This article confirms what has already been well-established about age and fitness:
1. Starting a fitness routine is beneficial regardless of when we start. There is no upper age limit on the health benefits of exercise. Individuals who start moderate exercise at 90 still gain muscle mass and the benefits of improved fitness.
2. Consistent moderate exercise is sufficient to build and maintain fitness. The extreme routines of elite athletes are not necessary.
3. Brief bursts of intense exercise provide additional benefits when added to moderate / easy exercise of longer duration.
4. Any amount of regular exercise is better than none; adding more increases health benefits and then plateaus. Adding more above this level yields decreasing benefits.
https://charleshughsmith.substack.com/p/what-can-we-learn-from-the-93-year