Like many WTF riders - I don't have a lot of upper arm strength. No matter how much I pump iron (which isn't often... if at all) - my arms are just never going to be super buff. And sometimes it can be an issue when you need to remove a dirty bottom bracket, or loosen a quick release skewer that you put on just a little too tight. But creativity and leverage are the key to these problems! Even if you aren't very strong, using leverage can help you loosen or open something that would have been difficult to loosen otherwise.
For example - the other day I was helping my brother pack up his bike, and we needed to take off his front wheel - we both had injured hands at the time and couldn't use all our strength. So instead I took off the seat/seat tube of the bike, put the seat tube over the quick release skewer, and then pushed down on the seat - and no problem the skewer was opened!
For most parts of the bike, extending the length of the tool you are pushing or pulling on will help give you more leverage. If you are using an adjustable wrench to loosen something, but its just too tight, slide a pole over the handle of the wrench to extend its length and then push down on the end of the pole. Most times using these tricks make it a lot easier!