Training in a hypoxia chamber (experiences)

A friend of mine will try do to some training in a hypoxia chamber. Who here has tried this and what are you experiences? My gut feelings tells me this is a waste of money.

Any good articles or scientific papers are also welcome.

Thx!!

edit: The training will last 2hours/2times a week and the simulated height will be around 2700m

To give a bit more context: The training will last 2hours/2times a week and the simulated height will be around 2700m.

I know someone who actually bought (maybe leased) his own IHT (intermittent hypoxic training) machine and would sit with the mask on each night for a couple of hours. I can’t really say if that made him faster or not - he was already a fast rider - but it did make his wallet substantially lighter

Came across a lit review recently on hypoxic training that suggests 2hrs 2/week may be insufficient to elicit adaptations.

Sinex & Chapman, 2015. Hypoxic training methods for improving endurance exercise performance
https://www.sciencedirect.com/science/article/pii/S2095254615000836

Their conclusion:

Exposure to sufficiently high altitude (2000–3000 m) for more than 12 h/day, while training at lower altitudes, for a minimum of 21 days is recommended.

However a more recent study found beneficial effects in swimmers from 6 weeks of 3 days/week of 120min/day of what sounds like a mix of continuous and high intensity interval training.

Park et al, 2018. Efficacy of intermittent hypoxic training on hemodynamic function and exercise performance in competitive swimmers

So… your mileage may vary?