title: Comparing the lactate and EMG thresholds of recreational cyclists during incremental pedaling exercise.
abstract: The purpose of this study was to determine the validity of using the electromyography (EMG) signal as a noninvasive method of estimating the lactate threshold (LT) power output in recreational cyclists. Using an electromagnetic bicycle ergometer and constant pedaling cadence of 80 rpm, 24 recreational cyclists performed an incremental exercise protocol that consisted of stepwise increases in power output of 25 W every 3 min until exhaustion. The EMG signal was recorded from the right vastus lateralis (VL) and right rectus femoris (RF) throughout the test. Blood samples were taken from the fingertip every 3 min. The LT was determined by examining the relation between the lactate concentration and the power output using a log-log transformation model. The root mean square (RMS) value from the EMG signal was calculated for every 1-second non-superimposing window. Sets of pairs of straight regression lines were plotted and the corresponding determination coefficients (R(2)) were calculated. The intersection point of the pair of lines with the highest R(2) product was chosen to represent the EMG threshold (EMGT). The results showed that the correlation coefficients (r) between EMGT and LT were significant (p < 0.01) and high for the VL (r = 0.826) and RF (r = 0.872). The RF and VL muscles showed similar behavior during the maximal incremental test and the EMGT and LT power output were equivalent for both muscles. The validity of using EMG to estimate the LT power output in recreational cyclists was confirmed.
authors.affiliation: Universidade do Vale do Rio dos Sinos, Curso de Educação Física, São Leopoldo, Brazil.
authors.forename: Cláudia Tarragô
authors.initials: CT
authors.lastname: Candotti
authors.forename: Jefferson Fagundes
authors.initials: JF
authors.lastname: Loss
authors.forename: Mônica de Oliveira
authors.initials: Mde O
authors.lastname: Melo
authors.forename: Marcelo
authors.initials: M
authors.lastname: La Torre
authors.forename: Maicon
authors.initials: M
authors.lastname: Pasini
authors.forename: Lucas Araújo
authors.initials: LA
authors.lastname: Dutra
authors.forename: José Leandro Nunes
authors.initials: JL
authors.lastname: de Oliveira
authors.forename: Lino Pinto
authors.initials: LP
authors.lastname: de Oliveira
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold; D001642:Bicycling; D004576:Electromyography; D015444:Exercise; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D052097:Quadriceps Muscle / Q000378:metabolism*; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D019344:Lactic Acid