Presentation Type

Poster

Abstract

The intent of our study is to determine the mechanisms associated with muscle performance loss resulting from short-duration, high intensity muscular contraction. Previous studies conducted by Dr. Bundle and colleagues established a performance duration relationship for muscle fatigue at high and low duty cycles (Duty cycle = time of muscle contraction / total time of contraction cycle). The purpose of the current study is to show that despite higher rates of blood flow occurring at lower duty cycles, oxygen extraction by the active muscle is the same between high and low duty cycles. Thus, allowing us to assume performance loss is not associated with decreased oxygen availability, but rather decreased clearance of metabolic byproducts.

To perform this study we used Doppler Ultrasonography to acquire real-time measurements of blood velocity while subjects performed single-leg knee extension exercise. The knee extensions were performed at randomized intensities and at high, medium and low duty cycles of 0.7, 0.5, and 0.3 respectively. Each subject participated in a minimum of 12 testing sessions. Femoral artery diameter was recorded via screen capture allowing for acquisition of arterial dimension changes throughout the trial duration countenancing for precise calculation of flow volume. Along with blood flow volumes, indirect calorimetry was used to assess oxygen consumption by the contracting muscle. Blood flow volumes will be compared to the performance duration relationship for each duty cycle. We expect that despite greater periods of rest at the low duty cycle, rates of oxygen uptake by the working tissue will be similar. Thus, greater flows, providing more oxygen delivery, do not enhance muscular performance. Rather, sustained higher force outputs are possible because of the clearance of contractile byproducts which delays the onset of muscle fatigue.

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Physical Sciences

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Apr 11th, 3:00 PM Apr 11th, 4:00 PM

Continuous measures of blood flow during all-out dynamic exercise

The intent of our study is to determine the mechanisms associated with muscle performance loss resulting from short-duration, high intensity muscular contraction. Previous studies conducted by Dr. Bundle and colleagues established a performance duration relationship for muscle fatigue at high and low duty cycles (Duty cycle = time of muscle contraction / total time of contraction cycle). The purpose of the current study is to show that despite higher rates of blood flow occurring at lower duty cycles, oxygen extraction by the active muscle is the same between high and low duty cycles. Thus, allowing us to assume performance loss is not associated with decreased oxygen availability, but rather decreased clearance of metabolic byproducts.

To perform this study we used Doppler Ultrasonography to acquire real-time measurements of blood velocity while subjects performed single-leg knee extension exercise. The knee extensions were performed at randomized intensities and at high, medium and low duty cycles of 0.7, 0.5, and 0.3 respectively. Each subject participated in a minimum of 12 testing sessions. Femoral artery diameter was recorded via screen capture allowing for acquisition of arterial dimension changes throughout the trial duration countenancing for precise calculation of flow volume. Along with blood flow volumes, indirect calorimetry was used to assess oxygen consumption by the contracting muscle. Blood flow volumes will be compared to the performance duration relationship for each duty cycle. We expect that despite greater periods of rest at the low duty cycle, rates of oxygen uptake by the working tissue will be similar. Thus, greater flows, providing more oxygen delivery, do not enhance muscular performance. Rather, sustained higher force outputs are possible because of the clearance of contractile byproducts which delays the onset of muscle fatigue.