The objective of this randomized clinical trial is to compare the effects of a standardized exercise program alone versus the same program combined with neuromuscular electrical stimulation in patients undergoing heart failure . The main questions it aims to answer are:
* Assessing the ultrasonographic parameters: echo intensity (echogenicity), cross-sectional area, thickness, and pennation angle of the rectus femoris muscle in both lower limbs. * Evaluating the strength of the femoral quadriceps muscle * Evaluating the changes in the chronaxie of the rectus femoris muscle in both lower limbs.
The protocol will have a total duration of 32 days, with an initial intervention period of 18 days, followed by a 14-day follow-up period.
Age ≥ 18 years
Intra-aortic balloon pump (IABP) for more than 48 hours
Dobutamine ≤ 20 mcg/kg/min
Norepinephrine ≤ 0.2 mcg/kg/min (35)
Need for invasive mechanical ventilatory support
If the patient or responsible family member fails to sign or withdraws the informed consent
Parallel
Isolated Resistance Training Program
Other interventionThe hip range of motion (ROM) will be fixed at 45 degrees due to the limitation imposed by the femoral insertion of the intra-aortic balloon pump in both lower limbs to allow for a 45-degree knee extension ROM. Four sets of 10 knee extension repetitions will be performed with a 90-second rest interval between sets. The intensity (resistive load) will be set at 60% of the baseline load, calculated using the one-repetition maximum (1RM) test and increased by 10% after every 5 interventions.
Neuromuscular electrical stimulation
Other interventionFor NMES, two electrodes (area of 5 x 9 cm) will be positioned perpendicular to the muscles of the femoral quadriceps. The parameters of NMES will remain fixed throughout the study: pulsed, biphasic current, with a frequency of 35Hz, pulse width of 1000µs, on-time of 7 seconds (with 3 seconds of rise, 1 second of sustainment, and 3 seconds of descent), and off-time switched off. These settings allow the onset of NMES to be synchronous with the start and end of hip extension for simultaneous execution with resistance exercises and a total of 40 stimulations. The intensity will be gradually adjusted until evoked contractions of grade 4 to 5 (partial muscle recruitment and total muscle recruitment) or the maximum intensity tolerated by the patient is achieved.
To investigate echo intensity of the rectus femoris muscle.
The ultrasonographic images will be obtained by a portable device in B-mode, using a 6 cm linear array transducer with a frequency range of 6-13MHz. The echointensity value will be acquired through quantitative analysis using the square method, in grayscale, where the average value will be calculated using the histogram function of the dedicated software, in arbitrary units (AU).
To investigate cross-sectional area of the rectus femoris muscle.
The cross-sectional area will be determined by the number and size of individual fibers within the rectus femoris muscle, using the measurement of the anatomical area (cross section of a muscle perpendicular to its longitudinal axis) in centimeters square.
To investigate pennation angle of the rectus femoris muscle.
The pennation angle will be calculated by the intersection of the path between the fascia with the lower aponeurosis of the rectus femoris muscle, measured in degrees.
To investigate changes in quadriceps femoral muscle strength.
It will be obtained using digital dynamometry through 3 measurements, with a one-minute interval, and the highest obtained value will be considered, measured in Newtons (N).
To investigate changes in arterial blood pressure during the protocol.
Assessed by blood pressure measured by intra aortic baloon pump.
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