Stretch to match your goals

As mentioned in Understanding Hamstring Function and the Related Injury Risks, the hamstring is at a higher risk of injury when exposed to a lack of flexibility, decreasing its ability to efficiently transfer eccentric load to the tendon and increasing myofibrillar strain. 

Therefore, aiming to maintain adequate flexibility to reduce injury risk makes sense. The stretching method, the duration, and the frequency you choose to employ will determine the effectiveness of the program. The timing of your stretching protocol is also an important factor as it will impact your sport performance.

Static stretching (SS) is the most common and also the most researched type of stretching. It involves holding a certain position to passively stretch the muscle tissue and has proven to be an effective method to increase range of motion [1,2].

Static stretching’s adverse effects on performance have been widely validated by research. Indeed, SS protocols preceding exercise particularly hindered sport performance requiring high levels of power production (sprinting, jumping). 

It is believed that stretching-related decrease in performance may be due to changes in muscle compliance, alteration of the length-tension relationship and a decrease in muscle activation [5].

Proprioceptive neuromuscular facilitation (PNF) is a method of stretching involving a stretch-contract-stretch mechanism. The individual holds a static stretch position, contracts isometrically against the stretch for a few seconds, and then relaxes prior to returning into the same position which should lead to a stretch within a deeper range of motion (ROM).

Both PNF and SS have been found to be effective methods to increase active and passive ROM at the knee [5] but PNF appears to be more effective SS [4].

PNF stretching, although proven to be a valid way to increase ROM, represents a method with higher risk of injury in uninjured subjects and a greater risk of re-injury in rehabilitation patients  due to the eccentric contraction occurring during the stretch [6].

Ballistic stretching (BS) refers to movements using momentum and recoil to bring joints past their initial ROM, therefore increasing flexibility (leg swings, arms swings…). The results regarding flexibility seem to point towards BS being an effective mean to increase ROM [1]. 

However, its effect on performance remains unclear. 
Unick et al. found no change in vertical jump performance 15 and 30min following a BS stretching protocol, but Woolstenhulme’s research proved warm-up routine involving BS to lead to improved vertical jump performance when combine with 20min of basketball activity [3].

Finally, dynamic stretching (DS) demonstrated some level of increase in flexibility [7] but unlike most other protocols, it did not lead to a decline in muscle performance. Dynamic stretching describes  movements performed actively through a wide ROM, movements can be general or sport-specific. 

Moreover, DS was even proven to positively impact muscle performance in activities such as vertical jump [8,9].

Overview

PNF and ballistic stretching have yielded satisfying results in terms of flexibility and ROM improvements but require more precaution, coaching, teaching and experience in order to be prescribed safely and minimise the risk of injury.

You want to focus in improving your flexibility? – Static stretching seems to be the most viable option to safely improve flexibility but should not be performed as a prehab protocol for exercise as it may decrease your ability to perform power-based movements. 

You wish to improve range of motion without adverse repercussions on your upcoming performance? – Dynamic stretching is the best protocol to ally ROM gains with improvements in muscular performance and should be a staple component of your pre-practice and pre-competition routine. 

References

1. Wiemann K & Hahn K. Influences of Strength, Stretching and Circulatory Exercises on Flexibility Parameters of the Human Hamstring. Int J Sports Med, 18950, 340-346, 1997.
2. Woods K, Bishop P & Jones E. Warm-Up and Stretching in the Prevention of Muscular Injury. Sports Med, 37, 1089-1099, 2007.
3. Woolstenhulme MT, Griffiths CM, Woolstenhulme EM & Parcela AC. Ballistic Stretching Increases Flexibility and Acute Jump Height When Combined With Basketball Activity. J Strength Con Res, 20(4), 799-803, 2006.
4. Worrell TW, Smith TL & Winegardner J. Effect of Hamstring Stretching on Hamstring Muscle Performance. J Ortho & Sports Phys Therapy, 1994, 20(3), 1994.
5. Marek SM, Cramer JT, Louise Fincher A, Massey LL, Dangelmaier SM, Purkayastha S & Culbertson JY. Acute Effects of Static and Proprioceptive Neuromuscular Facilitation Strecthing on Muscle Strength and Power Output. J Athl Train, 40(2), 94-103, 2005.
6. Malliaropoulos N, Papalexandris S, Papalada A & Papacostas E. The Role of Stretching in Rehabilitation of Hamstring Injuries: 80 Athletes Follow-Up. Med & Sci in Sports & Ex, 36(5), 756-759, 2004.
7. Bandy WD, Irion JM & Briggler M. The Effect of Static Stretch and Dynamic Range of Motion Training on the Flexibility of the Hamstring Muscles. J Ortho & Sports Phys Therapy, 27(4), 295-300, 1998.
8. Yamaguchi T & Kojiro I. Effects of Statis Stretching for 30 Seconds and Dynamic Stretching on Leg Extension Power. J S&C and Res, 19(3), 677-683, 2005.
9. Jaggers JR, Swank AM, Karen L & Lee CD. The Acute Effects of Dynamic and Ballistic Stretching on Vertical Jump Height, Force, and Power. J S&C and Res, 22(6), 1844-1849, 2008.