Abstract
Flexibility is one of the key components of fitness. Stretching prior to engaging in exercise has long been a key aspect of any athlete’s routine. Traditional assumptions have been that pre-exercise flexibility will help prevent injury, prepare the body for the activity and, to a degree, improve performance. Although not arbitrary, static stretching has been the main stay of general pre-exercise flexibility routines.
More recent studies have found there to be almost no effect on injury prevention and some detrimental effect on performance.
Other types of flexibility have also been studied, including Proprioceptive Neuromuscular Facilitation (PNF), ballistic and dynamic stretching. Whilst the research is limited in comparison to static stretching, the current studies connote dynamic stretching can help improve performance but, as yet, it is inconclusive of whether it supports reduced injury susceptibility.
For pre-exercise warm up routines, dynamic flexibility offers the best support to the subsequent performance.
Introduction
Flexibility is an essential fitness component that decreases with age and physical inactivity. Traditionally, stretching as part of a warm-up has long been recommended for individuals who engage in exercise for rehabilitation, injury prevention, health improvement and athletic performance enhancement (American College of Sports Medicine [ACSM] 2006, Kovacs 2006, Shrier 2004). The proposed goals of acute, static stretching prior to physical activity to enhance performance include improved coordination and proprioception, increased range of motion (ROM), reduced injury potential, improved circulation and decreased muscle viscosity, which leads to smoother muscle contractions (Fredette 2001). However, in recent years there has been growing concern about whether or not stretching should be included in the warm-up phase. Mounting evidence suggests that pre-exercise stretching plays a limited role in injury prevention and may unfavourably impact exercise performance.
Two recent reviews on the topic have suggested that, contrary to popular belief, there isn’t adequate evidence to support the notion that pre-exercise static stretching reduces injury. In one review (Pope et al. 2000), the authors reported no significant reductions in the incidence of lower-limb injuries in people who stretched prior to exercise compared with those who did not. The other review concluded that pre-exercise static stretching does not lower the risk of local muscle injury (Shrier 1999). There does appear to be some benefit in reduced injury risk if static stretching is performed at other times, including postexercise and in the evening (Shrier 2004).
Effects of Static Stretching on Performance
Static stretching is what fitness professionals most commonly advocate for the general population. This form of stretching is recommended over other types because it involves minimal risk of injury, is time-efficient, requires little assistance and is effective at improving joint ROM. The following research evaluated the ways that static stretching affects different aspects of performance.
Muscle Strength and Power. Deficits in strength and power measurements following static stretching have ranged from 5% to 30%, according to Young and Behm (2003). Other researchers who measured one-repetition maximum (1RM) performances for knee flexion and knee extension found reductions of 7.3% and 8.1%, respectively, following acute static stretching (Kokkonen, Nelson & Cornwell 1998).
Jumping Performance. Numerous researchers have reported that jumping performance is impaired following an acute bout of static stretching. One study found that drop jump performance decreased by 6.9% in subjects who warmed up with a static-stretching routine compared with a group of controls who warmed up without stretching (Young & Elliot 2001).
Running Speed. There have been equivocal findings on the effect of pre-event static stretching on running performance. Two studies reported an inhibitory effect on running speed after an acute bout of static stretching (Nelson et al. 2005; Siatras et al. 2003).
Muscular Strength Endurance. One study investigated the effects of an acute bout of static stretching on knee-flexion muscle strength endurance in a group of males and females (Nelson, Kokkonen & Arnall 2005). Muscle strength endurance was 28% lower after the stretching bout than it was after no stretching.
Other Types of Stretching and Performance
Since studies have not been supportive of static stretching prior to exercise, researchers have begun to study other types of stretching to identify whether any of them might enhance exercise performance. Proprioceptive neuromuscular facilitation (PNF), ballistic and dynamic stretching are all effective at increasing ROM; however, they differ in their effectiveness for improving exercise performance.
PNF stretching . PNF involves having the client contract against resistance for approximately 5–6 seconds and then relax to accept an assisted static stretch for up to 30 seconds. For enhancing ROM, this method has proved to be superior to static and ballistic stretching (Heyward 2006).
Two studies looked at the effects of pre-exercise PNF stretching on exercise performance. One examined the short-term effects of PNF stretching on ROM; peak torque and mean power output, determined by isokinetic strength testing; and EMG signal amplitude (Marek et al. 2005). The other study compared the effects of different warm-up protocols on explosive-force production and jumping performance (Young & Elliot 2001). The results of the first study showed significant decreases in peak torque, mean power output and EMG signal amplitude (decreased neural activation). Overall, this study demonstrated that decreased neural activation will lead to decreases in muscular performance during slow and fast muscular-contraction speeds.
The other study compared the effects of different warm-up protocols on explosive-force production and jumping performance (Young & Elliot 2001). The warm-up trials consisted of 5 minutes of jogging followed by lower-body static or PNF stretching; exercise at 100% MVC; or rest (control group). Subjects held each stretch for 15 seconds and performed two vertical-jump tests after each warm-up trial. Investigators found no differences in jumping performance following the different warm-ups (including the rest protocol).
Ballistic stretching is performed by quickly bouncing through ROM to produce a stretch in the muscle. Although this has been shown to increase ROM, it is not recommended, owing to the risk of injury and muscle damage (ACSM 2006). Only one study has been designed to determine the acute effects of ballistic stretching on exercise performance. Nelson & Kokkonen (2001) studied the effects of ballistic stretching on lower-body maximal muscular strength determined by 1RM. Subjects performed maximal knee-extension and knee-flexion exercises following either 10 minutes of sitting or 20 minutes of lower-body ballistic stretching. The results demonstrated significant decreases in both maximal knee-extension (5.6%) and knee-flexion (7.5%) strength following ballistic stretching. These losses were attributed to the same factors associated with decreases in strength due to static stretching.
Dynamic stretching involves movements that mimic specific actions that will occur during exercise. The major advantage of this type of stretching is that it involves controlled movement and therefore enhances the overall warm-up. Dynamic stretching also provides a rehearsal effect that may increase coordination and provide specific benefit to involved muscles. Fletcher and Jones (2004) compared the effects of static- and dynamic-stretching protocols on 20 m sprint performance. Subjects who performed dynamic stretching prior to sprint performance significantly improved (decreased) sprint time compared with those assigned to other warm-up protocols.
Summary and Recommendation
Overall, there is a lack of research involving other than static forms of stretching. Therefore, it is important to summarise and make recommendations with some degree of caution. Current findings suggest that warm-up routines incorporating ballistic and PNF stretching do not enhance performance. However, research involving dynamic stretching as part of a warm-up routine looks more promising. Studies on this topic have shown significant improvements in acceleration, speed and agility during exercise. Early recommendations by some authors to include dynamic stretching in the pre-exercise routine are indeed appropriate, based on limited research, but further studies are warranted.
HOW WE CAN HELP
At Physio Fitness, we offer bespoke guidance and advice on flexibility exercises to optimise your sports performance. We offer this via an online consultation or at our rehab clinic in Gosport, Hampshire. Contact us today to find out more.
Email: info@physiofitness.uk
Tel: +44 (0)77 863 34567
