INSTRUMENTED-MANUAL PHYSIOTHERAPY VERSUS NONINSTRUMENTED

The Visual Analogue Scale (VAS) was designed to allow a subjective assessment of pain. A VAS is usually a horizontal line of 10 cm. with perpendicular lines at the ends, which are defined as the extreme limits of the painful experience. Previous studies have shown that the VAS has adequate psychometric properties, including test-retest reliability (r = 0.78) and convergent validity with other measures of pain such as the McGill Pain Questionnaire (r = 0.49 to 0.65) (Sriwatanakul K ., 1983).

Stiffness characteristics will be measured using a handheld MyotonPRO device (MyotonPRO, Myoton Ltd, Estonia). MyotonPRO has shown high levels of reliability in a session or between sessions both by the same operator (intra-rater) and between different operators (inter-rater), both in young subjects and elderly (Aird et al., 2012) (Mullix et al., 2012). Stiffness (N/m) will be calculated by software of MyotonPRO (Vain, 1994, 1995). Stiffness is the ability of tissue to restore it shape after removing of external force acting on the muscle.

Sono-myoelastography uses an external vibration source with a frequency less than 1000 Hz in conjunction with Doppler techniques to identify localized regions of increased tissue stiffness (Muro-Culebras, 2013). In this study vibrations will be produced in the right upper trapezius muscle using an external massage vibrator (Model NC70209, North Coast Medical, Gilroy, CA, USA) modified with a flat and elongated applicator (with an application area of 1 x 4 cm). This vibration source will be placed approximately 2-3 cm away from each of the points marked as ''positive'' in the clinical examination and induce vibrations of about 92 Hz. By use of the power Doppler technique, the sono-myoelastography images will be collected while applying vibrations.

This instrument will be used to measure grip strength of both physiotherapist upper limbs. The dynamometer has proven to be the safest [ICC = 0.98] and most valid [ICC = 0.99] method to measure grip strength of the hand. (Bellace JV, 2000).

For this study we will use the Spanish version (SFI-Sp), since it has proven to be a valid and reliable measure of the spinal region result. This regional tool reflects the status and any change in the kinetic chain of the spine. This questionnaire has demonstrated high internal consistency (α = 0.85) and reliability (r = 0.96) (AI Cuesta-Vargas, 2014).

Neck Disability Index is the most widely used neck pain scale in the largest number of populations and has been validated most often against multiple measurements of function, pain, and clinical signs and symptoms. (Cleland et al., 2006). For this study we will use the Spanish version (NDI-Sp), since it has proven to be reliable (r = 0.98), valid, and sensitive to change. (Andrade et al., 2010).

Circulation will be studied using the Doppler technique, since it has been shown for other studies (Sikdar et al., 2009). The resistive index (RI) is determined in the ascending branch of the transverse cervical artery and in other arteries or arterioles that will be in the vicinity of points marked as ''positive'' in the clinical examination. The waveform of blood flow, based on Doppler flow, will be scored on a scale of 0-2 (Sikdar et al. 2009).

Muscle tone characteristics will be measured using a handheld MyotonPRO device (MyotonPRO, Myoton Ltd, Estonia). Muscle tone will be calculated by software of MyotonPRO (Vain, 1994, 1995). Muscle tone (Hz) is the frequency of damped mechanical oscillation of muscle tissue, is an index of the tension in the muscle

Muscle elasticity characteristics will be measured using a handheld MyotonPRO device (MyotonPRO, Myoton Ltd, Estonia). Elasticity (logarithmic decrement of oscillations amplitude damping) will be calculated by software of MyotonPRO (Vain, 1994, 1995). Elasticity is the ability of muscle to restore its initial shape after contraction. A lower level of decrement reveals a better muscle elasticity and ability of contraction.

It will be obtained from a sonographic examination using the B-mode of a clinical ultrasound scanner with a linear transducer (Esaote Mylabs25, Milan, Italy) set to a frequency of 12 MHz and depth of 4 cm, since some studies have described the possibility of using sonography in the diagnosis of myofascial trigger points. (Sikdar et al., 2009). Finally, the operator will use the ''ellipse'' tool of the ultrasound to delineate and calculate the size of the largest hypoechoic area found.