There is a way of achieving muscle fatigue if all you have are a pair of light dumbbells kicking around in your spare room. As long as you stick to some guidelines you will be able to feel the burn with all your workouts.

Here are the rules:
#1 Perform high repetitions
#2 Use a short rest between each set

If you have a pair of adjustable dumbbells, ones where you are able to make one heavy dumbbell from the two opt for single limb exercises to achieve more intensity if possible.

Example exercises using dumbbells:

Legs
Squats, progress to split squat or lunges. Advanced option is to squat, curl and overhead press or squat holding the dumbbells overhead.

Chest
Dumbbell Chest fly – with back on the floor.
Press ups – no weights required.

Back
Bent over rowing holding the body in static bent over position and bringing the dumbbells to the side of the chest.
Upright rowing – row the dumbbells as high as the collarbone.

Shoulders
Side raises followed by overhead pressing.
Bent over side raise.

Biceps
Curls and hammer curls.

Triceps
Triceps extension – with back on the floor.
Close grip press ups. No weights required.

Abs
Seated reverse wood chops.
Abdominal crunches holding the dumbbells with straight arms directly above the chest.

Repetition range
Don’t be afraid to try anything up to 50 repetitions per exercise. Just because you are lifting light dumbbells doesn’t mean you can rush the set. Never sacrifice proper training technique no matter what the circumstances are. A strict training technique makes the targeted muscle group work harder and brings quicker results.

Recommended sets and rest
If you choose to work on one exercise at a time and you are doing over 15 repetitions because of the light dumbbells it is recommended to rest no more than 60 seconds before you repeat the set. Depending on how difficult the next sets are will determine if you can afford to shave seconds from your rest time in between sets.

For best results at least 2-3 sets per exercises is required to create a training response.

An example legs, chest and abs workout using light dumbbells:

50 bodyweight squats.
No rest and immediately followed by:
25 dumbbell squats.
Up to 60 seconds rest and repeat until 2-4 rounds are completed.

25-50 Chest flies.
No rest and immediately followed by:
Press-ups to failure.
Up to 60 seconds rest and repeat until 2-4 rounds are completed.

Seated reverse wood chops – up to 30 each side.
No rest and immediately followed by:
Up to 30 abdominal crunches holding the dumbbells with straight arms directly above the chest.
Up to 60 seconds rest and repeat until 2-4 rounds are completed.