Acupuncture Improves Hamstring Flexibility

Acupuncture was found to significantly improve hamstring flexibility in healthy young adults in a randomized, blinded, and controlled study. The study demonstrated that verum (true) acupuncture produced statistically significant gains in flexibility, outperforming both sham and placebo interventions [1].

 

Fifteen volunteers (nine male, six female; ages 18–35) were enrolled and randomized into a three-arm crossover study. The sample size was limited, in part, due to the COVID-19 pandemic. Each participant underwent all three interventions—verum acupuncture, sham acupuncture, and placebo—across three sessions, with a 7-day washout period between each treatment to mitigate carryover effects. Flexibility was measured using the sit-and-reach (SR) test [1]. Acupuncturists performed bilateral acupuncture at six standardized acupoints:

 

Each point was chosen for its function in opening meridian channels, relaxing tendons, reducing cold stagnation, and enhancing microcirculation—factors contributing to muscle extensibility. [1]. Sterile, single-use stainless steel needles (0.25 × 0.25 mm) were used. Insertion depths varied by anatomical site but followed consistent depth standards across sessions. All needles were inserted perpendicularly and retained for 20 minutes without further stimulation or manipulation. No thrusting, twirling, or other reinforcing/reducing techniques were employed to preserve procedural consistency across participants [1].

 

In the sham acupuncture condition, subcutaneous insertions were performed at non-acupoint locations near the true points. For the placebo group, a blunt wire within a guide tube was applied to true acupoints without skin penetration. This non-invasive stimulation mimicked needle placement and duration but did not induce a physiological needle response. In all groups, patients were placed prone with their faces in cutouts to prevent observation of the intervention [1].

 

The sit-and-reach test revealed a statistically significant improvement in hamstring flexibility following true acupuncture [1]. Neither sham (p = 0.86) nor placebo (p = 0.18) conditions produced statistically significant changes. These results point to a specific physiological effect associated with the activation of acupoints [1]. Measured by the VAS, there was a modest 4.5% reduction in perceived discomfort following true acupuncture, compared to a 2.3% decrease in the placebo group and a 4.7% increase in the sham group [1].

 

The acupoints chosen were based on the principle that cold stagnation and  impairment of qi and blood circulation contribute to diminished hamstring flexibility, especially of the local areas at the bladder meridian. By targeting bladder meridian points (e.g., BL36, BL37, BL40, BL58), the acupuncture protocol aimed to restore circulation and relieve soft tissue restrictions.

 

The observed flexibility improvement may relate to previously demonstrated physiological effects of acupuncture, including enhancement of local microcirculation and muscle relaxation [1].

 

One strength of this pilot study was the inclusion of both sham and placebo groups, which allowed researchers to differentiate between the specific and non-specific effects of acupuncture. The use of a standardized needle gauge, insertion depth, and retention time increased procedural reliability. However, limitations include the small sample size (n=15) and the absence of long-term follow-up to evaluate sustained flexibility gains or cumulative effects of repeated treatment [1].

 

Furthermore, the needle technique was intentionally limited to passive retention without manipulation, and more dynamic approaches may yield stronger results but were not employed [1]. Techniques such as lifting, thrusting, and twirling along with moxibustion, electroacupuncture, and other techniques could be administered in future investigations to test for optimal protocols.

 

This investigation provides evidence that acupuncture, when applied at specific acupoints along the bladder and gallbladder meridians, significantly improves hamstring muscle flexibility in healthy individuals without increasing discomfort during stretching. While this study was limited in scope and sample size, the findings suggest that acupuncture can play a clinically useful role in flexibility enhancement, potentially reducing injury risk among athletes and individuals with musculoskeletal imbalances. Further research with larger cohorts and advanced imaging or biochemical assays is warranted to elucidate the underlying mechanisms and optimize clinical protocols.

 

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