Effect of Low Intensity Strength Training Combined With Moderate Blood Flow Restriction on Muscle Vasodilatation and Arterial Stiffness in Elders With Low Gait Velocity.

The dynamic force of the lower limb muscles will be evaluated by the maximal repetition of knee extension and leg press exercise, according to the protocol presented in a previous study \[37\]. The elderly will perform a warm up consisting of 1 series with 10 unloaded repetitions. After the warm up, the mass to be lifted will be progressively increased until the maximum load that can be lifted is reached, with a maximum limit of 5 attempts and a 3 to 5 minutes interval between them. The test will be conducted by a physical education professional who will verbally encourage participants throughout these steps and perform the load adjustment at week 5 and 10 (Radaelli, 2014).

To measure the gait speed of participants they will walk 4.6 metres and the time needed to cover this distance is measured. The mean of three attempts is recorded and divided by the distance. The participants included must achieve in the walking test an average of \< 0.,9 m/s (Guralnik, 1994).

A mercury-filled silastic tube, connected to a low-pressure transducer and a plethysmograph (D.E. Hokanson), will be placed around the largest circumference of the calf region. One cuff will be placed around the ankle and another around the thigh. The ankle cuff will be inflated to a supra-systolic pressure 30 seconds before starting the measurements. At 15-second intervals, the cuff around the thigh will be inflated above the venous pressure for a period of seven to eight seconds. Increased tension in the silastic tube reflects an increase in leg volume and vasodilation. The signal of the muscle blood flow wave will be recorded on a polygraph and analysed every minute, averaging three records per minute. The protocol will be performed during 5 minutes of rest, 3 minutes isometric exercise and 2 minutes of recovery (Bahia, 2006).

Arterial stiffness will be estimated from the carotid-femoral aortic pulse wave velocity \[33\]. Carotid-femoral aortic pulse waves will be recorded by tonometry (SphygmoCor, AtCor Medical, Australia). At the same time, an electrocardiogram will be obtained to calculate the wave transit time. Two distances will be measured: the recording point of the carotid artery and the sternal furcula (distance 1) and the sternal furcula and the recording point in the femoral artery (distance 2). The distance travelled by the pulse wave will be calculated as "distance 2" - "distance 1". The carotid-femoral aortic pulse wave velocity will be calculated as: carotid-femoral aortic pulse wave velocity = ¼ \* distance travelled by the pulse wave (m) / transit time(s).

In a supine position, the maximal voluntary handgrip force will be determined as the highest force in 3 consecutive attempts using a Jamar hydraulic palmar dynamometer (Asimow Engineering, CAL, USA). For activation of the central command, mechanoreceptors and muscular metaboreceptors the individual will perform, after 5 minutes of rest (baseline records), 3 minutes of exercise at 30% MVC. This manoeuvre isolates the activation of muscle metaboreceptors, observing the selective activation of these. After the isometric handgrip exercise, 2 minutes of recovery will be performed. Throughout the protocol muscle blood flow, blood pressure and heart rate will be recorded.

The vasodilatory capacity will be calculated as the percentage of increase of the diameter of the brachial artery and femoral post occlusion in relation to its basal values.

Images of the brachial artery will be recorded by a two-dimensional ultrasonography device with a spectral Doppler and linear transducer (Ultra-0122, Philips, The Netherlands).

This questionnaire is used to estimate the quality of life in participants before and after the study.

Anthropometric measurements will be made before and after the training program following the standardization of the International Society for Anthropometric Assessments. The body mass will be measured with an accuracy of 0.1 kg (Filizola). The stature will be obtained by means of the stadiometer with an accuracy of 0.5 cm. The BMI will be calculated as body mass divided by height squared. The circumference of the quadriceps will be measured with a tape measure (Seca) with a precision of 0.1 cm.