Determination Of The Trends In The Hemoglobin Concentrations In Inactive Muscles During Cycling Exercise

Abstract

As compared to the rest condition, blood flow is redistributed during exercise, when a considerable amount of blood is supplied to the active muscles while the supply to inactive muscles falls. However, the changes in respiration and circulation at the muscle tissue level during exercise remains unclear. PURPOSE: We determined the trends in the oxy-, deoxy-, and total hemoglobin concentrations ([O2Hb], [HHb], and total-[Hb], respectively) in inactive muscles during cycling exercise by using near-infrared spectroscopy (NIRS). METHODS: Four healthy subjects (mean age, 25.3 ± 7.2 y) performed 4 min of baseline exercise at 10 W followed by cycling exercise for 15 min at intensities of anaerobic threshold (AT) + 20%, 40%, or 60% of the difference between the AT and peak pulmonary oxygen uptake (Δ20%, Δ40%, or Δ60%, respectively). [O2Hb] and [HHb] in the vastus lateralis muscles (VLMs) or the flexor digitorum superficialis muscles (FDSMs) were estimated using NIRS. Further, the rate of gas exchange, heart rate, and eardrum temperature were assessed throughout the experiment. RESULTS: After the baseline exercise, the increase in [HHb] in the FDSMs during exercise was higher at Δ40% and Δ60% than at Δ20%. This trend was reflected by the changes in eardrum temperature. The increase in total-[Hb] in the FDSMs during exercise was similar irrespective of exercise intensity. The change in total-[Hb] in the FDSMs was similar to that of eardrum temperature during exercise. CONCLUSIONS: It was suggested that total-[Hb] in the FDSMs increases with increase in eardrum temperature. Further, it was possible that the higher is the elevation in body temperature, higher is the elevation in [HHb] in the FDSMs.