If I do exercises with dumbbells each day, will that be sufficient to build strength and tone muscle? I don't care to large biceps, I am just after some strength and definition.
While doing other exercises would probably be better, would using dumbbells alone be sufficient?
Yes.
To build strength, you need to progressively overload your muscles during a workout. Overloading the muscles causes muscle growth. If you start out with 20lb dumbbells and progress to 40lb dumbbells over a month or so; it means you got stronger.
It doesn't matter whether you use dumbbells, barbells, or weight training machines. If you're progressively increasing the resistance, you're getting stronger.
Dumbbell training is deceptively harder in many respects than barbell training. You can go a long way with just dumbbells, and you can get monstrously strong with them. The key is about programming (structuring your routine) to allow you to go heavy and increase weights regularly. However, you should use a variety of tools to help you in your efforts.
In the long run, you'll probably want to include all three in your training. For now, you can get started with dumbbells or barbells and make great strides.
The nice thing about dumbbells is that you can add them to many bodyweight exercises easily. Many body builders use dumbbells to help ensure that their routine/results are symmetric, each side of the body needs to lift the same amount - where barbells allow a person to 'cheat' and shift some of the load to one side of the body. If you put a good routine together, hitting each part of the body you should see good results from a dumbbell program in about 3 months (depending on your current state and intensity you go with).
Strictly speaking, yes. The biggest problem I see with strength gains with dumbbells though is at the top end. I've never seen any in person over 90lbs. 2x90lbs is fine for doing presses, but for deadlifts you'll probably hit that pretty quickly. If your heaviest dumbbells are 50lbs, you'll likely be starting out at the max weight and you'll be more training endurance as 5-10 reps at 100lbs is really nothing.
Of course if you're aiming to do 25 reps fairly quickly, then dumbbells would provide the necessary resistance for quite a while longer, but for maximal strength gains you'll grow out of them quite quickly.
I lift dumbbells every day and I am huge I start with the heaviest weight i can do 25 reps or so then I reduce the weight ;) It's very affective
