Pain threshold in selected trigger points of superficial muscles of the back in young adults

Monitoring of pain threshold is the basis for verification of the effectiveness of therapy or assessment of the patient's condition. This study aimed to determine the pain threshold of selected superficial muscles of the back taking into account trigger point activity in young and healthy males and females, with the evaluation of intrarater reliability of algometric measurements.

The study examined 30 young adult participants (15 males and 15 females) aged 26.23 ± 3.21, and BMI of 23.80 ± 3.43. The Pain Test FPX Algometer (Wagner) was used for the study. Trigger points on the levator scapulae and trapezius muscles (superior and inferior portion) on both sides were examined. It was also verified whether the trigger points studied are active or inactive. Furthermore, an author's survey questionnaire was used.

Within the trigger points of the right (p = 0.04) and left (p = 0.02) superior trapezius muscle and the left (p = 0.04) levator scapulae muscle, the pain threshold values were higher in the male group. There was a statistically significantly higher number of active trigger points in the female group compared to that in the male group (2.49 ± 1.51 vs. 1.07 ± 1.16, respectively), p = 0.01. For all muscles tested, mean pain threshold values were significantly higher for inactive trigger points. A greater number of active trigger points is associated with lower pain thresholds at these points (left: the superior trapezius, r = -0.597, the inferior trapezius, r = -0.609; the levator scapulae, r = -0.746; right: the superior trapezius, r = -0.610, the inferior trapezius, r = -0.604; the levator scapulae, r = -0.747). The evaluation of the intrarater reliability showed excellent agreement between the first and second measurements, ICC > 0.987 for all examined trigger points.

(1) Women who reported pain more than once a week in the studied muscles showed a greater number of active trigger points. (2) A greater number of active trigger points in female is related to a lower pain threshold (which is associated with greater pain sensitivity) in female than in male. (3) A sample size of 30 people seems sufficient to detect variations in the pain threshold at active and inactive trigger points of selected back muscles, especially when the frequency of occurrence of both types of points is comparable.