The Monitoring Of Multiple Physiological Parameters And The Evaluation Of Aerobic Exercise Capacity By Combining Near Infrared Spectroscopy

Aerobic exercise capacity （AEC） indices [e.g., maximal oxygen uptake (.V O_2max),lactate threshold （LT）, gas exchange threshold （GET） and heart rate threshold （HRT）] aregenerally obtained during incremental exercise tests （IET） and instructive for athleteselection, exercise training, and so on. These indices are determined from systemicphysiological monitoring techniques （e.g., blood analysis and cardiopulmonary test）,however, these techniques are either invasive （blood sample collection） or uncomfortable（involving breathing masks during the cardiopulmonary test）. These disadvantages havelimited the use of related techniques during the assessment of AEC indices. Additionally,some exercise physiological phenomena were still incompletely explained by systemicphysiological monitoring. For example, the difference in exercise performance amongindividuals with similar AEC indices; the lower mechanical efficiency during IET ingroups with higher exercise performance. Combination of systemic and local monitoringtechniques might provide further insight into these phenomena. Near infraredspectroscopy （NIRS） and surface electromyography （sEMG） can monitor local muscularoxygenation and neural electric activity noninvasively and in real time. In this study, bothlocal and systemic physiological responses were monitored to evaluate AEC morecomprehensively, in different types of subjects, exercise modes and muscles. CombiningNIRS, sEMG and systemic physiological monitoring techniques, local muscular andsystemic physiological responses were simultaneously measured in8rowers,31finswimmers, and20free combat players during IET. The local oxidative capacities in oneor more of the following muscles: biceps brachii （BB）, vastus latearlis （VL）,gastrocnemius lateralis （GL）, rectus femoris （RF） and vastus medialis （VM）, together withthe systemic AEC indices were analyzed. During rowing IET, breakpoints （Bp） of muscle oxygenation at both BB [BpBB,45（3.8）%.V O_2max] and VL [BpVL,55.6（2.4）%.V O_2max] in trained rowers were highlycorrelated with systemic AEC indices （r>0.81, p <0.05）. In the rowers with higherexercise performance, the BpBB and BpVL appeared at higher work intensity, and theBpBB occurred nearer to the BpVL. These results indicated that the rowers with higherexercise performance owned higher local muscle oxidative capacities, and better matchingof muscular oxidative capacities between BB and VL. A further explanation for the higherexercise performance was provided from the view of local muscle oxygenation.During cycling IET, both the BpVL and the Bp at GL （BpGL） in finswimmers werehighly correlated with systemic AEC indices （r>0.839, p <0.01）. Meanwhile, the BpVLoccurred earlier than the BpGL, which might be due to lower percentage of oxidativefibres and higher contribution during crank cycles in VL than in GL. Both the BpVL andBpGL were separately used as a regressor to predict AEC indices, better goodness-of-fitwere found in the BpVL （p <0.05）, which indicated better assessment （predictive） abilityof the BpVL for AEC indices and that the muscular difference should be consideredduring AEC evaluation by NIRS. In finswimmers with higher exercise performance, moreincrement of oxygen uptake was needed to meet the same increment of work rate （lowermechanical efficiency）, coincidently, the muscle oxygenation index decreased slower. Thisresult explained the low mechanical efficiency in athletes with high exercise performancefrom the view of local muscle oxygenation.During incremental static knee extensions, the muscle oxygenation Bp at threecomponents of quadriceps femoris （VL, RF and VM） in free combat players occurred at45.0（1.7）,46.6（2.1） and45.3（2.2）%MVC respectively, and sEMG threshold （EMGT） inVL, RF and VM appeared at45.3（1.9）,49.5（2.2） and49.2（1.9）%MVC respectively. Boththe Bp and EMGT at VL, RF and VM appeared at similar work intensity as HRT did, this indicated that local and systemic physiological thresholds would be similar when onlyseveral muscles were involved during IET. There was no significant difference in thephysiological thresholds （Bp and EMGT） among VL, RF and VM. This result indicatedthe coordination among muscles from the same muscle group might be different from thatamong muscles from different muscle groups during IET.