Here’s What 7 Days of Running Half Marathons Did to This Guy’s Body
Men's Health 2hrs ago

In a new video from the Global Triathlon Network, YouTuber and former professional triathlete Mark Threlfall is set a grueling physical challenge: running a 21.1 km half marathon every single day for an entire week. While his background stands him in fairly good stead, Mark admits that he has maintained little to no consistency in his training over the last few years, and his half-marathon running has been "horrifically sporadic."

"Even when I was running professionally, I typically averaged 60 to 75 km of running per week," he says. "This week, I'll be doing around double that, and crucially, all in single runs per day and around my daily working life. I really don't know how my body's going to hold up, whether I'm going to crumble after a few days, whether I might struggle with a lack of sleep, struggle with my nutrition."

For his first run, Mark keeps to a canal path with no incline or elevation. "I'm just making it as easy as possible for myself, and making sure I don't regret something I do early on," he says. "The hillier I go, the slower I go, which means the earlier I have to get up."

While he completes the first 21 km run with relative ease, Mark soon begins to feel the impact of both the running itself, and the lack of recovery time in the challenge. "I can't believe I'm saying this on Day 2, but I'm struggling already," he says. "I'm quite fatigued and aching from a half marathon yesterday, that's understandable, I can deal with that. My issue is, I'm just tired. Really sleep-deprived this morning... I feel like I could close my eyes and fall asleep while I'm running."

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He factors this into his plan for the week, and starts going to sleep earlier to ensure he's getting as much rest as possible, in addition to incorporating more mobility work and stretching into his daily routine. These small changes end up making a major difference to Mark's energy levels and performance in his subsequent running. "It's just highlighted to me just that importance of recovery when you are tired and fatigued, and listening to your body," he says.

Over the course of the week-long challenge, Mark loses around 2.5 pounds despite keeping his body fueled throughout each run. His main takeaways, however, relate to just how easily insufficient recovery and nutrition can affect performance.

"It's been quite a tough one, both physically and mentally, which is not a surprise at all," he says. "Just the process of getting my head around running 21.1K each day was quite tough. You can't just wing that sort of distance, and I definitely struggled towards the sixth and seventh day, just getting myself out of the door. I've learned a heck of a lot about myself and the importance of HRV (heart rate variability)... I've found it very, very important and useful."

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