Decades of research finds most types of stretching increase flexibility—but with nuances

For decades, stretching has been treated as a general prescription for something you’re supposed to do before and after exercise or whenever your body feels stiff or sore. Many fitness experts and manual therapists have recommended stretching as a way to prevent injury and improve flexibility.

But how much of such recommendations are based on current science? This story takes a deeper dive into what stretching may help, including:

• Muscular strength
• Flexibility and range of motion
• Athletic performance
• Pain and muscle soreness

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Muscular strength

In a 2022 systematic review and meta-analysis by Thomas et al., the researchers found that when stretching exercises are performed as the only activity, muscular strength could be slightly improved. “Conversely, when stretching exercises are added to [resistance] training protocols, despite no significant effect being observed overall, there might be a time-dependent negative effect on the [resistance training]-induced strength gains,” they wrote. The studies’ qualities ranged from medium to high with a high confidence level.

Thomas et al. reported that flexibility and strength can be improved with resistance training when the eccentric phase of muscle contraction is emphasized, such as lowering the weight during a dumbbell bicep curl or a seated hamstring curl.

Lead researcher Dr. Ewan Thomas from the Department of Physiology at the University of Palermo told Massage & Fitness Journal that there are several different theories on the effects of stretching:

• Mechanical (the muscle physically gets longer)
• Neurological (Golgi tendon organ, muscle spindles)
• Thixtropic (connective tissues and fluids allow greater compliance
• Sensory (pain perception decreases)

“Nowadays, the one that explains most of the gains [is] sensory mechanisms,” he said. “While stretching, we desensitize the pain receptors within the muscle and the pain interpretation within the brain so that continuing stretching allows greater [range of motion]. This explains almost all acute adaptations. For chronic adaptations, other theories provide [the] contributing factors.”

“Resistance training is always suggested for active or sedentary individuals if strength is the main aim of training,” Thomas continued. “However, if individuals do not want to engage in [resistance training] and only want to stretch, this might allow small strength gains.”

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Flexibility and range of motion

A 2024 systematic review found no extra immediate benefits in flexibility when the volume per stretching session is beyond four minutes per muscle group; and no long-term benefits beyond 10 minutes per muscle group per week. The review is based on 189 studies with a total of 6,654 adults. Lower-body muscles are the most stretched areas.

The researchers, led by Dr. Lewis Ingram from the University of South Australia, reported benefits are shown the most among those who started the trial with poorer flexibility than the average population. Also, the trials tend to be of poor quality randomized-controlled trials and observational studies, they added.

“Neither the acute or chronic improvement was moderated by stretching intensity, age, sex, participant training status, or weekly session frequency and intervention length,” they wrote. “

They also did not find significant differences in flexibility changes in training status, muscle groups, gender, age, and intervention length.

Training status

The researcher found training status to have no effect on improving range of motion after acute or chronic static stretching. However, they mentioned that different sports demand different levels of range of motion, such as the flexibility requirements of an elite gymnast versus an elite distance runner. 

“As such, it is more likely that stretching responses will differ by sporting demands, rather than competition level,” they wrote.

Muscle groups

Ingram et al. reported the effects of acute state stretching on hamstrings are greater than muscles along the spinal column. However, they reported no differences in effect size between hamstrings and other muscle groups after acute and chronic static stretching.

However, they caution that the apparent spine-related effect is likely due to methodological issues, since the “spine” category combined cervical and lumbar regions and relied heavily on the sit-and-reach test, which is a weak measure of actual lumbar spine flexibility. These measurement choices likely reduced the observed effect for spinal muscles and distorted comparisons, Ingram et al. reported.

Although the researchers expected different muscle groups to respond differently based on their structural properties, such as tendon length and tissue composition, the lack of consistent differences suggests that flexibility gains from stretching are not primarily driven by mechanical features of specific muscles or joints. Instead, the underlying mechanisms “are not exclusively dependent on the mechanical and structural properties of the muscle” and the effects are more general than specific muscle groups.

Gender

Ingram et al. reported that studies with men only tend to have greater stretching effects than mix-gender studies. They hypothesized that since women typically have greater flexibility than men, stretching would have a greater impact on men than women.

“Such sex differences have traditionally been attributed to musculoskeletal factors including differences in muscle mass, the shape of specific joints and the relative proportion of collagen within the muscle–tendon unit,” they wrote, adding that the menstrual cycle may influence women’s flexibility.

Age

Ingram et al. did not find a significant difference in stretching effects between older and younger adults.

“This was surprising given that older adults tend to be less flexible because of age-related increases in connective tissue, particularly collagen,” they wrote. “It is possible that the older adults who participated in the studies included in our review were, on average, more physically active than others of similar age.”

Intervention length

The researchers found no difference in stretching improvements between the shorter or longer stretching periods. They wrote that acute improvements are mainly driven by short-term neural and mechanical changes, such as reduced muscle spindle sensitivity, increased muscle–tendon 

Short-term improvements in flexibility from static stretching are mainly driven by temporary neural and mechanical changes, including reduced muscle spindle sensitivity, increased muscle–tendon compliance, and greater stretching tolerance. 

In contrast, long-term stretching may lead to structural adaptations in muscles, such as increases in muscle fiber length and changes in fascicle structure. However, they suggest that these permanent morphological changes likely play a smaller role than the immediate neural and sensory effects.

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Athletic performance

A 2024 meta-analysis of 36 studies with a total 169 outcomes among healthy adults found that resistance training was associated with a medium to large improvement in flexibility. However, they noted the large variability of study protocols that make it difficult for them to confidently predict whether future studies will consistently find positive effects.

The authors did not find age and activity levels to be significant factors to influence or predict how much flexibility was improved. Because most studies focused on sedentary populations, the researchers could not draw conclusions about how resistance training affects flexibility among already active people. Also, most of the studies focused on hamstring flexibility, so there is less evidence on how resistance training affects other muscles, they wrote.

The researchers found the following to have significant impact: 

• High-intensity resistance training produced greater improvements in joint flexibility than low-intensity training, likely due to higher mechanical tension, greater motor unit recruitment, and improved coordination between muscles.
  
  “High-intensity training could simply have a greater effect because it imposes higher internal loads compared with low-intensity training,” they wrote, “For example, [resistance training] promotes better intermuscular coordination, that is, an improvement in coactivation patterns between agonists and antagonists muscles.” 
• Longer rest periods between sets were also associated with greater flexibility gains, though this likely reflects their connection to higher training intensities rather than an independent effect.
• Gender may moderate results with studies including mixed-gender groups showing different effects than single-gender studies, but no clear differences were found between men-only and women-only studies, and the reasons for this remain unclear.
• Eccentric training did not show a clear advantage over traditional resistance training for improving flexibility, partly because all resistance training includes an eccentric phase, focuses highly on the hamstrings, and too few studies isolated eccentric-only protocols.

In practical terms, the authors wrote that resistance training has the potential to improve joint flexibility while also increasing strength, which could make training more time-efficient and appealing across age groups. This may strengthen the case for resistance training as a core component of physical activity guidelines. 

“Still, the results of this work should not be interpreted as a basis to discard stretching exercise routines,” they wrote.

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Musculoskeletal pain

For musculoskeletal (MSK) pain, a 2024 systematic review of six studies (658 subjects total) by Konrad et al. found static and dynamic stretching may reduce pain over four to six months of training. These studies primarily focused on low back and neck pain.

Only one study by Shamsi et al. found no effect of stretching on low back pain, according to Konrad et al. This study compared stretching with strength training and a control group that received traditional treatments, such as cold therapy and electrical skin stimulation.

Konrad et al. proposed several overlapping biological mechanisms through which stretching may reduce MSK pain, particularly in the spine and lower limbs. 

One pathway is mechanical where stretching increases joint range of motion, especially at the hips, which can improve pelvic and spinal alignment and reduce compressive or tensile forces on spinal nerves. 

“Increased flexibility can improve hip/pelvis orientation positively affecting spinal nerves, alleviating back pain and compensatory overuse syndromes,” they wrote. “Reduction in sciatic nerve stiffness following stretch training was reported by Andrade et al., which can decrease pain levels, especially in the lower limbs.”

Another mechanism involves changes in nociceptors in the skin and fascia. They wrote that stretching has been shown to reduce stiffness in nerves, such as the sciatic nerve, which may lower mechanical sensitivity and pain, particularly in the hip extensors and flexors and the piriformis. This refers to improved range of motion and pain reduction may be changes in stretch and pain tolerance rather than large structural changes in muscle and connective tissues. 

The authors added that the pain-reduction effect can occur even in the opposite, non-stretched limb. This raises the possibility that regularly stretching muscles around a painful joint could reduce pain by desensitizing local nociceptors.

Muscle soreness

Stretching a sore muscle may feel good temporarily, and current research finds little benefit of stretching for muscle soreness. A 2025 systematic review and meta-analysis by Zhang et al. found no “statistically significant improvements” and “compelling evidence” that stretching can decrease pain perception, threshold, and soreness.

The study is based on 15 trials with a total of 465 participants, mostly young adults.

“The complex and multifactorial nature of DOMS, which involves peripheral inflammation, microtrauma, and central sensitization, may limit the potential of stretching to significantly modulate pain perception,” Zhang et al. wrote. “Since stretching mainly works on muscles and joints rather than directly on the body’s pain pathways, its ability to reduce pain is quite limited and not strong enough to have real therapeutic value.”

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So which type of stretching should I use?

Taken together, the research suggests that no single type of stretching is universally “best,” and the type you use depends largely on your goal. 

Static stretching is the most effective method for increasing flexibility and range of motion, particularly when performed regularly over weeks. Its effects appear to come mostly from increased stretch and pain tolerance, reduced muscle and connective tissue stiffness, and short-term neural adaptations. There are also small, long-term structural changes in muscle.

Static stretching may also help reduce pain by decreasing sensitivity of nociceptors, lowering nerve and tissue stiffness, improving force absorption, and changing how the nervous system interprets stretching sensations. Despite the lack of strong evidence that static stretching has long-term benefits from MSK pain, static stretching may provide short-term relief, especially when done gently and consistently.

Passive stretching is similar to static stretching except that you use an external force (e.g. gravity, devices that move your limb). Most of the flexibility and pain improvement come from increased stretch and pain tolerance rather than major structural changes in muscle or tendon. 

Currently, there’s little research on passive stretching, but studies from static stretching likely apply to it.

PNF stretching combines stretching with voluntary muscle contractions and often shows slightly larger effects than static or dynamic stretching in some studies. This is often done with another person assisting the stretch.

However, these differences are inconsistent and often disappear when study quality and sample size are taken into account. The apparent advantage of PNF may be driven more by the active muscle contractions involved, which increase neural activation and strength, rather than by any specific stretching mechanism.

Active stretching, where a person uses their own muscle contractions to hold a position, seems to offer similar flexibility benefits to static stretching while also promoting strength and motor control at end ranges of motion. This makes it useful in rehabilitation and general fitness context. 

Dynamic stretching, which involves controlled movement through a range of motion, appears less effective for increasing long-term flexibility but more appropriate as part of a warm-up. Unlike static stretching, dynamic stretching does not reduce strength or power and may help prepare the nervous system for activity by increasing muscle temperature, coordination, and readiness.

Further reading

Does strength training increase flexibility?

Does stretching increase muscle size?