Take a comic book, such as that of Phantom etc. Then take a drawing book and a drawing pencil. Observe one scene in the comics and then draw the scene or figure in the drawing book.
After that observe carefully another figure in the comics and then remove it from your sight and draw the figure in the drawing book from your memory. After this is done, look at the original picture and find out where you have made mistakes.
To compare the strength of the muscles of your hand, knees and elbows, take a bathroom scale and press it between your hands, knees and elbow one by one and ask an adult to note the reading.
This will tell you which muscles are stronger and which ones are weak.