This invention provides methods for treating a variety of disorders using electromagnetic radiation directed at excitable tissues, including nerves, muscles and blood vessels. By controlling the wavelength, the wavelength bandpass, pulse duration, intensity, pulse frequency, and/or variations of those characteristics over time, and by selecting sites of exposure to electromagnetic radiation, improvements in the function of different tissues and organs can be provided. By monitoring physiological variables such as muscle tone and activity, temperature gradients, surface electromyography, blood flow and others, the practitioner can optimize a therapeutic regimen suited for the individual patient.