Does a low heart rate always mean an enlarged heart size?

I am not a doctor either, but I believe I could pass in parts of Appalachia as a beloved "fake doctor" whose patients love and defend him even as the authorities are putting him in the paddy wagon en route to trial. With this as preamble, I have written about some of the changes that the heart undergoes in reaction to heavy exercise. The basic concepts are these: Strength training--because of the incredible high blood pressure generated by heavy dead lifts, world class weight lifters tend to develop thicker heart chamber walls, the better to withstand these pressures. People with untreated high blood pressure often get a condition called LVH, for left ventricular hypertrophy--a similar, albeit pathological, thickening of the wall of the left ventricle. It appears that when such thickening occurs in reaction to weight training, it's not harmful. When it results from untreated hypertension, however, it is harmful. Anyhow, wall chamber enlargement is one form of cardiac remodeling. It does not affect heart rate. Aerobic training--endurance sports requires large volumes of blood being pumped through your body to supply the demands of the skeletal muscles that are doing the work. With enough training, endurance athletes can undergo all sorts of adaptations. For instance, they actually increase their blood volume and may undergo the formation of collateral vessels to better supply different parts of the body (including the heart) that need oxygen and nutrients. In terms of the heart itself, the major change is that the interior volume of the pumping chambers can enlarge. This allows the heart to pump more blood per single beat. Pure aerobic athletes don't see the enlargement, or thickening, of the heart walls per se. But they can get more expandable pumps. Thus one reason your heart rate goes down at rest is that a single beat is circulating more blood than it used to, meeting your body's needs. Final note: All of the above notwithstanding, to get a significant remodeling of the heart--either thickened walls or enlarged pumping chambers--requires very hefty amounts of exercise, much more than even dedicated masters swimmers are likely to do. Think Lance Armstrong, who has 2 liters more blood than most of us mortals; or Bjorn Borg in his prime, whose resting heart rate was measured at 28 beats per minute.

I am not a doctor either, but I believe I could pass in parts of Appalachia as a beloved "fake doctor" whose patients love and defend him even as the authorities are putting him in the paddy wagon en route to trial. With this as preamble, I have written about some of the changes that the heart undergoes in reaction to heavy exercise. The basic concepts are these: Strength training--because of the incredible high blood pressure generated by heavy dead lifts, world class weight lifters tend to develop thicker heart chamber walls, the better to withstand these pressures. People with untreated high blood pressure often get a condition called LVH, for left ventricular hypertrophy--a similar, albeit pathological, thickening of the wall of the left ventricle. It appears that when such thickening occurs in reaction to weight training, it's not harmful. When it results from untreated hypertension, however, it is harmful. Anyhow, wall chamber enlargement is one form of cardiac remodeling. It does not affect heart rate. Aerobic training--endurance sports requires large volumes of blood being pumped through your body to supply the demands of the skeletal muscles that are doing the work. With enough training, endurance athletes can undergo all sorts of adaptations. For instance, they actually increase their blood volume and may undergo the formation of collateral vessels to better supply different parts of the body (including the heart) that need oxygen and nutrients. In terms of the heart itself, the major change is that the interior volume of the pumping chambers can enlarge. This allows the heart to pump more blood per single beat. Pure aerobic athletes don't see the enlargement, or thickening, of the heart walls per se. But they can get more expandable pumps. Thus one reason your heart rate goes down at rest is that a single beat is circulating more blood than it used to, meeting your body's needs. Final note: All of the above notwithstanding, to get a significant remodeling of the heart--either thickened walls or enlarged pumping chambers--requires very hefty amounts of exercise, much more than even dedicated masters swimmers are likely to do. Think Lance Armstrong, who has 2 liters more blood than most of us mortals; or Bjorn Borg in his prime, whose resting heart rate was measured at 28 beats per minute.