What challenges did Michelangelo face when he was painting the ceiling of the Sistine chapel

He suffered unspeakably in that chapel. There were about eleven thousand square feet to paint and he was not a painter but had to obey an order given by the Pope.

He sat on the wooden plank of the scaffolding up in the air with his legs dangling and worked looking up. All the time he rubbed his neck, it ached so. For fun he drew a little caricature of himself painting a saint on the ceiling, his head bent back as far as it would go.