Most weight lifting workouts incorporate some kind of static stretching. Stretches are most commonly performed at the beginning of a workout as part of a warm-up, some people stretch between working sets, and others at the end of their workout.
I’ve seen people at the extreme end of the scale who stretch at the beginning, during and after a workout.
But what’s the reason for all this stretching and is it really beneficial to a bodybuilding program?
In this post I will be answering this question by taking a closer look at the main reasons why people stretch around their workout, what science has to say about it, and I will share some of my own views on the subject.
Reduce Risk of Injury
This is probably the most common reason why people stretch. The belief here is that some form of stretching as part of a warm-up before hitting the weights will reduce the risk of injury.
Unfortunately, the research on stretching and injury prevention doesn’t agree.
A number of studies have looked at the effects of stretching on sport and fitness injury and could not find any supporting evidence that stretching reduces injury. .
One very in depth systematic review  of 361 studies for the effectiveness of stretching to prevent injury could not find any sufficient evidence to endorse stretching before exercise as a way to reduce the risk of injury.
Improve Muscular Performance
A recent study published in the Journal of Strength & Conditioning Research  assessed the response to 10 weeks of static stretching before and during a strength training program.
Thirty people with training experience were randomly assigned to one of three groups.
Group A) Performed a static stretching protocol before weight training.
Group B) Performed static stretches between each working set.
Group C) No stretching performed at all.
Guess which group showed the greatest increase in strength over the 10 weeks?
Correct… group C experienced a significantly greater increase in strength when compared to group A and B.
Furthermore, group C – that trained without any kind of stretching – showed the highest levels of Insulin-like growth factor 1 (IGF-1) release compared to the groups that included stretching before and during training.
IGF-1 is an anabolic (muscle building) hormone and any increase will aid in muscle growth.
This particular study showed that weight training without stretching resulted in a greater increase in strength and IGF-1 levels.
Research shows that stretching before and/or during a workout does not reduce the risk of injury, improve strength or increase muscle growth.
My Thoughts on Workout Stretching
The whole point of a weight lifting program is to stimulate muscle growth by contracting and shortening a specific muscle group under tension. Stretching does the complete opposite to this goal by lengthening and relaxing the target muscles.
In a way, this is giving your CNS (central nervous system) conflicting signals.
Stretching will relax the muscle fibres and reduce CNS activation. This could be one of the reasons that stretching before and during a workout results in a slight reduction of strength output.
Your warm-up should consist of a few “rehearsal” sets of the first exercise you’re about to perform, using a light weight. Gradually increase the weight with each warm-up set to warm up the muscles and prepare the CNS for the heavy working sets.
Best Time to Stretch
Your muscles and tendons are getting somewhat of a stretch at the starting position of each repetition so there is already an element of stretching going on in your workout.
For example, as you lower dumbbells on a flat bench press your chest will get a stretch at the starting position before you press the weight.
Emphasising this stretch at the starting position on the first few sets may be more beneficial because it’s a “loaded stretch” while the muscle is under tension, as opposed to a static stretch which relaxes the muscle and eliminates tension.
I recommend one 20 – 30 second static stretch after working out. This will help improve flexibility and relax the trained muscles as you go into the post workout recovery phase. Stretching at this time will also help increases blood flow bringing nutrients to the muscles, flushing out waste by products and lactic acid.
References:1: Clin J Sport Med. 1999 Oct;9(4):221-7. Stretching before exercise does not reduce the risk of local muscle injury
2: Clin J Sport Med. 2005 Mar;15(2):113. Effect of stretching on sport injury risk
3: Med Sci Sports Exerc. 2004 Mar;36(3):371-8. The impact of stretching on sports injury risk: a systematic review of the literature.
4: Chronic Effect of Static Stretching on Strength Performance and Basal Serum IGF-1 Levels Image credit to Flex Online