From Ergo Log
Doing static stretching before your strength training will decrease the quality of your workout. But that doesn’t mean that static stretching exercises are worthless for strength athletes. Quite the reverse, says sports scientist Joke Kokkonen from the Brigham Young University Hawaii. Kokkonen discovered that strength athletes make more progress by doing stretch exercises on the days that they don’t do strength training.
Let’s just refresh our memories. There are two ways to stretch your muscles: dynamic and static. Dynamic stretching means ‘pumping’ your muscles: you adopt a stretch pose, then keep on gently pushing the stretch to the point where you feel it in your muscle, and then release so that the muscle returns quickly to its original length. This type of stretching improves performance if you use it before or during an explosive training session.
With static stretching you also adopt a stretch pose. You stretch until you feel the stretch in the muscle, and then you maintain that position for a longer amount of time. This type of stretching is safer than dynamic stretching, but if you use it just before a weights or running session then your performance will suffer.
Nevertheless there are animal studies in which rats gained 13 percent more calf muscle mass when the researchers stretched their soleus muscle 3 times a week for a period of 4 weeks. [J Appl Physiol. 1994 Jul; 77(1): 58-62.] What’s more, fundamental research has shown that stretching has much the same effect on muscles as weight training does. Both stretching and training cause minute tears in the muscle tissue – Z-line ruptures – which stimulate the muscle cells to produce growth factors. And these growth factors in turn prompt the manufacture of new muscle fibres.
That’s why Kokkonen decided to do a trial with 16 male and 16 female students, none of whom had ever done weight training.
Kokkonen divided the students into 2 groups. One group trained their leg muscles for 8 weeks. [WT] On Mondays, Wednesdays and Fridays the students went to a gym where they did leg curls, leg extensions and leg presses using a weight at which they could just manage 8 reps. They did 3 sets of each exercise, and rested for 2-3 minutes between sets.
The other group followed exactly the same programme, but on Tuesdays and Thursdays they did leg stretching exercises. [WT+ST] The stretch exercises took 30 minutes to do, and consisted of 15 exercises that covered all the leg muscles.
After 8 weeks there was no difference in bodyweight between the groups. Kokkonen says nothing about body composition.
But when it came to body strength, there were clear differences between the groups. The WT+ST group had built up more strength than the WT group. The tables below show the results for the weight at which the test subjects were able to just do 1 repetition [1RM]. This had increased in the WT group, but it had increased more in the WT+ST group.
In the WT group the increase in the 1RM was 86 Newton for the leg extension exercise, 46 for the leg curl and 80 for the leg press. [Divide by ten for the number of kilograms.] In the WT+ST group the figures were 160, 81 and 273 Newton. So the progression in the WT+ST was clearly greater.
We would make one critical remark here about this study: the progression of the WT group is very low. If you have a group of healthy young people who have never done strength training before, and then get them to do leg presses for 8 weeks, how likely is it that their 1RM only increases by 8 kg? This is an improbably low amount. Even if you train like a wet dishrag, it’s still ludicrously low. The progression that the test subjects in the WT+ST group made on the other hand is pretty normal.
If you’re thinking of experimenting with stretch days, just don’t have too high expectations.
J Strength Cond Res. 2010 Feb; 24(2): 502-6.