Loss of flexibility as a result of strength training is a very common myth!
Once upon a time athletes were advised not to do strength training because it would make them stiff and reduce their flexibility. We now know this to not be true. Strength training does NOT lead to shortening of tendons and ligaments, nor does it lead to loss of flexibility. Research has shown that weight lifting when using full range of motion, actually increases flexibility just as well as, or even better than, static stretches.
In a study conducted by the University of North Dakota, researchers divided participants into 3 groups; a control group (who did nothing), a static stretching group, and a strength training group, and tested flexibility in hip flexion and extension, shoulder extension, and knee extension. After 5 weeks they found no significant difference between the static stretching and strength training groups in all the measures of flexibility.
In fact, another study conducted by Castelo Branco University in Brazil tested flexibility in shoulder flexion and extension, horizontal shoulder abduction and adduction, and trunk flexion and extension, and found that 8 weeks of strength training actually improved flexiblity more than static stretching, in all but one of the measurements.
Flexibility may not be one of your main training goals, but it is critical to your success. Without proper flexibility, not only are you more prone to musculoskeletal pain and injury, but your muscles may resist certain movements making it difficult to perform a skill. For example, if you have tight hip flexors, your running stride will shorten due to hip tightness when extending the leg.
So, in addition to preventing injuries and improving strength, improved flexibility is another reason to train using full range of motion. Flexibility is increased because you’re repeatedly moving muscles, joints, and ligaments through their full range of motion. Some exercises actually provide deep stretches that are hard to beat, such as the dumbell fly, stiff-leg deadlift, dumbell pull over etc.
So don’t be afraid to lift weights to your maximum ability. Flexibility is just another benefit of weight training to add to your collection!
