Flexibility training is considered to be an integral part of most athletic training programmes, yet in some sports there is much debate as to the importance of flexibility training and how it should be structured within a programme. The purpose of this chapter is to discuss issues surrounding the use of muscle stretching in the context of the athletic performance program design for athletes. The term ‘flexibility’ will be used in this chapter to encapsulate both range-of-motion (ROM) and muscle-tendon extensibility (i.e. stiffness) aspects simultaneously.
Why stretch? While much is known about the neuromuscular and soft tissue adaptations to strength, endurance and other forms of training, very little is known about the adaptive process elicited by stretching training, despite what is often written in textbooks and articles. It is well known that increases in ROM and, sometimes, reductions in resistance to stretch (i.e. increased tissue extensibility) result from both acute and chronic stretch training;
however, the changes in muscle fibre (or fascicle) and tendon properties predicted to occur, and often discussed in book chapters and on websites, have not been found by researchers. Nonetheless, it is known that even short (e.g. 5s) bouts of stretching can increase the energy stored within a muscle or muscle-tendon unit for a given load application (although longer bouts of stretching of up to an hour are required to prolong the effect).
Alterations in force production, as well as increases in both the stretch length and force handled before injury (failure), are known to occur under these conditions. However, to best program the stretching training, it is also important to consider the following: 1 Increases in ROM, a shift in the torque-angle relation about a joint (i.e. the force-length relation for a muscle-tendon unit) toward longer muscle lengths, 1 and an increase in eccentric muscle strength, 2 can result from stretch training and may infl uence force production and assist with injury minimisation.
2 Chronic static-passive stretching regimes have been shown to reduce injury rates, and particularly reduce the incidence of soft tissue (muscle, ligament, tendon) injury; 3,4 less fl exible athletes are often found to have a greater rate of injury. 5,6 Stretching is probably more effective for injury prevention when other forms of training (e.g. strength and balance training) are simultaneously added to a conditioning program 7,8 – a varied injury prevention strategy is clearly ideal.