Running with Watts?

How Polar and Concept2 helps runners and bikers with more efficient training?

Darius Silaghi

Understanding Effort Beyond Pace or Heart Rate

When it comes to training, many athletes rely almost exclusively on pace, speed, or heart rate to gauge how hard they are working. While these metrics are useful, they each have limitations:

• Pace or speed is heavily influenced by conditions such as wind, terrain, or even fatigue. Running the same speed on a flat treadmill versus a hilly trail can feel completely different and demand very different energy outputs.
• Heart rate is a great indicator of cardiovascular strain, but it can lag behind sudden changes in intensity, be affected by hydration, stress, sleep, or temperature, and doesn’t tell you exactly how much mechanical power your muscles are producing.

This is where watts — or power output — come in. Watts provide a direct, objective measure of work, independent of external conditions or delayed physiological responses. Essentially, they tell you exactly how much energy you’re putting into moving your body or the bike, which allows for precise, data-driven training.

Two tools make this particularly practical for endurance athletes:

1. Concept2 BikeErg
   • This indoor bike measures mechanical power directly from the flywheel. Every pedal stroke translates into a measurable wattage, giving instant feedback on effort.
   • Unlike running pace, watts on a BikeErg aren’t affected by environmental factors — your effort today can be accurately compared to your effort tomorrow.
2. Polar Watches (running watts)
   • Modern Polar watches can estimate running power using a combination of GPS, accelerometers, and heart rate data.
   • This allows runners to track running-specific wattage, helping them gauge effort more objectively than pace or HR alone, and fine-tune workouts for intensity and recovery.

By the end of this article, you’ll understand watts from the very basics and learn how to apply them in both cycling and running. You’ll also understand why cycling watts and running watts aren’t the same, and how to interpret and use them effectively for smarter, safer training.

This article was produced with the support of Danubius Track Club, Polar, and Concept2 Hungary. The Danubius Track Club provides professional training conditions for numerous athletes, while Concept2’s cutting-edge technology—especially the BikeERG—enables modern, precise, and conscious training. Special thanks to Smasher Training gym on Margaret Island and Francisco Escalante for providing us with a Concept2 BikeERG. Proper load management is now essential for injury-free development and optimal race preparation, and the contributions of these partners are key to achieving that.

The Very Basics: What Are Watts?

Before we dive into comparisons between running and cycling, let’s strip things down to the fundamentals. What is a watt?

A watt is simply a unit of power. Power means the rate at which work is done.

If you remember physics class:

• Work is force × distance.
• Power is work ÷ time.
• A watt is one joule of energy per second.

That might sound abstract, so let’s make it practical:

• Imagine lifting a heavy box off the floor. If you take five seconds to lift it, the power is relatively low. If you lift the same box in one second, the power is much higher — even though the total work is the same.
• Or picture cycling: pedaling softly at 100 watts is like keeping a dim lightbulb lit. Sprinting at 400–500 watts? That’s more like powering a microwave.

In endurance sports, watts are the language of effort. They strip away the guesswork of how hard you’re working, because they measure the actual energy you’re producing, not just how fast you’re moving or how tired your heart feels.

Why Watts Matter More Than Pace or Heart Rate

To see why watts are so powerful (pun intended), let’s compare with the two most common metrics athletes use:

• Pace / Speed
  • Running 4:30/km on a cool, flat course might feel easy. But try the same pace in 30°C heat, or on a steep hill — suddenly it’s much harder, even though the pace number hasn’t changed. Pace tells you how fast you’re moving, but not how much energy it costs you.
• Heart Rate
  • Heart rate is fantastic for showing your body’s internal response, but it lags behind sudden changes. Start a sprint, and your power spikes instantly — but your heart rate might take 30–60 seconds to catch up. Heart rate is also influenced by stress, caffeine, dehydration, and fatigue.
• Watts
  • Watts cut through all this noise. They show your output in real time, second by second. Whether it’s hot, windy, uphill, or on a bike indoors, watts don’t lie. They reflect exactly how much power you’re producing.

This makes watts a gold standard in training for sports like cycling, rowing, and — increasingly — running.

A Universal Language of Training?

In theory, watts should give us a universal, sport-independent way to measure effort. But as you’ll see later in this article, running watts and cycling watts aren’t directly comparable.

That’s because the way your body produces and transfers power differs depending on whether you’re pushing pedals in a fixed position or propelling your whole body through space with every stride.

Still, at the most basic level, watts allow us to understand:

• How hard we’re working right now
• How much energy we can sustain for a given time
• And how to structure training sessions so they’re targeted, efficient, and safe

How Watts Work on a Concept2 Bike

The Concept2 BikeErg is not just “an indoor bike.” It’s a measurement device. What makes it special compared to most gym bikes is that its readings aren’t just estimates — they’re based on physics you can trust.

The Flywheel and Resistance

At the heart of the BikeErg is a flywheel — a large wheel with fan blades that spins when you pedal. As the wheel spins, it encounters air resistance. The harder you pedal, the faster the flywheel spins, and the more resistance it creates.

This is important:

• On many indoor bikes, resistance is controlled by magnets or friction pads, and the “wattage” you see on the screen is a computer guess.
• On the Concept2, watts are calculated directly from how fast the flywheel decelerates between pedal strokes. That’s real physics, not an estimate.

The Measurement Process

Every single stroke, the Performance Monitor (PM5) measures:

• How much the flywheel slows down between pedal strokes
• How much force you applied to keep it spinning

From that, it calculates power output in watts.

This makes Concept2 watts:

• Accurate (based on actual mechanical energy)
• Repeatable (your 200 watts today equals your 200 watts tomorrow, under the same setup)
• Comparable (athletes anywhere in the world using a BikeErg can compare sessions fairly)

Watts vs. Pace on Concept2

The BikeErg also converts watts into an equivalent “pace per 1000 meters,” similar to the RowErg. But watts are the foundation metric — they tell you exactly how much energy you’re producing, independent of speed or cadence.

For example:

• 200 watts sustained for 30 minutes is a solid endurance effort for many athletes.
• 350–400 watts may be an all-out sprint effort lasting only seconds.

Unlike running pace, where 4:30/km could feel easy one day and crushing the next, 200 watts is always 200 watts. Your body might perceive it differently depending on recovery, but the output is the same.

Why This Matters for Runners

If you’re coming from a running background, this is a big shift. Running pace is heavily influenced by terrain, wind, and even your shoes. Running watts (like those measured on a Polar watch) are helpful, but they’re calculated using sensors and formulas.

On the Concept2 BikeErg, watts are directly measured mechanical output. That means:

• You can precisely track improvements over time.
• You can hold a specific watt target for intervals (e.g. 240W for 4 minutes × 6).
• You can see fatigue trends — if you usually hold 200W at HR 135, but suddenly need HR 150 for the same 200W, something’s off (maybe recovery, sleep, or illness).

This reliability is why many endurance athletes — even runners — use the BikeErg as a cornerstone of their training. It’s a way to build and measure aerobic power without the unpredictable noise of running conditions and without the impact stress that can trigger or worsen injuries.

Running Watts: Power Without Pedals

Cyclists have been using watts for decades. But running is different — there’s no flywheel, no pedals, no crank to measure torque. So how do we get watt data in running?

That’s where modern sports technology, like Polar watches, comes in.

How Polar Measures Running Power

Polar watches don’t directly measure force the way a BikeErg does. Instead, they use a combination of sensors and algorithms to estimate running power:

• Accelerometers measure how your body is moving — forward, vertical, and side-to-side.
• GPS data tracks speed and changes in velocity.
• Barometer (in certain models) accounts for altitude changes, like when you run uphill or downhill.
• Body weight (entered in your profile) is used to calculate how much energy it takes to move you.

The watch then combines all of these inputs into an estimated watt value:

• Higher speed = more watts.
• Steeper gradient = more watts.
• Bigger vertical oscillation = more wasted energy → higher watt requirement.

So, while the number you see is not directly measured mechanical power (like on the BikeErg), it’s still an extremely useful indicator of how much effort your body is producing while running.

The Benefits of Running Watts

Why bother with this metric if it’s not 100% “real” like cycling watts? Because it helps with two key problems runners face:

1. Pacing in Difficult Conditions
   • Running against a strong headwind at 5:00/km might feel like 4:20/km effort. Pace doesn’t tell the truth, but watts do. If you keep your power output steady (say, 250W), you won’t blow up later.
2. Training Zones by Power
   • Just like with heart rate, you can create watt-based training zones for running.
   • Example: easy Zone 2 might be 180–220W, threshold around 280–320W.

This allows runners to hit the right effort every time, regardless of terrain or weather.

The Limitations of Running Watts

But — and this is important — running watts are not the same as cycling watts.

• Running watts are estimated from body movement and environment, not directly measured. That means small inaccuracies, GPS drift, or sensor issues can throw off the data.
• Impact forces in running mean your body is absorbing energy with every stride. Some of that power never translates into forward motion — unlike cycling, where nearly all power goes into the crank.
• Biomechanics matter more: inefficient runners (too much vertical bounce, overstriding) can show higher wattage without actually going faster.

In short:

• Concept2 BikeErg watts = measured mechanical power.
• Polar running watts = estimated metabolic cost of running.

Both are valuable, but you cannot directly compare them. Holding 250W on the BikeErg is not the same as holding 250W while running. They are two different languages describing two different motions.

Running vs. Cycling Watts: Same Unit, Different Meaning

At first glance, it seems simple: a watt is a watt, right? If you’re producing 250 watts on the bike, and your Polar watch says you’re running at 250 watts, then those efforts should be the same.

Not quite. While the unit of measurement is the same, the way your body produces and uses that power is very different between running and cycling.

Let’s break it down.

1. How the Power Is Measured

• Cycling (Concept2 BikeErg)
  • Direct measurement: torque applied to pedals → flywheel speed → watts.
  • 100% mechanical, physics-driven calculation.
  • Highly repeatable and comparable across sessions, athletes, and machines.
• Running (Polar watches)
  • Indirect estimation: sensors + algorithms combine GPS, accelerometer, barometer, body weight.
  • Influenced by running technique, surface, and external factors.
  • Less precise, but still gives a usable indicator of effort.

Key takeaway: BikeErg watts are measured; running watts are modeled.

2. Efficiency of Movement

• Cycling
  • Efficiency is relatively high. Around 20–25% of energy is lost as heat, friction, or wasted motion. Most of your effort goes directly into turning the crank.
  • The setup is fixed: your feet stay clipped in, the motion is smooth, the muscles used are consistent.
• Running
  • Efficiency is much lower. Up to 70–80% of energy can be lost to ground impact, vertical oscillation, braking forces, or poor mechanics.
  • Your body absorbs shock with every stride. Some energy is stored in tendons, some is wasted in bouncing, twisting, or stabilizing.

Key takeaway: 250W running usually feels harder than 250W cycling, because more of that “power” is absorbed by your body instead of moving you forward.

3. Muscles and Mechanics

• Cycling
  • Primarily uses quadriceps, hamstrings, glutes, calves — in a controlled, circular pedal motion.
  • Minimal eccentric loading (no “braking” forces), which makes recovery easier.
• Running
  • Involves almost every muscle group, especially stabilizers.
  • Heavy eccentric loading with every step — your muscles must absorb impact as well as generate force.
  • Higher strain on joints, tendons, and connective tissue.

This is why you can cycle for hours daily with less injury risk, but try running the same volume and most athletes break down.

4. Perception of Effort

• Cycling
  • Power feels smoother and more controlled. Heart rate tracks fairly closely with watts.
  • Sustaining 200–250W may feel manageable for long periods.
• Running
  • Even at the same watt number, perceived effort is higher because of impact, muscle recruitment, and less efficiency.
  • 250W running might feel closer to cycling at 300W+.

So, when athletes try to “match” watts across sports, they usually find running watts feel tougher.

5. Why You Can’t Directly Compare

To summarize:

• Running watts are not the same as cycling watts.
• Both use the same unit, but the physiology, biomechanics, and measurement methods differ.
• Think of them as two different currencies: 250 “running watts” is valuable in its own context, and 250 “cycling watts” is valuable in its own — but you can’t convert one directly into the other without losing meaning.

6. The Real Link Between Them

So, is there a point in looking at both? Absolutely. Here’s why:

• Both allow you to train by effort, not by pace or terrain.
• Both can establish training zones that help you stay consistent.
• Both show trends in your fitness — if your sustainable power is going up on the bike, your aerobic engine is growing, and that benefit will carry over to running (even if the watt numbers don’t match exactly).

The key is not to compare the numbers side by side, but to use each within its own sport. Cycling watts to manage load on the bike; running watts to guide pacing on the run. Together, they give you a complete picture of your engine.

Practical Uses: How to Train with Watts

Now that we understand what watts are, how they’re measured, and why cycling and running watts differ, the big question is: what do we actually do with this information?

Here are the main ways endurance athletes — especially runners and cyclists — can use watts to train smarter, recover better, and stay consistent.

1. Building Training Zones with Watts

One of the most powerful (pun intended) uses of wattage is creating training zones. These zones allow you to target specific physiological adaptations — aerobic endurance, lactate threshold, VO₂max — without guesswork.

• On the BikeErg, zones are usually based on a test like a 20-minute FTP (Functional Threshold Power) ride.
  • Example: if your 20-minute max average power is 250W, your threshold power is around 240W. Training zones are then percentages of that.

 

Zóna	Küszöb %-a	Példa (FTP = 240W)	Cél
Z1	<55%	<130W	Active recovery, easy spins
Z2	56–75%	135–180W	Base building, long rides
Z3	76–90%	180–215W	Sustainable hard efforts
Z4	91–105%	215–250W	Lactate tolerance
Z5	106%+	255W+	High-intensity intervals

• On running with Polar, zones can be set similarly based on a 5K or 10K effort, but keep in mind the numbers won’t match cycling watts.
  • Example: A runner might have a sustainable running power of 280W, but their cycling threshold might only be 220W. Both are correct in their own contexts.

2. Monitoring Fatigue and Recovery

Here’s where watts pair beautifully with Polar’s heart rate and recovery metrics.

Example:

• Normally, you ride 180W at a heart rate of 135 bpm.
• One day, the same 180W gives you a heart rate of 150 bpm.

That’s a red flag — you might be fatigued, under-recovered, or fighting illness. The watts show your output hasn’t changed, but your body’s response has. That’s invaluable data for avoiding injury or burnout.

3. Cross-Training for Runners

For athletes returning from injury (like with a hernia, shin splints, or knee pain), the BikeErg is a gift.

• You can maintain aerobic load with precise watts without pounding your joints.
• A runner can build fitness at 200–220W on the bike, then translate that aerobic strength back into running later.

This makes watts a bridge between sports: your cardiovascular system doesn’t know whether you’re cycling or running — it just knows you’re working at a certain percentage of max power.

4. Group Training and Competition

Because watts are objective, they level the playing field in group sessions:

• On a BikeErg, two athletes of different sizes can both target 200W, even if their speeds differ.
• In running, Polar power lets you compare effort across different terrains — a hill session at 300W vs. a flat session at 250W are both “hard” in comparable ways.

This makes watts a great tool for structured club workouts, where everyone can train to their own zones but still share the session.

 

Smasher Training gym, located on Margaret Island, is the perfect place for cross-training and cycling workouts. Danubius Track Club members receive 15% off all memberships or sessions. Learn more and join here: PLUS level

 

Integration with Polar: Making the Most of Your Data

One of the most powerful aspects of training with watts today is that devices don’t exist in isolation anymore. Tools like the Concept2 BikeErg and Polar watches can now be linked into a single ecosystem, giving you a complete view of effort, recovery, and long-term progress.

1. Polar and Running Watts

Polar has been a pioneer in making running power mainstream. Unlike cycling, where external sensors or power meters are required, Polar can measure running watts straight from the wrist (on models like the Polar Vantage V, Vantage V2, and newer generations).

That means:

• No foot pods, no extra sensors.
• You get instant watt data for every run, whether it’s a track session, trail, or treadmill.
• Combined with heart rate and GPS, this creates a full performance profile of your runs.

For runners, this is revolutionary: you can now pace races, structure intervals, and monitor recovery using watts — just as cyclists have done for years.

2. Polar with Concept2 BikeErg

On the bike, Polar doesn’t generate watts (the Concept2 already does that). Instead, Polar serves as the hub for tracking and integrating data:

• Heart Rate + BikeErg Watts
  
  • The BikeErg PM5 monitor can pair with Polar sensors (like the Polar H10 chest strap).
  • This allows you to track both your watts and your heart rate simultaneously, syncing seamlessly into Polar Flow.
  • You can then compare heart rate response to watt output over time — a powerful indicator of fitness and fatigue.
    
• Cross-Sport Integration
  
  • Because everything uploads into Polar Flow, your running sessions (with estimated watts) and cycling sessions (with measured watts) sit side by side in the same training diary.
  • This lets you spot patterns: Are your running watts improving after weeks of BikeErg base training? Is your HR lower at the same cycling power?
    

3. Recovery Metrics

Where Polar truly shines is in combining watts with recovery data:

• Nightly Recharge / Sleep Tracking: See how well your body recovers after a hard BikeErg session.
• HRV (Heart Rate Variability): Detects stress, fatigue, and readiness to train.
• Training Load Pro: Balances cardiovascular strain (measured via HR + watts) against muscle strain and perceived effort.

This makes it possible to do something athletes have always struggled with: balancing workload across sports. If your BikeErg sessions are accumulating a lot of load, Polar can flag when you may need to ease back on running volume — and vice versa.

4. The Athlete’s Perspective

For a club like ours, this integration solves a critical challenge:

• Cycling power (BikeErg) gives us clean, accurate watt numbers.
• Running power (Polar) gives us useful but sport-specific estimates.
• Polar’s ecosystem connects both, layering in heart rate, HRV, and recovery.

The end result: a 360-degree picture of training that isn’t limited to one sport or one metric.

 

With Polar watches, you can accurately track your heart rate and recovery, making every workout effective and safe. As a Danubius Track Club member, you receive 15% off all Polar purchases. Join the club here: PLUS level

Limitations & Caveats: What Watts Can’t Tell You

By now, it should be clear that watts are one of the most powerful tools endurance athletes can use. They cut through the noise of pace, weather, and terrain, and they provide an objective lens on effort.

But watts are not magic. Like any metric, they come with limitations — and if you don’t respect those, you can easily misuse the data.

1. Watts Don’t Measure Everything

• On the BikeErg: Watts tell you how much mechanical power you’re producing — but they don’t reflect fatigue, motivation, or biomechanical strain. You might produce 200W easily one day and struggle to hold 200W another day, even though the number looks identical.
• In Running: Watts don’t measure joint stress, impact, or subtle biomechanical imbalances. Two runners can both run at 250W — one with smooth efficiency, the other with pounding impact that leads to injury risk. The watts look the same, but the strain is not.

This is why pairing watts with heart rate, RPE (Rate of Perceived Exertion), and recovery metrics is so important.

2. Running Watts Are Estimates

Unlike the BikeErg, where watts are measured directly, running watts from Polar are modeled. That means:

• Accuracy can vary depending on GPS quality, terrain, or how well the watch is reading movement.
• Very steep climbs, descents, or technical trails may throw off the numbers.
• It’s best to look at trends over time rather than obsess over exact numbers in a single session.

3. Direct Comparison Is Misleading

It’s tempting to compare watts across sports — e.g., “I can hold 250W on the bike, so why is 250W in running so hard?” But this is a trap.

• Cycling watts are mechanical, external outputs.
• Running watts are metabolic, internal estimates.

They use the same unit but represent different things. Think of them as two different languages with the same alphabet.

The smarter approach: use each sport’s watts within its own system. Compare bike to bike, run to run — not bike to run.

4. Over-Focus Can Backfire

Chasing watts can be addictive. It feels like a game — always trying to push a little higher. But more watts isn’t always better.

• Recovery rides should stay easy, no matter how “low” the watts look.
• Form and efficiency should never be sacrificed just to push numbers higher.
• Individual variation matters: some athletes thrive at lower wattage but higher cadence, others at higher wattage and slower rhythm.

If you’re constantly trying to beat yesterday’s watt number, you risk missing the big picture — steady, sustainable progress.

5. Technology Isn’t Perfect

Both the Concept2 and Polar are incredible tools, but they rely on technology: sensors, firmware, connectivity. Sometimes data drops, sometimes numbers don’t sync, sometimes a watch misreads.

The point: never let tech replace how your body feels. Watts are guides, not dictators.

The Balanced View

Watts are a lens, not the whole picture. They’re at their best when used alongside:

• Heart rate (internal effort)
• RPE (subjective perception)
• Recovery metrics (HRV, sleep, soreness)

Together, they form a complete triangle:

• Watts = output
• Heart rate = physiological response
• RPE/recovery = subjective experience

Ignore one of these, and your training view becomes one-dimensional. Use all three, and you gain depth and clarity.

Conclusion: Training Smarter with Watts

At their core, watts are a universal measure of power. Whether you’re riding the Concept2 BikeErg or running with a Polar watch, watts give you a clearer, more objective view of how hard you’re really working. They cut through the noise of pace, terrain, weather, and even mood — grounding your training in measurable effort.

But as we’ve seen, cycling watts and running watts are not the same.

• On the BikeErg, watts are measured directly, giving you clean, physics-based data that’s perfect for intervals, testing, and structured conditioning.
• In running, Polar’s watches estimate watts using advanced sensors and algorithms — less precise, but still a powerful tool for guiding pacing, especially on varied terrain.

The key isn’t to compare watts across sports, but to use them within their own context: bike watts to guide cycling, running watts to guide running. Together, they tell the bigger story of your aerobic engine.

When paired with Polar’s ecosystem, watts become even more valuable. Heart rate, HRV, sleep tracking, and recovery scores add depth and context, ensuring you don’t just train harder — you train smarter. For athletes returning from injury, managing load, or balancing multiple sports, this integration is a game-changer.

Of course, watts have their limits. They don’t measure everything, and they shouldn’t replace common sense or how your body feels. But when combined with heart rate and recovery data, watts are one of the most powerful tools we have today for sustainable progress.

At Danubius Track Club, we’ve seen firsthand how Polar and Concept2 together create a system that works. The BikeErg lets us train hard with low impact. Polar gives us the insights to balance stress, recovery, and running power. Together, they allow us — and the athletes we coach — to build fitness, avoid overload, and come back stronger.

The takeaway is simple:
Don’t chase numbers for the sake of it. Use watts as part of a bigger picture — a way to train consistently, recover properly, and stay in the game for the long term.

This is endurance sport at its smartest: not about going harder every day, but about going further, for years to come.