'hard' does a lot of work in that sentence. Try running up a few flight of stairs if you're sedentary compared to when you're in reasonable shape or try to take a fall if you're skinny compared with some more muscles on your skeleton, or just sitting in your chair for eight hours for that matter.
This is basically 'torture the data long enough until it tells you what you want' to finding an excuse to not hit the gym. Some studies on elderly people with vague exercise programs with probably no change in physique tells you nothing about middle-aged adults.
The specific question is if elderly people starting exercise late in life received similar levels of benefits. They then look at studies lasting between 1.4 and 5 years where the median participant age was between 72 and 78. The exercise group did have lower mortality but it wasn’t considered statistically significant.
Unless you’re 70+ and only planning on exercising for a few years they don’t say much about what you should be doing. Especially as by this age a significant percentage of the most sedentary people have already died.
Most observational studies simply report spurious correlations, and cannot be trusted --- especially when "reverse causality" is a strong possibility. That is people who are healthier and fitter tend to exercise more, therefore they experience less disease, death etc.
Only by taking sedentary individuals, and coaching them to exercise significantly more, and comparing with a control group, you can be sure of the causal benefits.
I've always known that paleontology and astronomy are real sciences, but had no idea it was possible to do intervention studies in those fields!
Meshes with other studies I’ve read, like that people who were fitter in middle age have lower risk of alzheimers - so if you did an RCT of getting elderly people to do more exercise you’re not going to see much effect, since you’re not getting the years of cumulative protection from whatever it is that causes it and much of the damage is already done.
Exercise did not reduce all-cause mortality and incident CVD in older adults or in people with chronic conditions, based on RCTs comprising ∼50,000 participants
https://scholar.google.com/scholar?cluster=10512580439138189...
The average sedentary HN reader, take comfort! Being a gym rat is good for you. Forcing yourself to become a gym rat from being sedentary has unclear benefits regarding hard outcomes.