The purpose of this study was to determine if static stretching completed on non-lifting days would accelerate muscle and strength gains for beginners, compared to lifting weights alone. In essence, they had young beginners lift weights 3 times per week. One group stretched on two of the off days while the other group did not stretch. Afterwards, they observed growth between groups.
It's quite interesting to determine if something other than actually lifting can result in improvements. The fact that stretching on off days might improve performance is interesting to say the least.
Why Study This
This is interesting. In other articles, I've written about stretching and how it can negatively impact strength and performance. However, that's specifically when stretching is completed prior to exercise, such as during a warm up. Further, this negative effect is even greater if the stretch is static, or a "hold" stretch, rather than dynamic (2, 3.
As other research has shown, stretching on non-lifting days might actually improve performance. Why? It's uncertain, but doing so may provide greater range of motion and perhaps even a better body awareness. The authors also note, that it's possible that stretching might produce a similar muscle damaging effect as often observed with passive stretch as a result of weight training (4, 5, 6).
Fun Fact: Resistance stretches the muscle, which as a beginner can result in muscle damage in different forms, which can lead to a super-compensation once it repairs - i.e. you're bigger and stronger so that further damage can't occur. The authors of this study postulate that might be a reason for the results.
Essentially, it's good to study this because there are mixed messages with regards to stretching and performance. Further, it's quite interesting to determine if something other than actually lifting can result in improvements. The fact that stretching on off days might improve performance is interesting to say the least. Further, this sort of information can provide guidance for better usage of stretching.
32 young individuals (16 women, 16 men) were recruited for the study as beginners (exercise less than 2 times per week.
Once recruited, subjects participated in an 8 week resistance training protocol while being placed randomly into 1 of 2 groups:
Once placed into their respective groups, subjects completed a 1 RM test for the following exercises:
Participants of the stretching +weight training group underwent the following procedure on off days:
Both groups executed the workout 3 times per week, for a period of 8 weeks. Subjects completed 1 RM testing prior to the study. The group with stretching included then stretched on off days, 2 times per week for the duration of the study. The weight training group without stretching simply rested on off days.
Upon completion of the study, participants underwent a second testing of 1 RM to observe strength improvement differences.
In the above graph, you can see that upon testing 1 RM values the second time, both groups observed significant improvements in strength for all exercises. Further, the group that added stretching on off days also observed a significant improvement in strength gains OVER THAT of the weight training only group, for knee extension and leg press. As for knee curls, the improvement was still significant, just not from the weight training only improvements.
In essence, the group that stretched significantly improved over baseline and then were significantly greater than that of the weight training only group, which was also significantly greater than baseline. This means that it's likely the stretching had a very potent effect on amplifying strength gains from the training alone.
The fact that we don't know or have an idea of the mechanism also reduces our confidence that experienced individuals might observe the same effect. If we knew the mechanism, we could say "hey that won't apply to an experienced lifter" or alternatively "hey, that mechanism works regardless of experience."
1. These Were Beginners
Arguably, the most important consideration here is that these were beginners. Beginners see rapid advances in strength and muscle growth, regularly, since the exercise is a novel stimulus, promoting an adaptation. Thus, it's unknown if this will translate to people outside of the "beginner" phase.
It's suggested that if you want to use this information, play around with it and see if you notice an improvement. Just know, it may take a long time so if you decide to test it out for yourself, do so for a period of 8-12 weeks minimum.
2. The Training Plan
The training plan used in this study was pretty standard for research, and not the greatest for actually observing growth. If these individuals actually resistance trained as most would, with free weights and far greater volume, the results may have been even more profound.
3. No Mechanisms To Explain the Result
Unfortunately, the researchers didn't study or measure any potential mechanism behind the potent effect of stretching. Their hypothesis is that doing the stretching places mechanical stress on the muscle, as with resistance training, causing a stretch effect. As mentioned, stretching might create similar scenarios in the muscle as is observed while lifting, creating a stimulus to improve strength and muscle.
Some other research on animals indicates that stretching under load, might produce what is known as hyperplasia, or the generation of new muscle fibers. Otherwise, this is fairly uncommon, at least in human models, so it's difficult to say that's the likely mechanism.
Either way, there was a clear advantage of stretching on off days. Perhaps it lead to improved recovery at the hand of improved blood flow as a result of stretching. Pehaps stretching led to better muscular control or perhaps doing so improve range of motion, improving ability.
Really, we don't really know. Further, the fact that we don't know or have an idea of the mechanism also reduces our confidence that experienced individuals might observe the same effect. If we knew the mechanism, we could say "hey that won't apply to an experienced lifter" or alternatively "hey, that mechanism works regardless of experience."
If you're a coach, using stretching on off days for new clients or young athletes, may improve performance, accelerating growth. However, it's important to note that this effect is currently, beginner specific and may not prove useful for the experienced.
If you are a beginner yourself, it may be beneficial for you to use static stretching on off days, stretching target muscle groups each time.
If you're experienced, it's unknown if using this information will prove beneficial. However, it's certainly possible and in most cases, improved flexibility and range of motion won't be a bad thing. If you're experienced and interested, I suggest stretching target muscle groups on off days (not before or after workouts).
Why This Should Matter To You
It should matter because this is another resource to put the notion of stretching and performance to the test. As previous research has proven stretching before events to be detrimental, this information provides actual, potential benefit of stretching for beginners. Further, this information presents an additional variable you can use to potentially improve performance, muscle and strength.