How Stretching Affects Strength

From Iron Magazine


There’s nothing wrong with stretching your muscle groups: it prevents injury and may even speed up muscle growth. But you’re better off avoiding static stretches before starting a training session. Even if you’ve been training for years, you’ll reduce your strength, write researchers at the Universidade Nove de Julho in Brazil in an article soon to be published in the Journal of Strength and Conditioning Research.


You can stretch muscles ‘dynamically’ and ‘statically’. Dynamic stretching involves ‘pumping’: you adopt a stretch pose, then keep on stretching to the point where you feel the stretch in your muscle, and then release it so that the muscle returns quickly to its original length. Then you repeat the procedure. Dynamic stretching boosts performance when done before an explosive training session or during rests between sets.


Static stretching is done by stretching until you feel the stretch in the muscle, and then maintaining that position for a longer amount of time. This way of stretching is safer than dynamic stretching, but if you use it just before a weights or running session then your performance will suffer. The Brazilians examined this aspect in their study.


Most human studies on the effect of stretching used untrained students as the test subjects. But do men and women with years of weight training experience react in the same way? To answer this question the Brazilians performed a small study using 9 untrained [UT] and 11 trained [RT] males in their twenties. The trained men had been doing weight training for six months.


The researchers got their subjects to do static stretches for their chest muscles, upper back muscles, biceps and thigh muscles. They then measured how many kg the men were able to shift just once using these muscle groups, for the bench press, lat pull-down, biceps curl and leg press.


As the table below shows static stretching reduced maximal strength.


The figure above compares loss of maximal strength in the untrained men and the trained men. Although there’s a tendency for the negative effect of static stretching to be lower in the trained men, it’s clear that static stretching does reduce maximal strength by several percent in trained individuals.


“A passive static stretching program prior to resistance training is detrimental to maximum muscle strength development”, the Brazilians conclude. “From a practical standpoint for coaches and trainers, it seems inappropriate to encourage static stretching before athletic events or physical activities that require high levels of muscle strength.”


Combine strength training with stretching and you’ll get stronger


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.…2013/02/32.gif


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.


Experience in resistance training does not prevent reduction in muscle strength evoked by passive static stretching.


Serra AJ, Silva Junior JA, Marcolongo AA, Manchini MT, Oliveira JV, Santos LF, Rica RL, Bocalini DS.




1Andrey Jorge Serra, José Antonio Silva Junior, Martha Trindade Manchini e Danilo Sales Bocalini. Universidade Nove de Julho – Programa de Pós-Graduação em Ciências da Reabilitação/Curso de Educação Física, São Paulo, Brazil 2 Alessandra Amaral Marcolongo, João Victor Alves Oliveira, Luis Felipe Neves dos Santos e Roberta Luksevicius Rica. Universidade Federal de São Paulo – Escola Paulista de Medicina. Departamento de Medicina, São Paulo, Brazil.




This study examined whether passive static stretching reduces the maximum muscle strength achieved by different body segments in untrained and resistance-trained subjects. Twenty adult men were assigned to one of two groups: untrained (UT, N = 9) and resistance-trained (RT, N = 11). The subjects performed six one-repetition maximum load (1RM) tests of the following exercises: horizontal bench press, lat pull-downs, barbell curls, and 45o leg press. The results achieved in the last two 1RM tests were used for statistical analysis. A passive static stretching program was incorporated prior to the sixth 1RM test. The body fat content was significantly higher in the UT group compared to the RT group (P < 0.0001). Moreover, the RT group showed significantly higher proportion of lean body mass compared to the UT group (P < 0.0001). Maximum muscle strength on all four exercises was significantly reduced in both groups after stretching (P < 0.01). Furthermore, the magnitude of muscle strength reduction was similar for the UT and RT groups. The exception was for barbell curls, in which the muscle strength depression was significantly higher in the UT group compared to RT group (P < 0.0001). In conclusion, the passive static stretching program was detrimental to upper and lower body maximal muscle strength performance in several body segments. The negative effects of stretching were similar for subjects participating in resistance training regimens.


PMID: 23207883 [PubMed – as supplied by publisher]


Early-phase resistance training strength gains in novice lifters are enhanced by doing static stretching.


Kokkonen J, Nelson AG, Tarawhiti T, Buckingham P, Winchester JB.




Exercise and Sport Science Department, Brigham Young University-Hawaii, Laie, Hawaii, USA.




This study investigated differences in lower-body strength improvements when using standard progressive resistance training (WT) vs. the same progressive resistance training combined with static stretching exercises (WT + ST). Thirty-two college students (16 women and 16 men) were pair matched according to sex and knee extension 1 repetition maximum (1RM). One person from each pair was randomly assigned to WT and the other to WT + ST. WT did 3 sets of 6 repetitions of knee extension, knee flexion, and leg press 3 days per week for 8 weeks with weekly increases in the weight lifted. The WT + ST group performed the same lifting program as the WT group along with static stretching exercises designed to stretch the hip, thigh, and calf muscle groups. Stretching exercise sessions were done twice a week for 30 minutes during the 8-week period. WT significantly (p < 0.05) improved their knee flexion, knee extension, and leg press 1RM by 12, 14, and 9%, respectively. WT + ST, on the other hand, significantly (p < 0.05) improved their knee flexion, knee extension, and leg press 1RM by 16, 27, and 31, respectively. In addition, the WT + ST group had significantly greater knee extension and leg press gains (p < 0.05) than the WT group. Based on results of this study, it is recommended that to maximize strength gains in the early phase of training, novice lifters should include static stretching exercises to their resistance training programs.


PMID: 20124795 [PubMed – indexed for MEDLINE]



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