What will happen if i weightlift using a bar with has 8kgs on one side and nothing on the other side of the bar? Will it affect my body? If it affects, what will be the impacts?
Ordinarily you would want the bar to be balanced, but "unbalanced loading" is a recognized type of "specialty" or "exotic" training that you can mix into a routine at times. The NSCA believe that the technique can be useful for training athletes who "place varying loads on their bodies in multiple planes of movement."
It depends on the exercise but I wouldn't recommend it.
First of all you can develop muscular imbalances. Second thing, you could actually injury yourself due to uneven load on passive structures ( ligaments and joints ).
The only case in which you can use different loads is in isolated circumstances due to a recover from an injury. For exemple you are using a leg extensor machine first with one leg and then with the other leg that is actually recovering from an injury or vice versa.
Loading the barbell with highly uneven load in some cases will cause you majour balance issues and make impossibile to perform the exercise.
An asymmetrical load on a rigid barbell will move the center of mass to the end with the greatest load. Such asymmetrical loading is generally considered unsafe and inefficient, especially involving the spine.
You always want an even distribution of the load. If you have muscle imbalances, you should in most cases continue to do regular exercises with an appropriate load and perfect execution.
The idea of weightlifting is to have balanced range of motion, and have equal distribution of the load. When you alter the balance, your body has to do extra work on any particular side to work through the imbalance. It's unsafe and could lead to injury.
If you feel like any side of your body is weak, you need to work on both sides to get stronger. If left arm is weaker, do isolation exercises and you may add more reps, but curling with a barbel with more load on the left is not going to help.
Ignore the negative comments here. This is a great tool for pushing past plateaus! But I think you might be going far too extreme. Unbalanced loads should only be slightly unbalanced. EG: 20kg on one side, 19kg on the other. Obviously, be sure to switch sides to ensure both are worked evenly.
The great thing here is mentally focusing on the lighter side of the lift trying to ignore the fact that the other is slightly heavier. (Mind over matter).
As for 8kg on one side and none on the other? Sounds like an injury waiting to happen.