I can sling lobster traps 1000's of pounds and no headache.
But if I am cutting up meat or veggies on the kitchen counter, if I look and angle my head naturally looking at what I am doing, no headache, but if I let my head drop all the way down until my chin is almost to my chest and be looking upward, In two to three minutes of doing that I get a massive headache.
No stress or straining... just the position.