Analysis of the aerobic-anaerobic transition in elite cyclists during incremental exercise with the use of electromyography.

Abstract

Objectives-To investigate the validity and reliability of surface electromyography (EMG) as a new non-invasive determinant of the metabolic response to incremental exercise in elite cyclists. The relation between EMG activity and other more conventional methods for analysing the aerobic-anaerobic transition such as blood lactate measurements (lactate threshold (LT) and onset of blood lactate accumulation (OBLA)) and ventilatory parameters (ventilatory thresholds 1 and 2 (VT 1 and VT 2 )) was studied. Methods-Twenty eight elite road cyclists (age 24 (4) years; Ṽ O 2 MAX 69.9 (6.4) ml/kg/min; values mean (SD)) were selected as subjects. Each of them performed a ramp protocol (starting at 0 W, with increases of 5 W every 12 seconds) on a cycle ergometer (validity study). In addition, 15 of them performed the same test twice (reliability study). During the tests, data on gas exchange and blood lactate levels were collected to determine VT 1 , VT 2 , LT, and OBLA. The root mean squares of EMG signals (rms-EMG) were recorded from both the vastus lateralis and the rectus femoris at each intensity using surface electrodes. Results-A two threshold response was detected in the rms-EMG recordings from both muscles in 90% of subjects, with two breakpoints, EMG T1 and EMG T2 , at around 60-70% and 80-90% of Ṽ O 2 MAX respectively. The results of the reliability study showed no significant diVerences (p>0.05) between mean values of EMG T1 and EMG T2 obtained in both tests. Furthermore, no significant diVerences (p>0.05) existed between mean values of EMG T1 , in the vastus lateralis and rectus femoris, and VT 1 and LT (62.8 (14.5) and 69.0 (6.2) and 64.6 (6.4) and 68.7 (8.2)% of Ṽ O 2 MAX respectively), or between mean values of EMG T2 , in the vastus lateralis and rectus femoris, and VT 2 and OBLA (86.9 (9.0) and 88.0 (6.2) and 84.6 (6.5) and 87.7 (6.4)% of v O 2 MAX respectively). Conclusion-rms-EMG may be a useful complementary non-invasive method for analysing the aerobic-anaerobic transition (ventilatory and lactate thresholds) in elite cyclists. (Br J Sports Med 1999;33:178-185)

Comparison of Different Methods for Identification of Electromyography Threshold in Resistance Exercise

“…The stages where there was identification of EMGTh corroborate the bibliographic findings which was found around 30 and 40% of 1RM [13,15], this values were also found in this study, however, Lucia et al [16] had shown on a progressive test of a cyclic modality the anaerobic threshold at intensities close to 60 to 70% of VO 2max , suggesting that the EMGTh is related to the activity type and protocol, yet having a highly reproducible and significant ICC according to Lucia et al [17], the EMGTh shows no significant difference, and shows significant correlation to the lactate and ventilatory thresholds expressed in % VO 2max for heart transplanted.…”

Assessment of nervous-muscular system’s potentials of cyclic kinds of sports sportsmen

“…Results of our research and the researches of A. Lucia [14], F. Hug [13] showed the presence of two electromyography thresholds (EMGT1 and EMGT2). The authors explain the presence of two thresholds in elite sportsmen by their ability to switch in work different types of muscle fibers (transitive and glycolitic) in response to increase of load's intensity up to definite level.…”

“…Analysis of recent data [13,14,16] and our own researches [8,9] permitted to determine purposefulness of SEMG application for assessment of NMS functional potentials in cyclic kinds of sports sportsmen.…”

The influence of ambient temperature on power at anaerobic threshold determined based on blood lactate concentration and myoelectric signals

“…This effect has been subject to extensive research [5,7]; however, the underlying mechanisms remain unclear. [10][11][12]. The integrated electromyographic anaerobic threshold is regarded as the inflection point at which an abrupt non-linear increase in the integrated electromyogram occurs, representing the changes in the motor unit (MU) recruitment and/or MU firing frequency during incremental exercise [13].…”