Introduction: Effectiveness of light-emitting diode (LED) in biological tissue is due to the correct application of physical parameters. However, most studies found do not provide complete information on the physical characteristics of the diodes. It is necessary to carefully evaluate the diode parameters so that the results of research with this feature can be reproduced. The objective of this study was to develop a light-emitting device using LED, with proper measurements for application in clinical research. It was used 267 LEDs, powered with 12-V voltage and fixed on a plate of ethylene-vinyl acetate (25 × 42 cm), equidistant at 1.0 cm. For the calculation of red and infrared irradiation, a spectrometer was used, and the data were processed in routines implemented in the OriginPro 8.5.0 SR1 Software. The irradiance was determined by the integration of the spectral irradiation in the LED emission region. The red LED has a wavelength of 620 ± 10 nm, a power density of 52.86 mW/cm2, power of 6.6 mW, and total power of 1.76 W on the device. The infrared LED has a wavelength of 940 ± 10 nm, power density 33.7 mW/cm2, power of 6 mW, and total power of 1.6 W on the device. The LED characterization enables the generation and application of energy with greater precision and reproducibility. Besides, it is a light source, a device capable of framing large areas, reducing the time and cost of the application in different clinical conditions related to neuromuscular performance or rehabilitation.
