I personally find the bike pretty useless. The treadmill, though it is more high-impact, will get you in shape much faster. Another idea is the elliptical, which is less-impact than a treadmill, but still better than the bike.
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your: your book | you're: you are ||| its: possessive! | it's: it is
their: their book | they're: they are | there: over there
to: going to the store | too: too much | two: 2!
lose: opposite of win | loose: your mom |