Flexibility and mobility

Flexibility refers to passive range of motion: how far a joint travels when the movement is produced by something other than the muscles around it. A straight-leg raise performed by an examiner while the person lies relaxed is a flexibility test, mainly of the hamstrings.

Mobility refers to active range of motion under control: how far a person can move the same joint with their own muscles, hold the position and move smoothly through the range, often while balancing. Mobility depends on flexibility, but also on strength near the end of the range and on coordination.

The two can differ considerably. Many daily tasks, including getting down to the floor, turning to look behind, reaching a high shelf and stepping over an obstacle, depend on active range. A joint with a large passive range but little strength near its end position gives limited help when recovering from a stumble.

Three groups of factors set the range of a joint. The first is the joint structure itself (bone shape, cartilage and joint capsule), which training changes little. The second is the stiffness of the muscles and tendons that cross the joint. The third is the nervous system, in particular stretch tolerance, the amount of stretch a person accepts before discomfort stops the movement.

A 2016 systematic review of stretching trials in healthy active people found that static, dynamic and proprioceptive neuromuscular facilitation (PNF, a method alternating stretching with muscle contraction) stretching all increased range of motion, but that the increase after a single session typically lasted less than 30 minutes. The authors attributed the change to short-term reductions in muscle and tendon stiffness or to improved stretch tolerance [4].

With age, connective tissue tends to stiffen and joints often lose range, but disuse also contributes: positions that are rarely reached, such as a deep squat, a full overhead reach or sitting on the floor, gradually become harder to reach. This helps explain why flexibility varies widely among people of the same age.

The main study linking flexibility to survival followed 3,139 Brazilian adults aged 46 to 65 (66% men) between 1994 and 2022, for a mean of 12.9 years. Each participant was scored from 0 to 4 on 20 movements across seven joints, giving a "Flexindex" from 0 to 80. Women scored 35% higher than men on average (41.1 compared with 30.5). There were 302 deaths, 224 in men and 78 in women, and lower scores were linked to higher mortality in both sexes [1].

After adjusting for age, body mass index and health status, men in the bottom part of the Flexindex distribution had 87% higher mortality than men at the top (hazard ratio 1.87, 95% CI 1.50 to 2.33; a hazard ratio is the risk in one group relative to another). In women the estimate was larger but much less precise (hazard ratio 4.78, 95% CI 1.23 to 31.71), reflecting the small number of deaths [1].

The authors concluded that future studies should test whether flexibility gained through training is linked to longer survival [1]. That question has not been studied.

Stretching immediately before exercise has small effects on performance. In the 2016 systematic review, static stretching was followed by an average 3.7% drop in performance, PNF stretching by a 4.4% drop and dynamic stretching by a 1.3% gain, with testing usually done 3 to 5 minutes after stretching. Static stretches held for 60 seconds or more per muscle group reduced performance by 4.6%, compared with 1.1% for shorter holds [4].

When stretching was followed by other dynamic warm-up activity, no clear effect on performance was seen. The reviewers concluded that stretching within a warm-up that includes further dynamic activity has little effect on subsequent performance [4].

Stretching is also not the only way to gain range. A 2021 meta-analysis of 11 randomised trials with 452 participants found no difference in range-of-motion gains between strength training and stretching (standardised effect size -0.22, 95% CI -0.55 to 0.12), although the trials differed widely in design and populations [5]. Strength training through a full range of motion is described in resistance training.

Stretching is widely recommended to prevent sports injuries, but trial evidence does not support it. A 2014 meta-analysis of 25 randomised trials with 26,610 participants and 3,464 injuries found no protective effect of stretching (risk ratio 0.963, 95% CI 0.846 to 1.095; a risk ratio is the chance of an outcome in one group relative to another). By contrast, strength training reduced injuries to less than one-third (risk ratio 0.315), and proprioception (balance) training by nearly half (risk ratio 0.550) [3].

The 2016 review of acute stretching similarly found no clear effect of static or PNF stretching on all-cause or overuse injuries, and no data for dynamic stretching [4].

Flexibility training has not been tested on its own for fall prevention. The 2019 Cochrane review of 108 exercise trials in older adults found no trials that compared flexibility exercise alone with a control group [2]. Range-of-motion work does appear inside programmes that reduced falls, such as tai chi and multi-component balance training, but its separate contribution is unknown.

Range of motion is needed for several tests that predict survival. The sitting-rising test, in which a person sits down on the floor and stands up with as little support as possible, depends on both strength and flexibility, according to its authors; in 2,002 adults aged 51 to 80, the lowest scores were linked to 5.44 times the mortality of the highest [6]. That test is covered in functional fitness.

The survival evidence rests on a single study from one research group in Brazil, and flexible middle-aged adults may be more active and healthier in ways the adjustment did not capture [1]. The trial evidence on stretching comes mainly from young, active people and measures short-term outcomes such as performance and sports injury, not long-term health [4, 3]. Compared with aerobic fitness, strength and walking, which have large pooled analyses behind them (see exercise and longevity), flexibility remains the least studied component of fitness in relation to lifespan.