some excellent questions there and I am really glad you raised them. Unfortunately there is no 'quick' to the answers you seek
and I will take this opportunity you offered with your questions to explain away some misconceptions about stretching that will hopefully help everyone on this thread understand how to use it better.
So, let's get started: muscle responds with adaptations that make it stronger to three basic stimuli. These are, fatigue, muscle damage and tension. Stretching applies tension to muscles so over time it contributes to stronger muscles much as other resistance exercises, like lifting weights or working with body weight, do. There is a study on this here
. Traditionally stretching has been one of the five elements of fitness which are: (1) body composition, (2) flexibility, (3) muscular strength, (4) muscular endurance, and (5) cardiorespiratory endurance. So it has always been included in fitness. Yet a 2016 review study
showed that there are many recorded cases in which stretching leads to decreases in performance and contributes to injuries. So much so that in fact FIFA, (the governing body for football) has dropped stretching from its official warm-up recommendations
. Similarly, the Institute of Medicine dropped flexibility from its fitness measurements for youths in its 2012 report
because there was no credible data it could find that would support flexibility and healthier youths.
So now you see the current fog we are all in. We intuitively know that stretching helps fitness but the data we have doesn't show how and in some cases it appears to be contraindicatory. A 2021 study
that took a very carefully thought-through approach to the subject examined whether stretching needs to move from the "can I?" to "should I?" zone. Again the data on the benefits derived from stretching is mixed with some cases being pro and some against.
Obviously, ask any martial artist, ballet dancer or boxer and they will tell you it's next to impossible to perform at the level required by their sport without stretching. Yet, ask a distance runner, cyclist or power lifter and they could happily get through their entire life and sports career without even being able to touch their toes from a standing or sitting position. So what is going on?
To better understand this (which will also lead to an answer to your questions which I will recap, at the end) we need to ask what does stretching actually do? Well it does these things:
- It increases range of motion (ROM) of a joint by increasing the elasticity of the muscles and tendons that attach to it.
- It increases propioception, which is a fancy way of saying "body awareness".
- It increases our sense of mobility by improving overall flexibility.
In my opinion most studies to date that show that flexibility and stretching do not contribute to health outcomes or longevity or quality of life are flawed because of the scope of their research that looks for measurable tangibles that stem directly from stretching. As a component of fitness stretching is a contributory/enabling factor not an initiating one. A super-flexible person for instance who doesn't exercise regularly is neither fast nor powerful nor, necessarily, healthier than those who are less flexible but do exercise regularly. But a person who exercises regularly and is super-flexible enjoys an acknowledged advantage in range of motion, speed and power that is obvious even to the casual observer.
Luckily there are newer studies emerging that begin to support this view. I will take the three benefits mentioned above, in turn:
First, the body is a network of actions and reactions orchestrated by agonist and antagonist muscles. To throw a ball in an overhand throw, for instance, the shoulder and triceps work as agonist muscles that instigate the action while the biceps and deltoids act as antagonists helping balance the movement, stop muscles from over-extending and reducing the chance of injury. A 2018 study
that looked at how neuron receptors work in this agonist/antagonist coupling makes the same point.
A properly balanced agonist/antagonist coupling allows greater expansion of power which means greater strength and speed.
Second, when it comes to body awareness, a 2021 study
showed that regular stretching contributes to greater elasticity in nerves in muscles and tendons and a reduction in pain sensitivity. Nerves that are stiff become poor conductors of the signals passed by the brain and are more prone to peripheral neuropathy
which. with age, limits the body's mobility and damages its awareness of itself in the environment. So, stretching is a mind/body thing that actually contributes to the extension of consciousness we have of our body and the depth of the signals it reports back to us.
Finally, a 2017 study
shows that there is increased blood flow through stretched muscles and a distinct and persistent cardiovasculat effect to stretching that is not always calculated or even considered very much. This is not unlike the more recent discovery that strength training (which in the past used to be considered optional as an activity) leads to stronger bones which lead to a healthier brain
Now, this lengthy response, leads to slightly more direct answers to your questions:
When is the optimal time to stretch out muscles that have just been put through a strength workout? Let's say I did a pushup workout, would it be advisable to do a full chest and arms stretching workout right after or should I wait a day or two?
Seeing how stretching is a muscle workout (because of mechanical tension) which causes a de-strengthening of muscles because of mechanical damage, fatigue and central nervous system (CNS) fatigue, the best time to stretch, briefly is immediately after a workout when the muscles are already warm but the stretches will be less than 60 seconds in duration (and a study on this can be found here
) or, for longer stretches and a full stretching workout, the next day when the muscles have recovered sufficiently from the current workout.
Secondly, is it okay to stretch muscle groups multiple times (workouts) in one day? Lets say I do an upper body stretching workout in the morning, can I repeat the same workout multiple times that day or do I need to wait and rest for a day or two?
Stretching is like strength workouts. You wouldn't do strength workouts on the muscles multiple times a day because we know from research delivers weaker returns when, subsequent training sessions work muscles that have been de-strengthened by the first session so does stretching require the muscles to have recovered sufficiently so as to be able to respond with fresh adaptations. So you need to wait after your strength or stretching workout for muscles to recover and then work them again.
I will add to all this two more suggestions based on studies. First, a pre-workout stretch is great if A. It is movement specific (i.e. if you are going to practice punches or kicks if it stretches those specific muscles it will help) and B. It is under 60 seconds long or, for best results about 20 seconds long. A study supporting the first time increment is found here
. A study that supports the second time increment for extreme stretches can be found here
. Second, if you do static stretching before a workout for longer than the recommended time its negative effects can be counteracted if you then increase the warm-up time and do follow-up exercises that are dynamic and sports specific. The study on that can be found here
I will finish by adding that the latest research on stretching shows that it contributes to overall strength, power and muscle size (hypertrophy) so it should always be part of our training (to put this in context, each week I will allocate for myself a full training session - 90 mins to just stretching). The study for that can be found here
I am fairly sure that I have helped raise more questions than I answered here
so please feel free to ask away on anything you think would benefit from more information on this.