Light-emitting diode therapy (photobiomodulation) effects on oxygen uptake and cardiac output dynamics during moderate exercise transitions: a randomized, crossover, double-blind, and placebo-controlled study

Abstract

Light-emitting diodes (LEDs) might have a beneficial impact on cytochrome-c oxidase enzyme activity. Thus, it was hypothesized that photobiomodulation by light-emitting diode therapy (LEDT) could influence aerobic metabolism dynamics. Possible LEDT-mediated aerobic improvements were investigated mainly by a precise characterization of the pulmonary O₂ uptake dynamics during moderate exercise transitions. Eight healthy young adults were enrolled in this randomized, double-blind, placebo-controlled, crossover study. A multi-diode array of LEDs was used for muscular pre-conditioning 30 min and 6 h before exercise testing. Pulmonary O₂ uptake, carbon dioxide output, cardiac output, heart rate, stroke volume, and total arteriovenous oxygen difference dynamics were evaluated by frequency domain analysis. Comparisons revealed no statistical (p > 0.05) differences between LEDT and placebo, suggesting no significant changes in aerobic system dynamics. These results challenge earlier publications that reported changes in pulmonary O₂ uptake during incremental exercise until exhaustion after LEDT. Perhaps, increments in peak pulmonary O₂ uptake after LEDT may be a consequence of higher exercise tolerance caused by non-aerobic-related factors as opposed to an improved aerobic response.

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