Ability to lift weights quickly can mean a longer life

(2) The summary of the study says that muscle power quartile is correlated with six-year mortality for the members of the study. But it doesn't say whether muscle power is any better than other measures like muscle strength. I.e., muscle power isn't necessarily a better predictor; it's just another predictor.

Reading the study rather than the summary might be more helpful.

This seems like a hasty conclusion to me. The researchers found a correlation between muscle power and low mortality rates, not a causation. It could be, for example, that people with generally low health levels have lower muscle power and also higher mortality rates. The study does not provide evidence that people who improve their muscle power live longer, merely that people who already have high muscle power will live longer.

Fast contraction runs counter to old-school weight training advice. Interesting.