The Winter Arc Challenge is a 90-day self-improvement, personal development trend focused on health habits and goal setting. Learn the winter arc challenge rules. Oct 9, 2024 · In fitness culture, the "winter arc" refers to the practice of bulking in the winter and cutting fat before summer, with the "arc" beginning on October 1st of every year. Sep 30, 2025 · Ready to stop surviving and start thriving? These 11 Winter Arc (or 'Great Lock-in' of 2025) rules are your go-to guide for peace, rest and success. The “winter arc” refers to the “90 days before the end of the year where you can get ahead of the ‘New Year, new me’ crowd and hit your goals,” TikToker @jessback2earth explains.