Blood vs sweat lactate in research

The relationship between blood and sweat lactate during exercise is a topic of ongoing scientific debate. While some studies have found a strong correlation between the two, others report little to no correlation—or even a negative one. In this blog, we explore the possible reasons behind these differing findings.

Research demonstrating a positive correlation

Several research groups have demonstrated a close link between lactate levels in blood and sweat.

• Katsumata et al. (Japan): This team developed and tested a wearable sensor for detecting lactate in sweat. Their multiple publications show a strong correlation between sweat lactate thresholds and blood lactate thresholds, as illustrated in the graph below.

Sweat lactate and blood lactate during incremental exercise. (Figure from Seki, Y., Nakashima, D., Shiraishi, Y. et al. A novel device for detecting anaerobic threshold using sweat lactate during exercise. Sci Rep 11, 4929 (2021).)

• Gaston Crespo’s Research Group: The team behind the first IDRO sensor prototype has conducted various studies using different iterations of the device. One such study found a significant correlation between sweat lactate concentrations measured at the thigh and blood lactate concentrations during exercise, which is reflected in the high correlation coefficient in the graph below.

Correlation between sweat lactate and blood lactate during exercise. (Figure from Xuan, Xing, et al. "Fully integrated wearable device for continuous sweat lactate monitoring in sports." ACS sensors 8.6 (2023): 2401-2409.)

Studies Showing No Clear Correlation

Not all research groups have observed a consistent relationship between blood and sweat lactate.

• Klous et al.: Their study found no correlation between sweat and blood lactate across exercises ranging from 60% to 90% of maximal heart rate, as seen in the graph below.

Correlation between sweat lactate and blood lactate during incremental exercise. (Figure from Klous, L., de Ruiter, C.J., Scherrer, S. et al. The (in)dependency of blood and sweat sodium, chloride, potassium, ammonia, lactate and glucose concentrations during submaximal exercise. Eur J Appl Physiol 121, 803–816 (2021).)

Why Do These Results Differ?

Several factors may explain the discrepancies observed in the literature:

• Measurement Method: Traditional sweat lactate measurement techniques often involved sampling sweat over extended periods, leading to contamination and dilution. Modern wearable sensors, like the IDRO device, continuously collect sweat in real-time without dilution, ensuring more accurate readings.

• Body Location: Sweat lactate concentrations vary depending on the measurement site. For instance, the forehead and back have different types of sweat glands compared to other parts of the body, which can lead to variations in lactate levels. IDRO provides recommendations on optimal body locations for the most reliable results.

• Exercise Intensity: At lower intensities, blood and sweat lactate levels tend to be low, providing less actionable data. Only at higher exercise intensities do lactate concentrations rise significantly.

• Training Background: Untrained individuals typically exhibit higher lactate concentrations at the same exercise intensity compared to trained athletes. In trained subjects, higher intensities are required to observe noticeable increases in lactate levels.

Conclusion

While the correlation between blood and sweat lactate remains an area of scientific discussion, research continues to refine our understanding of how wearable lactate sensors can provide reliable insights. Advancements in sensor technology, measurement techniques, and exercise physiology will help bridge the gaps in existing findings. For more details, refer to the references below. IDRO will keep demonstrating measurements of sweat lactate showing a strong relation to trends in blood lactate and exercise intensity.

References

• Seki, Y., Nakashima, D., Shiraishi, Y. et al. A novel device for detecting anaerobic threshold using sweat lactate during exercise. Sci Rep 11, 4929 (2021).

• Xuan, Xing, et al. "Fully integrated wearable device for continuous sweat lactate monitoring in sports." ACS sensors 8.6 (2023): 2401-2409.

• Klous, L., de Ruiter, C.J., Scherrer, S. et al. The (in)dependency of blood and sweat sodium, chloride, potassium, ammonia, lactate and glucose concentrations during submaximal exercise. Eur J Appl Physiol 121, 803–816 (2021).

• Xuan, Xing, et al. "A wearable biosensor for sweat lactate as a proxy for sport performance monitoring." Analysis & Sensing 3.4 (2023): e202200047.

• Van Hoovels, Kevin, et al. "Can wearable sweat lactate sensors contribute to sports physiology?." ACS sensors 6.10 (2021): 3496-3508.