More than 1.2 billion people in the world use some kind of wearable. However, most take advantage of just 10% of the potential of these devices: they count steps, check calories and little else. The reality is that today’s wearables – from an Apple Watch to a Whoop to an Oura Ring – measure physiological indicators that, interpreted correctly, can reveal how your body is aging, how well you are recovering and whether you are accumulating a stress load that will eventually take its toll.
In this article we explain the six most relevant metrics that these devices record, why they matter especially after the age of 40 and how to read them to make better decisions about your training, your rest and your overall health. All this with the perspective of Dr. Alejandro Ramirez, Medical Director of Lumm Medical and specialist in Sports Medicine, with extensive experience in optimizing physical performance and healthy longevity.
HRV: the metric that measures how well your heart adapts to stress
Leart rate variability (HRV) (HRV, for its acronym in English: Heart Rate Variability) is the difference in milliseconds between one heartbeat and the next. Contrary to what you might think, a healthy heart does not beat like a metronome. It varies. And that capacity for variation reflects the flexibility of the autonomic nervous system to respond to stress and return to calm.
“What HRV seeks to measure is adaptability,” explains Dr. Alejandro Ramirez. “To the extent that these intervals between beats are not very constant, it means that my heart has a greater capacity to respond: if I generate stress, it reacts; if I am at rest, it relaxes.”
Uhigher HRV value indicates greater cardiovascular flexibility, while a persistently low value may indicate accumulated fatigue, chronic stress or insufficient recovery.while a persistently low value may indicate accumulated fatigue, chronic stress or insufficient recovery. But there’s a fundamental nuance: it’s not the single day’s number that matters, but the trend over weeks and months. The analogy is simple – you don’t understand the weather by looking at whether it’s raining or sunny today; you need to look at the trend over a broad period.
What influences HRV?
Several factors modulate this metric: age (the autonomic nervous system matures and changes with age), level of training, quality of sleep, diet and type of exercise.
An interesting fact highlighted by Dr. Ramirez: strength and muscle training is one of the most effective ways to increase parasympathetic tone – that branch of the nervous system responsible for recovery and repair – and thereby improve HRV.
How to read it on your device?
Don’t compare yourself to others. An elite athlete might have an HRV of 200; an active 50-year-old might be between 30 and 50. What is relevant is your own baseline and how it responds to the stimuli you give your body. If you trained intensely yesterday and today your HRV dropped, that’s normal. If it’s been dropping for weeks for no apparent reason, it’s a sign that something needs attention.
Sleep: the metric that defines whether you are really recovering
Sleep is not just about closing your eyes. Sleep has phases, and two of them are critical for health: deep sleep and REM sleep.
During deep sleepDuring deep sleep, the body enters its anabolic phase: muscle tissue is repairedgrowth hormone and testosterone are released, and the cardiovascular system recovers. It is literally the time of construction and repair. The peaks of release of these hormones occur mainly between 9:30 p.m. and 12:00 a.m., linked to the circadian cycle rather than the time you go to bed.
The REM phase (rapid eye movements) is where most brain activity occurs. Here dreams appear, but also something more relevant happens: a brain cleansing process. During the REM phase, there is an increase in the circulation of cerebrospinal fluid that allows toxins accumulated during the day to be eliminated. “People who do not have an active REM phase are at greater risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s, associated with the accumulation of Tau proteins,” says Dr. Ramirez.
The 40% rule
According to Dr. Ramirez, at least 40% of total sleep time should be composed of deep sleep and REM sleep combined. If you sleep eight hours, that means at least three hours and twenty minutes should correspond to these two phases. Your wearable shows you this breakdown every morning – and that’s where the information becomes actionable.
What ruins your sleep without you knowing it?
Diet has a direct and measurable impact on sleep quality – and your wearable can prove it to you. A large, high-fat dinner or one too close to bedtime raises cortisol and thermogenesis, altering sleep phases (for this correlation to be possible, you must add in the app you have, what foods and beverages you consume).
Alcohol consumption – even two glasses of wine – can limit the quality of your rest even if you feel you slept. And on the contrary: a protein intake appropriate for your age and activity level favors muscle synthesis during deep sleep and improves overall recovery.
The device records these correlations, especially if you feed the diary with information about your meals, supplements and habits for the day. Over time, this combination of data and the artificial intelligence built into platforms like Whoop allow you to generate personalized recovery recommendations.
Strain: the total load your body accumulates
The strain (from English, stress o load) is a metric that quantifies the total level of stress you put your body under during the day. It is not limited to exercise: it includes workload, worries, lack of rest and any factor that activates your sympathetic nervous system.
It is calculated by combining the intensity of the effort (measured through heart rate) with the volume or time of activity.
But there is one component that many people underestimate: stress not linked to exercise.. An executive who trains hard but carries a high level of work stress is accumulating a combined load that can overwhelm his or her body’s ability to recover.
“Nou gain nothing by training if the total stress load is supremely high,” warns Dr. Ramirez. “That’s where cardiac variability starts to decrease, VO2 goes down and perceived load goes up. If you don’t seek balance, you’re going to melt down ..”
Fatigue is not only muscular
There is fatigue of neurogenic origin – your brain is also exhausted.
The famous burnout is not only a psychological concept; it has a measurable physiological manifestation. When the strain remains elevated in a sustained way, the device generates alerts: you need to go to bed earlier, make a wind down (low lights, no screens, reading on paper, room temperature of 21°C) and prioritize recovery over the next workout.
VO2 max: the most powerful predictor of longevity
VO2 max measures the efficiency with which your mitochondria produce energy from fatty acid oxidation.
In simple terms, it is your body’s maximum capacity to use oxygen during physical exertion. The reference test to measure it is ergospirometry, but current wearables offer estimates with a margin of error of 8-15%, enough to observe trends.
¿Why is it so important? Because it has been consistently associated with all-cause mortality.
A high VO2 max correlates with lower risk of frailty, cardiovascular disease, cancer and metabolic disorders. To achieve this, your body needs adequate functional muscle mass, healthy body composition and sustained physical work capacity.
How to improve it?
The approach recommended by Dr. Ramirez is polarized: a majority percentage of low-intensity aerobic activity (zone 1 and 2) to increase the number of mitochondria, supplemented with 15-20% high-intensity interval training (HIIT) to improve mitochondrial efficiency, and strength work to increase muscle mass and GLUT4 receptor expression.
SpO2 and body temperature: early signs not to be ignored
The oxygen saturation (SpO2) indicates how efficiently your blood carries oxygen to the tissues. Levels consistently below 95% warrant medical attention. Although it became popular during the pandemic, its continuous monitoring through a wearable can reveal respiratory or blood problems early.
The body temperature is another indicator that modern wearables track during sleep. Thermal equilibrium (homeostasis) is essential for the body’s enzymes to function properly. Sustained alterations in temperature are associated with inflammatory processes, incipient infections or circadian cycle dysregulation. In fact, recent research on glycine and its effect on the suprachiasmatic nucleus of the brain shows that modulation of body temperature may be a more effective sleep inducer than melatonin.
Combined predictive power
Perhaps what is most valuable is not each metric separately, but what they reveal together. When HRV drops, resting heart rate rises, temperature is altered and VO2 drops, the pattern can predict a disease event up to two to three weeks before symptoms appear. That’s the difference between reacting and preventing.
Post-exercise recovery: the first 60 seconds speak volumes
One metric that few people check is the rate of heart rate recovery in the first minute after intense exertion. If after finishing a demanding workout your heart rate drops more than 5% in the first 60 seconds, it is a positive sign that your autonomic nervous system is responsive.
If that recovery is consistently slow, it may indicate that your body does not have sufficient adaptive capacity in the face of stress. It’s a simple indicator, accessible on most wearables, and hugely revealing for adjusting the intensity of your training.
It’s not for elite athletes: it’s for anyone who is committed to pro-aging.
It’s easy to think that all this only applies to athletes or people obsessed with performance. The reality is different. “This is not an issue for the person who runs races on the weekends,” Dr. Ramirez clarifies. “It’s for the person who trains in the gym two or three times, for the person who plays their weekend games. Doing it right implies understanding our organism a little better.”
What these devices allow, in essence, is something we at Lumm Medical call pro-aging responsible: it is not about slowing down time or pursuing eternal youth. It is about aging with more information, more awareness and better decisions. HRV, sleep, strain, VO2 max – each of these metrics touches on at least one of the five pillars of holistic health that guide our approach: movement, psyche, rest, food and appearance. A wearable, used well, gives you visibility into how these pillars interact in your daily life.
The wearables industry moves 92.9 billion dollars globally (2024) and is projected to reach 230 billion dollars by 2033. In Colombia, the market exceeds 522 million dollars. Latin America is growing at an annual rate of 18% in the adoption of these devices. The figures confirm a clear trend: more and more people are taking control of their health through data..
But data without interpretation is just numbers. The real value lies in understanding what they tell you, how they connect with each other and what decisions you can make based on them. A wearable does not replace a doctor, nor does it replace comprehensive professional support, but it can become a daily ally for those who have decided to live longer – and live better.
Frequently asked questions about wearables and health
Which wearable is best for monitoring health?
There is no universal “best”. Devices such as Apple Watch, Garmin, Whoop, Fitbit and Oura Ring offer similar metrics with differences in convenience, battery life and depth of analysis. The most important thing is to choose one that you can wear consistently – including during sleep – and learn to interpret its data in the context of your own story.
What is heart rate variability (HRV) and why does it matter?
HRV measures the differences in milliseconds between consecutive heartbeats. A high HRV indicates that the autonomic nervous system has a good capacity to adapt to stress and recovery. It is especially relevant after the age of 40, when the autonomic nervous system begins to show natural changes that can be monitored and optimized.
How many hours of deep and REM sleep do I need?
According to Dr. Alejandro Ramirez, at least 40% of your total sleep time should be deep sleep and REM sleep combined. In an eight-hour night, that equates to about three hours and twenty minutes between the two phases. Your wearable shows you this breakdown so you can assess the actual quality of your sleep.
Why is VO2 max a predictor of longevity?
VO2 max reflects the efficiency of the body to produce energy using oxygen. Higher values are associated with lower risk of all-cause mortality, including cardiovascular disease, cancer and metabolic disorders. Improving it requires a combination of sustained aerobic activity, high-intensity training and strength work.
Can wearables predict disease?
Yes. When multiple metrics are altered simultaneously – HRV goes down, resting heart rate goes up, temperature becomes dysregulated – the pattern can signal a disease event up to two to three weeks before symptoms appear. This predictive capability is one of the most valuable functionalities of continuous monitoring.
This article was compiled from the third episode of Lumm Talks, our series of conversations on science, longevity and wellness. In this episode, Nicolás Vega talks with Dr. Alejandro Ramírez, Medical Director of Lumm Medical and a specialist in Sports Medicine, about the role of wearables in health and longevity. You can watch the full episode on our YouTube channel and explore more content on responsible personalized medicine on the Lumm Medical blog.
