Seems like either finger tip or ear lobe can work out, just that maybe the lab prefer the ear lobe method
He is currently at 88%, while the pros are at 93%.
Metabolic/mechanical efficiency seems to matter a lot after watching the video. Could be attributed to running economy. Found this comment on running economy:
"Runner A and runner B have the exact identical VO2Max. We have them both run on a treadmill for 3 minutes at 5:00 pace. Runner A scored a Vo2 5 points lower than Runner B. Runner A therefore has a better running economy.
A lot can go into running economy. Form. Neuromuscular changes. Contractile properties of the working muscles. More miles over a lifetime improve running economy....ie: perfecting the "skill". Hills and sprints improve running economy....improving the mechanics. Strength training improves running economy....improving contractile properties. Also, running economy is very specific to the speed (neuromuscular coordination). Example: One of the reasons Runner A in the above example has better economy could be that he does a lot of interval training at 5:00 pace (pace used for the above example test) compared to Runner B."