Well, for biking you could do what you said. If you can lift, ( i don't remember if you said you could ) you can do leg press with low weights, leg extensions w/ low weights, and basically all legs things. (just don't over do it) Now here is an important thing, when you lift, do all of your sets, than lower the weight by one third. Do all of it over again. Than a third of the third. This is called exhaustion. It will help with endurance alot. For your arms, will not need so much attention, you sit flat on the floor and swing your arms like you would while running. Than add some weights, like 2.5 or even 5 lbs if your feeling saucy. This will help your arm drive.
Now if you can't do lifting what you can do is (which you already know is) biking. If you can, ride outside. Some things to try are mile repeats or longer, but not longer than 2.5 miles. Fartleks are good too, usually 35 to 45 minutes will suffice or longer if you feel up to it (sorry if this is too much, i usually write these for guys). If you are riding outside, you can do accelerations. Which is biking at a moderate fast pace. I hope that this helps.
(btw, don't worry about grammar. alot of the people who i hangout with now don't do use it either)
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