The Use of i/t Curve in Assessment of Phototherapy Effects

Conventional electrodiagnostic examination is useful in daily physiotherapeutic practice. Nevertheless, the subjective assessment of muscle contraction and perceived current vibrations carries the risk of error and thus is a limitation of the method. Therefore, the use of the I/T curve coefficient was proposed in this study. This coefficient is the arithmetic mean of the electrical charge needed to trigger a sensory or motor reaction at different widths of the electrical pulse. PILER (Polychromatic Incoherent Low-Energy Radiation) light affects the sensory and motor excitability of the tissue. The resulting changes may depend on the colour of the filter used in the irradiations.

The study aimed to:

1. To evaluate changes in neuromuscular excitability occurring after PILER irradiation using filters of different colours.
2. To evaluate the usefulness of the I/T curve coefficient in neuromuscular excitation test.

60 healthy volunteers were assigned to one of four groups irradiated with: 1 - Piler light + red filter, 2 - Piler light + blue filter, 3 - Piler light without a filter, 4 - placebo.

Main Outcome Measures were plotting I/T curve coefficient for rectangular (■I/T coeff) and triangular (▲I/T coeff) pulses and the pressure pain threshold (PPT).

Electrodiagnostic examination is a valuable addition to clinical trials and is useful in disorders of neuromuscular excitability.

The I/T curve is a non-invasive electrodiagnostic method for the quantitative assessment of neuromuscular excitation. Plotting it makes it possible to determine the rheobase (minimum stimulus amplitude to reach the stimulation threshold with a long pulse duration /1000 ms/) and chronaxie (minimum duration of a stimulus with an amplitude twice that of the rheobase needed to reach the stimulation threshold.

Traditional electrodiagnostic examination is popular among clinicians due to its availability, ease of administration and usefulness in physiotherapeutic practice. The subjective assessment of muscle contraction and perceived current vibrations carries the risk of error and thus is a limitation of the method. Therefore, use of the I/T curve coefficient was proposed in this study. This coefficient is the arithmetic mean of the electrical charge needed to trigger a sensory or motor reaction at different widths of the electrical pulse.

Polarized polychromatic incoherent low-energy radiation (PILER light) can affect the sensory and motor excitability of living tissue. The biological activity of light results from the energy of its ordered electromagnetic waves acting on living cells. No thermal effect is present, as the density of the energy transmitted to the tissues is low.PILER therapy often uses filters of different colours, each showing a slightly different effect on excitable tissue.

The research questions of this randomised experiment were:

1. Does PILER light affect sensory and motor excitation?
2. Does the electromagnetic wavelength of PILER light influence its effect?
3. Is the I/T curve coefficient a useful measure of sensory and motor excitation?

Eligibility Criteria:
Inclusion Criteria included: informed consent, good tolerance of current pulses, completion of all phototherapy sessions, declaration of alcohol/drugs/smoking abstinence

The exclusion criteria were: acute inflammatory processes and fever, the presence of pigmented moles in the irradiated area, exposure to any other physical factors, a history of upper limb trauma, and upper limb overload.