Hmm, that is a tricky question. The correlation between VO2 max and increased muscle mass is not crystal clear. However, the VO2 max is influenced by the total active muscle mass that is recruited during physical activity or exercise. Therefore, I would argue that muscle mass is the most important factor to reduce all-cause mortality.

muscle mass

Both are very important, but I choose VO2max because it reflects the organism' ability to collect (respiratory system), transport (circulatory system), and utilize oxygen (muscle system) (and the synergism among these three abilities) to maintain movement at relative high intensities.

Juliano Boufleur Farinha what a good response!!!!