Aim of this study was to investigate the oxygenation and the total hemoglobin concentration pattern in vastus lateralis and medial gastrocnemius muscle groups during a standardized treadmill exercise (n equals 6) by a new near infrared frequency-domain oximeter (ISS Oximeter model 96208). Vastus lateralis saturation and total hemoglobin concentration were 74 +/- 3% and 71 +/- 15 (mu) M at 0 mph and 72 +/- 5% and 79 +/- 16 (mu) M at 6 mph, respectively. Gastrocnemius saturation and total hemoglobin concentration were 74 +/- 2% and 107 +/- 18 (mu) M at 0 mph and 60 +/- 6% and 113 +/- 23 (mu) M at 6 mph, respectively. The saturation recovered gradually up to the baseline value when the speed was decreased.