Flexibility training is still very mitigated not only with runners but with most of us despite the fact that many studies have been published on this topic for quite a number of years.
Indeed, there have always been several myths surrounding this practice. This is what we will try to demystify them in addition to discuss the benefits for runners.
To begin, let's look at the two main mechanisms as well as the structures involved when talking about stretching. First, there is the myotatic reflex which is a contraction of the muscle following its stretching. Neuromuscular spindles (FNM) are mechanoreceptors, sensory neurons, located parallel to muscle fibers that respond to two factors related to the mechanical deformation of the muscle, ie the speed and amplitude at which it is stretched. So when the muscle fibers get longer, the FNMs send a signal to the spinal cord until a threshold is reached. By the time this threshold is reached, the spinal cord sends a motor command to the muscle to contract. The purpose of this contraction is to protect the muscle and joint tissues from stretching too much. In contrast, we find the inverse myotatic reflex. It acts through the Golgi tendon organs, which are also sensory neurons found in the junction of the muscle and tendons. These neurons send information to the spinal cord about the strain on the muscle. The higher the tension in the muscle, the greater the intensity of the discharge sent by the Golgi tendon organs. If the intensity of this discharge exceeds the intensity of the motor drive sent by the central nervous system to the muscle, then there will be an inhibition of muscle contraction. This inhibition is intended to protect the tendons of the muscle from a possible tear as well as from too much pressure on the joints.
The mechanisms discussed can help us understand what is happening in the muscle during different situations, but also be used to our advantage during a stretching period. Think of those who stretch often, but do not notice any improvement in their flexibility. This may be related, among others, to the myotatic reflex. Remember that the muscle contracts if it is stretched too quickly or with too much amplitude in response to the information sent by the FNM. For this reason, stretching should not cause pain and must be performed gradually. Certainly, there are different methods for stretching that require, in some cases, a speed component such as ballistic stretching. However, the pain constraint remains. Under no circumstances should stretching be painful. If this is the case, it is because the amplitude is too high or the stretching is not done in the right way. We will see various stretching methods further.
Now back to the flexibility that, as some may have forgotten, is a workout just like weight training or cardio. Running is a very repetitive sport with respect to biomechanics. Indeed, the same movement is repeated for several minutes or several hours, and more than once in the same week. It is not abnormal to find muscular tension in different places, especially in the lower limbs. Also, be aware that some injuries may be the result of tight muscles such as, for example, plantar fasciitis and shin splints. This is the first reason why flexibility training can be beneficial for a runner. It is not uncommon for a runner to experience a cramp during training or a race event. Although the cramp may be due to various factors including a lack of electrolytes or training longer or faster than usual, studies have shown that a runner not having a regular stretching routine is more at risk for cramps. Also, having good flexibility allows for a better range of motion which could limit some runners in the race pattern given a lack of flexibility in the muscles of the lower limbs.
Let's move on to the stretching methods and what would be the ideal time to do this type of training. We know that stretching just before or after a race would not have a beneficial effect, it could even be harmful. On the one hand, performing static stretching before training would have shown a decrease in performance. On the other hand, at the end of training, it has not been proven that it reduces aches. However, it is true that to carry out the post-workout stretches provokes an effect of well-being on the spot because it allows our body to relax after an effort. So, when do we stretch and how do we do it? Before a workout, it is important to warm up well to prepare the muscles for the work they will be forced to do. During this period, the movements made must be similar to those made during the effort period. To do this, the ballistic stretching method can be integrated. This consists of a strong muscle contraction that is repeated on a certain muscle to stretch the agonist. We can think of a movement of the leg balance from front to back to prepare the flexors and extensors of the hip which will be greatly solicited.
Following a workout, as mentioned above, stretching is not necessary if performed in order to alleviate muscle aches. However, nothing prevents us from taking 5 to 10 minutes to do light stretching in order to make a return to calm. In this case, the static stretching will be prioritized by maintaining them about thirty seconds each.
So flexibility training should be integrated during the week at a specific time that is neither before nor after the running session. A runner has no problem spending hours during the week to run, so it should not be a problem to do at least 3 stretching sessions of at least 15 minutes during the week. In addition to providing a relaxing effect, these periods could help improve performance. During these, static stretching or FNP (proprioceptive neuromuscular facilitation) will be used. Static stretching is done most of the time because it is easy to do and can be done alone. It would be effective in maintaining flexibility and decreasing tension without improving range of motion. As for the FNP method, although it requires a second person, it would be more effective in maintaining and improving flexibility and range of motion. It consists of a succession of contraction and relaxation of the targeted muscle. Following a contraction, the muscle should be able to stretch a little more than at the previous time. A series of 2 to 4 contractions/loosening can be performed for the same muscle. Since each method brings different benefits, it would be wise to practice both.
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