I use a TENS unit with an almost identical setup to the paper (ear clip is the same, duration is the same, frequency is 30hz instead of 25hz).

My use of vagus stimulation is for managing anxiety and promoting digestion / gut motility. I have neck issues that probably impinge on this nerve, contributing to these symptoms. Evidence suggests that the effect isn't purely psychosomatic; when laying on my back with TENS, I observe an increased frequency of GI tract "gurgles" relative to off. The observable product of my GI tract has also normalized somewhat.

This paper is relevant to Long Covid, where many patients have reduced parasympathetic function and suffer post-exertional malaise (PEM). The fact that vagus nerve stimulation improves VO2Max in healthy volunteers is a nice proof of concept for a treatment that could then be tried in sicker populations.

You can stimulate your vagus nerve simply by breathing out slowly while under moderate exertion. The sensation can be very unpleasant, but it also tends to take you slightly out-of-body for a while which can help with pushing through difficult tasks.

28 sample size. And sham reduced capacity by half as much as the real thing increased it? Anyone got any comment on tbe conclusion as I am sceptical but can be persuaded maybe.

So they stimulate the Vagus nerve, exercise them to exhaustion and measure vo2 peak during the exercise. Done for 7 days.

Would be interesting to see the effect on athletes, you would expect no effect on them, but if there's any benefit people will try it to get any performance gain.