Table 1.

Anaerobic Threshold Concept

1.  Muscle hypoxia occurs at ≈50–70% of V̇o2max

2.  Inadequate O2 ⇒ inhibition of the electron transport chain ⇒ insufficient ATP generation via oxidative phosphorylation and ↑ mitochondrial [NADH]

3.  Mitochondrial NADH build-up inhibits NADH shuttles (malate-aspartate and glycerol-phosphate) and ⇒ ↑ cytosolic [NADH] and ↓ cytosolic [NAD]

4.  ↑ Mitochondrial [NADH]/[NAD] inhibits TCA cycle ⇒ ↓ pyruvate use ⇒ ↑ mitochondrial [pyruvate] ⇒ ↑ cytosolic [pyruvate]

5.  Pyruvate becomes H+ acceptor in cytosol ⇒ ↑ HLa production

6.  Inadequate aerobic ATP generation ⇒ ↓ [ATP], ↓ [PCr] and ↑ [ADP], ↑ [Pi], ↑ [AMP] ⇒ ↑ glycolytic rate, and ↑ HLa production

7.  ↑ HLa production ⇒ ↑ muscle and blood [HLa]

[Modified with permission from ref. 21 (Copyright 1996, Oxford University Press).]