Numbness in fingers and hands ...
Most new riders suffer from this ...it is usually caused by something called "Chronic Exertional Compartment Syndrome of the Forearm" ... or more commonly "arm pump".
It is annoying and can ruin a days riding and is caused by squeezing the bars too tightly causing blood to pool in the forearms, which in turn causes muscles to harden, cutting off blood supply from the wrist to the hands and fingers. Seasoned riders tend not to suffer from this as much.
The good news however is that once you take a break from riding the numbness and tingling go away... usually withing seconds or minutes.
There are a few things that can relieve arm pump :-
1. Relax .... Loosen your grip on the bars.
2. Use your legs to grip the bike and give your arms a rest. ( this doesn't mean letting go of the handlebars )
3. Frequent riding.
If doing these things does not help fix the problem of arm pump then see a doctor.
Neck pain ....
I have found that the thing that gives me neck pain is:-
1. The force of the wind against the helmet on freeway runs. This causes me to force my head forward to counteract the wind.... result, muscles in the back of the neck becoming fatigued. The only answer I have for this is to take regular breaks and do neck excersises to help strengthen the neck.
2. Neck and shoulder pain sometimes caused by a forward riding position while arms are straight. This is a simple but bad habit to slip into on freeway riding where the rider takes the weight of the upper body on the arms. When riding on freeways remember to keep your arms slightly bent.
3. My neck maybe out and I need to take a trip to the chiro. Before I go on a long touring ride these days and my neck is playing up I tend to make a visit to the chiropractor to get things sorted out. It only means for the slightest thing to be wrong and just a nerve or two playing up that can result in a miserable days ride.
Lower back pain ...
Lots of people suffer from lower back pain at sometime during their lives. I personally have found that staying flexible tends to be the answer. The old saying of "Move it or Lose it" tends to apply here.
On a bike we tend to be hunched over a lot and I have found that there are a few excercises that can really help a lot. You don't need to go to the Gym although I find it helps for motivational reasons and if you need help then there are people there to assist.
Some of my favourite excercises:-
Stretch the hamstrings
Stretch the lower back
Incline Bench Press
Walking on the treadmill