How to Cross-Train with Lucy Charles-Barclay

For most athletes, cross-training is about balance — staying fit, avoiding injury, and building strength. No one knows that better than Lucy Charles-Barclay, the 2023 Ironman World Champion at Kona, who’s built her career on mastering that balancing act.

Whether you’re eyeing your first triathlon or just trying to fit multiple workouts into a busy week, Lucy shares how to find the right rhythm — and why consistency beats everything else.

Why Balance Matters

“Triathlon is the ultimate balancing act. You've got three disciplines and you can't put full focus into all three at once,” says Lucy. “I think it's really important to have periods of time where, okay, in this period of time I'm really gonna focus on my cycling and see how much I can lift that up. That doesn't mean you don't swim and run, but you are not so focused on them.”

For anyone mixing up workouts , whether that’s cycling, yoga, swimming, or lifting, the lesson is the same: don’t try to max everything at once. Rotate your focus to keep making gains without burning out.

Lean Into Lower-Impact Work

“In triathlon the bike is the biggest part of the day. Arguably, it's possibly the most important,” Lucy says. “If you're super fit and strong on the bike, the run's gonna take less out of you.”

Even if you’re not a triathlete, prioritizing cycling (or another lower-impact cardio option) can help you build endurance without overloading your joints.

Make Consistency Your Superpower

Lucy admits running has often been her toughest discipline, mostly because it’s where injuries creep in. But her biggest breakthrough wasn’t about chasing huge mileage — it was about showing up steadily.

“This year my main focus was just to be consistent on the run. Not do like hero mileage, but just set a mileage where I feel like I'm in a really safe zone, but I can also progress and just be consistent. Consistency is definitely key,” she explains.

That principle applies to every sport. Showing up regularly, even at lower intensity or volume, pays off more than sporadic, all-out efforts.

Switch Up Surfaces and Styles

Running is notoriously tough on the body, so Lucy makes smart choices about where she runs:

• Trails for softer landings and variety
• Treadmill for controlled, lower-impact sessions
• Pavement just once a week for harder efforts

“I’ll, maybe once a week, have a hard concrete-based session,” Lucy says. “Otherwise, yeah, just using the treadmill and the trails, which are just that bit easier on the body.” Mixing modalities keeps her improving while minimizing risk, which is a cornerstone of effective cross-training.

Recovery Still Counts as Training

On recovery days, Lucy doesn’t just sit still. She resets with light movement, whether that’s an easy swim or walking her dogs. “I feel like they're the best way to switch off from that all-consuming world of triathlon,” she says of her pups, Lola and Pickle. “Just going for a walk, clearing my mind, and being in nature.”

Small rituals like this don’t just recharge her body, but they also keep her motivated to show up the following day.

The Bottom Line

Cross-training doesn’t just build fitness. It builds resilience, balance, and longevity. Lucy’s playbook is simple:

• Rotate focus between disciplines
• Use low-impact training to support high-impact work
• Prioritize consistency over extreme pushes
• Mix up terrain and methods
• Treat recovery as training

With WHOOP, you can track the load of each activity, quantify and optimize your recovery, and see how cross-training is impacting your long-term health and performance. Listen to the full conversation between Lucy Charles-Barclay and WHOOP Director of Sports and Talent Marketing Jeremy Powers to learn more.