Why do we use dumbbells like in todays Workout?
Dumbbells fit into our general-physical-preparedness (GPP) program because they force unilateral work. Many people have strength or mobility imbalances from one side of the body to the other, and working with dumbbells is a great way to iron out these differences.
The humble dumbbell can expose many of these huge differences in strength from one side of the body to the other, these imbalances are going to affect performance and isn't beneficial for good health.
Stability is vital.
Dumbbells require greater stability so your core has to work to stabilise more especially when going overhead. They also require greater motor complexity and motor recruitment. Dumbbells force you to refine your movement because controlling two objects is harder than one, so the nervous system has to work harder. This also means your coordination gets taxed more. This can still be the case even when using a single dumbbell.
They are a great diagnostic and/or tool for people who have had injuries or lack mobility. Often it can be easy substitute to a barbell and you can build some capacity with them for less experienced athletes.
Dumbbells are available nearly everywhere and can be used in lots of different ways. Most Hotel gyms have them if you are on holiday, they're easy to have at home and take up little room. You just have to get creative with them if you design your workouts.