Like most things in the fitness industry stretching has contradictory findings in the literature. Stretching recommendations are heavily clouded by conflicting research and misconceptions. So I thought I would take this opportunity to go through some of the research findings and reasons behind current stretching recommendations as well as just giving some food for thought. I will go over some of the areas which are of importance for different clients.
Whilst it is very common to hear of and even see people stretching before exercise it is important to choose the most appropriate type before exercise. Static stretching shouldn’t be conducted before an exercise session as the muscles, ligament and tendons are still cool and stretching in this manner is known to increase the risk of strains as the muscles are tight and cold. If stretching is going to be conducted before the exercise session this should be dynamic stretching exercises and performed after the warm up, this will allow the muscles, ligaments and tendons to warm up enough to complete dynamic exercises. This will help warm up these structures further and prepare them for exercise. Due to the excessive strain placed on these structures with static stretching this should only be conducted after the exercise session when these structures are able to withstand the demands of static stretching without increasing injury risk.
Muscle soreness has been shown to be reduced by about 2% over the 72 hours post exercise when compared to individuals who did not stretch. Whilst the risk of injury is reduced by 5% in individuals who stretch after exercise, this is something to consider when a client comes to you saying that they do not wish to be sore from training. Even this mild reduction in soreness may mean the difference between keeping and losing a client.
Muscle strength and power output
Recent research has found that both static and proprioceptive neuromuscular facilitation (PNF) stretching have acute reductions in both strength and power output. The reductions whilst seeming small (2.8% reduction in strength and 3.2% reduction in power) will add up when it comes to a resistance training session. For instance if a client usually uses 100kg, if they stretch beforehand this weight would then be heavier than what they can actually lift safely, it would reduce the safe weight down to 97.2kg. This may not seem like much but in order to get the best out of the muscles during the session and achieve the greatest adaptations possible (whether muscle size, strength or power), it is very important to be placing the muscle under the greatest stress possible (safely of course). This further validates the reasoning for not conducting static of PNF stretching before a resistance training session.
Stretching and injury prevention
In general it is accepted that by increasing the flexibility of a muscle’s tendon this promotes higher performance and decreases the number of injuries sustained. Several authors have made the link between stretching and injury prevention, whilst there is also clinical evidence which suggests that stretching before an exercise program does not reduce the incidences of injury and can even increase the risk.
When talking about stretching and injury prevention we need to take into account the requirements of the spot or activity. For instance sports/activities which require high intensity stretch shortening cycles (elastic energy such as plyometric exercises/activities) for instance basketball, soccer, football etc. The properties of the muscle and tendons must allow for the storing and releasing the high amounts of elastic energy. When the requirements of storing and releasing this energy exceed the capabilities of the muscles and tendons this is when injuries occur. If the elastic properties of the muscles and tendons are stretched beyond optimum amounts before such activities the potential for causing injury will increase, so this must be taken into account when prescribing exercise to these clients.
That being said, these clients will still need to stretch as this will influence the viscosity of the tendon and make it significantly more compliant. When the demands of the sport or activity require stretch shorten cycles of high intensity the compliance of the tendons will play a big role and thus stretching should still be completed, just after the training session.
When the demands of the sport or activity only require low intensity stretch shortening cycles such as swimming, cycling or jogging there is no need for extremely compliant muscle tendons as the power for these activities comes from active muscle contractions instead of the stretch shorten cycle (elastic energy). The literature also suggests this as there are no significant reductions in injury prevalence in low intensity activities through stretching.
This is where we must be wary of what we prescribe to clients and best judgement made according to the evidence at hand. Static and proprioceptive neuromuscular facilitation stretching should only be conducted after the training session as the evidence doesn’t support a reduction in injury prevalence when conducted prior to activity. It is always best to be cautious when there is a potential for injury and since the evidence is still controversial, I highly recommend being cautious when prescribing exercise.