It’s almost Christmas/Hannukah and you may still be looking for some last minute gifts. The Medical Mailbag looks at a hot new gadget on shelves this season and the word on the street is…well, save your money.

Table of Contents

• Vagus Nerve Stimulators; Marketing that is way out …

• Jess Cerra-From pro cycling to energy bar baker to …

• Episode takeaways:

  • References used for the MMB

Vagus Nerve Stimulators; Marketing that is way out front of the evidence

The vagus nerve plays a central role in the parasympathetic nervous system—the “rest-and-digest” counterpart to the stress-driven sympathetic system. Higher vagal tone is associated with improved heart-rate variability (HRV), better emotional regulation, enhanced recovery from physical stress, and reduced inflammation. Because of this, athletes and coaches are exploring VNS as a tool to help the body shift more efficiently into a restorative state following training or competition.

There are two primary categories of vagus nerve stimulation: implanted medical devices and non-invasive external stimulators. Implanted VNS systems are FDA-approved for conditions such as epilepsy and treatment-resistant depression, but they require surgery and are typically not used for sports performance. Instead, athletes are turning toward non-invasive vagus nerve stimulation (nVNS), which uses transcutaneous electrical impulses applied to areas where the vagus nerve is accessible—most commonly the auricular branch in the ear or the cervical branch in the neck.

For athletes, the appeal of nVNS centers on potential benefits including faster recovery after intense workouts, improved sleep quality, enhanced focus under pressure, and reduced perception of pain or anxiety during competition. Preliminary research suggests that stimulating the vagus nerve can elevate HRV, blunt cortisol responses, and modulate inflammatory cytokines. These effects may support more stable training loads, reduced overtraining risk, and better adaptation to high stress environments such as altitude or heavy competition schedules.

However, evidence for performance enhancement remains early and somewhat inconsistent. Results can vary widely depending on device type, stimulation parameters, and the individual’s baseline vagal tone. Safety is generally good in healthy users, although side effects like tingling, mild dizziness, or transient changes in heart rate can occur. The somewhat scant and inconsistent evidence has not stopped companies from aggressively marketing these devices as the lates and greatest things for recovery and the marketing has been packed with promises and hyperbole commensurate with the hefty price tag that these devices command. Coming in around $400-600, it is fair to wonder how on earth the cost can be justified based on such poor quality research to date.

Ultimately, VNS shows promise as a recovery-oriented tool, but athletes should approach it as an adjunct—not a replacement—for fundamentals like structured training, nutrition, and sleep.

Jess Cerra-From pro cycling to energy bar baker to gravel race director and philanthropist

Jess according to Jess: Jess is the force behind JoJé Bar—an energy bar that started in her kitchen and is now part of Alete Active Nutrition. After a 12-year professional cycling career, she went on to combine her M.S. in Exercise Physiology with hands-on culinary and athletic experience, serving as Vice President of Product & Community Development for brands like Bonk Breaker and SaltStick. She’s driven by making nutrition approachable and enjoyable for athletes, especially women navigating the complex world of fueling for performance.

Jess Cerra is the co-founder of Montana's Last Best Ride. This gravel race isn’t just about pedaling through beautiful landscapes; it’s a 501(c)(3) organization that has dished out a whopping $130,000 in scholarships to women and underrepresented youth over the past five years. Jess recounts her journey of creating energy bars in her kitchen that morphed into the popular JoJé Bar, and her passionate advocacy for women in sports through Montana's Last Best Ride. The conversation is not just about cycling; it’s a heartfelt exploration of how sports can break down barriers, with Jess emphasizing the importance of accessibility and community engagement. The episode also dives into the organizational challenges and triumphs of running a nonprofit event in a stunning yet rugged Montana environment, emphasizing the significance of connection and shared experiences in endurance sports and life. Jess's story is an inspiring reminder that sports can be a vehicle for change, and her passion for community and empowerment shines brightly throughout the discussion.

Episode takeaways:

• Jess Cerra, today's guest, turned her passion for cycling and nutrition into a successful career, starting with energy bars made in her kitchen – because who needs a corporate job when you can bake your way to success?

• Vagal nerve stimulators are the latest buzz in recovery tech, but let's be real—if they cost up to $600, I better see some serious scientific backing before I plug myself into one

• Despite the hype, the science on these stimulators is still shaky so maybe hold off before you start wearing these gadgets like fashion accessories.

References used for the MMB

1. Non-Invasive Vagus Nerve Stimulation and Exercise Capacity in Healthy Volunteers: A

Randomized Trial. Ackland GL, Patel ABU, Miller S, et al. European Heart Journal.

2025;46(17):1634-1644. doi:10.1093/eurheartj/ehaf037.

• Study design: randomized crossover study where each participant (n=28, 14 female) had both a tVNS and a sham tVNS, each 30 minutes daily for 7 days. Participants also provided blood samples and completed cardiopulmonary exercise testing: ECG was recorded (supine for 10 minutes, standing for 3 minutes). Approximately 10 minutes after, participants engaged in indoor rowing to exhaustion. 

• Results: tVNS increased peak VO2max by 3.8% compared to sham condition. The statistics they report are a little confusing - main effect p-values for tVNs and sham compared to baseline are reported, but no interaction p-value is reported, just the 3.8% number. No significant differences in heart rate measures (e.g. RR interval, minimum heart rate). Transcriptomics were done on blood samples, with modest results showing differentially expressed genes (largely downregulated) in pathways related primarily to inflammation.

2. Effects of a Single Session of Noninvasive Auricular Vagus Nerve Stimulation on Sports

Performance in Elite Athletes: An Open-Label Randomized Controlled Trial. Çalι A,

Özden AV, Ceylan İ. E. Expert Review of Medical Devices. 2024;21(3):231-237.

doi:10.1080/17434440.2023.2299300.

• Study design: randomized study (n=30 treatment group, n=30 control group) recieved single aVNS and a sham aVNS. Outcome measures included pre- and post-treatment isometric quadriceps muscle strength, heart rate, lower extremity balance, and grip strength were measured.

• Results: no significant difference of aVNS in any measure.

Note: tVNS = transcutaneous vagal nerve stimulation. aVNS = auricular vagal nerve stimulation. taVNS = transcutaneous auricular vagal nerve stimulation. These terms are used interchangeably. taVNS is non-invasive. Notably, it is different from VNS, which has historically been administered via a surgically implanted device.

One example of tVNS devices on the market and misleading marketing: 

1. Pusletto

   1. Pulsetto boasts being “science-backed,” and the site has a link on their page (https://pulsetto.tech/pages/science) where they list “Ongoing and Upcoming Studies” - none of which have results or manuscripts available, let alone being peer-reviewed. They also include figures from studies that they have funded that I can only find linked on their site and appear to have no authors, no associated DOI, and therefore likely certainly have not been peer-reviewed.

   2. They also have some studies linked on their website from journals - these citations are not found under the “science” tab.

Machetanz, K., Berelidze, L., Guggenberger, R., & Gharabaghi, A. (2021). Transcutaneous auricular vagus nerve stimulation and heart rate variability: Analysis of parameters and targets. Autonomic neuroscience : basic & clinical, 236, 102894. https://doi.org/10.1016/j.autneu.2021.102894

• The author’s aim in this paper is clearly to examine various taVNS stimulation procedures’ effects on HRV to decide 1) an optimal stimulation procedure and 2) whether HRV can be used as an appropriate outcome variable in taVNS studies. There was no sham condition, and a small subject size (n=6). Authors note that left vs. right ear produce different HRV results, and that HRV seems to be an appropriate outcome variable (suggesting that vagal nerve stimulation does effect the autonomic system). 

Mouli, Surej, et al. “Tragus based Vagus Nerve Stimulation for Stress Reduction.” Proceedings of the 14th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2021), vol. 4, 2021, pp. 164–168, https://doi.org/10.5220/0010222201640168. 

• Study design: randomized crossover study of tVNS vs. sham tVNS (n=5). The outcome measure was LF/HF ratio, a measure associated with HRV (compares low-frequency to high frequency)

• Results: 64.5% reduction in LF/HF from pre- to post- tVNS, compared to a 6.8% reduction from pre- to post- sham sessions. P-values not reported.

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