slowpoke
07-16-2019, 07:49 PM
Has anyone heard of the idea that larger thighs help drive more blood to the heart, which means that folks with larger thighs need to focus more on their aerobic workouts?
[M]uscle mass in your legs can affect your cardiac zones in a way that can be deceptive. Here’s why: your veins in your legs have a series of one-way valves that prevent the blood from pooling in your legs since we walk upright and the legs hold a lot of blood. The one-way valves mean you can still move large volumes of blood from the legs without requiring a super high blood pressure.
When your muscles flex in your legs it actually *drives* blood to your heart and the heart rate responds sympathetically to accept the incoming blood. Some people call this a kind of “second” heart. However, when the legs are driving lots of blood volume to your heart while the *rate* increases to handle the incoming blood (making you think you’re in a higher zone) the *power* of the cardiac contraction (ergo actual cardiac training effect) can be less because legs have provided a service in moving the volume of blood along and refilling the heart.
Again, this is only relevant for people who have significant muscle mass in their legs — if you have slender legs genetically, then the volume/rate issue is balanced during exercise.
This effect is especially pronounced for people who have large muscle mass in their thighs, hamstrings and calves — their legs can drive a lot of blood to their heart and the heart responds accordingly by beating faster to accept the incoming blood. (Again, people’s muscle mass in their legs is determined again, by genetics and fitness). They might think they’re in X zone based on the rate, but not actually get the true cardiac benefit because of the amount of work in moving blood their legs are doing.
Source: Bob C. on SF Randonneurs, July 2018 (https://groups.google.com/d/msg/sfrandon/hHkpzmXeow8/Xw0l48pUAAAJ)
[M]uscle mass in your legs can affect your cardiac zones in a way that can be deceptive. Here’s why: your veins in your legs have a series of one-way valves that prevent the blood from pooling in your legs since we walk upright and the legs hold a lot of blood. The one-way valves mean you can still move large volumes of blood from the legs without requiring a super high blood pressure.
When your muscles flex in your legs it actually *drives* blood to your heart and the heart rate responds sympathetically to accept the incoming blood. Some people call this a kind of “second” heart. However, when the legs are driving lots of blood volume to your heart while the *rate* increases to handle the incoming blood (making you think you’re in a higher zone) the *power* of the cardiac contraction (ergo actual cardiac training effect) can be less because legs have provided a service in moving the volume of blood along and refilling the heart.
Again, this is only relevant for people who have significant muscle mass in their legs — if you have slender legs genetically, then the volume/rate issue is balanced during exercise.
This effect is especially pronounced for people who have large muscle mass in their thighs, hamstrings and calves — their legs can drive a lot of blood to their heart and the heart responds accordingly by beating faster to accept the incoming blood. (Again, people’s muscle mass in their legs is determined again, by genetics and fitness). They might think they’re in X zone based on the rate, but not actually get the true cardiac benefit because of the amount of work in moving blood their legs are doing.
Source: Bob C. on SF Randonneurs, July 2018 (https://groups.google.com/d/msg/sfrandon/hHkpzmXeow8/Xw0l48pUAAAJ)