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Comparison of oxygen uptake kinetics during concentric and eccentric cycle exercise
1Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 20, 2001
Summary
Oxygen uptake (VO2) kinetics during high-intensity concentric exercise show a slow component linked to increased muscle activation. This VO2 slow component is related to metabolic demand, not just work rate, during exercise.
Area of Science:
- Exercise Physiology
- Muscle Physiology
- Cardiorespiratory Fitness
Background:
- Understanding oxygen uptake (VO2) kinetics and electromyographic (EMG) activity is crucial for assessing exercise intensity and muscle engagement.
- Concentric and eccentric exercise modes present distinct physiological demands.
- The presence of a VO2 slow component indicates a progressive increase in energy cost during exercise.
Purpose of the Study:
- To investigate VO2 kinetics and muscle EMG activity during constant-load concentric and eccentric cycling.
- To compare the physiological responses between different exercise intensities and modes.
- To determine the relationship between VO2 slow component, muscle activation, and metabolic demand.
Main Methods:
- Six healthy men performed transitions to high-intensity eccentric (HE), high-intensity concentric (HC), moderate-intensity concentric (MC), and low-intensity concentric (LC) cycling.
- VO2 kinetics were analyzed using a two- or three-component exponential model.
- Surface EMG from vastus medialis, rectus femoris, biceps femoris, and medial gastrocnemius was recorded to assess integrated EMG and mean power frequency.
Main Results:
- A VO2 slow component (phase 3) and increased integrated EMG in vastus medialis and rectus femoris were observed only during HC exercise.
- The phase 2 time constant for VO2 kinetics was slower in HC exercise compared to HE and LC exercise.
- VO2 kinetics were similar between HE and LC exercise, suggesting metabolic demand, not absolute work rate, influences VO2 response.
Conclusions:
- The VO2 slow component during high-intensity concentric exercise is associated with increased muscle activation.
- Muscle activation appears to be a primary driver of the VO2 slow component, influenced by metabolic demand rather than absolute work rate.
- VO2 kinetics are faster when metabolic demand is lower, irrespective of absolute work rate, highlighting the importance of metabolic factors in exercise response.