'The legs know what they need to know. It’ll be in them or not' - Heather Jackson to defend her Unbound XL title just weeks after finishing the 250-mile Cocodona running race

Most defending champions spend the month before Unbound Gravel dialling in equipment, sharpening fitness and obsessing over recovery.

Heather Jackson spent hers running 250 miles across Arizona.

Less than a month before returning to Emporia to defend her Unbound XL title, Jackson finished fourth at the Cocodona 250, a punishing ultramarathon running race that stretches across the Arizona desert. She hallucinated ravens during the final night, survived on a pair of 15-minute naps, and emerged physically intact but mentally rattled after nearly 70 hours without sleep.

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For Jackson, though, Cocodona wasn’t a detour from her cycling season. It was part of it.

While the former professional triathlete first built her post-Ironman career around gravel racing, Jackson’s ambitions have drifted steadily toward the outer edges of endurance sport: ultrarunning, self-supported bikepacking, and multi-day races where sleep deprivation matters nearly as much as fitness. This summer, Unbound XL sits between two enormous objectives: Cocodona and the Tour Divide. And Jackson openly admits she isn’t sure whether it’s possible to perform at a high level in both ultra running and ultra cycling, at the same time.

"I have no idea," she told Cycling Weekly with a laugh. "That’s what we’re gonna find out."

Jackson is still recovering from Cocodona — physically, mentally and neurologically.

"The comedown was pretty crazy. It’s only been the last three days that I’m seeing the light again," she said roughly 10 days after finishing the race.

She's also just now getting back on the bike with Unbound XL looming nine days away.

There was a time in Jackson’s life when that timing would have caused major stress. During her years as a professional triathlete, she said, she became "super caught up in data and numbers and all that stuff." But Jackson’s approach to endurance sports has changed alongside her goals.

Rather than chasing perfect freshness for Unbound, Jackson and her coach are treating the race as part of a much larger ultra-endurance build centred around a Tour Divide attempt later this summer.

This final week before Emporia will consist mostly of long rides to reacclimate to the bike after weeks spent focused on running and strength work.

"At this point, it’s more like making sure the touchpoints are trained," Jackson said. "Your legs know what they need to know. It’ll be in them or not. It’s making sure I can be in the saddle and in the position for that long."

This philosophy represents a sharp departure from the highly structured specificity that once defined Jackson’s training. Preparing for Cocodona and the Tour Divide at the same time forced her to rethink what ultra-endurance fitness actually looks like.

"I would have thought I needed to run so much more than I did," she explained.

Instead of logging mega running miles ahead of the 250-mile race, Jackson spent much of the spring balancing 60-to-70-mile running weeks with heavy blocks of endurance riding, strength training and hill repeats wearing a 30-pound vest. The goal was less about maximising mileage than building durability.

That realisation—that surviving the longest events depends on far more than aerobic fitness—has only pushed Jackson deeper into the world of ultra-endurance racing.

Since stepping away from professional triathlon, Jackson has largely let curiosity guide her athletic evolution. Gravel initially offered the sense of exploration and adventure she felt Ironman had lost. But over the last several years, she has watched gravel become increasingly professionalised and tactical — familiar territory for someone who spent 15 years in elite triathlon.

She also realised that pure gravel racing never fully matched her strengths as an athlete.

"If you want me to TT all day long, I love that," she said, laughing. "Sometimes the antics of gravel racing just aren’t for me."

The longer the events became, the more naturally they suited her. Last year’s Unbound XL victory and a successful ride at Traka 360 only accelerated her interest in races that extend through the night and into sleep deprivation territory.

Running followed a similar progression. After racing one-day ultras like Western States and UTMB, Jackson became increasingly fascinated by multi-day events like Cocodona.

"It was like, ‘holy sh$t, how do people do this?’ And because I’d done all the other things, it’s been sort of a natural shift of now I want to try this," Jackson said.

So this year, rather than targeting a traditional gravel season, Jackson built her calendar around the events that intrigued her most. Cocodona was high on the list, as was the Tour Divide bikepacking race.

Which leaves Jackson heading into Unbound XL in an unusual position: defending champion, but also an athlete recovering from one ultra and looking toward the next.

"If it goes well, that’s amazing," Jackson said. "If not, it’s still a solid day out."