Comments on: Anaerobic Threshold on a Bike versus Treadmill – Q&A http://www.bodyrecomposition.com/training/qa-5.html Training and Nutrition advice, straight from the monkey's mouth. Sun, 22 Jan 2012 21:56:52 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Jacob Gudiol http://www.bodyrecomposition.com/training/qa-5.html/comment-page-1#comment-80 Jacob Gudiol Thu, 08 May 2008 08:36:31 +0000 http://www.bodyrecomposition.com/blog/2008/05/07/qa-5/#comment-80 Jens Bangsbo & Lars Michalsik brings up the subject in their book "aerobic and anaerobic training" (it's Swedish). They also claim that peak heart rate and maximum heart rate will differ between different activities. They don’t give a generic answer to why this is but they do write that when it comes to biking the lower heart rate comes from the loading being so high making it hard to pedal. Unfortunately there are no references in the book so I can’t tell where they got the information from. Bangsbo & Michalsik are solid guys though… I also found this in the book Cardiovascular Physiology Concepts “The point at which increased heart rate begins to decrease stroke volume varies considerably among individuals because of age, health, and physical conditioning. Furthermore, this point can vary within an individual depending on the type of exercise and the environmental conditions.” Regarding the gravity stuff that I wrote in a previous comment I learned that from the book Cardiovascular Physiology Concepts (http://www.amazon.com/Cardiovascular-Physiology-Concepts-Richard-Klabunde/dp/078175030X/). Body posture also influences how the cardiovascular system responds to exercise because of the effects of gravity on venous return and central venous pressure (see Chapter 5). When a person exercises in the supine position (e.g., swimming), central venous pressure is higher than when the person is exercising in the upright position (e.g., running). In the resting state before the physical activity begins, ventricular stroke volume is higher in the supine position than in the upright position owing to increased right ventricular preload. Furthermore, the resting heart rate is lower in the supine position. When exercise commences in the supine position, the stroke volume cannot be increased appreciably by the Frank-Starling mechanism because the high resting preload reduces the reserve capacity of the ventricle to increase its end diastolic volume. Stroke volume still increases during exercise although not as much as when exercising while standing; however, the increased stroke volume is resulting primarily from increases in inotropy and ejection fraction with minimal contribution from the Frank-Starling mechanism. Because heart rate is initially lower in the supine position, the percent increase in heart rate is greater in the supine position, which compensates for the reduced ability to increase stroke volume. Overall, the change in cardiac output during exercise, which depends upon the fractional increases in both stroke volume and heart rate, is not appreciably different in the supine versus standing position. Now that I’ve had time to think about it for a day or two I regret bringing up the gravity stuff in my previous post since the explanation from Bangsbo & Michalsik and the one you bring up about more active muscle mass makes a lot more sense than gravity differences between biking and running Jens Bangsbo & Lars Michalsik brings up the subject in their book “aerobic and anaerobic training” (it’s Swedish). They also claim that peak heart rate and maximum heart rate will differ between different activities. They don’t give a generic answer to why this is but they do write that when it comes to biking the lower heart rate comes from the loading being so high making it hard to pedal.

Unfortunately there are no references in the book so I can’t tell where they got the information from. Bangsbo & Michalsik are solid guys though…

I also found this in the book Cardiovascular Physiology Concepts
“The point at which increased heart rate begins to decrease stroke volume varies considerably among individuals because of age, health, and physical conditioning. Furthermore, this point can vary within an individual depending on the type of exercise and the environmental conditions.”

Regarding the gravity stuff that I wrote in a previous comment I learned that from the book Cardiovascular Physiology Concepts (http://www.amazon.com/Cardiovascular-Physiology-Concepts-Richard-Klabunde/dp/078175030X/).
Body posture also influences how the cardiovascular system responds to exercise because of the effects of gravity on venous return and central venous pressure (see Chapter 5). When a person exercises in the supine position (e.g., swimming), central venous pressure is higher than when the person is exercising in the upright position (e.g., running). In the resting state before the physical activity begins, ventricular stroke volume is higher in the supine position than in the upright position owing to increased right ventricular preload. Furthermore, the resting heart rate is lower in the supine position. When exercise commences in the supine position, the stroke volume cannot be increased appreciably by the Frank-Starling mechanism because the high resting preload reduces the reserve capacity of the ventricle to increase its end diastolic volume. Stroke volume still increases during exercise although not as much as when exercising while standing; however, the increased stroke volume is resulting primarily from increases in inotropy and ejection fraction with minimal contribution from the Frank-Starling mechanism. Because heart rate is initially lower in the supine position, the percent increase in heart rate is greater in the supine position, which compensates for the reduced ability to increase stroke volume. Overall, the change in cardiac output during exercise, which depends upon the fractional increases in both stroke volume and heart rate, is not appreciably different in the supine versus standing position.

Now that I’ve had time to think about it for a day or two I regret bringing up the gravity stuff in my previous post since the explanation from Bangsbo & Michalsik and the one you bring up about more active muscle mass makes a lot more sense than gravity differences between biking and running

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