Physiology

What benefits have you experienced? Based on feedback from runners using power, the top three benefits are: 1) Able to train to targets (based on your individual fitness); 2) Consistency. Runners experienced a powerful feedback loop: targets matched to fitness => able to run to target => confidence in the plan => increasing fitness without injury => adjusted targets matched to fitness => able to run to target; 3) Improved race-day performance – Power offers a couple of different race planners, both of which produce power-based targets for races and events that are not only achievable, but for many runners, accurate to within a few watts and to within a minute or two (over a marathon).

Feedback from runners using power. The posts in this topic group summarise feedback from two annual surveys, and feedback gathered while researching two of my books (‘Why’ and ‘Getting Started’), when asking runners the following questions: Why did you start running with power? What benefits have you experienced? What difficulties have you experienced? What advice would you give to someone not yet Running with Power?

How can I estimate my finish time? There are two different race calculators you can use to estimate your finish time: the web-based Stryd Race Calculator; the ‘Generate Race Power Scenarios’ feature in SuperPower Calculator (for Google Sheets). Whichever calculator you use, they work similarly, using your race-day running fitness (Threshold Power), your fatigue resistance (two different metrics, depending on your event distance), and how effectively you convert power into speed (Running Effectiveness) – to obtain a personalised race-day target.

Can you measure changes in fatigue resistance? You may be familiar with the term stamina, which is similar to, but not the same as fatigue resistance: Stamina – your ability to sustain effort for a longer duration; Fatigue Resistance – your body’s ability to resist the effects of fatigue. You can use Running Effectiveness to measure fatigue resistance. You can improve fatigue resistance through a well-structured training plan integrated with strength & conditioning.

Can you measure running form improvements? You can, but it’s not easy. You can use strength and conditioning, running drills, plyometrics, and other supplemental activities to improve ‘how’ you run (whether your movements are efficient, stable, and injury-free). And you can use Running Effectiveness to determine whether your changes have improved your ability to convert power into speed … or not.

How do I use Running Effectiveness? Running Effectiveness (RE) uses speed and power (effort) – both are measurable numbers, so RE is easy to calculate. But Running Effectiveness measures how effectively you convert power into speed, and there are many things that can affect that conversion: Your running intensity; Hills; Wind; Running shoes; Your power meter & weight changes. One way to monitor changes in RE is to use reference runs – runs you include every 3-4 weeks in your training plan, where you run the same route at the same target intensities in the same running shoes. Reference runs aim to minimise variations between runs, so that you can compare RE between runs and confirm improvements.

What is Running Effectiveness? Running Effectiveness (RE) was proposed by Andrew Coggan, PhD, and measures how effectively you convert power into speed. It’s a field-based measure similar to, but different from Running Economy (oxygen consumption at various speeds) or Running Efficiency (external mechanical power vs. metabolic power production), which both require lab-based testing. RE = speed / power, where speed is in metres per second and power is in Watts per kilogram.

Mixing your training intensities. A Training Intensity Distribution (TID) chart groups your time spent at each intensity into 3 or more zones, then displays the result as a stacked bar chart, with each stacked bar representing a week of training. The chart can show percentage of time in each zone (with the stacked bars all the same 100% height), or actual time spent in each zone (with the height of each zone representing the time spent in that zone). The TID chart is the third key metric for monitoring your training (along with Training Load Balance and Ramp Rate).

The danger of ramping up too quickly. Your Ramp Rate shows if you may be adding training load too quickly, replacing ‘the 10% rule’ with a metric based on your training volume and intensity and calculated from your completed runs. Your Ramp Rate is the week-on-week difference in your Chronic Training Load (CTL) or your 42-day weighted average, depending on which set of metrics you’re using. Why week-on-week? Because Long Runs will tend to impact your training load more than shorter interval sessions or easy/recovery runs. Using a week-on-week calculation will ‘smooth out’ any fluctuations caused by your workout mix while still producing a useful metric.

Balancing your training load. Training Load Scores, calculated for each workout, represent each workout’s metabolic stress. You can use these scores to model the shorter-term and longer-term impacts from each workout. Combining these, you can obtain a Training Load Balance (TLB), indicating whether your training is ‘productive’: A very positive balance indicates detraining or a lack of any meaningful training; A positive balance may indicate tapering or a missed workout; A negative balance indicates productive training – enough load to encourage adaptations, but not so much that there is a greater risk of injury or over-training; A very negative balance may indicate over-training, with a greater risk of injury.

The impact of training. On one side of the coin, the reason you’re training – improving your performance, your fitness, your speed, your ability to run further for longer. On the other, the impact of your workouts – fatigue, muscle soreness, dehydration, injury risk … the list could go on. How can a single Training Load Score (per workout) fully model training load – both the shorter-term impacts and the longer-term improvements?
The Performance Manager model (Coggan et. al) uses your Training Load Scores to calculate personal training metrics that indicate whether your training is productive – not too much, not too little, just right for you. And with two different load metrics (ATL and CTL), the model includes both the shorter-term impacts and the longer-term improvements.

What is Training Load? Your Training Load is the cumulative load from your training workouts. It’s easy to overdo it, leading to injury and time spent recovering (rather than training). But if you’re training for an event, regular (and repeated) workouts are a necessity. It’s a balance. Load your body too little, and it will not adapt; load it too much or too quickly, and it will break down instead of adapting; load your body correctly, and sustained long-term improvements are possible.
How can you monitor your Training Load? Using a Training Load Score calculated for each workout. Training Load Scores combine ‘how hard?’ and ‘how long?’. They represent each workout’s metabolic stress – its impact on your body from the workout intensities and durations. Training Load Scores are the foundation for metrics you can use to monitor your training load.

Is my PDC accurate? To ensure your PDC is accurate – that it represents what you can actually achieve right now: your training should include maximum effort runs for a range of different durations, so that your last 90 days of workouts includes a maximum effort for each duration; you should run maximum efforts every 4-6 weeks, alternating between durations, so that your Threshold Power (and your PDC) accurately reflects your current capability.

How do I use my PDC? Your PDC is individual to you, your fitness, and your abilities. It changes as you train (or detrain). If you’re training for an event, it should move up (higher power for same duration), to the right (longer duration for same power), or both. As long as your PDC is accurate (an up-to-date reflection of your capability), you can use it to: identify the power you should be able to maintain for every duration modelled on your PDC; estimate how well you might perform for a shorter event; estimate how well you might perform for a longer event. How do you know if your PDC is accurate? A good question, and one that deserves a separate post.

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 run, the shorter the time you can keep it going. What’s not obvious is that there is a mathematical (hyperbolic) relationship between your intensity (your effort) and how long you can maintain it. This relationship makes it possible to identify an exercise intensity that could be sustained for a very long time (your Critical Power) and the maximum amount of work that can be performed in a given time, both of which can be used to identify a race power target for shorter durations.

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 run, the shorter the time you can keep it going. What’s not obvious is that there is a mathematical (hyperbolic) relationship between your intensity (your effort) and how long you can maintain it. This relationship makes it possible to identify an exercise intensity that could be sustained for a very long time (your Critical Power) and the maximum amount of work that can be performed in a given time, both of which can be used to identify a race power target for shorter durations.

What is your PDC? The higher your power (your effort), the shorter the duration you can sustain it; the lower your power, the longer you can sustain it. There’s an inverse relationship between power and duration. You can chart this relationship. The result is a chart showing your Mean-Max Power (MMP) – the best effort you can sustain for each duration (measured using average power for each). Based on your MMP, your PDC models your best efforts over a range of different durations, showing (for each) the effort you could sustain.

What’s the best way to calculate threshold power? You can use any of the three most commonly used models. Why? Your threshold is a ‘phase transition’ over a narrow range of intensities, with lots of metabolic changes occurring at different rates and in parallel. And your Threshold Power is an intensity that’s within (or close to) the phase transition. In this context, any of the three most commonly used models can produce a usable Threshold Power. So which should you use? The answer typically depends on the app you’re using to review your power metrics: (1) Using WKO? You’ll most likely use auto-calculated FTP; (2) Using Stryd PowerCenter? You’ll most likely use Auto-CP; and, (3) Using another app? You’ll most likely use Critical Power tests.

Is Threshold Power better than VO2max? VO2max is a measure of your body’s maximum aerobic capacity – the highest amount of oxygen your body can use during hard exercise. Threshold power is the highest intensity (effort) you can maintain without rapidly fatiguing and needing to slow down or stop. Think of VO2max as ‘the size of your engine’ and Threshold Power as ‘your highest cruising speed’. A bigger VO2max means you could go further and faster, but it doesn’t mean you’ll use that capacity effectively; a higher cruising speed means you can run harder for a longer period of time. Both are important, but of the two, threshold power responds more easily to training, and is a more direct and practical predictor of performance in endurance events from 5k up through the marathon.