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Determining the Contribution of the Energy Systems During Exercise
Published on: March 20, 2012
Lactate distribution in the blood during steady-state exercise
E W Smith1, M S Skelton, D E Kremer
1Department of Health & Human Performance, Auburn University, AL 36849-5323, USA.
Medicine and Science in Sports and Exercise
|September 19, 1998
Summary
Plasma and red blood cell (RBC) lactate levels show a constant ratio during exercise, even above the lactate threshold (LT). This indicates an equilibrium, refuting the hypothesis of decreased RBC lactate uptake during intense exercise.
Area of Science:
- Exercise Physiology
- Biochemistry
- Sports Science
Background:
- Lactate accumulation is a hallmark of intense exercise.
- Understanding lactate kinetics between plasma and red blood cells (RBCs) is crucial for interpreting exercise physiology.
- Previous hypotheses suggested altered RBC:plasma lactate ratios during exercise above the lactate threshold (LT).
Purpose of the Study:
- To investigate the plasma to RBC lactate concentration ([La]) gradient and RBC:plasma [La] ratio during steady-state exercise below and above LT.
- To determine if RBC lactate uptake changes significantly at exercise intensities exceeding the lactate threshold.
Main Methods:
- Eight healthy subjects performed 30-minute cycle ergometer exercise below and above their individual LT.
- Blood samples were collected from a heated forearm vein, with plasma and RBCs separated at 4°C.
- Lactate concentrations in plasma and RBCs were measured.
Main Results:
- Plasma lactate increased significantly above LT, reaching 8.8 mM, while RBC lactate remained lower, creating a gradient.
- Below LT, plasma lactate increased slightly and then stabilized around 2 mM.
- Despite differing gradients, the RBC:plasma [La] ratio remained constant (0.58) across all conditions, including rest.
Conclusions:
- The study refutes the hypothesis that the RBC:plasma lactate ratio decreases above LT.
- A constant RBC:plasma lactate ratio suggests an equilibrium between plasma and RBC lactate in arterialized venous blood.
- This equilibrium implies efficient lactate exchange between plasma and RBCs, even during strenuous exercise.
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