Whether it was a lung-busting run in a desert, a calf-straining Himalayan hike or a cycle ride into the clouds in Snowdonia, our friends at The Guardian want to hear about it.
They're looking for stories of great fundraising challenges, family hikes, open water swims, canoeing adventures and cycling sportives and tours the world over. They can be self-guided or organised, competitive or individually challenging, as long as you were stretched somewhere close to your limits.
The best tips will appear in print in Guardian Travel and the winner, chosen by Tom Hall of Lonely Planet, will receive a £200 hotel voucher from UK.hotels.com, allowing you to stay in more than 260,000 places worldwide. You'll have to be quick though as entries close at 10am on Wednesday, 17 January 2018 and don't forget to mention EC!