Does resistance training reduce flexibility? Should you always stretch after lifting to prevent muscles from shortening? Do bigger muscles reduce one’s flexibility? These are some of the most common questions/concerns new clients have when starting a program involving resistance training. How much should you be concerned about your flexibility when you start a resistance training program?
The answer to all of these questions is an emphatic NO! In fact, resistance training when performed through a full range of motion actually IMPROVES flexibility! This may be hard to believe if you typically are “tight” a day or two after training; this “tightness”, however, is an acute transient effect due to muscle damage. Consistent resistance training through a full range of motion actually improves flexibility.
A recent study comparing static stretching and strength training found the following:
- Stretching and strength training increased hamstring flexibility to the same degree.
- Resistance training outperformed static stretching at improving hip flexibility.
- Resistance training improved strength around all joints while stretching did not.
- This is an important side note: Most injuries are due to a lack of strength around a joint, not poor flexibility. If you have the strength to prevent a fall, or catch yourself, you will not overstretch the muscle. Strength training is superior to flexibility training for injury prevention because you improve flexibility and strength simultaneously.
The mechanisms for improved flexibility due to strength training are different than static stretching. Static stretching improves flexibility primarily through increasing stretch tolerance and decreasing pain associated with reaching a specific muscle length. This basically means that nothing within the structure of the muscle changes; you are just able to stretch the muscle MORE before you feel pain and your brain tells the muscle to tighten up.
Strength training, on the other hand, increases stretch potential by changing the structure of the actual muscle. Think of it like this: each whole muscle is divided up into smaller fibers that sit in line with one another. Resistance training results in a certain degree of muscle growth, which allows more fibers to sit in the same space. Since each fiber within that space has the same flexibility potential as the original fibers, the muscle can be stretched farther. This is believed to be a protective mechanism the body has developed so that fewer muscle fibers can be torn.
Contrary to common gym lore, resistance training does not reduce flexibility. When an exercise is performed properly, through a full range of motion, it will actually help increase your flexibility. For individuals looking to significantly improve flexibility, a combination of resistance training and static stretching would optimize results.