zone 2 training, thoughts on which exercise

I've considered stationary bike, rowing machine, walk/run treadmill or outside (maybe even barefoot.) Any advantage to the "whole body" aspect of rowing vs the leg predominant other choices? I also assume you'll be covering heuristics short of full on lactate measurements, I'm 66, MD PhD, interested in longevity/vigor/healthspan and not particularly in competing.

How should I make decisions about an action or intervention in the absence of data from a rigorous, randomized controlled trial?

What is Peter's framework for how he thinks about various interventions one can do?

Can you explain the various cancer screening terms: sensitivity, specificity, false positives, false negatives, and positive and negative predictive values?

What is a diffusion-weighted MRI?