Surface EMG Study On VO₂ Slow Component

The VO₂ slow component is an important metabolic reaction in high-intensity exercise,which reduces the muscle work efficiency and muscle fatigue occurs sooner.In this thesis,we investigated the mechanism of VO₂ slow component in terms of the muscle fiber recruitment pattern and the oxygen uptake kinetics.Characteristics of VO₂ slow component for different types of athletes?endurance runners versus sprinters?,different exercise patterns?running versus cycling?,and different exercise intensity?moderate/heavy/severe?were analyzed by surface EMG and oxygen uptake kinetics.We invited 10 endurance runners and 12 sprinters to participate.The VO_2max test was performed first,followed by a constant work rate test?moderate,heavy,severe?.Oxygen uptake was modeled using an exponential equation.The wavelet transform combined with principal component analysis was used to analyze the EMG signal.The main work of this paper is divided into the following two parts.?1?VO₂ slow component in sprinters and endurance runners during heavy and severe exercise.The bi-exponential model was used to analyze the amplitude and onset of the VO₂slow component.The amplitude of the VO₂ slow component is significantly higher at severe than at heavy exercise intensity,and sprinters show a significantly higher slow component amplitude and a significantly earlier slow component onset than endurance runners.The EMG mean power frequency?MPF?of the tested muscles increased significantly during the slow component phase.These results support the hypothesis that the slow component of the overall VO₂ response is associated with progressively recruitment of type II fibers of the contracting muscles.?2?VO₂ slow component in sprinters during cycling and running at heavy and severe exercise.The amplitude of VO₂ slow component is significantly higher during cycling than running at both heavy and severe exercise intensity.This may be due to the fact that muscles are relatively more prone to fatigue during cycle ergometry exercise,and muscle work efficiency declines more quickly,resulting in greater VO₂ slow component amplitude.As the classical phenomenon of MPF's decline when muscle fatigued,the rise of MPF in the slow component phase might be concealed by muscle fatigue.We used the principal component analysis to analyze the high-frequency and low-frequency contents of the EMG signal which improved the sensitivity of signal processing.The results show that the MPF of the rectus femoris muscle and soleus muscle increased significantly during heavy exercise of the cycle ergometry,whereas EMG?decreased significantly for the rectus femoris,biceps femoris,tibialis anterior,medial gastrocnemius,and soleus muscle.Our results show that?is more sensitive to detect the muscle fibers recruitment pattern.Our results will help to further reveal the mechanism of VO₂ slow component.It is of great practical significance for appropriate training to reduce the magnitude of slow components,delay fatigue,and improve athletic performance.