Myofascial trigger points are hyperirritable points located within a taut band of skeletal muscle or fascia, which cause referred pain, local tenderness and autonomic changes when compressed. They are classified as either active myofascial trigger points (ATrPs) or latent myofascial trigger points (LTrPs). ATrPs can be inactivated by different treatment strategies; however, they never fully disappear but rather convert to the latent form. Therefore, the diagnosis and treatment of LTrPs is important. Invasive and noninvasive techniques are available for management of LTrPs. Invasive techniques include trigger point injections and dry needling whereas noninvasive techniques include manual therapy techniques and electrotherapy modalities. Manual therapy techniques for the treatment of myofascial trigger points include joint manipulation, strain/counterstrain, ischemic compression and pressure, massage therapy, myofascial release therapy, muscle energy techniques, point pressure release and transverse friction massage. Additionally, recent studies showed that the myofascial trigger point therapy combined with stretching exercise may be an effective for decreasing the pain level. However, there is insufficient evidence to determine what type stretching exercise is most effective and its immediate effects on muscle length in people with LTrPs. Therefore, the aim of this randomised-controlled trial is to investigate the effect on muscle length, pain perception threshold, and respiratory function after a single intervention of manual pressure release combined with stretching exercise on LTrPs in the pectoralis minor muscle.

The sample size and power calculations is performed with the sample size calculator (InStat). The calculations is based on a standard deviation of 0.5 points, the minimal clinically important difference (MCID) for Pectoralis Minor Index of 0.89 points, an alpha level of 0.05, a β level of 5%, and a desired power of 95%. These parameters generate a sample size of at least 9 participants for each group. Total of 40 subjects will be recruited into the study in order to allow for a loss to follow-up.

Potential participants will be invited through the posting of flyers at Istanbul University, Turkey. Flyer recruitment method will be used in this trial because it is the most effective, yielding the highest number of enrolments. All participants will be completed an informed consent form that described the purpose and procedures of testing. prior to participating in the study. Forty participants fitting the inclusion criteria will be randomly assigned to one of four parallel groups (ratio 1:1:1:1). For allocation of the participants, "Randomization.com" which is an online, randomisation web service will be used (http://www.randomization.com/). Simple randomisation procedures (computerized random numbers) will be done and sequentially numbered index cards with the random assignment will be prepared by an investigator with no clinical involvement in the study. The index cards will be folded and placed in sealed opaque envelopes. Then, the blind investigator will open each envelope and allocate the participants to group according to selected index card. The interventions will be performed by the same physiotherapist at a university research clinic, and assessments and data collection will be made by another therapist. Whereas interventionist will be aware of the allocated arm, patients and outcome assessor will be kept blind to allocation.

The data will be evaluated using the Statistical Package for the Social Sciences 21.0 program for Windows and by analyzing descriptive statistics (frequency, mean and standard deviation). Kolmogorov-Smirnov Test will be used to assess the distribution of data. The one-way analysis of variance (ANOVA) for repeated measures with the Bonferroni post hoc test will used to determine whether differences in the mean scores of outcome measure among three time points (baseline, immediate after and 24 hours later) between study groups. In this study, p values less than 0.05 will be regarded as statistically significant.