You fatigue faster at higher intensities

A Power-Duration Curve (with accompanying Mean-Max Power curve)
A Power-Duration Curve (with accompanying Mean-Max Power curve)

𝐘𝐨𝐮 𝐟𝐚𝐭𝐢𝐠𝐮𝐞 𝐟𝐚𝐬𝐭𝐞𝐫 𝐚𝐭 𝐡𝐢𝐠𝐡𝐞𝐫 𝐢𝐧𝐭𝐞𝐧𝐬𝐢𝐭𝐢𝐞𝐬

Intuitively, this is obvious.

If you sprint, you can’t sprint for a long time, and the faster you sprint, the shorter the time you can keep sprinting.

What’s not obvious is that there is a mathematical relationship between your intensity (your effort) and how long you can hold it.

𝐓𝐡𝐞 𝐫𝐞𝐬𝐞𝐚𝐫𝐜𝐡

Monod and Scherrer’s research into single muscle groups showed that the fast component of fatigue follows a hyperbolic curve.

This research identified the bottom of the curve (the asymptote) as ‘an exercise intensity that could be sustained for a very long time’, naming it Critical Power (CP).

The research also identified that the curve’s hyperbolic shape makes it ‘possible to define the maximum amount of work that can be performed in a given time, as well as the conditions of work performed without fatigue.’

They called this maximum amount of work W’. Anaerobic Work Capacity (AWC) and Reserve Work Capacity (RWC) are other names for W’; Functional Reserve Capacity (FRC) describes a similar concept with a different calculation method (but still hyperbolic).

Further research by Hill extended and validated these concepts for whole-body exercise, noting that ‘for a very long time’ was usually 30 to 60 minutes of exercise at CP.

𝐖𝐡𝐲 𝐢𝐬 𝐭𝐡𝐢𝐬 𝐮𝐬𝐞𝐟𝐮𝐥?

Knowing the maximum amount of work you can perform and the event distance, you can calculate a race power target for a shorter event (e.g. a 5k), where the fast component dominates.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

For more information on the research, please see:
🔹 Monod, H. & Scherrer, J., (2007) The Work Capacity of a Synergic Muscle Group
🔹 Hill, D., (2012) The Critical Power Concept

You fatigue faster at higher intensities

What are you capable of?

A Power-Duration Curve (with accompanying Mean-Max Power curve)
A Power-Duration Curve (with accompanying Mean-Max Power curve)

𝐖𝐡𝐚𝐭 𝐚𝐫𝐞 𝐲𝐨𝐮 𝐜𝐚𝐩𝐚𝐛𝐥𝐞 𝐨𝐟?

This is a subtle question, as the answer depends on:
❓ how hard you run – your effort
❓ how long you can sustain that effort
❓ how well you’re able to convert that effort into forward motion

Your Power-Duration Curve (PDC) can help answer the first two – the third depends on your Running Effectiveness.

𝐌𝐨𝐝𝐞𝐥𝐥𝐢𝐧𝐠 𝐲𝐨𝐮𝐫 𝐏𝐃𝐂

There’s an inverse relationship between power and duration: the higher your power (your effort), the shorter the duration you can sustain it; the lower your power, the longer you can sustain it.

You can chart this relationship. The result is a curve showing your Mean-Max Power (MMP) – the best effort you can sustain for each duration (measured using power) .

Based on your MMP curve, your PDC models your best efforts over a range of different durations, showing (for each) the effort you could sustain.

The picture accompanying this post shows a typical PDC (with accompanying MMP).

It’s usually charted using a logarithmic duration scale – which expands the left side of the curve and compresses the right side, revealing that the PDC is actually two separate curves.

𝐘𝐨𝐮𝐫 𝐏𝐃𝐂 𝐢𝐬 𝐫𝐞𝐚𝐥𝐥𝐲 𝐚 𝐟𝐚𝐭𝐢𝐠𝐮𝐞-𝐫𝐞𝐬𝐢𝐬𝐭𝐚𝐧𝐜𝐞 𝐜𝐮𝐫𝐯𝐞

How long you can sustain a particular effort level depends on how much you can do before tiring – it depends on how you fatigue.

Fatigue has two components: a fast component and a slow component.

Both elements of fatigue are always present, but the fast element of fatigue dominates at higher intensities, and the slow element dominates at lower intensities.

The next couple of posts explore the two components of fatigue.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

From its first introduction in ‘Training and Racing with a Power Meter’ (Allen, H., Coggan, A. & McGregor, S.) in 2006, and its subsequent incorporation into WKO4 in 2015, the PDC has become the standard for modelling your power over all time periods. For more information on the PDC as implemented in WKO, see ‘Scientific Basis of the New Power Duration Model in WKO4‘.

What are you capable of?

Max efforts are hard – is there any alternative?

Hand raised to ask a question

𝐌𝐚𝐱 𝐄𝐟𝐟𝐨𝐫𝐭 𝐫𝐮𝐧𝐬 𝐚𝐫𝐞 𝐡𝐚𝐫𝐝 – 𝐢𝐬 𝐭𝐡𝐞𝐫𝐞 𝐚𝐧𝐲 𝐚𝐥𝐭𝐞𝐫𝐧𝐚𝐭𝐢𝐯𝐞?

This is a common experience for runners new to power.

A Maximum Effort run is a run at the maximum (average) power you can maintain for a specific duration.

For example, your 3-minute max is the highest average power you can maintain over a 3-minute run.

𝐖𝐡𝐲 𝐝𝐨 𝐭𝐡𝐞𝐦?

👉🏼 By running max efforts over two or more durations (e.g. 3-minutes and 12-minutes) you can calculate your Threshold Power.

❓ Without max efforts, you won’t truly know what you’re capable of, and your training targets, training load and race/event targets will probably be understated.

𝐈𝐬 𝐭𝐡𝐞𝐫𝐞 𝐚𝐧𝐲 𝐚𝐥𝐭𝐞𝐫𝐧𝐚𝐭𝐢𝐯𝐞?

Yes.

💉 You can pay for lactate testing. But this typically involves a graded exercise test with increasing intensity every few minutes (max efforts in disguise).

🧮 You can estimate your Threshold Power using easy runs, but this method is only recommended until you’re able to complete maximum effort runs.

𝐃𝐨 𝐭𝐡𝐞𝐲 𝐠𝐞𝐭 𝐞𝐚𝐬𝐢𝐞𝐫?

They do … and they don’t.

❌ They don’t because you’re running at the highest average power you can manage – that’s never going to be easy. And it’s typical to start out too fast and fade towards the end, which may mean you didn’t really run to your maximum.

✅ And they do. You get used to how they feel. You get used to starting out a little slower, then pushing it towards the end. And you can use previous max effort results to gauge how hard to run the first part of your upcoming max effort.

And then you realise (in the words of Dr Andrew Coggan) ‘testing is training, too’.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

Max efforts are hard – is there any alternative?

Power Apps – point solutions

Power apps - calculating metrics

𝐏𝐨𝐰𝐞𝐫 𝐀𝐩𝐩𝐬 – 𝐩𝐨𝐢𝐧𝐭 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧𝐬

Power is still relatively new for runners. And while there are some apps that cover most of the important metrics, you may find that you need additional apps to plug the gaps.

Here are a few apps that can fill those gaps.

𝐔𝐬𝐢𝐧𝐠 𝐀𝐩𝐩𝐥𝐞 𝐰𝐫𝐢𝐬𝐭-𝐛𝐚𝐬𝐞𝐝 𝐩𝐨𝐰𝐞𝐫

Apple Health doesn’t provide any of the important metrics.

Which means you’ll need to transfer your workout data from Apple Health into an app that can provide these, like WKO or Intervals.icu.

There are a few apps that will do this. I’ve successfully used HealthFit; other options are RunGap or Health Sync.

𝐑𝐮𝐧𝐧𝐢𝐧𝐠 𝐄𝐟𝐟𝐞𝐜𝐭𝐢𝐯𝐞𝐧𝐞𝐬𝐬 (𝐑𝐄)

The only app to provide this (natively) is WKO.

If you’re a Stryd user, or if you’re using Intervals.icu, you’ll need to calculate RE manually or use SuperPower Calculator for Sheets (SPCs).

Steve Palladino’s video ‘Running Effectiveness and the SuperPower Calculator’ demonstrates how to use SPCs to calculate RE for a workout or a workout section.

𝐎𝐭𝐡𝐞𝐫 𝐚𝐩𝐩𝐬

‘Getting Started’ covers other apps that can calculate power metrics, while the book’s online content provides a more complete comparison of Power Apps.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

point solutions

Power Apps – Intervals.icu

Power apps - calculating metrics

𝐏𝐨𝐰𝐞𝐫 𝐀𝐩𝐩𝐬 – 𝐈𝐧𝐭𝐞𝐫𝐯𝐚𝐥𝐬.𝐢𝐜𝐮

Intervals.icu analyses your rides, runs, swims and other activities (with and without power). It provides basic and advanced analytics and planning in an easy-to-use web interface with support for desktops, phones, and tablets. Intervals.icu is free to use, with additional features should you choose to subscribe.

It can calculate and display all the most important metrics … and then some.

𝐈𝐧𝐭𝐞𝐫𝐯𝐚𝐥𝐬.𝐢𝐜𝐮 𝐌𝐞𝐭𝐫𝐢𝐜𝐬

✅ Threshold Power. Intervals.icu can calculate threshold power (using your choice from several models) based on the last 90 days of completed workouts or using a custom date range.

✅ Stress Score. Intervals.icu uses the term ‘Training Stress Score’ (TSS) and can calculate a power-based TSS for each completed workout.

✅ Stress Balance. Intervals.icu uses the term ‘Form’ to show the balance between ‘Fitness’ and ‘Fatigue’.

✅ Ramp Rate. Intervals.icu shows your week-on-week Ramp Rate (RR), overlaid onto the same chart as fitness, fatigue and form.

✅ Running Effectiveness. Intervals.icu doesn’t calculate Running Effectiveness, although you can manually calculate this using the detailed workout review pages, or by adding a custom calculation.

𝐖𝐡𝐲 𝐮𝐬𝐞 𝐈𝐧𝐭𝐞𝐫𝐯𝐚𝐥𝐬.𝐢𝐜𝐮?

If you’re not using the Stryd ecosystem or TrainingPeaks/WKO, Intervals.icu is a great way to track your power metrics.

Getting Started’ covers other apps that can calculate power metrics, while the book’s online content provides a more complete comparison of Intervals.icu vs. other Power Apps.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

WKO

Intervals.icu

Power Apps – WKO

Power apps - calculating metrics

𝐏𝐨𝐰𝐞𝐫 𝐀𝐩𝐩𝐬 – 𝐖𝐊𝐎

The WKO app is an analysis and charting tool that runs under MS Windows or on a Mac and provides a wide range of charts and graphs of your power data.

It can calculate and display all the most important metrics … and then some.

𝐖𝐊𝐎 𝐌𝐞𝐭𝐫𝐢𝐜𝐬

✅ Threshold Power. WKO uses the term ‘Functional Threshold Power’ (FTP) and offers an automatically calculated FTP, as well as the option to manually record your FTP history (and use it in charts).

✅ Stress Score. WKO uses the term ‘Training Stress Score’ (TSS).

✅ Stress Balance. WKO uses the term ‘Training Stress Balance’ (TSB).

✅ Ramp Rate. WKO can chart your week-on-week Ramp Rate (RR).

✅ Running Effectiveness. WKO can show your Running Effectiveness (RE) for an entire workout or just for part of a workout (e.g. an interval).

𝐖𝐡𝐲 𝐮𝐬𝐞 𝐖𝐊𝐎?

WKO comes with hundreds of pre-configured charts. You can also build your own charts and calculated metrics using a powerful charting language. WKO integrates seamlessly with TrainingPeaks, syncing planned and completed workout data and a range of health metrics.

Getting Started’ covers other apps that can calculate power metrics, while the book’s online content provides a more complete comparison of WKO vs. other Power Apps.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

Power Apps – Stryd PowerCenter / Stryd Mobile

Power apps - calculating metrics

𝐏𝐨𝐰𝐞𝐫 𝐀𝐩𝐩𝐬 – 𝐒𝐭𝐫𝐲𝐝 𝐏𝐨𝐰𝐞𝐫𝐂𝐞𝐧𝐭𝐞𝐫 / 𝐒𝐭𝐫𝐲𝐝 𝐌𝐨𝐛𝐢𝐥𝐞

The Stryd PowerCenter / Mobile app is available to anyone using a Stryd footpod (most features are free, some need a subscription).

It calculates and displays some (but not all) of the most important metrics.

𝐒𝐭𝐫𝐲𝐝 𝐌𝐞𝐭𝐫𝐢𝐜𝐬

In the following, the term ‘Stryd’ includes Stryd PowerCenter and Stryd Mobile

✅ Threshold Power. Stryd uses the term ‘Critical Power’ (CP) and offers an automatically calculated CP (Auto-CP) as well as a manually-set CP (using various protocols).

✅ Stress Score. Stryd uses the term ‘Running Stress Score’ (RSS) and offers a unique calculation which includes a term representing the additional biomechanical stress put on your body from running (vs. cycling).

✅ Stress Balance. Stryd uses the term ‘Running Stress Balance’ (RSB) and offers guidance for how to interpret your RSB.

❌ Ramp Rate. Stryd does not show your Ramp Rate (RR). You’ll need to calculate RR manually using Stryd’s 42d Avg (in Stryd Mobile) or use another system to track this.

❌ Running Effectiveness. Stryd does not show your Running Effectiveness (RE). You’ll need to calculate RE manually using another system, or use one of Stryd’s alternate metrics – for example Form Power, Leg Spring Stiffness, Impact Loading Rate.

𝐖𝐡𝐲 𝐮𝐬𝐞 𝐒𝐭𝐫𝐲𝐝 𝐏𝐨𝐰𝐞𝐫𝐂𝐞𝐧𝐭𝐫𝐞 / 𝐌𝐨𝐛𝐢𝐥𝐞?

The Stryd ecosystem is probably the most power-friendly app at the moment, designed with power in mind, and aimed at runners who are getting started with power.

Getting Started’ covers systems that can calculate the missing metrics, while the book’s online content provides a more complete comparison of Stryd vs. other Power Apps.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

⏪ Choosing Power Apps

Stryd PowerCenter / Stryd Mobile

WKO

Choosing Power Apps

Power apps - calculating metrics

𝐂𝐡𝐨𝐨𝐬𝐢𝐧𝐠 𝐩𝐨𝐰𝐞𝐫 𝐚𝐩𝐩𝐬

Power is a complete system using effort as its fundamental metric.

Power uses your second-by-second effort from completed workouts to calculate metrics that build a detailed picture of your individual running capabilities.

Imagine you run 3 times per week for around an hour each time. That’s 60 pieces of data per minute, 3600 per hour and over 3 runs, over 10,000 pieces of data. That’s a lot of data!

Which is why power relies on power-aware applications (‘apps’) to calculate your metrics.

𝐂𝐚𝐧 𝐲𝐨𝐮 𝐮𝐬𝐞 𝐚𝐧𝐲 𝐚𝐩𝐩?

The choice is yours, but some apps are more power-aware than others, with the best apps able to calculate the most important metrics.

𝐖𝐡𝐢𝐜𝐡 𝐦𝐞𝐭𝐫𝐢𝐜𝐬 𝐚𝐫𝐞 𝐦𝐨𝐬𝐭 𝐢𝐦𝐩𝐨𝐫𝐭𝐚𝐧𝐭?

✅ Threshold Power. Represents your current running fitness.

✅ Stress Score. A score (per workout) that combines ‘how hard?’ and ‘how long?’ to represent the workout’s metabolic stress – its impact on your body.

✅ Stress Balance. Indicates whether your training is ‘productive’  – enough stress to encourage adaptations, but not so much that there is a greater risk of injury or over-training.

✅ Ramp Rate. Replaces ‘the 10% rule’ with a metric based on your training volume and intensity, to monitor whether you’re adding training load too quickly.

✅ Running Effectiveness. Measures how effectively you convert power into speed, used to estimate finish times, to assess changes to your running form and to evaluate your fatigue resistance.

There are other criteria that will influence your choice of apps, but being able to obtain these metrics may be the most important.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

Choosing Power Apps

Getting Started

A power rhyme based on 'for want of a nail'

𝐆𝐞𝐭𝐭𝐢𝐧𝐠 𝐒𝐭𝐚𝐫𝐭𝐞𝐝

Power is a complete system using effort as its fundamental metric.

So how do you get started?

𝐄𝐪𝐮𝐢𝐩𝐦𝐞𝐧𝐭 & 𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬 (𝐚𝐩𝐩𝐬)

At a minimum you’ll need a power meter, but there are a few other choices you’ll need to make and the options are not independent.

Making a choice in one area almost always affects another, but the primary choice is your power meter.

𝐇𝐨𝐰 𝐝𝐨 𝐲𝐨𝐮 𝐜𝐡𝐨𝐨𝐬𝐞?

The following are some of the criteria you might consider (each bullet indicates whether the Stryd Footpod 🦶 or wrist-based power 👋 has the advantage)

🦶 Can you use any running watch?

Stryd works with many older watches; Wrist-based power is only found in newer watches.

👋 Do you need to buy a separate power meter?

Wrist-based power meters are built into your running watch; The Stryd footpod is a separate purchase.

🦶 Is it easy to obtain power metrics from supporting apps?

The Stryd ecosystem provides most of the key metrics; There’s no ecosystem for wrist-based power (you’ll need multiple apps).

🦶 Has the power meter been independently validated?

There have been at least 10 independent studies validating Stryd’s power numbers; I’m not aware of any independent studies for wrist-based power aside from my own (N=1).

🦶 Can you easily use power on a treadmill, or in GPS-poor areas?

Stryd provides power numbers without needing GPS; Wrist-based watches need GPS to provide power numbers (Garmin is the exception, but is Garmin Power valid on a Treadmill?)

𝐑𝐮𝐧𝐧𝐢𝐧𝐠 𝐰𝐢𝐭𝐡 𝐏𝐨𝐰𝐞𝐫 – 𝐆𝐞𝐭𝐭𝐢𝐧𝐠 𝐒𝐭𝐚𝐫𝐭𝐞𝐝

The book provides a more complete comparison and detailed information on how to get started with power, using a Stryd footpod or wrist-based power.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

Getting Started

Racing your personal best

A power rhyme based on 'for want of a nail'

𝐑𝐚𝐜𝐢𝐧𝐠 𝐲𝐨𝐮𝐫 𝐩𝐞𝐫𝐬𝐨𝐧𝐚𝐥 𝐛𝐞𝐬𝐭

A truth: power isn’t a guarantee that you’ll run a Personal Best (PB) at every race.

So what does ‘racing your personal best’ mean?

𝐏𝐨𝐰𝐞𝐫 𝐢𝐬 𝐩𝐞𝐫𝐬𝐨𝐧𝐚𝐥

It’s a system of metrics based on you as you are right now – your ability, your current fitness, your current form.

Your power metrics are calculated from your completed workouts (for better or worse).

From what you’re able to do.

Right Now.

👉🏼 Power is Personal.

𝐑𝐚𝐜𝐢𝐧𝐠 𝐲𝐨𝐮𝐫 𝐛𝐞𝐬𝐭

If it’s personal to you, how does that translate into racing your best?

Power enables identification of your current running fitness – your Threshold Power.

👉🏼 Which means you’re starting from a known position.

It bases your training targets on your Threshold Power, with incremental progressions (in volume or intensity) to improve your fitness while minimising injury risk.

👉🏼 Which means you can focus on consistently completing planned workouts.

It provides metrics to monitor your changing fitness and your training load, based on your Threshold Power and your completed workouts.

👉🏼 Which means you can adjust your plan if needed (rather than blindly following it).

It uses your training load metrics to plan your taper (more on that in a future post).

👉🏼 Which means you minimise missed training and arrive at the start line with fresh legs, ready to run.

It bases your race day power target on your most recent metrics

👉🏼 Which means you’re running based on you – your race-day fitness, ability, and form.

Power provides a complete system that prepares you to race your best – the rest, as they say, is up to you.

𝑺𝒉𝒐𝒖𝒍𝒅𝒏’𝒕 𝒚𝒐𝒖 𝒃𝒆 𝑹𝒖𝒏𝒏𝒊𝒏𝒈 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓?

Questions?
📖 Getting Started

Racing your personal best