Effects of Acute Photobiomodulation on Heart Rate Variability in Physically Active Individuals: A Randomized and Controlled Clinical Trial.

Approximate entropy (ApEn) was slightly reduced in the PBM group compared with controls.

• The reduction in ApEn was statistically significant (p = 0.011)
• ApEn is a non-linear HRV index reflecting autonomic complexity
• This was the only HRV index showing a significant difference between groups
• PBM was applied to the vagus nerve in the infra-auricular region with a total energy dose of 12 J

No significant differences were observed in other HRV indices across time, frequency, and non-linear domains.

• HRV was analyzed across three domains: time domain, frequency domain, and non-linear domain
• Apart from ApEn, none of the other HRV indices showed statistically significant differences between groups
• This suggests PBM induced minimal acute modulation of cardiac autonomic function beyond autonomic complexity

The study enrolled 34 volunteers divided into an exercise crossover group and a control group.

• 17 volunteers underwent PBM or sham PBM in a crossover design combined with resistance exercise
• A control group of n = 17 received PBM without exercise
• Participants were described as healthy, physically active adults
• The design was an acute randomized controlled trial

PBM was delivered to the vagus nerve in the infra-auricular region with a total energy dose of 12 J.

• The infra-auricular region was targeted as the site of vagus nerve stimulation
• Total energy dose was 12 J
• A sham PBM condition was used as a control within the crossover arm of the study
• The therapy was assessed in the context of tissue recovery, performance enhancement, and post-exercise optimization

The authors concluded that further studies with different dosimetries and exercise protocols are warranted.

• The minimal autonomic modulation observed suggests the 12 J dose may be insufficient to produce broader HRV effects
• The authors noted that variations in dosimetry and exercise protocols could yield different outcomes
• The findings indicate that acute PBM application to the vagus nerve has limited impact on overall cardiac autonomic function in healthy, physically active individuals