TetraTrack: Unified Coaching Intelligence for Multi-Discipline Athletes

My daughter competes in Pony Club winter series Tetrathlon. Four disciplines: show jumping, cross-country riding, shooting, and running. Four separate coaches. Four separate perspectives on her training.

The problem was visibility. Her showjumping coach saw her riding performance. Her running coach saw her run times. Her swimming coach tracked her technique. Her shooting coach monitored her balance and composure. But none of them saw the whole picture.

Meanwhile, I was noticing something watching her train across all four: improvements in one discipline were directly affecting the others. Better running symmetry improved her riding stability. Shooting balance translated to jumping composure. It wasn’t four separate training tracks. They were connected. But her coaches didn’t have a way to see those connections.

The Framework

This insight didn’t come from me. It came from Becky Lynn, a running coach who pioneered a framework for breaking down specific training—take running, for instance—into measurable biomechanical components, then look across disciplines to find the common pillars they share. Where does running inform riding? Where does shooting technique feed swimming? What universal skill domains connect everything?

That framework became TetraTrack’s foundation. Six universal skill domains: Stability, Balance, Symmetry, Rhythm, Endurance, Calmness. Every session, across every discipline, gets evaluated against these pillars. Running develops symmetry and rhythm. Shooting demands stability and calmness. Riding requires all of them.

But here’s the thing: it’s not about doing more. It’s about doing the right thing, given your body’s current state. HRV, sleep, recovery metrics—the Apple Watch captures all of this. Knowing you improved your running time by 10 seconds is useful. Knowing you improved it while your HRV was elevated and you’d only had 6 hours of sleep is something completely different. That’s coaching intelligence.

The Real Problem

She has four coaches. They don’t talk to each other. She trains every day and they see maybe one session per week, if that. The actual training data—all the sessions she logs, all the metrics the Watch captures—lived in HealthKit, invisible to anyone except her.

TetraTrack is the bridge. She records every session on her Apple Watch. Every session. Running. Swimming. Riding. Shooting. The Watch does what it does best—capture heart rate, motion, elevation, all the native HealthKit metrics. TetraTrack adds a thin layer on top that translates those raw metrics into tetrathlon-specific coaching insights mapped to the six skill domains.

Then I review the data. I look for patterns. Where is she improving? Where is she stagnating? Where is her training load not aligned with her recovery? Where might one coach’s approach be affecting another? I brief her coaches. Here’s what I’m seeing. Here’s where you might focus. Here’s how her other training is supporting or hindering this discipline.

It’s not about replacing coaches. It’s about giving four independent coaches unified visibility into one athlete’s training.

The Apple Watch Foundation

Rather than reinvent something Apple already solved, TetraTrack uses native HKWorkoutSession as the primary capture mechanism. The Watch has built-in capabilities—heart rate zones, motion analysis, GPS, fall detection. We apply a thin layer that makes those capabilities tetrathlon-specific.

But building this exposed something ugly about Apple’s ecosystem: the APIs are fragile and the guidance changes. WWDC22/23 clearly stated: phone is primary, mirror to Watch. Then WWDC24 completely reversed it. Documentation broke. Recommended patterns became deprecated. Blog posts and conference talks are often more reliable than official docs.

This isn’t theoretical. It means shipping features that might break next release. It means relying on workarounds because the “official” path doesn’t work. Building Apple apps at this level is more art than science.

But it works. The Watch captures everything. The data flows. The insights emerge.

How She Actually Uses It

She’s 13. She logs sessions. That’s it. Ride, run, swim, shoot—record it on the Watch, sync it to the iPhone. She sees graphs and metrics, but the real value is what I see afterward.

I review the history. I spot the patterns she can’t see because she’s focused on that day’s performance. I notice when running is getting faster but her HRV is dropping. I see when she’s improving shooting steadiness but her sleep is degrading. I see the cross-connections—when she had a great ride, what had she done in running that week? When her shooting was off, was it a recovery issue or a form issue?

Then I brief her coaches. A paragraph to her showjumping coach. A message to her running coach. A note to swimming and shooting. Here’s what the data shows. Here’s where you might focus.

The coaches don’t know TetraTrack exists. They don’t need to. They just get better insight into what’s happening with their athlete.

What Changed

Before TetraTrack, each coach worked in isolation. After, they’re coordinated by data. Not by me second-guessing them. By metrics. By what the Watch is actually measuring.

She’s more aware of recovery. Training isn’t just “do more.” It’s “do the right thing given your body’s current state.” That’s a WHOOP-level insight, but for a multi-discipline athlete where the question isn’t “should I run faster” but “should I run at all today, or would recovery be more valuable?”

Her coaches started seeing improvements that made sense across disciplines. Better running symmetry actually does improve riding stability. Shooting composure improvements actually do carry over. They’re not connected by theory. They’re connected by data.

Building for Someone You Care About

There’s something about building an app for a 13-year-old who depends on you that strips away all pretense. You can’t hand-wave features. You can’t build something flashy. She’ll use it or she won’t. The coaches will find it useful or they won’t.

What matters is: does this help her get better? Do the coaches have better insight? Is the training more coordinated? Yes on all counts.

TetraTrack isn’t trying to be a general fitness app. It’s trying to solve one specific problem: give four separate coaches unified visibility into one young athlete’s training across four disciplines, informed by recovery metrics, and revealing the biomechanical connections that most training plans miss.

That’s what it does.

TetraTrack is available on the App Store.