Effects on Muscle Activity After Dry Needling in Myofascial Trigger Points of the Gastrocnemius Muscles

Trigger points (TrPs) are a common musculoskeletal cause of local and referred muscle pain, as well as local inflammation in the muscle and fascia. From a clinical and sensory viewpoint, TrPs may be classified as active or latent. The principal difference is the reproduction of symptoms experienced by an individual (active) with or without stimulation. Local and referred pain elicited from latent TrPs may be transient in duration upon stimulation, and latent TrPs may be present without spontaneous symptoms.

Both active and latent TrPs induce motor dysfunctions such as stiffness, restricted range of motion, and accelerated fatigability in the affected muscle. The interrater reliability of manual identification of latent TrPs in the calf muscles has been found to range from small to moderate. The clinical relevance of latent TrPs has increased in the last decade,4 and some studies have investigated the effects of treating them. Among all manual therapies targeted to latent TrPs, ischemic compression, or TrP pressure release, is the most commonly used. Although TrPs may affect any muscle, the gastrocnemius muscle may be the most susceptible in the lower extremity to developing them. It has been reported that 13% to 30% of the asymptomatic population has latent TrPs in these muscles, and their presence may affect sport practice.

The purpose of this study will be to evaluate changes in muscle activity in myofascial trigger points (TrPs) after a single treatment session of dry needling in the gastrocnemius muscle.

A randomized controlled clinical trial with blinded assessor will be conducted. 90 asymptomatic volunteers with MrPs gastrocnemius -muscle TrPs will bilaterally explored. After exploration the volunteer will be asigned to either Control (no treatment), experimental (60 seconds of dry needling on the TrP that refers more pain on the randomly assigned extremity) or sham group (60 seconds of dry needling on the TrP that refers more pain with a sham needle with no tip). To be part of the sham group patients should not have received any dry needling before.

Muscle activity is commonly recorded in research using surface electromyography (sEMG). sEMG has previously been used in similar studies because it is less invasive than intramuscular electromyography. Electromyography will be performed using the mDurance® surface electromyograph (mDurance Solutions SL; Granada, Spain) in order to capture muscle activity of the lateral and medial Gastrocnemius muscles (Electrodes will be placed as described by the mDurance application) during an unilateral countermovement Jump (in both extremities) and 20 meter Sprint. There will be a resting period of at least 2 minutes between exercises to prevent the results from being affected by fatigue.