July 27, 2007Journal of Applied Physiology
Hepatic lactate uptake versus leg lactate output during exercise in humans
Why the study?
How does hepatic lactate uptake compare to leg lactate output during prolonged and incremental exercise in healthy men?
Population
7 healthy men
Design
Other
Authors
Discussion
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Member takes
Implication
Should not alter exercise guidance; hypothesis-generating for hepatic glucose regulation in prolonged activity.
Key Points
- To determine how hepatic lactate uptake compares with leg lactate release during prolonged and incremental exercise in humans.
- Seven healthy men completed 2 hours of cycling at 62 ± 4% VO2max followed by an incremental exercise test to exhaustion.
- Hepatic blood flow was measured by indocyanine green dye elimination, and leg blood flow was assessed using thermodilution.
- During prolonged exercise, leg lactate output (3.0 ± 1.8 mmol/min) was roughly fourfold higher than hepatic lactate uptake (0.7 ± 0.3 mmol/min) at an arterial lactate concentration of 2.0 ± 0.2 mM.
- During incremental exercise, arterial lactate reached 6.0 ± 1.1 mM as leg lactate output rose to 8.9 ± 2.7 mmol/min while hepatic uptake reached only 1.1 ± 0.6 mmol/min.
- Relative hepatic lactate uptake dropped to approximately one-tenth of leg lactate output during intense exercise, driving the accumulation of lactate in arterial blood.
Structured PICO
How does hepatic lactate uptake compare to leg lactate output during prolonged and incremental exercise in healthy men?
P
Population
7 healthy men
I
Intervention
2 h prolonged cycling (62 +/- 4% of maximal O2 uptake) followed by incremental exercise
O
Outcome
Hepatic lactate uptake and leg lactate outputsurrogate
The exponential rise in blood lactate during intense exercise is partly driven by a relative decrease in hepatic lactate extraction compared to the massive increase in leg lactate output.
Cite This Study
Nielsen et al. (2007) studied this question.