Frequently Asked Questions

We know there's a lot of complicated stuff going on with AI Endurance. Diving straight into it could be confusing. We've gotten a lot of questions from our users, and we've compiled the most common ones into this list. We hope you find the answer you're looking for here, but if you can't, feel free to give us a shout. Or, join our Facebook group and check out our community there!

Half Marathon Predictions

General Questions

We can offer you truly personalized training because our AI algorithm can predict your performance from your data. So we can provide you the best possible training results for your time constraints and tell you what performance you're going to achieve if you stick to the plan.

We deeply care for a scientific and data-driven approach. We know AI Endurance works because not only have we compared it to the most recent peer-reviewed research in exercise physiology, we have shown how our AI optimized training easily outperforms even the best one-size-fits all approach current research has to offer.

We can predict your future performance at about 5% if you have at least 100 runs with GPS data or rides with power data.

With AI Endurance every user gets their own 'digital twin' - a machine learning model that represents all the possible ways you would respond to different training routines. The model is updated every 24 hours for every user taking into account each new activity you have uploaded via Garmin, Suunto, Coros or Strava.

Running, cycling and triathlon.

Garmin Connect, Suunto, Coros, Strava and Apple Watch via Watchletic.

Gradient Averaged Pace takes into account the elevation gains and losses during your run and normalizes your running pace to an equivalent pace on a flat course. For example, if you're running up a steep hill your raw pace might be slow but your GAP can be high as it takes the steepness of the hill into account. AI Endurance uses GAP to predict your running performance. Your pace instructions are always in GAP.

Alternatively to GAP you can use running power.

Yes. We import your running power data from Garmin Connect, Suunto, Coros and Strava.

You can base your training plan entirely on running power and export your workouts to Garmin Connect, Suunto Guides, Coros or TrainingPeaks.

Indirectly via TrainingPeaks: Connect AI Endurance -> TrainingPeaks -> Stryd Workout app.

Yes, at least for some activities. Power is the only metric in cycling that we found to be predictive. There are too many variations in speed and heart rate data that are not indicative of performance. You don't need all your activities to be recorded with a power meter. If your activity has heart rate and cadence data, we estimate power from those measurements.

Yes. Please make sure your FTP tests have both the words 'test' and the duration in the activity title, e.g. '20 min FTP test' for a twenty minute FTP test. For Ramp Tests include the word 'ramp' in the title, e.g. 'Ramp Test'. To change your activity title, click on the activity in the calendar and click 'View Analysis'. Click on the pen symbol next to the activity title.

You can also mark your race performances by selecting 'Race' for your 'Run Type'/'Ride Type' in 'Edit Activity' on Strava.

Yes. If you don't have enough data yet we will predict your performance based on the accumulated data of athletes in our database similar to you. We will automatically switch to your personal data as you accumulate more data on your connected apps.

First, make sure that if you manually set your current performance level it is reflective of your actual current fitness state and not an all-time best that might not be representative of your current level. The best way to gauge your current level is to do an FTP test for cycling or a 15 min time trial for running (if you're training for shorter distances) or a 30 min time trial (for longer distances). Our algorithm will automatically pick these up and adjust your current level (see Do you detect my race performances and FTP tests? ). There can also be situations where it's hard for our algorithm to detect your fitness level, for instance if you have rarely done a test or pushed yourself in the past. In this case, our AI might underestimate your level systematically - however the predicted improvements relative to the level we detect are still going to be realized if you follow the plan. Finally, if you have always trained 10 hours a week and you are requesting a plan with 3 hours of training there might be no way to hold your current level. Our predictions are based on the learnings from your data and not just wishful thinking. Rest assured that if this is the case our algorithm is finding the plan that lets you decrease the least for your time constraints.

Here are a few possible reasons:

1. Garbage in garbage out - is your data clean, i.e. from a well calibrated GPS device or power meter? If not you can exclude time intervals where bad data was taken under 'Data Exclusions' in the Dashboard. A common culprit are saved runs that are actually bike rides. You can usually identify those via spikes in pace in your 'My Past Data' plot in the Dashboard.

2. For cycling, have you been riding with multiple bikes and not all of them are equipped with a power meter? If you record an activity without a power meter but wear your heart rate monitor and preferably have a cadence sensor installed, we estimate your power from those measurements. However, if there are lots of rides without heart rate data the model would be blind for a significant fraction of the actual training. Also if you have/had multiple power meters/smart trainers and those read inconsistently relative to one another that can cause issues.

3. Similarly, if you are not recording all your runs with a GPS device the model is blind to those activities you are not recording.

Yes, under 'Account' you can choose between metric (min/km) and imperial (min/mile).

AI training plans

Running: 5k, 10k, (Half-)Marathon, Ultra Endurance Pace, Critical Running Power, and Ultra Endurance Power.

Cycling: FTP, Critical Cycling Power and Ultra Endurance Power.

Triathlon: Sprint, Olympic, (Half-)Ironman.

You can also create Custom Configurations which can include any of the above goals at your chosen prioritization.

Yes, you can train for multiple goals simultaneously. Aside from your main A race, you can train for B and C priority races in your build up to your A race.

No - we do not recommend any structured training in this case. Focus on getting healthy first. The more you focus on getting healthy as opposed to a feared loss of performance the more you minimize your time away from structured training and racing. We always advise you to consult with your physician before following any exercise plan. Our AI does not detect injuries in any form and it is very important that you listen to your body and make game time decisions before and during the workouts that are most beneficial to your health.

We always advise you to consult with your physician before following any exercise plan. The predicted performance is based on the workouts we provide. However, it is very important that you listen to your body and use your own judgement before doing a workout. Pushing yourself too much can lead to injury. We always offer alternative instructions for an easier workout if you're not feeling great and sometimes you just need to skip a workout for extra rest and recovery and that's ok too!

- Directly execute the workouts from your Garmin device if you connect 'Garmin - Export Workouts' with AI Endurance.

- Directly execute the workouts from your Suunto device if you connect Suunto with AI Endurance.

- Directly execute the workouts from your Coros watch if you connect Coros with AI Endurance.

- Directly execute the workouts from your Apple Watch by creating a Watchletic account and connecting with AI Endurance.

- Export your training plan to TrainingPeaks where you can execute your workouts in Wahoo, Polar, and many more.

- Download our Zwift workouts.

Simply go to the 'Apps' page and connect your account. If you make changes to your AI Endurance training plan, these will automatically be forwarded to your connected apps. We continuously export your workouts up to one week into the future.

You may require a TrainingPeaks Premium account to access your full week of AI Endurance workouts in TrainingPeaks.

Yes simply connect Watchletic for uploading your activities to AI Endurance and executing your workouts on your Apple Watch.

If your readiness isn't sufficient for the upcoming workout, we recommend changes to your workout schedule. If you missed a workout we propose adaptions that keep your fitness on track. Also, if you haven't been following your current plan, there might be a better option available for your current fitness state. If your prescribed training significantly deviates from your actual training, we propose you to request a new plan that includes the updated information on your fitness state.

We deliberately do not include test workouts. Our data analysis is sophisticated enough to detect your fitness level from your regular training via a combination of critical power/pace measurements, HRV thresholds data, races, intensity distributions and more.

We can automatically calculate your running and cycling zones for you from your historical data. We use the following system to estimate your zones: first, we try to find enough DFA a₁ threshold data to set your zones. In a second attempt, we are using the distribution of your historical power/pace data to set your zones. You can also manually adjust your zones.

We calculate your swimming zones from our critical swim speed (CSS) estimate. We estimate your CSS for you from your historical swim pace distribution. You can also manually adjust your CSS.

No. The workouts are currently taken from a workout database created by an experienced coach. We are not providing AI swim workouts (yet) because it is harder to provide our AI with clean data to predict swimming performance as the data is inherently more noisy and less abundant.

Data Import

Yes we automatically avoid duplicate activities during import. In the odd case that activities get imported at exactly the same time, we delete duplicates every 24 hours. Activities from Garmin Connect and Suunto always override Strava activities as Strava does not pass on HRV data.

If you have 'Garmin - Import Data', Suunto, Coros or Strava connected, only a few seconds to minutes after you upload the activity. If you have multiple connections, we import your Garmin/Suunto/Coros activity first and sync with Strava a few minutes later to check if there is any additional information, such as if your activity was a 'Race' or if the activity name tells us you did an FTP test prior to re-training our machine learning model for each user. We make sure there are no duplicates between Garmin, Suunto and Strava even if you have multiple connections.

If your import data includes HRV, it can take a few minutes for your activity to show up in AI Endurance as the DFA alpha 1 analysis is computationally expensive.

Garmin does not pass on third party activities to AI Endurance. To import your Zwift or other third party activities please additionally connect with Strava.

Yes, if your recording device is not covered by our import options or you accidentally deleted an activity, you can upload FIT files on the Apps page.

If you're using Stryd and a Garmin watch that records Garmin's native running power, both power recordings will be stored in your activities fit file. To turn off Garmin's running power go to 'Select Running Activity' -> 'Running Activity Settings' -> 'Disable recording Garmin running power data'. We recommend you consistently stick to a single power source as different manufacturers have different algorithms for calculating running power that can have vastly different values.

Heart rate and heart rate variability

We use your heart rate data to gauge your performance. For instance, if you were able to run 5 min/km or at 200 W for an hour at a significantly lower heart rate than last week, the AI notices this as an improvement in your performance. However, generally heart rate is a much worse predictor for performance than power and GAP.

We calculate your aerobic and anaerobic heart rate thresholds from your DFA alpha 1 data, see this blog post.

For your cycling activities without power, we use heart rate and cadence to estimate your power through a personalized machine learning model.

We track your activity HRV data if you have 'Garmin - Import Data' or 'Suunto - Import Data' enabled and HRV logging enabled on your device. You can easily track your aerobic and anaerobic thresholds from your HRV data via DFA alpha 1.For more information, see also this blog post.

We also use DFA alpha 1 to track your readiness to train, durability and overall fitness improvements. Learn more here.

Enable HRV logging:

- Garmin: Settings -> System -> Data Recording -> Log HRV or Settings -> Physiological Metrics -> Log HRV. Connect to a heart rate strap - preferably Polar H10 - via Bluetooth not ANT+.

- Suunto: all devices connected to a heart rate chest strap automatically log HRV.


- Garmin: includes Forerunner 620, 630, 645, 920, 235, 255, 735, 935, 945, 955; Fenix 3, 5, 6, 7; Edge 520, 530, 820, 830, 1000, 1030, 1040, Explore; Epix.

- Suunto: all watches connected to a heart rate chest strap.

Unfortunately at this point Coros devices do not record activity HRV data.

Unfortunately at this point Strava does not pass on activity HRV data. If you want to track your HRV data, please connect Garmin Connect or Suunto directly to AI Endurance.

We automatically attempt to detect your DFA alpha 1 threshold for every activity with HRV data that you import into AI Endurance. For a threshold test, simply export the DFA alpha 1 ramp test to Zwift or your Garmin device from the Apps page.

Go to the Account pageand set your intensity zones.

- If your Endurance ceiling (aerobic/VT1) was determined, set the first blob (Endurance - Tempo boundary) to the determined value.

- If your Threshold ceiling (anaerobic/VT2) was determined, set the third blob (Threshold - VO2Max boundary) to the determined value.

We also automatically track if your thresholds are not in-tune with your current zones and notify you if an update is appropriate.

In order to detect DFA alpha 1 thresholds automatically, AI Endurance has to detect an intensity ramp during your activity as this is the method that is backed by current research on DFA alpha 1 threshold detection.Our algorithm has to be able to identify a time frame that fulfills the following criteria for automatic threshold detection:

1. Steady and smooth increase of intensity, i.e. monotonically decreasing alpha 1 values and monotonically rising pace/power values.

2. Sufficient data points on both sides of the threshold, e.g. alpha 1 < 0.5 and alpha 1 > 0.5 for the anaerobic threshold detection.

3. A not too high ramp speed for increasing the intensity. If you ramp up the intensity too quickly there is a delay in your cardiovascular response relative to your power/pace that would lead to overestimated power/pace thresholds.

You also have the option to download the activity data from the activity page as a csv file and manually perform the ramp detection.

5-10% artifact corruption. Artifact corruption indicates the quality of your HRV data. For minimal artifact corruption, we recommend the Polar H10 heart rate monitor. In your activity page, we show your DFA alpha 1 threshold for any artifact corruption but for analysing your readiness to train we only take into account activities with less than 10% corruption. To be taken into account for AI predictions, we require less than 5% corruption.

The Polar H10 reliably records HRV data with artifact corruption of less than 5%. Other heart rate monitors can also in some cases deliver this quality but you will have to check with your particular heart rate monitor on a case to case basis.

Bluetooth. Recording with ANT+ generally leads to significantly less quality HRV data. If the heart rate monitor is already added as an ANT+ device in your Garmin unit, make sure to first unpair it. Then, add a new heart rate monitor, skipping the default ANT+ option and selecting to search for more or search Bluetooth.

Bruce Roger's DFA alpha 1 FAQ is an excellent resource for all topics related to DFA alpha 1.

More Support

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