I attempted an adventure race in the middle of winter several years back while I was still in school...the night before the race it snowed 2.5 feet. I had been running for months in preparation for the race, but nothing could have prepared me for that much snow. I ended up only making it 28 of the 64 miles in just under 13 hours before my hip flexor could take no more. Luckily there was a manned rest station close enough for me to hobble to.