The soleus pushup When the SPU was tested, the whole-body effects on blood chemistry included a 52% improvement in the excursion of blood glucose (sugar) and 60% less insulin requirement over three hours after ingesting a glucose drink. https://medicalxpress.com/news/2022-09-muscle-glucose-fat-fuel-metabolism.html
Looks like a seated calf raise. Interestingly, I like to have my feet raised while working at my desk, so I use a very small footstool. Often during the course of the day, I push up from the stool on the balls of my feet, and so my knees push up against the desk. I've been inadvertently doing isometric soleus work the whole time. How cool is that!
When I first read the article posted, I thought it was a bit of a joke. But it seems to be getting some traction, including here: https://neurosciencenews.com/soleus-pushups-metabolism-21471/ The thing I don't get is, even if true, the exercise, without added resistance as shown in the video, seems far too easy for the purported benefits. So while I have no problem doing my under-the-desk isometric "soleus push ups," since I do that anyway throughout the day, and even throwing in a variation of a seated calf raise to failure at the end of my workouts, I'm not going to put too much stock into these findings just yet.