In the latest Ask a Cycling coach podcast the hosts discussed at some length the prospect of doing key sessions with supplemental oxygen to increase work capacity. Coach Jonathan (@Jonathan) seemed particularly excited by this, and concerned about potential muscular-skeletal damage from increased work capacity. Sorry to be the bearer of bad news, but I’m not sure this would help at sea level. Below is a theoretical arguement based on physiology, rather than a data based study, so feel free to prove me wrong with some solid data (@chad !)!
Haemoglobin (Hb) binds four oxygen molecules. The binding of one oxygen molecule increases Hb’s ability to bind further oxygen molecules, and so you end up with a sigmoidal oxygen (dis) association curve - see the curve here.
Supplemental oxygen shifts our position on the Hb-Oxygen association curve to the right by increasing partial pressure of Oxygen (ppO2). At low ppO2 (at elevation) this would increase the amount of oxygen in the blood. However, once all the Hb molecules are saturated with oxygen the blood stops being able to carry any more oxygen. At sea level the blood is already saturated with Oxygen (as explained in the podcast) and so any supplementary oxygen will not increase the amount of oxygen in the blood.
This would also explain why the studies that Chad cited used such high levels of supplemental oxygen - theoretically you would expect no change by getting the oxygen levels too high, but you would by getting the oxygen levels too low.
The one caveat with this argument is that some (very little) oxygen is dissolved in the blood plasma, and comes out of solution at the lower ppO2 found at the working muscles. This would continue to go up with increased lung ppO2, thus delivering slightly more oxygen to the muscles. However, this effect is pretty tiny compared to how much oxygen haemoglobin can deliver.
I hope this makes sense and clarifies things! Great podcast and product as always.