Notes on VO2max and CrossFit Athletes

What is VO2max?

• Definition: The maximal amount of oxygen an athlete can take up during hard exercise.
• Measurement: Typically assessed through a ramp test to exhaustion (running, biking, rowing) where intensity increases until exhaustion.
• Components:
  • Cardiac output: Amount of oxygenated blood delivered to tissues.
  • Arteriovenous oxygen difference: How much oxygen muscles can extract from blood.

Key Physiological Insights

• Bengt Saltin's Research:
  • High VO2max seen in endurance athletes (e.g., cross-country skiers, runners).
  • Elite endurance athletes often exceed 90 mL O2/kg.
• CrossFit Athletes:
  • Study conducted with 60 well-trained CrossFit athletes (30 men, 30 women).
  • Average VO2max: 56 mL/kg for men; 51 mL/kg for women—moderate levels, not as high as endurance specialists.

Physiological Reasons for Lower VO2max in CrossFit Athletes

1. Strength-Biased Training:

   • Historically, CrossFit competitions prioritize strength (e.g., high snatch weights).
   • Successful athletes need a balance of strength and endurance, but strength training can limit aerobic capacity.

2. Interference Effect:

   • Concurrent training (strength + endurance) leads to diminished gains in one modality due to training for both.
   • Endurance athletes focus primarily on aerobic work and thus develop higher VO2max levels.

3. Muscle Fiber and Capillary Density:

   • CrossFit athletes have larger muscle fibers but fewer capillaries relative to muscle size.
   • This limits oxygen diffusion into muscles, impacting aerobic capacity.

4. Method of Testing:

   • Common testing methods may not accurately reflect VO2max for CrossFit athletes.
   • More familiar movements (e.g., thrusters, pull-ups) could yield different results.

Implications for Coaches and Athletes

• Performance Correlation:
  • In the study, no strong correlation between VO2max and performance in CrossFit Open.
  • Anthropometric factors (e.g., limb lengths) were more significant determinants.
• Focus Areas:
  • Coaches might benefit from focusing on movement efficiency rather than just VO2max.
  • Testing should include measures of oxygen uptake during specific movements.

Conclusion

• CrossFit athletes demonstrate lower VO2max due to a combination of training biases, physiological factors, and testing methods.
• Understanding these factors can help coaches design better training programs that enhance overall athletic performance.