Work-Out was recently featured in a national Belgian newspaper following our presence at the very first Belgian Defence Exhibition in Brussels. The event brought together over 200 companies from across the defence and innovation sector, including a selection start-ups.
Why Zones Change Everything And Why coaches swear by them There’s a moment almost every runner recognises. You lace up, you start “easy”… and somehow you’re already breathing harder than you planned. Ten minutes later you glance at your watch and think: “This doesn’t feel easy” But you keep going anyway, because it’s training, and training is supposed to feel like effort… right? Well, that’s how most people train. Not intentionally, not out of stubbornness, just because they don’t have a clear framework. And that’s exactly why heart rate zones matter. Not because they’re fancy numbers, not because coaches love graphs. But because zones protect the thing that actually makes you fitter: the right effort, repeated consistently, over time. The Invisible no-zone Problem Here’s what happens when you train without zones: Easy runs drift faster and faster Hard sessions aren’t hard enough to truly stimulate improvement Recovery gets compromised You feel tired more often Progress slows down, even though you’re training more Many athletes end up living in the same intensity zone, that “grey area” where you’re working, sweating, and feeling productive… but not building the foundation you need. It’s common, because it feels like training, but it doesn’t always produce training adaptations, and in endurance sport, it’s not effort that builds progress, but the right dose of that effort. And that is exactly what zones are. What zones are based on Zones are built around measurable physiological markers Heart rate zones in beats per minute (bpm) Pace zones in minutes and seconds per km (min/km) Together, these values define both your internal load and your external output. Two athletes can run the same pace, but internally, they may be working in completely different zones. That’s why proper zones must be personal. Generic formulas like “220 minus age” are averages and averages are not coaching. Inside the Work-Out platform, your zones are calculated from your own data. HEART RATE ZONES INTERNAL LOAD Heart rate zones show you what is happening inside your body when you train. They tell you how much physiological stress your system is under to produce a certain movement. That difference between what you see and what is happening internally is fundamental. Two athletes can run at exactly the same pace. From the outside, they look identical. Internally, however, one may be comfortably running while the other feels like dying. The mechanical output is the same, the metabolic cost is not. Heart rate zones make that invisible difference visible. Heart rate is also valuable because it adapts to context. Sleep, stress, dehydration and temperature all affect internal load. On a hot day, your heart rate will rise faster at the same pace. After a poor night of sleep, an easy run may feel harder than expected. Heart rate reflects that shift and helps you adjust accordingly. Heart rate zones typically range from Zone 1 (very easy) to Zone 5 (maximum effort), and each zone trains a different physiological system: Zone 1 → Recovery and circulation Zone 2 → Aerobic base and fat metabolism Zone 3 → Aerobic capacity Zone 4 → Threshold performance Zone 5 → VO₂ max and high-intensity performance The key is not that one zone is better than another. The key is that each has a role. When those roles blur, training becomes inefficient. When they are clearly defined, progress becomes measurable. Calculation Zones only work if they are personal. That is why Work-Out does not use generic “one-size-fits-all” formulas. Instead, your heart rate and pace zones are calculated from values that reflect your own body and current fitness. To calculate your heart rate zones, the Work-Out platform uses three simple inputs: your resting heart rate, your maximum heart rate, and your threshold heart rate. If you’re not sure where to find these values, don’t worry, you can usually get them from your wearable data, recent tests, or with the help of your coach. The important part is that the numbers are yours, not estimated from age. Pace ZONES external LOAD Pace zones are slightly more complex than heart rate zones. Not because they are less useful, but because they require a clear reference point to be accurate. While heart rate tells you how hard your body is working internally, pace tells you what you are producing externally. It reflects performance, output and real speed. But pace only makes sense if it is anchored to something meaningful. That anchor is your threshold running pace: the fastest pace you can sustain for roughly 30 to 60 minutes at a controlled, hard effort. Without that reference, pace zones are just numbers. Just like heart rate zones, pace zones are divided into five intensity ranges. Each zone aligns with a specific training purpose: Zone 1 → Easy recovery pace Zone 2 → Aerobic endurance pace Zone 3 → Steady / controlled tempo Zone 4 → Threshold pace Zone 5 → High-intensity interval pace The purpose is not to chase speed every day. In fact, most endurance development happens in Zones 1 and 2. Pace zones simply help you see what “easy” and “hard” actually mean in real numbers. The challenge with pace is context. Hills, wind, surface, heat and fatigue all influence how a pace feels. That is why pace zones work best when combined with heart rate. Heart rate protects your internal load. Pace sharpens your external performance. Calculation To calculate your pace zones, the Work-Out platform uses one key value: your threshold running pace. Once you enter this pace in the Endurance section of the app, Work-Out automatically generates five personalised pace zones in min/km. These zones align with your heart rate structure and evolve as your fitness improves. If your threshold pace becomes faster, your zones shift accordingly. That means your training always reflects your current capacity. If you are unsure about your threshold pace, you can determine it through: A structured 30-minute time test Recent race results A guided test with your coach Again, the most important rule applies: your zones must be based on your
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