During the holy month of Ramadan, Muslims across the world observe a fast.
They abstain from all food and drink - including water - for 30 days and nights, from sunrise to sunset.
It is one of the five pillars of Islam, and is intended to be a time for reflection and prayer.
The end of Ramadan is marked by Eid al-Fitr, also known as the festival of breaking the fast.
Throughout Ramadan, many Muslims continue to work - including Sergeant Yesef Nagdi, a Leicestershire Police officer.
Mariam Kacime is a personal trainer.
This is her advise for those who want to safely exercise during Ramadan: