What is Power?

    Power is another name for ‘effort’.

    At least, that’s the easiest way I’ve found to describe it.

    Second-by-second as you run, power provides numbers representing your effort.

    Run harder, and the numbers increase; run easier, and they decrease … whether you made the change, or whether the change is a result of your route or the conditions.

    The change is in real-time with minimal delays or lags. And the magnitude of the change in your power numbers reflects the magnitude of your change in effort.

    Some examples of changes and whether they result in a higher or lower power, are:

    Change in
    Higher power when running
    Lower power when running
    Speed
    faster
    slower
    Gradient
    uphill
    downhill
    Wind
    (if your power meter detects it)
    into a headwind
    with a tailwind
    Heat
    in lower temperatures
    in higher temperatures
    Humidity
    in lower humidity
    in higher humidity
    Altitude
    at lower altitudes
    at higher altitudes (until acclimatised)
    Running shoes
    Runners have reported differences, but there's no consistent way to predict the impact
    Soft surfaces (e.g. sand)
    Power meters are unable to detect soft surfaces and typically show no change in effort

    Why Power?

    Power is a measure of how hard you’re running. It’s not the only measure – runners also use:

    • Pace – how fast you’re running, usually expressed as Minutes per Kilometre (min/km) or Minutes per Mile (min/mile).
    • Heart Rate – how fast your heart is beating, usually expressed as Beats per Minute (BPM).
    • Perceived Effort – how hard it ‘feels’. Perceived effort measurements use various scales, but the key thing is that it’s your perception of your effort, rather than something measured by a sensor.

    Which is best?

    There’s no agreement among runners or coaches about which is best. It depends on:

    • The equipment you have access to. For example, if your watch doesn’t have a Heart Rate sensor, then Heart Rate won’t be best for you.
    • What you (or your coach) are used to using. If you’re used to using a specific measure, you’re more likely to continue using it – it’s something you’re familiar with.
    • Whether you know how to use the measure. The better you understand something, the more likely you are to decide to use it (or not).

    Comparing the advantages and disadvantages of each:

    Measure
    Advantages
    Disadvantages
    Pace
    • Most watches and phones can measure it
    • Easy to understand
    • No delays or lags
    • Impacted by hills and wind
    • May encourage 'hopeful' goal times
    Heart Rate
    • Most watches can measure it
    • Easy to understand
    • Can 'lag' behind changes in how hard you're running
    • May 'drift' higher on longer runs
    • Difficult to stay in 'Zone 2' (you may end up walking)
    • Won't exceed maximum HR (even if your effort does)
    • Affected by age, stress, fatigue, temperature (and more)
    Perceived Effort
    • Easy to understand
    • No delays or lags
    • Affected by age, stress, fatigue, temperature (and more)
    • Takes time and training to develop a good 'feel' for effort
    • Cannot be recorded for later analysis
    Power
    • Easy to understand
    • No delays, lags or maximums
    • Quantifies your effort (recorded for later analysis)
    • Can be used to assess your running fitness
    • Can be used to calculate individualised targets
    • Still new and unfamiliar as a measure
    • Need a Power Meter to measure it
    • No universal standard for calculating running power

    In brief:

    Power is an objective number representing the effort you’re putting into your running

    … and once you can measure your effort, all sorts of things become possible …