
 
For example:
  • Jogging
  • Cycling
  • Swimming
Is a human is participating in these activities and their ROM is adequate to perform the ROM necessary to complete the required movements, is then stretching (and thus increasing joint ROM and making the muscle/tendon more compliant) more advantageous? 
 
It boils down to the movement, ROM needed for that movement and if the reasons to stretching was I need more ROM then YES THE EVIDENCE IS CLEAR!
 

Stretching is great for increase joint ROM, decreasing muscle/tendon stiffness and not much else!!

References: 19
Total Subjects: 10K+
Research Date Ranges: 1957-2018
 
References
  1. Blazevich, A. J., Gill, N. D., Kvorning, T., Kay, A. D., Goh, A. G., Hilton, B., Drinkwater, E. J., & Behm, D. G. (2018). No Effect of Muscle Stretching within a Full, Dynamic Warm-up on Athletic Performance. Medicine & Science in Sports & Exercise, 50(6), 1258. https://doi.org/10.1249/MSS.0000000000001539
  2. Chen, C.-H., Nosaka, K., Chen, H.-L., Lin, M.-J., Tseng, K.-W., & Chen, T. C. (2011). Effects of Flexibility Training on Eccentric Exercise-Induced Muscle Damage. Medicine & Science in Sports & Exercise, 43(3), 491. https://doi.org/10.1249/MSS.0b013e3181f315ad
  3. Cheung, K., Hume, P., & Maxwell, L. (2003). Delayed onset muscle soreness: Treatment strategies and performance factors. Sports Medicine (Auckland, N.Z.), 33(2), 145–164. https://doi.org/10.2165/00007256-200333020-00005
  4. Connolly, D. A. J., Sayers, S. P., & McHugh, M. P. (2003). Treatment and prevention of delayed onset muscle soreness. Journal of Strength and Conditioning Research, 17(1), 197–208. https://doi.org/10.1519/1533-4287(2003)017
  5. Dupuy, O., Douzi, W., Theurot, D., Bosquet, L., & Dugué, B. (2018). An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation: A Systematic Review With Meta-Analysis. Frontiers in Physiology, 9. https://doi.org/10.3389/fphys.2018.00403
  6. Fletcher, I. M., & Anness, R. (2007). The acute effects of combined static and dynamic stretch protocols on fifty-meter sprint performance in track-and-field athletes. Journal of Strength and Conditioning Research, 21(3), 784–787. https://doi.org/10.1519/R-19475.1
  7. McHugh, M. P., Connolly, D. A., Eston, R. G., Kremenic, I. J., Nicholas, S. J., & Gleim, G. W. (1999). The role of passive muscle stiffness in symptoms of exercise-induced muscle damage. The American Journal of Sports Medicine, 27(5), 594–599. https://doi.org/10.1177/03635465990270050801
  8. Herbert, R. D., & Gabriel, M. (2002). Effects of stretching before and after exercising on muscle soreness and risk of injury: Systematic review. BMJ (Clinical Research Ed.), 325(7362), 468. https://doi.org/10.1136/bmj.325.7362.468
  9. Herbert, R. D., de Noronha, M., & Kamper, S. J. (2011). Stretching to prevent or reduce muscle soreness after exercise. The Cochrane Database of Systematic Reviews, 7, CD004577. https://doi.org/10.1002/14651858.CD004577.pub3
  10. Herda, T. J., Cramer, J. T., Ryan, E. D., McHugh, M. P., & Stout, J. R. (2008). Acute effects of static versus dynamic stretching on isometric peak torque, electromyography, and mechanomyography of the biceps femoris muscle. Journal of Strength and Conditioning Research, 22(3), 809–817. https://doi.org/10.1519/JSC.0b013e31816a82ec
  11. High, D. M., Howley, E. T., & Franks, B. D. (1989). The effects of static stretching and warm-up on prevention of delayed-onset muscle soreness. Research Quarterly for Exercise and Sport, 60(4), 357–361. https://doi.org/10.1080/02701367.1989.10607463
  12. Johansson, P. H., Lindström, L., Sundelin, G., & Lindström, B. (1999). The effects of preexercise stretching on muscular soreness, tenderness and force loss following heavy eccentric exercise. Scandinavian Journal of Medicine & Science in Sports, 9(4), 219–225. https://doi.org/10.1111/j.1600-0838.1999.tb00237.x
  13. McGRATH, R. P., Whitehead, J. R., & Caine, D. J. (2014). The Effects of Proprioceptive Neuromuscular Facilitation Stretching on Post-Exercise Delayed Onset Muscle Soreness in Young Adults. International Journal of Exercise Science, 7(1), 14–21.
  14. Rodenburg, J. B., Steenbeek, D., Schiereck, P., & Bär, P. R. (1994). Warm-up, stretching and massage diminish harmful effects of eccentric exercise. International Journal of Sports Medicine, 15(7), 414–419. https://doi.org/10.1055/s-2007-1021080
  15. Samuel, M. N., Holcomb, W. R., Guadagnoli, M. A., Rubley, M. D., & Wallmann, H. (2008). Acute effects of static and ballistic stretching on measures of strength and power. Journal of Strength and Conditioning Research, 22(5), 1422–1428. https://doi.org/10.1519/JSC.0b013e318181a314
  16. Woletz, T., & Choi, S. (2010). Do Stretching Programs Prevent Work-related Musculoskeletal Disorders? Journal of Safety, Health and Environmental Research, Vol 6, Feature 2.
  17. Smith, L. L., Brunetz, M. H., Chenier, T. C., McCammon, M. R., Houmard, J. A., Franklin, M. E., & Israel, R. G. (1993). The effects of static and ballistic stretching on delayed onset muscle soreness and creatine kinase. Research Quarterly for Exercise and Sport, 64(1), 103–107. https://doi.org/10.1080/02701367.1993.10608784
  18. Weerapong, P., Hume, P. A., & Kolt, G. S. (2004). Stretching: Mechanisms and Benefits for Sport Performance and Injury Prevention. Physical Therapy Reviews, 9(4), 189–206. https://doi.org/10.1179/108331904225007078
  19. Witvrouw, E., Mahieu, N., Danneels, L., & McNair, P. (2004). Stretching and injury prevention: An obscure relationship. Sports Medicine (Auckland, N.Z.), 34(7), 443–449. https://doi.org/10.2165/00007256-200434070-00003