Stretching was first used by the ancient Greeks and across Asia as a form of torture technique. The Greeks and Romans used stretching as a preparation tool for their athletes and soldiers to keep them in shape. In the 18th century the first osteological studies were carried out. Stretching has now evolved and is commonly used in preparation for training (warm up and activation) and as a form of injury prevention method (Alter 1996; Woodsetal 2007). Studies by Ekstrand (1982) show contradictory evidence surrounding the role of stretching and the impact on injury where 31% of elite footballers had poor flexibility and were injured, compared to 18% that had good flexibility. Jeffreys suggests that stretching is used to increase the range of movement whilst Smith outlines the enhanced muscular coordination obtained when preforming stretches. It also provides a reduction in muscular resistance to movement (Shrier 2004). Post training stretches are often used as a recovery technique. Other benefits of stretching include improved blood flow and circulation as well as a reduction in stress. Whether we should stretch before a training session or sport is a debatable topic. Whether one should stretch before and/or after exercising or partaking in sport is a common debate and a confusing subject for coaches and individuals at different sporting levels.
Various types of stretching include static (SS), dynamic (DS), ballistic (BS) and proprioceptive neuromuscular facilitation (PNF). Static stretching can be active (self-stretch) or passive (partner assisted). This involves the application of a slow and constant force relax and elongate the muscle with the aim of improving range of motion. A passive stretch involves no voluntary muscle action as the external force (partner, gravity, stretching equipment) is used to provide the stretch. The use of stretching machines may cause increased individual stretch intensities (Avela et al. 1999; Avela et al.,2004; Fowles et al.,2000). Studies show that static stretching prior to training can have adverse affects on performance. Smith and Shrier (2004/1994) proposed that static stretching can reduce performance levels by 4-20%. There are minimal benefits, on reducing injury risk by preforming static stretching pre training (Gleim & McHugh, 1997; Pope, Herbert, Kirwan & Graham, 2000; Woods et al. 2007). There are studies that mention that this type of stretching would be more appropriate if performed post-training, or as part of the cool down. Lack of flexibility can be an injury inducing factor for athletes, so it is important that SS is included in their training program, provided it is done at the right time. Improving flexibility in specific muscles will be beneficial as it provides increased range of motion which for certain movements such as sprinting are important.
Dynamic stretching is an active movement stretch that mimics the speed of movement. This type of stretching is useful to prepare athletes for specific movement, such as a pre match warm up in team sport. DS requires voluntary muscular activation and plays and important role in preparing joints and muscles for the range of movement (ROM) required in sports. Ballistic stretching is a type of dynamic stretching that involves a bouncing movement. The end positioning is not held and can cause injury if preformed by athletes who are not as flexible as it is a relatively uncontrolled movement. Swanson (2006) & Thomas (2000) suggest the following sequence prior to engaging in sporting activities - An aerobic warm up prior to sports performance followed by DS and finally a sport specific warm up. PNF stretching involves the contraction and relaxation or the “hold and relax” method to alternate between the two states of muscular contraction and relaxation.
The RAMP warm up method developed by Ian Jeffreys is currently the most common one used by coaches and elite athletes. The RAMP acronym stands for raise, activate, mobilise and potentiate. This sequence provides a structured system for warming up athletes. It starts off by increasing muscle temperature, blood flow, muscle elasticity and neural activation followed by a sequence of movements that engage the muscles in preparation for the session. The mobilisation part focuses on dynamic movement patterns which will be used during the game, and finally increasing the stress on the body for the game in the potentiation phase.
Research shows that lower volumes of stretching may limit the negative effects produced by SS if required by the athlete to improve their flexibility and not be detrimental to their performance. <2-3 sets x <15 seconds of SS, PNF, DS or BS showed no effects on strength or power performance (Christensen and Nordstrom, 2008; Torres et al. 2008; Unick et a, 2005; Knudson et al. 2004). SS, PNF and BS produce negative effects and DS produces positive effects when performing 3-8 sets of 2-6 stretches per muscle group at 30-60 repetitions or seconds. (Behm et al. 2006; Church et al., 2001; Cramer et al. 2004; Knudson & Noffal, 2005; Kokkonen, Nelson, & Cornwell, 1998; Marek, et al., 2005; Nelson & Kokkonen,2001;Little &Williams,2006). This study assessed the effects of SS on vertical jump performance at 50%, 75% and 100% of the maximum level of discomfort and found that vertical jump performance was reduced by around 4% at all intensities. Research examining performance with loads of 50-85% of 1 rep max show similar responses in muscular endurance following SS (Franco et al. 2008; Garcia-Lopez et al.2010;Gomes et al.2010;Nelson et al.2005). Wilson et al, (2010) concluded that SS reduced the total distances run and Daniels and Daniels (1992) showed that SS reduced running economy. Interestingly, a study by Mojock et al (2001) provided some insight on SS and potential gender differences, as SS had no effect in female runners.
Athletes should aim to complete an active warm up. If SS is required this should be completed 10-15 minutes pre-performance. Multi joint assessments have shown a reduction in performance following SS after 5mins. Allowing the additional >15 minutes time makes the SS effect negligible on performance allowing athletes who need the extra static stretches to still perform them provided they are completed at the right time. SS increases ROM for up to 6min, with a non-significant increase in ROM for up to 30-60 minutes (DePino,Webright, & Arnold, 2000; Spernoga, Uhl,Arnold, & Gansneder, 2001). This highlights the thought of whether the short term gains in ROM balance off the potential decreases in performance. If post SS performance levels are reduced for up to 16 minutes, with the greatest decline shown in the first 5 mins we need to emphasise the importance of allowing that time window between completing the SS and the DS in the athlete’s warm up to offset the potential decline in performance within the first 15 minutes post SS.
So what triggers this decline in performance? SS increases ROM, which reduces muscular stiffness and promotes blood flow thus increasing circulation. This produces a lack of return of elastic energy which could be one of the factors that reduce performance (Lopes et al.,2010; Wilson,et al.,2010). When performing movements such as a countermovement jump or a vertical jump an element of stiffness is required to allow for the quick reflex of the muscle to contract and expand to produce the jump height. The change in muscle-tendon length and increased muscle slack following SS is one of the factors that hinders performance (Cramer et al. , 2004; Evetovich et al, 2010; Marek, et al. , 2005). Various research indicates that a combination of both neuromuscular and mechanical mechanisms contribute to stretch induced performance alterations.
The intensity of the active warm up element and the DS are vital if they are to aid performance (Fletcher and Jones, 2006). DS is essential for warm ups for team sport athletes, especially in high impact and fast paced sports such as basketball, football, rugby and netball to prepare the athletes for the movements they are required to complete in the game. For example, dynamic hamstring stretching is essential for runners as it will switch on one of the main posterior chain muscles used to perform this movement. Various exercises such as dynamic leg swings and B skips would be used in this case. DS also enhances muscular activation (Herda et al.2008;Hough et al. 2009) and may enhance performance via enhanced metabolic processes (Dixon et al.2010;McMillan et al., 2006).
Conclusion: Stretching has evolved over time, and has an important role in athletic performance and health. Stretching provides additional psychological benefits (Beckett et al., 2009) as well as enhanced proprioception (Costa et al.,2009; Handrakis et al. 2010). SS acutely reduces performance if performed prior to training, however low volume (1-2 sets) of short duration (10-25 seconds) at a moderate intensity is completed 10-15 minutes has a negligible effect on performance. Mechanical and neuromuscular mechanisms are important, which highlights the importance of performing dynamic stretching, prior to engaging in sporting activities to achieve a positive performance outcome.
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