How Much Running Data Do You Need? Coaches and Wearable Experts on Tech in Running (2026)

Runners have more data than ever: heart rate, HRV, sleep scores, training load, readiness scores. During UTMB week in Chamonix, TrainingPeaks hosted a panel to ask whether all of it is making us better runners. FTLR host Jon Levitt moderated a conversation with a pro athlete and coach, a wearable tech marketer, a sensor company founder and a PhD researcher who coaches elite trail runners.

In this post

Corrine Malcolm has been a professional athlete and a coach for about a decade, working with everyday runners up to pro trail and ultra athletes. She raced on the US biathlon team, studied environmental physiology in grad school and works as a podcast host and sports commentator.

Alison Lynch is marketing director for Amazfit's run category and has worked in wearable tech for more than a decade, including at Whoop and Coros.

Arnar Larusson is a co-founder of Tymewear, which measures breathing and heart rate in the field. He's a mechanical engineer who previously worked on prosthetics for amputee athletes and exoskeletons for the US military.

Doug Stewart is the founding coach of Elite Trail Team, a support team for elite trail runners, and a PhD researcher studying how technology shapes the coach-athlete relationship in remote endurance coaching.

The panel agreed that technology's job is to describe what happened in your body as accurately as possible, so a runner and coach can make better decisions. Arnar put it simply: the role of a sensor is to get as close as possible to the truth of what happened physiologically, because how a run feels and what actually happened often don't match.

The coaches added a condition. Corrine, who has used TrainingPeaks for her entire coaching career, said a workout file and heart rate data only go so far without the athlete's own account. A voice memo or post-workout comment gives her the context she needs to read the numbers correctly.

Doug's process starts with the athlete's subjective feedback: comments, voice notes, how the session felt. From there, the numbers he leans on for trail and mountain runners are:

Durability matters most in ultras. Doug pointed out that at UTMB, a big lead pack early in the race thins out one runner at a time, and the winner is often the athlete who slows down the least.

Alison's priority is recovery: HRV, sleep and fatigue levels, viewed as trends over weeks instead of single days. One bad morning reading during a hard training block tells you very little. She also noted research showing HRV can rise during heavy training as the body works to recover, which is one more reason to look at trends and share them with a coach.

Pace stops being useful the moment a runner hits a climb, and heart rate starts to separate from actual effort after 10 or so hours, or when the temperature climbs. Arnar argued that the tools runners have relied on for decades are poorly suited to measuring load in the mountains, and if you can't measure load, it's hard to design good training.

He compared it to cycling, where power meters give a much tighter link between output and internal effort, and coaching has become far more precise as a result. Tymewear's work with Salomon athletes uses breathing data to show things pace and heart rate miss, like how downhill running affects an athlete and how their ability to hold pace drops as fatigue builds.

His broader point was that runners collect data often but not widely. A watch samples heart rate every second, which feels like a lot of data, but it covers a tiny slice of what's happening physiologically.

VT1, the first ventilatory threshold, is the intensity where your breathing begins to rise faster than your oxygen use. It marks the top of zone 2, the easy aerobic zone most endurance training is built on, and it typically falls somewhere between 50% and 75% of VO2 max. It sits at roughly the same intensity as LT1, the first lactate threshold, which is measured in the blood instead of the breath.

Arnar said that even with huge volumes of power and heart rate files, VT1 can't be reliably estimated for an individual. Population averages exist, but the spread is wide and the number shifts as fitness changes. When Jon asked whether an estimate is better than nothing, Arnar said no: wrong data can be more harmful than no data, because you don't know how far off it is. Set VT1 too high and an athlete's easy runs are too hard, which leads to overtraining. Set it too low and they stop progressing.

He also described the upside of getting it right. Runners who have stalled for months often improve quickly once they identify the correct intensity and train those lower zones properly.

Most sports science and performance research has used mostly male subjects, and those findings feed the algorithms inside the watches women wear. Alison framed what's needed:

She shared that Amazfit acquired Wild AI, the menstrual cycle training tool from Stacy Sims, and is building its own version into the Zepp app to give phase-specific guidance on training intensity and nutrition.

Corrine explained why the research itself is still thin. Most studies that account for the menstrual cycle estimate ovulation and phase length from cycle length, when cycles vary between women and from month to month. Good research would require daily hormone panels from urine or blood. Many women are also excluded from studies because of hormonal birth control, even though different methods affect circulating hormones very differently. She raised a further concern about data privacy, noting that some women have stopped using cycle tracking apps over worries about how that data could be used.

Doug, whose university has several female athlete studies underway, described the practical hurdle: these studies can require months of daily sample collection, so recruiting and keeping participants is hard, and results can take 2-3 years to reach publication.

Until better data exists, Corrine's advice is to track how you feel in each phase of your cycle alongside HRV and resting heart rate, and to share that with your coach.

Corrine argued that everyday runners may benefit the most from good tools. They are often the athletes at highest risk of overdoing it: parents with demanding jobs, running at 4 a.m. after a late night, skipping breakfast. They may only train six or eight hours a week, but as she put it, stress is stress is stress.

Alison described watching first-time GPS watch buyers discover features like multi-week battery life, route navigation and sleep tracking, and how much confidence that gives them heading into a first trail race or marathon.

Arnar cited a stat that only about 20% of endurance athletes have ever worked with a coach. For everyone else, he sees an opportunity for sensors and apps to show whether a workout matched what the athlete should have been doing.

Doug added that part of coaching mid-packers is teaching them what their metrics can and can't show. Some of his runners post great workouts after a bad readiness score, and the reverse happens too.

Not yet, according to the coaches on stage. Corrine said the value of a human coach is the relationship: knowing what a particular athlete's frowny face in TrainingPeaks means, and combining their feedback with the data to decide whether to push or pull back.

Doug said the athletes he watches most closely are the ones with every workout marked green, because they may be sacrificing other parts of life to hit every session. A coach can't predict a sick kid or a brutal week at work weeks in advance, and he said a good plan has to adjust when life happens. The panel allowed that an AI model with enough context might get closer, but adapting a plan to real life is still where a coach earns their keep.

What running metrics matter most for trail runners?
The coaches on this panel prioritize the athlete's own feedback first, then normalized graded pace, VAM (vertical speed), heart rate decoupling to measure durability, and HRV and sleep trends for recovery.

Is heart rate accurate for ultramarathons?
It becomes less reliable deep into long efforts. Arnar Larusson of Tymewear said heart rate starts to separate from actual workload after roughly 10 hours or as temperatures rise.

What is the difference between VT1 and LT1?
Both mark the top of zone 2. VT1 is measured from breathing, while LT1 is measured from blood lactate. They usually occur at similar intensities.

Should women train differently across their menstrual cycle?
The research isn't settled. Corrine Malcolm said most studies rely on approximations instead of daily hormone testing, so for now the best approach is tracking how you feel in each phase and adjusting with a coach.

Can an AI app replace a running coach?
The coaches on this panel said not yet, because a coach adapts to life context like illness, travel and work stress, and knows how to read an individual athlete's feedback.

Hear the full panel on For The Long Run: Are We Overthinking Running?