Running Economy – all you need to know about Garmin’s new running efficiency metric
What is Garmin’s metric “Running Economy”?
An important new running metric from Garmin
Running Economy (RE) is a complex and multifactorial concept. It represents the energy required to run at a given, steady pace below what the runner is maximally capable of. Runners with better RE use less energy than others at the same pace. RE is widely considered a crucial metric for runners aiming to maximise performance and is a strong predictor of performance in distance running.
Consider VO2max:VO2max describes your body’s maximal performance
Consider vVO2max: This is the specific, maximal speed at which you reach your peak oxygen uptake (VO2max)
Running Economy: Is similar to vVO2max, but as RE considers lower speeds, it is a more useful concept for endurance runners over an extended period
Traditionally, RE is measured in a laboratory setting by analysing oxygen consumption while wearing a mask while running on a treadmill at constant speeds. It is expressed in units like millilitres of oxygen consumed per kilogram of body weight per minute (mL/kg/min). Lower values are better.
It is essential to understand that many factors affect RE, including metabolic, cardiorespiratory, biomechanical, and neuromuscular characteristics, as well as training, footwear, and environmental conditions. Improving any component of RE can improve the metric.
Garmin’s Implementation
Garmin defines Running Economy as a personal measure of the energy cost of aerobic running, reflecting how efficiently the body converts energy into performance. The company uses a variation of the standard unit of measurement – mL/kg/km (you don’t need to remember that) and highlights that a low value is better.
Garmin’s Measurement Method
Garmin’s approach differs from the scientific literature and uses a less accurate but more convenient sports watch. The measurement is only expected to be added to high-end watches like the Forerunner 970. Also, it requires the latest HRM 600 chest strap, which, at launch, was the only accessory capable of measuring Step Speed Loss (SSL). Unlike laboratory tests, Garmin requires you to run outdoors or on a track, not on a treadmill.
How does Garmin capture Data & Calculate Running Economy?
Garmin’s metric relies on several data inputs: heart rate, speed, and running dynamics data, specifically stride length, ground contact time, vertical oscillation, and Step Speed Loss, are mentioned by the company. The latter, SSL, is an essential input for measuring horizontal braking during footstrikes.
SSL in cm/s is measured by the HRM 600 heart rate monitor and is influenced by running form characteristics like cadence and overstriding. It too is a complex metric adjusted for hills and normalised for pace. While SSL is related to braking forces and the ground contact phase, it is distinct from other metrics like Stryd’s Leg Spring Stiffness or Impact Loading Rate, making it tough for competitors to introduce the same metrics.
Data Processing and Exclusions
Garmin’s RE estimate is based on at least 4 to 5 runs and combined before the first estimate is provided. Contributory runs should exceed 30 minutes.
The company claims to contextualise all inputs with the runner’s overall history. It excludes indoor runs, trail runs (due to rugged terrain and frequently changing conditions that obscure true RE), and runs recorded with a pack weight. This exclusion of trail runs makes sense as uneven surfaces will increase energy demand.
Trainability and Improvement
Garmin acknowledges that both genetic and trainable factors influence RE. They state that RE is trainable and can be improved, recommending gradual increases in weekly mileage and incorporating strength training and sprint workouts.
Numerous other sources also support these recommended training methods (increased mileage, strength training, plyometric/sprint workouts).
What running Economy Metrics Can I display?
Running Economy is viewable in Garmin Connect and as a Performance Glance (widget)
Select > Performance Stats > Running Economy.
Limitations of Garmin’s RE
Garmin has not provided any validation of its RE calculation. How can a field-based test be as accurate as a lab-based test in controlled conditions with superior data-capturing abilities?
It is important to note that neither the sensor inputs nor the calculations have been validated. Furthermore, contributory metrics like SSL are not continuously captured, so parts of the dataset are missing.
We don’t know if Garmin’s metric is ‘good enough’ to be actionable.
Doubts aside, RE is an important new metric from Garmin that runners should look closely at and monitor over time. There are competitor alternatives with drawbacks – Polar, Coros, and Suunto.
Garmin Forerunner 970
Premium GPS triathlon smartwatch. Features a bright AMOLED touch screen and a built-in LED flashlight.
> Performance Stats > Running Economy.
