Primary exertional headache is the term used to describe a headache that is precipitated by exercise. The pain is typically felt both sides of the skull and is throbbing at onset. This headache can last anywhere between 5 min and 24 h. The exact mechanism is unclear but acute venous distention likely explains the headache caused by lifting high loads whilst breath holding (e.g doing a PB with your barbell back squat).
If you suffer from constant headaches it is advisable to visit your GP to ensure there is no underlying pathology. Should a diagnosis of Primary exertional headache be confirmed this can generally be managed by your personal trainer easing you into the high intensity aspects of your sessions and by taking Indomethacin 30-45 minutes before your exercise session. Confirm with your GP that this medication is appropriate for your circumstances and advise your trainer whenever you are commencing a new drug therapy as exercise can potentially effect drug concentrations in the body