Anaerobic ATP production in skeletal muscle and the accumulated oxygen deficit (O2D) incurred during an exhaustive cycle bout (duration = 173 +/- 24 s; intensity = 112 +/- 3% VO2peak), were determined in 10 male cyclists (mean +/- SD: VO2peak = 69.8 +/- 4.2 ml.kg-1.min-1). Anaerobic ATP production (mmol.kg-1 d.w.) was determined from changes in lactate, phosphocreatine, ATP, and ADP in vastus lateralis. Muscle buffer value and the activities of glycogen phosphorylase (PHOS), phosphofructokinase and citrate synthase (CS) were also determined. The anaerobic ATP production determined from measured muscle metabolites was 202.7 +/- 46.9 mmol.kg-1 d.w. and was correlated (P < or = 0.05) with muscle buffer value (r = 0.81), PHOS (r = 0.69) and the ratio of PHOS to CS activity (r = 0.77). The O2D was 55.2 +/- 10.3 ml O2 Eq.kg-1, but was not correlated (P > 0.05) with anaerobic ATP production (r = -0.38), buffer value (r = -0.50) or PHOS (r = -0.39). These latter findings could be explained by error in measuring the O2D and/or muscle anaerobic ATP production in well-trained cyclists.