Training Zones and Muscle Oxygen Saturation in Cyclists and Triathletes

Training Zones and Muscle Oxygen Saturation in Cyclists and Triathletes

The Cutting-Edge of Performance Measurement

In the realm of cycling and triathlon, understanding and optimizing performance is paramount. Traditional methods have largely relied on physiological parameters such as heart rate, oxygen consumption, and power output. However, a groundbreaking study led by Aldo A. Vasquez Bonilla et al. introduces a novel parameter: Muscle Oxygen Saturation (SmO2), measured using portable near-infrared spectroscopy (NIRS) technology.

The Significance of Muscle Oxygen Saturation

SmO2, although validated as a significant performance factor, has not been extensively used to delineate training zones. This study pioneers the use of SmO2 in identifying crucial training zones like maximum lipid oxidation zone (Fatmax), ventilatory thresholds (VT1 and VT2), and maximum aerobic power (MAP) during a graded exercise test (GXT).

The Study: Approach and Findings

The study enrolled 40 trained cyclists and triathletes, who underwent a GXT. Measurements included power output, heart rate, VO2, energy expenditure, and crucially, SmO2. The analysis revealed distinct decreases in SmO2 across different training zones, notably:

  • A significant drop from baseline to Fatmax.
  • A further decrease from Fatmax to VT1, and from VT1 to VT2.
  • Additionally, SmO2, along with weight, heart rate, and power output, was found to predict VO2 and energy expenditure with high accuracy (89% and 90%, respectively).

This indicates that SmO2 is not just a reliable marker for muscular oxygen use but can also be instrumental in distinguishing between aerobic and anaerobic workloads in athletes.

Implications and Applications

The findings of this study have profound implications for endurance athletes:

  1. Training Optimization: With SmO2, athletes and coaches can more accurately determine training zones, optimizing workouts for specific metabolic pathways.

  2. Performance Prediction: The ability of SmO2 to predict VO2 and energy expenditure provides a new avenue for performance assessment, offering a viable alternative to more traditional, often less accessible methods.

  3. Individualized Training: As SmO2 readings can be individual-specific, they allow for more tailored training regimens, potentially improving both efficiency and outcomes.

Future Directions

While the study is groundbreaking, it also opens up new questions and areas for future research, such as:

  • The exploration of SmO2 in different athletic populations.
  • Longitudinal studies to ascertain the impacts of training adjustments based on SmO2 readings.
  • The integration of SmO2 data into wearable technology for real-time monitoring and feedback.


The study by Vasquez Bonilla et al. marks a significant leap in the understanding and utilization of muscle oxygen saturation in endurance sports. It not only enhances our knowledge of athletic performance but also paves the way for more sophisticated and personalized training methods. As we continue to delve deeper into the nuances of human performance, parameters like SmO2 will undoubtedly play a pivotal role in shaping the future of sports science.

Read the full research article by clicking here.


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