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Increase your heart smarts with info on how exercise impacts your heart, how to measure fitness via heart rate, and top cardio concerns fitness pros should know.

How it Works

Your heart weighs only about 10 ounces and is roughly the size of an adult fist. This four chamber, centrally located pump pushes five to six quarts of blood, per minute, throughout your body.

• Each heartbeat is initiated by a specialized area called the sinoatrial node (SA node) in the heart’s upper right chamber. The SA node is often called the pacemaker (or primary pacemaker) of the heart, triggering electrical impulses that squeeze this part of the heart slightly earlier than the rest of the heart, forcing blood into the lower chambers for each beat.

• When you exercise, your muscles require more oxygen and nutrients, at a quicker rate, to fuel contractions. Your heart will beat faster to deliver more blood to meet this demand. In addition, the arterioles (smaller blood vessels leading from the arteries to the capillaries) serving the exercising muscles dilate to accommodate the increased flow. As these vessels open, other arterioles constrict in less active parts of your body, including your digestive system, skin, and the skeletal muscles you’re not using.

• Exercise makes your heart stronger. A stronger heart pumps blood more easily throughout this entire process, keeping blood pressure healthy or reducing blood pressure that’s too high. It can also improve circulation, lower heart disease risk, improve blood cholesterol levels, and lower resting heart rate.

Training with Heart

Heart rate is a good exercise-intensity gauge. Here are two ways to track heart rate to help improve and monitor fitness.

Can a person be fit, yet also be fat? For most of us, a fair assumption would be to believe (at least initially) that the answer is ‘no’, but when you examine the research on this relationship, and the subsequent effects on mortality rates, there is no universal agreement. While plenty of research supports the ‘no’ assumption, a growing number of studies now also support the notion that a person could be fat, yet also be healthy (1, 2). So what are we to believe and use as our compass when it comes to education and programming for activity and weight loss?

First, we should examine definitions of ‘fit’ and ‘fat’ as they alone contribute to this confusion, Then, we should also examine the nature of some of the studies conducted that may have received widespread media coverage without proper merit.

Let’s start first with definitions of overweight and obesity. A measure of body fat percentage would appear to provide a logical assessment of an individual’s level of fat, but the unfortunate reality is that the validity and reliability of in vivo, cost-efficient, field testing for measuring percent body fat remains highly questionable. Consequently, much of science relies upon the more objective measurement of body mass index (BMI) or the Quetelet Index that has replaced the older height-to-weight tables used prior to the mid-1980s. Research supporting mortality to BMI scores (not % fat) is quite strong and defined within the categories established for normal, overweight, obese and morbidly obese (18.5 – 24.9; 25.0 – 29.9; 30.0 – 39.9; 40.0+ respectively) (3, 4). We generally believe that the more body fat a person has, the greater their risk for disease, and because higher BMI scores generally reflect excess fat in most individuals, these scores have been correlated to increased risk of disease (Table 1-1) (3).

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