The ability to navigate one's body through the environment and perform the functional activities present in everyday life, such as bending over to pick up an object, tying shoelaces, getting up out of a chair, and even seemingly rudimentary tasks like eating and getting dressed, all have one thing in common: they all require the ability to move the joints.
Flexibility is measured by the range of motion available at the joints, but in simpler terms, it can be described as the ability to change the position of the joints. Thus, a lack of flexibility means a reduced ability for the joints to change position and a diminished capacity to move and fulfil the demands of daily life.
Despite the glaring need for flexibility throughout the entire lifespan, there has been a trend for people within the health and fitness industry to insist that flexibility is not essential. Recent research has also challenged the importance of flexibility as a component of physical fitness; Nuzzo (2019) stated that flexibility has little predictive or concurrent validity with health and performance outcomes in apparently healthy individuals. However, if common sense informs us that flexibility is necessary, why do these individuals make such claims against it?
A big part of the issue is that flexibility is region-specific - there is minimal relationship between the flexibility of one joint and another. So, for example, a person with flexible shoulders may not necessarily have flexible hips, or their right shoulder might even be more or less flexible than their left shoulder.
Researchers and coaches alike tend to favour tests that cover groups of joints simultaneously in their physical fitness assessments. Time and cost are usually the motivating factors; measuring the range of motion of every joint in the body can take an hour! The most utilised flexibility test is the sit-and-reach test (and its modified version: the back saver sit-and-reach test), which assesses hamstring, back, and hip flexibility. Consequently, a person may achieve a high sit-and-reach score but be woefully lacking in the regional flexibility required for their chosen sport or activity. However, it is not accurate to claim that flexibility is unimportant simply because researchers and coaches do not use the appropriate test (as Nuzzo did in his paper).
Unfortunately, due to researchers' preferences to save time and money, most of the available data regarding flexibility across the lifespan is drawn from results of the sit-and-reach test. Such data show a yearly increase in range of motion between the ages of six and eighteen before flexibility hits its natural peak by the early twenties (Ross & Pate, 1987). There are also noticeable sex-based differences: females routinely achieve higher scores than males across all ages.
Furthermore, there is an accompanying decrease in flexibility with age that affects most of the body's joints. For example, Stathokostas et al. (2013) reported that shoulder abduction decreases by 5° per decade in males and 6° per decade in females. The rate of decline accelerates to a loss of about 0.80° per year at age 71 in males and about 0.74° per year at age 63 in females. Similar results were observed in hip flexion: males experienced a rate of decline of 1.16° per year starting at age 71, while females experienced an average linear decrease of 0.66° per year between ages 55 and 86.
Much of the loss of joint flexibility can be offset by performing flexibility training exercises, to the extent that older people benefit from a stretching programme just as much as younger people (Haab & Wydra, 2017; Stathokosatas et al., 2012). Improving lower limb flexibility should be a particular priority for the elderly since it has been associated with poor balance and chronic low back pain, both of which can increase the risk of life-threatening falls (Reddy & Alahmari, 2016; Hasarangi & Jayawardana, 2018).
It is important to remember that some flexibility loss due to physiological changes cannot be prevented even with dedicated training. Such changes include alterations to synovial fluid, joint surfaces, ligaments, tendons, and muscles. For example, with age, the connective structures of joints become less resilient, resulting in cracking and fraying. In addition, synovial fluid viscosity changes and articular cartilage becomes frequently damaged from everyday use. There is also a greater incidence of multifactorial degenerative joint diseases in older age, such as osteoarthritis: approximately 80% of 55-64 years olds will have signs of osteoarthritis in at least one joint.
The take-home message is this: flexibility should be prioritised at all stages throughout the lifespan, particularly in later life when physiological changes associated with biological ageing tend to occur, and ideally before such changes have taken effect. Understand that "prioritising flexibility" does not necessarily mean "prioritising flexibility training." If a person does not require the extensive ranges of motion necessary to perform such feats as splits and back bridges, simply moving through their normal ranges of motion regularly (including while handling external loads) is usually enough to maintain sufficient levels of flexibility.
Nuzzo, J. L. (2020) The Case for Retiring Flexibility as a Major Component of Physical Fitness. Sports Medicine vol. 50, no. 5, pp. 853-870.
Ross, J. G. & Pate, R. R. (1987) The National Children and Youth Fitness Study II: A Summary of Findings. Journal of Physical Education, Recreation, and Dance vol. 58, no. 9, pp. 51-56.
Stathokostas, L. et al. (2013) Flexibility of Older Adults Aged 55-86 Years and the Influence of Physical Activity. Journal of Ageing Research article 743843.
Haab, T. & Wydra, G. (2017) The Effect of Age on Hamstring Passive Properties After a 10-Week Stretch Training. The Journal of Physical Therapy Science vol. 29, no. 6, pp. 1048-1053.
Stathokostas, L. et al. (2012) Flexibility Training and Functional Ability in Older Adults: A Systematic Review. Journal of Ageing Research, article 306818.
Reddy, R. S. & Alahmari, K. A. (2016) Effect of Lower Extremity Stretching Exercises on Balance in Geriatric Populations. International Journal of Health Sciences vol. 10, no. 3, pp. 389-395.
Hasarangi, L. B. S. & Jayawardana, D. G. S K. (2018) Comparison of Hamstring Flexibility Between Patients with Chronic Lower Back Pain and the Healthy Individuals at the National Hospital of Sri Lanka. Biomedical Journal of Scientific & Technical Research vol. 5, no. 2.