The science
Your muscles adapt to training. Your nervous system decides how fast you recover from it. Glint uses gentle vagus nerve stimulation at the ear to switch on your body's rest-and-repair mode, built on decades of research
01 · The problem
Serious runners dial in sleep, fuel and mileage. Recovery still stalls, and the cause often sits outside the training plan
A work deadline, a short night or a rough week at home hits the same stress system as a hard interval session. Your brain reads all of it as load and keeps the body in fight-or-flight
How stress loads the nervous system
Simplified
1 · Stressors
It all adds up as load
2 · Brain appraisal
The brain reads it as a threat
3 · Autonomic shift
Adrenaline and cortisol rise
4 · What runners see
Your watch flags it
Where Glint acts
Glint stimulates the vagus nerve at the ear to activate the parasympathetic side, so your body shifts back into rest-and-digest sooner
People under higher life stress recovered muscle strength and energy more slowly over the four days after a hard leg workout1
02 · The recovery engine
Your autonomic nervous system has two sides. The sympathetic side drives effort. The parasympathetic side drives repair. Recovery starts when the parasympathetic side takes back control
Illustrative values
When HRV climbs back after a session, your body has switched into repair mode
Fitter athletes reset faster
Stanley, Peake & Buchheit, Sports Medicine, 20132
Recovery is a skill you can build
This system responds to training. Across 58 studies, training it with HRV biofeedback showed its largest effects on athletic performance, anxiety and mood3
04 · How Glint works
Plays on its own. Tap a step to pause on it
05 · The evidence
Ear-based vagus nerve stimulation has been tested in controlled human trials across fitness, recovery, stress and sleep. Here's what matters for a runner
Fitness · the hero study
+1.04
mL/kg/min VO2peak after one week of ear stimulation, about 4%
Peak power rose 6 W too, and stimulation calmed the blood's inflammatory response. VO2peak is the ceiling on your aerobic engine
Ackland et al. · European Heart Journal · 20259
Post-run recovery
3.5×
Lactate cleared faster after a treadmill session
60 young adults · 20 minutes right after exercise. A 2026 systematic review also reports lower perceived fatigue, post-exercise pain and perceived effort
Ertürk & Mutuş · Scientific Reports · 202610 · Saldanha et al. · 202611
Sleep
+4.2 pts
Better sleep quality than sham, held for 20 weeks
Sleep is when your body does most of its repair. A 2026 meta-analysis of 13 randomized trials (690 people) confirms better sleep quality and fewer insomnia symptoms
Zhang et al. · JAMA Network Open · 202412 · Choi et al. · 202613
Stress balance
HRV ↑
Stress output drops, measured right at the nerve
Life stress keeps the fight-or-flight side switched on. Ear stimulation raised HRV and cut sympathetic nerve activity, shifting the body toward parasympathetic control
Clancy et al. · Brain Stimulation · 20148
Inflammation
FDA 2025
The vagus is the body's built-in brake on inflammation
The vagus nerve controls inflammation in real time, the same way it controls heart rate.14 In 2025 the FDA approved an implanted vagus nerve stimulator for rheumatoid arthritis on the strength of a randomized, double-blind trial.15 Hard training triggers inflammation too
06 · Watch
Four talks worth your time, from a neuroscientist, an exercise physiologist, the surgeon who discovered the inflammatory reflex and a sleep scientist
Start here · 2025
Andrew Huberman, neuroscientist at Stanford
A clear tour of how the vagus nerve carries signals between body and brain, and how it shapes calm, heart rate variability and alertness
Jump to
Recovery · 2023
Andy Galpin, exercise physiologist
How recovery works for athletes: overreaching vs overtraining, breathwork to flip into recovery, and tracking stress with HRV
Inflammation · 2016
Kevin Tracey, neurosurgeon and immunologist
The origin story of bioelectronic medicine, from the scientist who found that the vagus nerve controls inflammation
Sleep · 2019
Matthew Walker, sleep scientist at UC Berkeley
Why sleep is the foundation of recovery, and what short nights do to your brain and body
08 · Safety
No needles, no implants, no drugs. Ear-based vagus nerve stimulation is one of the most studied forms of neuromodulation
177
studies reviewed
6,322
participants
No higher
side-effect risk than control
Reported side effects were mild and short-lived, mostly ear discomfort, headache and tingling. No serious adverse event was linked to stimulation19
If you have an implanted device such as a pacemaker, a heart condition or epilepsy, or are pregnant, check with your doctor first
09 · Our research
The studies above ran in labs and clinics. We're taking the research to runners
We'll share what we learn
References
