Technology can be an excellent tool for runners looking to improve performance, assess progress, and keep track of useful metrics. Apple Health is one of the most used apps for active individuals, but the vast amount of data available can be overwhelming. Knowing which metrics to focus on can help runners understand and document their stats, tailor training sessions and improve performance.

What can you measure with Apple Health?

If you have an iPhone, Apple Health automatically tracks distance, steps and other metrics, by using the phone’s built-in accelerometer. 

However, the most valuable metrics require the use of an Apple Watch. With the Watch, you can track runs and workouts, including distance, pace, heart rate, and calories burned, as well as sleep and environmental sound levels. It also integrates with other popular fitness products and apps (such as Garmin, Strava, and Peloton) so you can get the most out of your workout.

Let’s start off by discussing how the Apple Watch measures heart rate, which is one of the most important metrics used to understand athletic progress and recovery time.

Heart rate

Apple Watch measures your heart rate continuously throughout a workout, and once the workout ends, it will continue to measure for three minutes to determine a workout recovery rate. It uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist [10]. When your heart beats, the blood flow in your wrist is greater, and less in-between beats. By flashing its LED lights hundreds of times per second, Apple Watch can calculate your heart rate by the number of beats/minute [10]. But heart rate is more than just beats/minute; it’s broken down into two metrics, resting heart rate and heart rate variability, both of which are important for performance levels.

Resting heart rate

Resting heart rate (RHR) is one of the most basic measures of health and fitness. Lower resting heart rate is associated with longer life expectancy and better cardiovascular health outcomes [1]. Endurance exercises (such as running) can help lower your resting heart rate, which means that athletes tend to have a lower RHR than the general population [1]. This is because the heart muscle becomes more efficient at pumping blood, and therefore needs fewer beats per minute to transport blood throughout the body. 

Your resting heart rate can also determine recovery levels and alert you to potential overtraining. If you notice a resting heart rate that is higher than your average, you may not be fully recovered from a hard workout or run. An elevated RHR may signify a rest day, while a lower RHR may indicate increased readiness to perform at your best [2]. 

Heart rate variability

Heart rate variability (HRV) is a less commonly understood metric, but it’s an important measure of health and fitness. HRV is defined as a measure of variation in time between heart beats and comes from simultaneous influences from the parasympathetic and sympathetic nervous systems. Your sympathetic nervous system (also known as “fight or flight”) causes the heart rate to increase, while your parasympathetic nervous system (also known as “rest and digest” causes your heart to beat slower. These competing systems result in heart rate variability [3]. 

Like resting heart rate, HRV can be used to assess training levels and gauge recovery. A higher HRV can be used as an indicator to train [4]. Conversely, lower HRV suggests that you may need more time to recover. 

HRV is highly individualized and dependent on several factors, including training volume and intensity, nutrition, alcohol intake, sleep, stress, age, gender, and genetics [5]. Rather than comparing your HRV to a standard number, it is more useful to keep track of your individual trends through tools such as Apple Health.

VO2 max

VO2 max is defined as the maximum amount of oxygen utilized by the body during periods of exercise [6]. Higher VO2 max levels are associated with lower risk of cardiovascular disease and all-cause mortality and tend to be positively influenced by high intensity exercise, such as running [6,7]. Other factors that influence VO2 max are training intensity, altitude, age, and biological sex.

VO2 max values can be used to assess your progress during a training cycle. The best way to improve your VO2 max is by incorporating higher intensity running workouts, and alternating between continuous and interval training. Apple Watch uses Watch sensors like the heart rate monitor and accelerometer to calculate VO2 max [10].

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Exercise minutes

One of the more basic metrics you can get from Apple Health is exercise minutes. Every minute of movement that is equal to or exceeds the intensity of a brisk walk will contribute towards your exercise minutes and this is a great way to keep a log of your total running and training time. 

For adults, physical activity recommendations are at least 150-300 minutes per week of moderate intensity or 75-150 minutes per week of vigorous-intensity aerobic physical activity, plus muscle-strengthening exercises at least twice a week [8]. Many athletes significantly exceed these recommendations but keeping track of weekly exercise minutes can be used to quantify training output and progression.

Tracking exercise minutes also helps prevent overtraining, especially during long runs. Runs that exceed 3 hours can increase your risk of injury, and the benefits start to diminish. 

Environmental sound levels

Another useful metric for runners is environmental sound levels. Your Apple Watch can track both headphone and environmental sound exposure, measured in decibels (dB). If you run with headphones in, participate in fitness classes with loud music, or attend sporting events, the Apple Watch will display volume and length of exposure. Noises above 70 dB over an extended time can damage your hearing and result in permanent hearing loss [9]. 

Sleep tracking

Proper rest is crucial for performance and recovery and sleep is another useful Apple Health metric for runners. Sleep features available in Apple Health include monitoring sleep trends, setting bedtime hours, and updating your sleep goals. Moreover, Apple Health integrates with Apple Watch, Oura and other sleep trackers for runners who want more granular information about sleep quantity and quality to improve performance and assess readiness to train. 

Summary

Apple Health can be an excellent tool for runners looking to monitor their progress, develop a training plan, log runs, and prevent overtraining. By understanding key metrics such as resting heart rate, heart rate variability, VO2 max, exercise minutes, and environmental sound levels, you can get a more complete picture of your overall fitness levels. While the data from Apple Health is not always 100% accurate, the app provides numbers and trends that can be used to assess readiness to train as well as training progress. Knowing and monitoring your metrics can make you a stronger, faster, and healthier runner.