The Effect of Manual Therapy on Respiratory Functions in Healthy People: A Randomized, Sham-Controlled Clinical Trial of Efficacy and Safety

Background: Chronic respiratory disease is currently a global health problem. Secondary problems, such as skeletal muscle disorders, among which cervical spine and diaphragm dysfunctions are two of the most common, can affect the lung function of these subjects. Manual therapy could be a suitable treatment for these problems. However, although this is a very broad area of research, there is no consensus on its usefulness. Objectives: To investigate the effects of the diaphragmatic stretch technique and the high-speed, low-amplitude C3–C4 rotational thrust technique, applied alone or in combination, on respiratory function in healthy adults. Peak expiratory flow (PEF) was the primary outcome; forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were secondary outcomes included to assess safety. Methods: A randomized, sham-controlled clinical trial with blinded outcome assessment with 152 healthy participants distributed in four groups was conducted: Group 1 subjects underwent the Diaphragmatic Stretch Technique, Group 2 subjects underwent the high-speed, low-amplitude thrust technique in C3–C4 rotation, Group 3 underwent both techniques, and Group C (control group) received a simulation of one of the two techniques. The three outcome variables were recorded immediately after the intervention and 5 min after. Study registered on ClinicalTrials.gov (NCT03732222). Results: The results show a significant increase in PEF for Group 1, visible in the immediate post-intervention and at 5 min post-intervention. Group 3 also showed a significant increase in PEF, although only at 5 min post-intervention. Conclusions: High-speed, low-amplitude C3–C4 rotation thrust technique and Diaphragmatic Stretch Technique can improve the PEF in healthy subjects.