Strength training is just as efficient as stretching to become more flexible.
In the 1960s, flexibility was classified as one of the 5 components of “physical proficiency” though done so under scepticism that flexibility and human motor performance are “probably not as highly correlated as traditionally believed”. In 1980, it was called a “major component of physical fitness" and claims were made about its health benefits. The notion that flexibility is important to fitness has since led to the traditional thought that specific flexibility exercises (forms of ‘stretching’) are necessary. But are they?
Flexibility assessments have not been shown to be predictive of all-cause mortality while body composition, cardiovascular endurance, muscle endurance, muscle strength, and muscle power all have. Flexibility assessments have been shown to have some predictive ability for quality of life and to a smaller extent, falls in older adults and injury and pain, but so have muscle endurance, strength, and power. In many cases, the muscle qualities have greater predictive ability.
So, is it possible that strengthening the body may provide a better ‘bang for your buck’ when it comes to being efficient with time and improving flexibility? The answer is yes! Numerous research studies have shown that flexibility has improved range of motion in both upper and lower body joints as well as Sit-n-Reach measurements for men and women, young and older, trained and untrained by just participating in a strength training routine.
Improvements in pre-and post-training flexibility have been shown for strength training routines ranging from 1-5 sets of moderate-intensity exercises of both free weight and machine-based exercises, with the best results typically coming from the 3-5 set range. However, with individuals with little strength training experience, using a progressive model of increasing sets over time (e.g. 1 set for 4 weeks, 2 sets for 4 weeks, 3 sets for 4 weeks, etc.) has also resulted in improved flexibility. Research has also shown that strength training is just as effective for improved flexibility when compared to both static and dynamic forms of stretching.
Bottom Line: there is nothing wrong with stretching, but if you’re looking to be efficient with your time then warm-up adequately, progress systematically to 3-5 sets of strength training exercises that complement the whole body 2-3 days per week (more is great with proper training age, programming, and recovery), and adequately cool down and recover.
References
Fragala, M. S., Cadore, E. L., Dorgo, S., Izquierdo, M., Kraemer, W. J., Peterson, M. D., & Ryan, E. D. (2019). Resistance Training for Older Adults. Journal of Strength and Conditioning Research, 33(8), 2019–2052. https://doi.org/10.1519/jsc.0000000000003230
Nuzzo, J. L. (2019). The Case for Retiring Flexibility as a Major Component of Physical Fitness. Sports Medicine, 50(5), 853–870. https://doi.org/10.1007/s40279-019-01248-w
Leite, T., de Souza Teixeira, A., Saavedra, F., Leite, R. D., Rhea, M. R., & Simão, R. (2015). Influence of Strength and Flexibility Training, Combined or Isolated, on Strength and Flexibility Gains. Journal of Strength and Conditioning Research, 29(4), 1083–1088. https://doi.org/10.1519/jsc.0000000000000719
Leite, T. B., Costa, P. B., Leite, R. D., Novaes, J. S., Fleck, S. J., & Simão, R. (2017). Effects of Different Number of Sets of Resistance Training on Flexibility. International Journal of Exercise Science, 10(3), 354–364.
Todd, J. S., Shurley, J. P., & Todd, T. C. (2012). Thomas L. DeLorme and the Science of Progressive Resistance Exercise. Journal of Strength and Conditioning Research, 26(11), 2913–2923. https://doi.org/10.1519/jsc.0b013e31825adcb4
Morton, S. K., Whitehead, J. R., Brinkert, R. H., & Caine, D. J. (2011). Resistance Training vs. Static Stretching: Effects on Flexibility and Strength. Journal of Strength and Conditioning Research, 25(12), 3391–3398. https://doi.org/10.1519/jsc.0b013e31821624aa