Whoop-Dee-Duped?—The Power and Peril of Persistent Performance Data Tracking
I am excited by the potential of new consumer health technology—wearables, home testing kits, and so-called digital therapeutics—to help better quantify and monitor our health status. I abhor relying on crude, biased assessments like a 24-hour dietary recall to get a picture of a patient’s food choices. I am bullish on the democratization of continuous glucose monitors to help all of us better understand how our metabolism functions, or dysfunctions. Below the surface, each of us has a unique physiology. Objective, real-time data that reveals cause and effect—you ate this, and now your blood sugar level spiked to this—is critical for revealing insights, showing trends, and triggering behavior change.
That said, let’s acknowledge the downsides and signal caution to taking an entirely data-driven, quantify-everything approach to our health. I have learned this repeatedly along my quest for better health and performance, most recently by wearing a WHOOP Strap 3.0. Given my focus on recovery and the importance of pairing stress with rest in order to create adaptive change, this fitness tracker is definitely the go-to tool on the market.
The WHOOP Strap provides in-depth health metrics such as heart rate variability (HRV), training load, and sleep patterns to recommend when to push through a tough workout and when to take a recovery day. Worn on the wrist, the device uses LEDs and photoplethysmography to take these measurements, which it then sends to the WHOOP app to analyze. The sleep tracking function analyzes how long you sleep, your sleep stages, your sleep efficiency, and your required sleep for optimal fitness performance based on your previous sleep patterns. The recovery function uses HRV, resting heart rate, and sleep quality to provide a recovery score and relay your readiness for a tough workout. And the strain function tells you how much you exert yourself during a workout based on a sustained elevated heart rate.
In my daily sleep report, the WHOOP app displays my time in bed and my sleep efficiency—the amount of time I am actually asleep each night. All of us have sleep disturbances or so-called microawakenings at night. Some we remember; some we don’t. These days, I am more consistent with being in bed with lights out for about 7 ½ hours nightly. I sense that I sleep solidly. And my wife, who struggles with insomnia, enviously confirms. The next morning, my WHOOP app tells me that I only got 6 hours of sleep! No matter how I felt when I first got out of bed, I instantaneously feel more tired when I see this report. Could I possibly have been awake for 90+ minutes last night and not even known it?
The WHOOP strap estimates sleep based on measures of movement and heart rate derived from actigraphy and photoplethysmography. Summative data shows limitations in the accuracy of wearable sleep technology when compared to the gold standard, polysomnography. That said, the WHOOP appears to be one of the most accurate sleep trackers on the market based on a recent independent validation study. Perhaps the actigraphy measurements confuses my light sleep with wakefulness, which is a documented issue. Regardless, this overestimation of my awake time has been a consistent error of the strap. And given that sleep is a core input for the recovery score, this calls into question the accuracy of its value proposition.
On days that I go for a relaxed swim, my strain score—valued on a scale from 0 to 21—can be as high as 15 or 16 after spending an hour or so in the pool. Swimming is a form of active recovery for me that gets my blood flowing, stretches out skeletal muscles and decompresses my joints. The next day, I am ready for what feels to me like a much more aggressive and taxing workout, such as lower body strength training with high volume squats and deadlifts. I finish that workout completely gassed and my strain score is about 8 or 9, significantly lower than after yesterday’s swim. What gives?
The WHOOP’s Strain score is based on heart rate data. But your heart is one of many muscles that can be working hard during a training session. And there are certain types of workouts that do not tax your cardiovascular system but bludgeon your skeletal muscles like high volume strength training. Perhaps the WHOOP is useful for endurance athletes who focus primarily on cardiovascular training. But for someone like me, who practices multiple modalities of physical training, a proper estimation of my total body strain is more nuanced. And even though the strain score is not a factor in the ultimate recovery score, my heart rate and sleep may indicate high recovery while my muscles may be sore and screaming for rest. The WHOOP provides recommendations for day-to-day cardiovascular strain and recovery but cannot consider the full context and architecture of a comprehensive training plan.
To be clear, none of this is to say that the WHOOP and some of the other performance-focused wearables out there are useless gimmicks. The exact opposite, in fact. With its exceptional data analytics and visual display, the WHOOP provides potent insights that can spark awareness and motivate behavior change. It provides constructive feedback and actionable insights personalized to you and your behaviors. For example, even if my WHOOP does not accurately capture my sleep each night, the data does show a clear trend that my sleep is of higher quality when I stop working and shut it down before dinnertime. If I get back online at night, the stimulus definitely disrupts my sleep quality. Or when my stress level is higher, as it generally is midweek, I see this in a lower HRV and lower recovery score. Perhaps I knew this intuitively before wearing the WHOOP, but the objective confirmation helps trigger behavior change.
To date, however, our technology cannot capture a complex, multidimensional metric like recovery in a single score. Yet my WHOOP app is the first thing that captures my attention each morning. I want to see how I slept and my level of recovery. I want my sleep efficiency to be higher even if I feel well rested. After a workout, I want my strain score to confirm that I worked hard. And when my WHOOP data does not map to my self-assessment, I inevitably feel a pang of failure. Who cares how I actually feel if my WHOOP does not validate my progress? There is a subtle yet palpable pressure before I hit the gym and go to bed because I know my WHOOP is watching.
The question, then, is who exactly am I trying to perform for—myself, or my WHOOP? If we are not careful, the technology that we use to track our health can become an added stress, or worse, a source of anxiety. Indeed, sleep trackers can paradoxically exacerbate sleep anxiety. This is, of course, completely counterproductive to the intended goal of health itself.
And so, as I work with my clients along their health journeys, I remain wondrous but wary of wearables. Certain metrics provide marvelous insights. Yet over-quantifying your physiology risks messing with your psychology. As I assess new technologies to measure and monitor health behaviors and health status, here are a few questions on my decision tree:
1) Is this technology accurate? -- Inaccurate data is not only unhelpful, it can be harmful.
2) Even if it is not entirely accurate, is it at least precise such that it can reveal helpful trends?
3) Will the data generated be reliable, focused, and communicated in a way that provides actionable insights? -- Data is only useful to the extent that it activates behavior change to reduce risk and improve health outcomes.
4) Is there a point at which continued generation of data or tracking becomes counterproductive such that the risks outweigh the marginal gains?
All of this begs a more philosophical discussion about the relative utility of objective metrics versus subjective feeling to monitor health status. There is profound wisdom in the adage “listen to your body.” Our bodies are quite good at telling us how they feel if we take the time to learn and listen to their unique signals. If we outsource this listening to trackers, we risk losing this beautiful dialogue and building this powerful intuition. As I explain to my clients, with proper training, patience, and some very targeted and time-limited tools, you can become the expert of your body.
What then are the proper tools and tests that will sharpen and enhance this intuition in a way that does not cause dependency or harm? In my own health journey, and in the VIM Medicine practice, I continue to seek the best answers.