The internet is jam-packed with sources of "news." Most of these sources don't produce news themselves; rather they re-post articles, press releases, etc. And so it came to pass that a post I saw this week referenced a press release from March that prompted this post. End backstory.
The post from March (which showed up in lots of places...see previous paragraph) looked like this one: http://www.sciencenewsline.com/news/2017030718000015.html . It's about a study that showed exercise--especially High Intensity Interval Training (HIIT)--"...caused cells to make more proteins for their energy-producing mitochondria and their protein-building ribosomes, effectively stopping aging at the cellular level."
It's easy to see why so many outlets picked it up--it's anti-aging!--but the part that prompted this post had nothing to do with the veracity of the claims. Rather, it was this bit: "...exercise--and in particular high-intensity interval training in aerobic exercises such as biking and walking--caused cells..." (Emphasis mine.)
(For those who don't know, HIIT involves short bursts--usually 20-30 seconds--of demanding activity interspersed with short rest periods. Read more here.)
The study said nothing about "aerobic exercises" and most certainly did not reference walking. The HIIT modality for the study was cycling on an exercise bike, as it almost always is on such studies (going way back to the seminal Tabata et al study) because it's well-controlled.
Let's start with the "aerobic" part. Whoever wrote the press release no doubt considers cycling to be an aerobic exercise and thus inserted the "aerobic" claim even though it didn't appear in the study. While long duration cycling is aerobic, HIIT--by definition--is anaerobic. That is, it's not so much about what you're doing as how you're doing it. If your muscles can't get enough oxygen to keep up with demands, it turns to other energy sources (which don't last long) to do work without oxygen ("anaerobic"). HIIT requires an intensity level that can only be sustained for short periods of time; hence anaerobic.
The "walking" reference was a direct result of the inaccurate assumption about aerobic activity. Yes, walking is an aerobic activity. Indeed, it's really hard to make it anaerobic unless you're extremely unfit in which case you shouldn't be thinking about doing HIIT anyway. But the study didn't use walking for HIIT or suggest that it could or should be used as a substitute for cycling in trying to replicate study results. (It was used for some additional exercise for the HIIT group but that's not the same as saying "...high-intensity interval training in aerobic exercises such as biking and walking...")
One caveat is that the study used cycling work intervals of four minutes, which strains the definition of HIIT because it's impossible to maintain anaerobic activity for that long...you body would simply run out of fuel. Thus you'd have to either pace yourself (reduce intensity) throughout or drop off substantially after 30-120 seconds (depending on intensity level) to allow aerobic recovery. I have no idea why they chose four minute work periods. Regardless, the observations above still apply.
This has been just one example but it's a common problem so keep an eye out!
Be seeing you.
-gary