"Tucson Treadmills: Dark Skin Hiding Heart Data?"

By Franklin Everett Shaw

January 5, 2026

The rhythmic thump of the treadmill, the focused gaze ahead, the steady increase in speed – it’s a familiar scene in gyms across Tucson. But beneath the surface of this seemingly universal fitness experience lies a potential disparity: are the heart rate monitors on these machines accurately serving everyone?

The question of whether treadmill heart rate sensors accurately measure heart rate across all skin tones is not just a matter of convenience; it’s a matter of equitable access to health data. In Tucson, a city with a diverse population, this issue takes on particular significance.

The problem stems from the technology itself. Most treadmill heart rate monitors use photoplethysmography (PPG). PPG sensors shine a light onto the skin and measure the amount of light reflected back. This reflection changes with blood flow, which is then used to calculate heart rate. Melanin, the pigment that gives skin its color, absorbs light. Higher levels of melanin can affect the amount of light reflected back to the sensor, potentially leading to inaccurate readings.

This isn’t just theoretical. Studies have shown that PPG-based heart rate monitors can be less accurate in individuals with darker skin tones. A 2020 study published in the Journal of the American Medical Association (JAMA) found that pulse oximeters, which use similar technology to PPG, were significantly less accurate in Black patients compared to white patients. While pulse oximeters measure blood oxygen saturation, the underlying principle of light absorption and reflection is the same.

So, what does this mean for someone in Tucson trying to get a good workout at LA Fitness on Speedway or the YMCA on University? It means the heart rate displayed on the treadmill might not be a true reflection of their actual heart rate. This can lead to:

Inaccurate training zones: Training zones are based on heart rate. If the heart rate is inaccurate, individuals may be training at the wrong intensity, potentially hindering their progress or increasing their risk of injury.
Misleading fitness data: Many people track their workouts to monitor their progress. Inaccurate heart rate data can skew these metrics, making it difficult to assess fitness improvements.
Potential health risks: For individuals with underlying health conditions, accurate heart rate monitoring is crucial. Inaccurate readings could lead to mismanagement of their condition.

Fortunately, there are solutions. The first step is awareness. Knowing that treadmill heart rate monitors may not be accurate for everyone is crucial.

Here are some alternative methods for monitoring heart rate in Tucson gyms:

Chest Straps: Chest straps are generally considered more accurate than wrist-based or hand-grip PPG sensors. They measure electrical activity directly from the heart. Brands like Polar and Garmin offer reliable chest straps. You can often pair these with your phone or smartwatch.
Smartwatches: While smartwatches also use PPG, some models are more advanced and may offer better accuracy. Look for smartwatches with multiple sensors and algorithms designed to compensate for skin tone variations. The Apple Watch and some Fitbit models have shown promise in this area, though independent testing is always recommended.
Manual Pulse Check: The old-fashioned way still works. Find your pulse on your wrist or neck and count the beats for 15 seconds, then multiply by four to get your heart rate in beats per minute (BPM). This is a good backup method to verify the readings from other devices.

Beyond individual solutions, Tucson gyms can take steps to improve inclusivity and accuracy.

Here are some recommendations for local fitness centers:

Offer a variety of heart rate monitoring options: Provide chest straps for members to use, or allow them to easily connect their own devices to the treadmill.
Invest in treadmills with more advanced sensors: Some manufacturers are developing treadmills with sensors that are less susceptible to skin tone variations.
Provide education and training: Train staff to understand the limitations of PPG sensors and to advise members on alternative monitoring methods.
Transparency: Be upfront about the potential limitations of the treadmill’s heart rate monitor. Post a sign explaining that accuracy may vary based on skin tone and suggest alternative methods.

A Tucson Gym Directory of Inclusive Heart Rate Monitoring (In Progress):

This is a work in progress, but we aim to compile a list of Tucson gyms that are actively working to provide inclusive and accurate heart rate monitoring. If you know of a gym that fits this description, please contact us!

[Gym Name 1]: [Brief description of their inclusive practices]
[Gym Name 2]: [Brief description of their inclusive practices]
[Gym Name 3]: [Brief description of their inclusive practices]

One challenge developers face is the lack of diverse datasets for training PPG algorithms. Most datasets used to develop these algorithms are based on predominantly white populations. This leads to biased algorithms that perform poorly on individuals with darker skin tones.

To overcome this, researchers and developers need to prioritize the collection of diverse datasets that accurately represent the population. This requires a concerted effort to recruit participants from different racial and ethnic backgrounds.

Another pitfall is the assumption that all PPG sensors are created equal. There is significant variation in the quality and accuracy of PPG sensors. Some sensors are more sensitive to skin tone variations than others.

Developers should carefully evaluate the performance of different sensors on diverse populations before incorporating them into their products. They should also consider using multiple sensors and algorithms to improve accuracy.

Finally, a common mistake is relying solely on heart rate data for fitness tracking. Heart rate is just one metric. It’s important to consider other factors such as perceived exertion, breathing rate, and muscle fatigue.

By combining heart rate data with other metrics, individuals can get a more complete picture of their fitness level and training progress.

The issue of heart rate monitor accuracy is a complex one, but it’s one that we can address with awareness, education, and technological innovation. In Tucson, a city that prides itself on its diversity, it’s crucial that we ensure everyone has access to accurate health data, regardless of their skin tone. Let’s work together to make our gyms and fitness experiences more inclusive and equitable for all.