I have a long history of being sedentary, but I began exercising regularly at the start of the pandemic. I've worked really hard to achieve a decent level of cardio fitness, but now I'm in danger of some serious backsliding.

For various reasons that aren't relevant here, I can't really do swimming. What other options do I have?

I suppose I can switch to strength training, but I don't have any equipment, and I worry that it wouldn't be aerobic enough.

I also thought about buying an elliptical machine, but I've heard mixed reports about whether plantar fasciitis is exacerbated by elliptical training. Plus, those machines are expensive.

Any suggestions from people who are knowledgeable about fitness?