This one?
Fitness Has Fallen Since The Days Of Ancient Greece &
science in action: the trireme Olympias – purple motes
It is definitely interesting, but there are a number of variables to consider in my opinion. First of all, design efficiency (whether the boat in the test actually matches the peak of evolution of boats of that type), which is also mentioned in the articles, second the construction and use of the sails (I'd guess there is a lot of - potentially unharvested - potential there) and finally, the distance difference between modern rowing competitions and ancient "practical" rowing. Modern rowing basically is a short distance event. Comparing modern rowers to ancient rowers basically would be similar to taking 400 or 800 meter runners, testing them in an ultramarathon and then drawing conclusions on their fitness level. After all, "fitness" according to Darwin means selection for and adaptiation to a given demand, and that includes the duration of said demand. Selection definitely shouldn't be overlooked here - if you look at runners, someone with a perfect genetic makeup for sprinting usually won't be a champion ultramarathoner, and vice-versa. Adaptation further increases this gap. You would probably get a more reliable comparison by recruiting from the people who are into these 12, 24 or 48 hour rowing competitions.
Now, I do think that experimental archaeology could indeed benefit from recruiting more athletes for testing. Mr. Junkelmann mostly liked to recruit people with a background in full contact sports and combat sports for his gladiator games, since they already had a lot of the qualities he was looking for (including a good feel for distance, which is vital in fighting with weapons, especially the gladiator armaturae which usually operate without a "bind" of the weapons, unlike modern and historic fencing). However, all of this needs to be seen in context. For a competitive athlete today, everything he does outside of his sport is going to be a side hustle (guilty as charged - I won almost all my gladiator matches thanks to my athletic background in wrestling and boxing, not to the time I'd practiced with weapons). Therefore, he will tend to only improve to a certain extent, unlike somebody who has a life-threatening incentive to do so. In other words, you'd have to find a way to make it essential for the athlete to perform at his best in the given test. I'd argue that, legality aside, that is a lot easier to do for logistically simpler things depending on fewer outside variables, such as lifting weights, shooting a bow, running or jumping. The other thing to consider is the pool of potential - you will have a hard time these days to recruit the top potential for such a test, because most people have other things to do, and earn good money with it. Back in ancient Greece, basically the coolest thing you could strive for (if you lacked the high birth necessary for a political career) was winning the old Olympics, followed by a military career.