The effect of photobiomodulation versus placebo on functional capacity and fatigability in post COVID-19 elderly

Introduction
Post-pandemic syndrome has lasting functional and psychological consequences, especially for the elderly. This timeline requires a quick search for procedures that will enable us to implement safe and non-invasive therapeutic instruments as prophylactic or adjuvant therapies for post-COVID-19 consequences. Photobiomodulation (PBM) may decrease inflammation and improve leg circulation. So, this study aims to assess the impact of PBM on post-COVID-19 functional capacity and fatigability.

Material and methods
Two groups of 100 elders with a positive COVID-19 history were established. The PBM group got photobiomodulation on both lower calf muscles for four weeks (diode laser, Continuous output, stationary in skin contact mode, 100mW, 808 nm, beam spot area of 0.0314 cm2, 127.39 J/cm2/point, 40 s). The control group got placebo PBM for four weeks. Both groups' exhaustion was measured using the FSS. Functional ability was evaluated using the KATZ score before and after the trial.

Results
After four weeks of PBM, there was a substantial suppression in the FSS level from 4.57 ± 0.26 to 3.97 ± 0.23 and the KATZ score was significantly elevated from 2.98 ± 0.79 to 3.94 ± 0.77, P value for both was < 0.05. In addition, the placebo intervention improved the FSS level and KATZ score to an acceptable level.

Conclusions
PBM enhanced functional capacities as evaluated by the KATZ score and fatigability perception as measured by the FSS scale in post-COVID-19 older people. Also, placebo intervention had a considerable effect on the elderly, with an 8.1 percent improvement in fatigue perception and a 19.1 percent improvement in functional ability evaluation.