A little food for thought.
If there were giants in the earth in Genesis 6 and the flood came and killed every air breathing creature on the face of the earth except for the animals in the ark and the 8 souls of the family of Noah. Where did the Giants come from in the book of Joshua if Giants in Genesis 6 all died in the flood???
It could be one of Noah's sons wives had that DNA in her and we know that after the flood it speaks of all 3 sons and their genealogy that were different ethnic groups.
Gen 10:2 The sons of Japheth; Gomer, and Magog, and Madai, and Javan, and Tubal, and Meshech, and Tiras.
Gen 10:6 And the sons of Ham; Cush, and Mizraim, and Phut, and Canaan.
Gen 10:21 Unto Shem also, the father of all the children of Eber, the brother of Japheth the elder, even to him were children born.
Gen 10:22 The children of Shem; Elam, and Asshur, and Arphaxad, and Lud, and Aram.
All 3 sons all had children that covered different ethnic groups.
But if all came from Adam and Eve then where did the different ethnic groups come from unless they were all in Adam and Eve.
Unless at the tower of Babel where God confounded their language and gave them different languages He also changed their DNA to produce the different ethnic groups so they would not come together as one to try to do their own thing going against the operation of God on earth hindering it.
Goliath was 6 cubits which a cubit is 1.5 feet so he was 9 feet tall.
The tallest person recorded which they say is irrefutable is Robert Wadlow at 8 feet 11.1 inches.
Which the 10 tallest people are all over 8 feet.
But it would seem like the giants back then would be healthier and like a normal person at their height and normal body function than the things that cause people to be tall today.