The prevalence of latent myofascial trigger points and diagnostic criteria of the triceps surae and upper trapezius: a cross sectional study.

OBJECTIVES: To determine the prevalence of latent myofascial trigger points (MTrPs), specific diagnostic criteria and the association between gender and MTrP prevalence in the triceps surae and upper trapezius.
DESIGN: Cross-sectional study.
SETTING: University, Faculty of Health and Life Sciences. PARTICIPANTS: Two hundred and twenty healthy volunteers (132 females and 88 males; mean age 29.7 (SD 11.0).
INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Prevalence of latent MTrPs in the triceps surae and comparative upper trapezius; specific diagnostic criteria and pressure pain threshold (PPT).
RESULTS: Latent MTrPs were prevalent in all triceps surae (range: 13 to 30%), left upper trapezius (23%) and right upper trapezius (20%). No MTrPs (0%) identified in the middle fibres of deltoid. For each specific diagnostic criterion, taut bands were most prevalent in the right gastrocnemius medial head (81%); tender spot in left gastrocnemius medial head (52%) and nodules in the right upper trapezius (35%). Local twitch response (0.5%), the least frequent diagnostic criterion was only found in the left gastocnemius medial head. A significant increase in latent MTrP prevalence for females compared to males in five of the six triceps surae MTrP sites, with no significant association for gender and latent MTrP prevalence in the left or right upper trapezius.
CONCLUSIONS: This study established the prevalence of latent MTrPs, specific diagnostic criteria and baseline normative data in the triceps surae. The middle fibres of deltoid were identified as a potential MTrP control site for future clinical research in the upper limb.