>>76285907 (OP)
Walking specifically has a strong correlation with a reduction in all-cause mortality rates:
https://www.strongerbyscience.com/research-spotlight-walking/
It also has direct benefits in multiple categories: a 2015 meta-analysis found that group-based walking interventions, all lasting one year or less, led to significant decreases in systolic blood pressure, diastolic blood pressure, resting heart rate, body fat percentage, body mass index, total cholesterol, and depression scores, while increasing VO2max, 6-minute walk distance, and score on the SF-36 physical functioning inventory. (from article I linked)
It is likely that these benefits are seen in other forms of cardio, but walking provides them in an easy, low-impact, sustainable form. I think a combination of resistance training + a minimum of 30 minutes of walking a day (preferably aiming for a minimum of 10,000 steps a day) is one of the best combinations of physical activity for health, quality of life, and longevity. If not walking, some form of LISS cardio that's low impact.
It is likely heart rate zones are somewhat of a meme in use as a health indicator, as indicated by the multiple studies we have on walking specifically and the fact that these benefits are seen in populations that are getting in lots of steps but aren't likely hitting higher than zone 1. I am guessing we'll see more studies/data in the coming years indicating movement is more important overall as a metric for health benefits vs heart rate zones.
