I do exercise regularly: swim nonstop 30-40 minutes at least 3 days per week, and walk (briskly) 45 minutes 3-4 days per week, plus a smattering of yoga type stuff.
Apologies -- I got you mixed up with someone else.
My issue is keeping muscle (or even fat) on my body....I have a tendency to slip below 100lbs very easily. Swimming and walking sure don't build muscle needed for things like burpees, which is part of my purpose in doing them. I also have chronic pain issues, and tend to get derailed easily from weight bearing exercises, so I'm hoping this kind of challenge will boost me to actually be strong enough to work with weights, and finally keep some weight and muscle on.
That's a tough one! Is it possible that your 225-300+ minutes of cardio-based exercise per week might be working against your desire to gain weight?
If your primary goal is weight gain, and you don't have an underlying disease, metabolic disorder, or eating disorder, it's possible that you would have better luck cutting back on some of your swimming/walking. It's hard for me to say that, because I believe exercise is one of the best ways known to improve current and longterm health (and longevity). On the other hand, reduced lean body mass (especially on the lower end of BMI) is also strongly correlated with all cause mortality.
IMO burpees are more about endurance than strength. Have you considered basic bodyweight exercises like pushups, pullups, etc.? If you lack the strength initially you can work up to them (incline pushups, pull-ups with bands). Maybe it's worth thinking about a beginning strength training program + dietary assistance to make sure you're getting enough calories to put on weight?
Yeah, I'm just bitching about stuff that isn't easy to fix. I have had all the low-hanging medical stuff tested for. I do have several diagnosed disorders (autoimmune, endocrine, etc.) that have not been id'd as specifically responsible for being underweight, but who knows? My digestion is glacially slow and it makes eating enough calories challenging, which is annoying b/c I love food. I am already pretty careful not to do any high-aerobic-intensity stuff, like interval training, or I drop weight frighteningly (even if could eat a lot, which I used to be able to do). But I can't give up swimming b/c i LOVE IT, and it controls a chronic pain condition. Plus, I'm just built to be a wiry person. But my eventual goal is, indeed, to do enough body-weight work to eventually work up to weight work/build muscle mass.
So, I just finished my 7 burpees for today. I thought my core was pretty good, but I'm even feeling these there a little bit....
Btw, my much stronger, more athletic and muscular husband decided he would start doing burpees with us so he's sorta in on the 'challenge' now, as well. He did 2 sets of 10 today. He's planning to stick with 20 total per day for the first 2 weeks, and then step up.