Lower Limb and Respiratory Muscle Oxygenation During 800-m Running

Abstract

800-m running is supramaximal exercise, which naturally require oxygen supply to lower limbs muscle. In addition, respiratory muscle work specifically is severe to prevent acidosis attributing to lactate because of increasing by prompting CO2 output. Therefore, the event is performed with tolerating severe strain of both lower limb and respiratory muscles. However, how to changes in lower limb and respiratory muscles oxygenation during 800-m running remains unclear. We hypothesized that during 800-m running, respiratory muscle oxygenation would be reduced by redistribution of blood flow giving priority to lower limb muscles. PURPOSE: To investigate changes in lower limb and respiratory muscles oxygenation during 800-m running. METHODS: Nine male 800-m runners (age; 20±2.1 yrs, record; 115.7±4.9s) performed 800-m running with maximal effort during on outdoor track. Maximal inspiratory (MIP) and expiratory (MEP) pressure were measured before and after 800-m running. OxyHb/Mb and totalHb/Mb of vastus lateralis and of intercostal muscle were evaluated using portable near-infrared spectroscopy (NIRS) during 800-m running. Two-way ANOVA (distance×muscle) with repeated measures was used to identify statistically significant differences in NIRS parameters across each 50-m distance interval. RESULTS: The running speed peaked at 100-m interval (7.4±0.4 m/s), and then gradually decreased until the finish (6.0±0.3 m/s). After 800-m running, MIP was significantly decreased (-47 %; p<0.0001), although MEP was no significant (-8 %; p=0.095). OxyHb/Mb of vastus lateralis was significantly decreased immediately after start and followed by maintaining until finish. By contrast, OxyHb/Mb of intercostal muscle was gradually decreased from start and followed by further decreasing in latter half (from 450-m to finish) of 800-m running. In addition, although totalHb/Mb of intercostal muscle was gradually decreased from start until finish, totalHb/Mb of vastus lateralis was maintaining at resting level. CONCLUSIONS: Our findings in NIRS data suggest that the decrease in respiratory muscle oxygenation maybe greater than lower limbs muscle oxygenation in latter half of 800-m running. No grant for this study.