Echointensity and echotexture have been used as a physiological marker for changes in skeletal muscle quality and structure caused by physical training, low activity, ageing and some neuromuscular disorders. However, there are some influencing factors on muscle echo-intensity and echotexture, such as temperature, which may not be taken into account when performing an ultrasound assessment and may alter the results.

This study aims to investigate the effects of muscle temperature on echointensity and other 2nd order echotextures variables such as homogeneity, contrast, correlation and entropy of muscle tissue, in order to gain a better understanding of this correlation and minimise its influence, which would allow greater precision in the use of muscle ultrasound as a diagnostic tool.

The methodology of this study includes firstly the acquisition of ultrasound images of the vastus lateralis muscle. This acquisition will be performed during the continuous recording of muscle temperature, carried out during a passive cooling process after 20 min of heating using microwave equipment. In addition, to standardise the results, a correction factor will be calculated to compensate for the influence of subcutaneous adipose tissue thickness on echogenicity and echotexture.

Inclusion Criteria:

• Acceptance of participation in the study.
• Healthy subjects.
• Subjects between the ages of 18 and 65.

Exclusion Criteria:

• Have known neurological, cardiovascular, metabolic or orthopedic conditions that prevent them from participating in the study.
• Present metal implants in the heating area.
• Wear a pacemaker.
• Perform physical activity during the 48 hours prior to data collection.
• Contraindications of dry needling such as: Belonephobia, history of abnormal reaction to the puncture or injection, anticoagulant treatment or thrombocytopenia, lymphedema over the area of intervention, severely compromised immune system, vascular diseases, diabetes mellitus, pregnancy, epilepsy, allergy to metals or that the intervention area has wounds, scars, tattoos, or stains.

Access to identified personal information will be restricted to the principal investigator of the study/collaborators, the Research Ethics Committee and authorized personnel, when necessary to verify the data and procedures of the study, but always maintaining their confidentiality in accordance to current legislation.

The personal data of the participants, obtained during their participation in the project, will be kept for the time necessary for the development of this research, which is estimated to be 6 months, and will subsequently be destroyed, and cannot be kept without having previously been anonymized.