Stretching: the what, the when and the why of stretching
There are various opinions about the benefits of stretching and what it actually achieves from flexibility to injury prevention and how it affects performance.
This blog includes current evidence on stretching as well as my practical thoughts on stretching from 20 years experience in Physiotherapy and will include what is happening during a stretch, how we can use the various types of stretching effectively and when they are most appropriate to be used.
What is muscle tone?
Muscle tone is a term we use to describe a muscles tension or essentially how prepared a muscle is to work. High tone muscle has more resting tension and as a result has more definition or shape. It is also more easily activated and ready to load. This is why athletes with well-trained muscles have the shape and definition we see. Low tone muscle is more relaxed or floppy, it isn’t as ready to fire and actually takes a lot of effort to get going. People with low tone tend to do less exercise resulting in poorer motor skills and they don’t enjoy weight-bearing exercise because it’s hard, resulting in further weakness, postural issues and increased weight.
Types of stretching
• Static stretching
• Ballistic or dynamic stretching
• PNF stretching.
The properties of each can make them useful at particular times with associated effects on mobility and performance.
Static Stretching
This is the classic long steady stretch where one position is held for 30secs or longer. Evidence shows that static stretching can increase joint range of motion (ROM) for only a temporary period of time. Static stretching involves prolonged holds with low levels of force resulting in a reduction of muscle tone allowing increased joint range of motion.
It is important to develop strength through the full range of a muscle’s length and movement or the changes are unlikely to last (Page, 2012). If a muscle is lengthened but does not have the appropriate strength to stabilise a joint through its range, the potential for injury is increased. This is the reason why static stretching is rarely used before sports or activities requiring dynamic movements. In fact the evidence shows the longer the stretch is held, the greater the potential loss of strength (Rubini, Costa, & Gomes, 2012). Therefore specific strength exercises along with static stretching are important.
Dynamic Stretching/Ballistic Stretching
This is a faster, more powerful movement that is typically associated with large, or increasing ranges of movement. This means the muscles are taken to extreme lengths under high loads. Dynamic stretching does not increase the muscle length to the same extent as static stretching. Sports requiring balance, agility, and short-term movement speed, dynamic stretching has been shown to significantly be more beneficial than static stretching (Chatzopoulos et al, 2014).
Unlike static holds which are performed under a low force and held for a prolonged period, dynamic stretching requires a forceful muscle contraction immediately after a 3-5 second hold. The muscle contraction through a greater range of motion benefits performance by increasing muscle tone in the extended range and therefore overall power production. In a study performed by Hough (2009), dynamic stretching was shown to have a positive impact on vertical jump performance in comparison to static stretching, which has a negative impact (Hough et al, 2009).
However there is some definite risk involved when including dynamic stretching into your warm-up routine. Initially, the heavy loading in an unfamiliar range for the muscle is likely to lead to an episode of Delayed Onset of Muscle Soreness (DOMS), or even a muscle strain. Dynamic stretching is best performed after the muscle has warmed up, as there is a risk when rapidly loading a cold muscle can lead to injury in the form of a tear. Try to increase safety with this type of activity by incorporating them late in a dynamic warm-up where the muscles will be warm, and the range of movement will have progressively increased beforehand.
Proprioceptive Neuromuscular Facilitation (PNF) Stretching
This is a clever form of stretching where we use muscle contractions to activate specialised muscle fibres within a muscle (intrafusal fibres) that feedback to the rest of the muscle regarding muscle length and the Golgi Tendon Organ (GTO) that monitors tendon tension to control muscle tension and tendon loads. PNF stretching is the most effective form of stretching for improving joint range of motion
PNF stretching uses a combination of resisted muscle contractions and stretching to manipulate these receptors, allowing us to make the muscle think it’s longer than it is, causing it to ‘let go’ and lengthen. This has been shown to effectively decrease Achilles tendon stiffness, improve ankle ROM without losing any torque/power at the ankle (Konrad, Conrad, & Tilp., 2015). This is beneficial for sports like basketball, AFL, volleyball, dancing because power remains but mobility is improved for performance. This is done under resistance at each point, which leads to strengthening at points through the new range, increasing the likelihood of maintaining the gains in range without the speed, and risk that comes with ballistic stretching.
There are various types of PNF stretching where a muscle performs a contraction or hold before being placed into a relaxed position either passively or actively (see table below). Without going into too much detail, the goal is to use the antagonists (opposing) muscle’s contraction to stretch the targeted muscle. Unlike static stretching where holds of >30secs are used; PNF stretching uses holds up to 3secs. The evidence is still limited to why PNF stretching is so effective. However studies are indicating changes in pain modulation may be the reason (Sharman, Cresswell, & Riek., 2012).
How Can Stretching Benefit Performance?
When preparing for sports or physical activity the goal isn’t necessarily to gain range. The goal is to prepare the muscles and connective tissues so they can generate maximal force for the activity by storing and releasing energy. This brings us back to the effect each type of stretching has on tone.
The warm up needs to be sport/activity specific, with the goal to increase tissue temperature by gradually increasing mobility and intensity.
For example;
Sprinting is an important aspect of majority sports. Studies have identified a significant negative impact on sprinting and high power short-term exercise performance after static stretching of the hamstrings, calf muscles and quadriceps (Nelson et al, 2005). This is because an increase in range needs to be accompanied by increases in strength. So we choose to avoid static stretching prior to majority of team sports and incorporate the dynamic stretching concepts discussed earlier.
Individuals with high tone might need to look at reducing tone to an optimal level, to reduce the likelihood of developing an overuse injury. However high tone is not necessarily a bad thing. Research has identified running economy is significantly better in individuals with muscle stiffness. Elastic energy is more efficiently stored and released in stiff muscles by reducing braking forces (Saunders et a, 2012).
For people with normal tone, stretching should be unnecessary and could risk reducing tone to less than ideal level. The focus should be on increasing the readiness to load muscle and connective tissue with a dynamic warm up, gradually increasing range of movement and intensity.
For people with a generally low level of tone the introduction of a progressive loading program would be of great benefit. Low tone results in a loss of strength resulting in an increased risk of acute joint injuries like rolling an ankle, ligament injuries at the knee etc. These individuals need to consider a prolonged warm up to gradually increase tone and load. Recommendation is to avoid static stretching.
PNF Techniques have been shown to reduce performance slightly in high intensity activities such as those involving sprinting and fast agility but helped in activities such as distance running by improving running velocity. (Caplan et al, 2009) & (Yuktasir & Kaya, 2009).
Injury Prevention and Rehabilitation
To the best of my knowledge there isn’t any evidence that stretching reduces rates of injury but my experience and current evidence shows that high tone and a degree of tightness can correlate with good performance in many sports. However this can be tricky, as there is a very fine line between high tone and the risk of injury. In my experience, stretching and other methods of managing high tone can be used to control ‘tightness’ with very low risk while other issues such as strength are addressed.
Low tone can reduce the control of joints and contributes to instability. Implementing a progressive resistance program can help develop a protective level of muscle tone to reduce the likelihood of instability injuries.
Stretching is a common treatment modality post orthopaedic surgery or musculoskeletal injuries to improve muscle length and joint ROM. Research has shown the use of static stretching in individuals recovering from a hamstring strain helps align collagen fibres and improve recovery (Page, 2012).
Summary
- Stretching is sport/activity specific
- Static stretching can be useful in the cool down and rehabilitation setting to increase muscle length, range of motion, and alignment of collagen fibres during a healing muscle. May also be of benefit in sports and activities requiring static lengthening of the certain muscles.
- Dynamic stretching may be beneficial as part of an individuals or team warm-up when the sport and activity requires agility, balance and short-term movement speed, as this improves performance.
An example;
During low intensity conditioning such as body weight circuits, include mobility and stretching in the warm up. Followed by resistance exercise through full range of motion. The goal is to increase functional range of movement to a point where you have optimal strength for your specific sports/hobbies and mobility without feeling the sensation of “tightness” link dynamic warm-up to a post about what to include in the warm-up.
If you feel stiff and tight or find you’re always stretching or if you look after athletes or teams and want advice on designing appropriate warm ups and conditioning programs give us a call or book a session with us now.
References
Caplan, N., Rogers, R., Parr, M. K., & Hayes, P. R. (2009). The effect of proprioceptive neuromuscular facilitation and static stretch training on running mechanics. The Journal of Strength & Conditioning Research, 23(4), 1175-1180.
Chatzopoulos, D., Galazoulas, C., Patikas, D., & Kotzamanidis, C. (2014). Acute effects of static and dynamic stretching on balance, agility, reaction time and movement time. Journal of sports science & medicine, 13(2), 403.
Hindle, K. B., Whitcomb, T. J., Briggs, W. O., & Hong, J. (2012).
Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function. Journal of human kinetics, 31, 105–113. doi:10.2478/v10078-012-0011-y
Hough, P. A., Ross, E. Z., & Howatson, G. (2009). Effects of dynamic and static stretching on vertical jump performance and electromyographic activity. The Journal of Strength & Conditioning Research, 23(2), 507-512.
Konrad, A., Gad, M., & Tilp, M. (2015). Effect of PNF stretching training on the properties of human muscle and tendon structures. Scandinavian journal of medicine & science in sports, 25(3), 346-355.
Nelson, A. G., Driscoll, N. M., Landin, D. K., Young, M. A., & Schexnayder, I. C. (2005). Acute effects of passive muscle stretching on sprint performance. Journal of sports sciences, 23(5), 449-454.
Page, P. (2012). Current concepts in muscle stretching for exercise and rehabilitation. International journal of sports physical therapy, 7(1), 109.
Rubini, E. C., Costa, A. L., & Gomes, P. S. (2007). The effects of stretching on strength performance. Sports medicine, 37(3), 213-224.
Sharman, M. J., Cresswell, A. G., & Riek, S. (2006). Proprioceptive neuromuscular facilitation stretching. Sports medicine, 36(11), 929-939.
Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports medicine, 34(7), 465-485.
Yuktasir, B., & Kaya, F. (2009). Investigation into the long-term effects of static and PNF stretching exercises on range of motion and jump performance. Journal of bodywork and movement therapies, 13(1), 11-21.
