Aerobic Endurance Analysis

User guide index: https://marcoaltini.substack.com/p/hrv4training-pro-user-guide

The aerobic endurance analysis includes two features: aerobic efficiency and cardiac decoupling. In both cases, aerobic endurance relates to your ability to sustain a given workload. To determine your aerobic endurance we compute the ratio between external load or output (pace or power) and internal load or input (heart rate) across workouts (efficiency) and within a workout (decoupling). Intuitively, a lower heart rate for the same output (pace or power), when consistently shown over periods of weeks, translates into better aerobic endurance.

The ability to track over time this metric makes it easy to determine when meaningful improvements are made, and how long it took, which is useful information.

First, we can select a sport (running or cycling), a timeframe, and a smoothing window, which means that our workouts will be averaged over a moving window that goes from 1 to 4 weeks. Smoothing helps in getting rid of day to day fluctuations that are not representative of longer-term changes in fitness, hence I would recommend using average or heavy smoothing for this feature.

Accounting for confounding factors

There are many factors that can affect the relationship between pace (or power) and heart rate. A few examples are: running or cycling on trails or difficult terrains, (which reduces pace and makes your data not really representative of your fitness), very short workouts where heart rate does not reach a steady state, environmental factors such as hot days or training at altitude, etc. — the list goes on.

While many of these parameters are simply impossible to account for, what we can do is give you more control over what data is used to track changes in aerobic endurance. In particular, via the panel below you can filter workouts so that the resulting data is more representative of your aerobic endurance.

In particular, you can configure the analysis based on a number of parameters related to the workout, internal load, and environmental conditions:

Pro will show you which workouts are filtered for the last time window included:

Aerobic efficiency

Good endurance athletes tend to have high aerobic endurance, meaning that they can sustain a relatively high workload (for example pace or power), at a relatively low effort (typically measured in terms of heart rate).

To determine your aerobic efficiency we compute the relation between external, load or output (pace or power) and internal load or input (heart rate). Intuitively, a lower heart rate for the same output (pace or power), when consistently shown over periods of weeks, translates into better aerobic efficiency.

Similarly, a higher power or faster pace at the same heart rate is linked to improved aerobic efficiency. By analyzing the relationship between input and output for running or cycling activities, you can easily track aerobic endurance changes over time, as you progress with your training.

Note that there is no ideal (absolute) value when it comes to aerobic efficiency, the whole point is to track progress relative to your historical data and to see how training is progressing.

Cardiac decoupling

Cardiac decoupling relates to your cardiac drift during an aerobic effort. What’s your cardiac drift? Basically, your heart rate increases as a result of your body getting fatigued, during the second part of a workout.

To determine your cardiac decoupling, we compute the relation between output (pace or power) and input (heart rate) during the first and second half of a workout.

Intuitively, if your heart rate increases at the same pace during the second part of a workout, or if your pace reduces in an attempt to keep your heart rate below a certain value, it means that your aerobic endurance for the distance is not well developed. Similarly, a ratio close to one or below 1.03–1.05 shows that your heart rate does not drift much during the second part of the workout, which is a sign of good aerobic endurance.

Please note that for this feature to work, you will need to use Strava and log Laps (typically, sport watches log laps automatically to Strava).

I hope you’ll like the new Aerobic Endurance Analysis page and the improvements we implemented.

Please feel free to comment below in case of any questions or feature requests.

Thank you for your support.

Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching.

He has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.

He is co-founder of HRV4Training, advisor at Oura, guest lecturer at VU Amsterdam, and editor for IEEE Pervasive Computing Magazine. He loves running.

Twitter: @altini_marco

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