Hmm, depends if you want to train your body or your mind

As the years go by i have learned that you need the gym to play chess....

Gym. 

It brings you way more benefits than chess. 

Mens sana in corpore sano

https://en.wikipedia.org/wiki/Mens_sana_in_corpore_sano

I just did some Rook lifts. See those biceps babe?

It depends upon where you want to take a selfie, apparently.

This shouldn't be in off-topic

play chess while you work out

"Better" has different degrees. In choosing between these two, I prefer play chess because I rarely can find someone to play to (of course in real world) while I can always go gym by myself, although there is always the possibility of injury and damage! . In addition, there is no reason that anything or anyone that would win is better! 

Some quotes somehow related to the issue:

• " Chess is the gymnasium of the mind. " -- Pascal
• " Chess is mental torture. " -- KASPAROV
• " When in doubt -- play chess. " -- TEVIS
• " Life is too short for chess. " -- BYRON
• " The loser is always at fault. " -- PANOV
• 

True, it is easy to focus in other things while playing chess, but sadly it doesn't work the opposite way!

Some people think that chess is actually a sport LOL, so they would tell you "It makes no difference if you chose one or another". 

Brain and body belongs together as a one unit, when u gym the brain is more ready to think and the body is more relaxed!

 I might be choosing a lot of gym in the months too come. I need to lose some weight.

Gym.

One should train mind,body and spirit

I prefer Chess and then I also do Race walking in the mornings 5kl averige 

Who knows?