Oh you only lift 5lb weights? Go on about how big your bag is!

I think that line would be a great sarcastic Wonka meme! Don't you?

It seems to me that the myth that women shouldn't lift heavy weights because they will get bulky is still prevalent.  Not a day goes by that I see women just using 3lb or 5 lb weights.  Or maybe an occasional 8lber thrown in there.  Now its bad enough that I see this, but what makes it even worse is that I will see a woman go from bent over rows on the bench right into tricep kick backs(if you can even call them that) with the same 3-5lb weight.  Sorry, but if you think that is going to make your arms toned, then you might as well do 100 of them( which oddly enough, a certain celebrity trainer prescribes).

Lifting heavy weight has numerous benefits, of which include building muscle, bone density, and strength.  But wait, " don't want to build muscle" you say.  You don't want to look "bulky."  Good news, you're in luck, lifting heavy weights wont make you bulky unless you are training that way.  It takes training to get bigger and eating to get bigger.  Oh and there's that little thing called testosterone, that as a woman you don't have enough of to warrant that kind of muscle growth.  But you keep doing
your light weights and your endless cardio.  Hows that working out for your fat loss?

Oh yea one more benefit of building muscle: increased metabolism. 

Benefit #2 of lifting heavy is an increase in bone density.  This happens because as the muscle gets stronger, it pulls harder on the bone it is connected to, and the bone cells need to react and produce more bone cells to support to added strength in that particular muscle.  Most women do not lift heavy enough to warrant such a response in those cells.  Most likely because of the #1 excuse of not wanting to get bulky. 

Lastly, getting stronger is super important, because why not be stronger.  Why would you want to be weaker?  Think of how many things you pick up in a day.  Wouldn't it be amazing if it didn't strain you so much to pick something off the ground, or carry out the trash, or pick up your child/grandchild/dog/whatever.  I woulds say yes.  I had a client that was so proud of how strong she became because she was able to lift a big pack of water bottles, and another that picked up her 70lb dog and was amazed that she was able to.  That's why you train heavy, that's why you strength train. 
Well that, and the stronger you are, the more stable your joints, the more balanced you are.  And when you get older, balance gets a little tricky and wouldn't it be nice to say that your strong enough that if you stumble, you'll have the strength to not fall and go boom?
I know many who have had near misses and if it wasn't for training heavy, they probably would have gone down. 

So please do yourself a favor and lift a little heavier than you are used to.  I promise the benefits will be worth it.