CORRELATION BETWEEN SURFACE ELECTROMYOGRAM, OXYGEN-UPTAKE AND BLOOD LACTATE CONCENTRATION DURING DYNAMIC LEG EXERCISES

Very few data are found in the literature on the adjust:ment of the mo tor drive to contracting muscles to their oxygen uptake ((V)over dot(O 2)). The present study examines in seven untrained and trained individ uals, who performed a progressive 8 min and two 5 min constant-load cy cling exercises, the changes in the ratio between total EMG energy (ro ot mean square or RMS), recorded in a leg extensor (vastus lateralis), to the corresponding (V)over dot(O2) value and their correlations wit h the anaerobic threshold ((V)over dot(O2)AT) a.nd the peak blood lact ate concentration. In all circumstances, the RMS/(V)over dot(O2) ratio began to increase, then it decreased progressively despite (V)over do t(O2) continued to rise (progressive exercise) or plateaued (constant- load exercises preseted at a sub- or suprathreshold level). The decrea se in RMS/(V)over dot(O2) ratio persisted and it was often accentuated during the first 2 min of the recovery period. In all exercise protoc ols, the rate oi. RMS/(V)over dot(O2) decrease Ras positively correlat ed with the initial peak increase in this ratio. During progressive ex ercise, the peak increase in RMS/(V)over dot(O2) ratio as well as its rats of decrease were negatively correlated with (V)over dot(O2)AT. Th us. training and/or the reduction of anaerobic muscle metabolism atten uate the changes in RMS/(V)over dot(O2) ratio. During constant-load ex ercise trials, the rate of decrease in RMS/(V)over dot(O2) ratio was p ositively correlated with the plateau (V)over dot(O2) value and also t he peak blood lactate concentration. This suggests that information on the magnitude of the anaerobic muscle metabolism play a key role in t he mechanisms which adjust RMS to (V)over dot(O2). (C) 1998 Elsevier S cience B.V. All rights reserved.