Alternative index for lactate threshold –preliminary study using a non-invasive bioimpedance cardiography

Lactate Threshold(LT) defined as an inflection point of blood lactate concentration(BLC) during physical load is used for index of physical fitness. However, it requires cumbersome blood sampling. To overcome this drawback, we proposed a new method for estimating physical fitness using a non-invasively obtained cardiovascular variables. 27 healthy male adults were involved and their heart rate(HR), stroke volume(SV) and cardiac output(CO) were measured during ergometer exercise using a hemodynamic monitor (PhysioFlow, NeuMeDx). BLC was also monitored using a BLC monitor (LactatePro2, Arkray) . From the results, it was confirmed that the values of work load at the inflection point of CO were coincide well with those of LT (correlation coefficient: γ=0.903), suggesting superiority of CO in estimating physical fitness rather than HR (γ=0.765) nor SV (γ=0.354). These results could be explained that HR and SV reflect myocardial chronotropic and inotropic condition, respectively, on the other hand, CO reflects both. © 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.