improving strength without added weight?

Question

how do you improve body strength without being bulky and heavier
kind of like, you look skinny on the outside but really you are really strong

Answer 1

Get a personal trainer to help you with this, there is a reason they've specialized. It is there job to be able to get you to do just this (other things as well). Basically you're going to do high reps with medium weight. You'll alternate this this with endurance building, high reps low weight. You'll need a split program to do it, I recommend super setting. This is the goal of many women and its rather easy to accomplish. Now if you don't have much fat mass now, you'll end up being heavier but smaller and looking better. If you do have a good amount of fat to loose 10-20 lbs, you'll likely stay around about the same weight (minus up to 5 - 10 lbs) but again, you will be smaller and better built. Just keep in mind, muscle weighs more than fat so a little good-looking amount of muscle will make you heavier then being a little flabby looking.

Your strength will improve about 6 fold if you can recruit all your motor neurons, (nerves that stimulate muscle) so that you use ALL your muscle. This is one of the reasons you can be strong but stay small. On average, less then 1/4 of the muscle is used at a time in people who don't exercise.

Answer 2

Higher numbers of repetitions and lower weight.
Mass is added thru lower reps (3-5) and higher weights.
Don't worry, it takes an awful lot of work to "bulk" up especially as you're female(an assumption from your name)
Stay at 10-14 reps of a weight that takes you to fatigue (meaning you can't do any more) start with 2 sets and work up to 3. repetitions=the number of times you do each move 12curls=12 reps
sets= the number of times you do each move 12 curls= 12 reps=1 set

Answer 3

You really can't. Muscle strength and muscle size are relative.