Lower back pain, hand numbness

Congrats on your new bike......your pain can definately be associated with improper fitting. Did you have your LBS fit you? However you should understand that if you are new to cycling your muscles/body are not use to this position and some soreness my happen. Hand numbness is very common. Make sure you use a good pair of padded gloves when riding.....I typically don't ride with gloves now - but they are very helpful when starting out. Keep your hands and arms relaxed and your elbows slightly bent. Change your hand postion around - top of bars to the drops - to aerobars (if you have them)....this will also help. Cycling is no different from say running - when your body starts to get fatigued you tend to sacrafice good body position which in turn can make you sore.

So I would have someone reputable check your fitting (small minor adjustments can make a huge difference in comfort).

Watch your body position and concentrate on keeping your muscles relaxed while riding.

Then ease into it....these muscles are doing something different and need time to adapt....

Good luck and enjoy the bike!!!