Question

“Scott, I’ve noticed my heart rate has been lower when I run now. I’ve reduced my caffeine intake, could this be the cause?”

This is a question I received from one of my athletes last week, and he was not the first and probably won’t be the last to ask it. I gave him an answer, which I think he was pretty happy with and will be described in this post.

Heart rate is an input metric that measures the internal changes in your body as a response to stress or in our case training. So, when you run, your body needs to send blood to the working muscles in the body at a much faster rate compared to when you’re sitting on the couch watching American Idol, and as a result your heart must beat faster. Thus, an increased heart rate when you exercise. Easy right? However, there are many external or environmental factors that have an effect your heart rate. Sleep patterns, diet, weather, and caffeine consumption play a role in heart rate. It is for this reason that training with heart rate alone is not the most accurate marker of effort. For example, an athlete has an early morning training run scheduled, but is unable to get ample sleep and wakes up rather groggy. As a result, he drinks two cups of coffee before heading out to run in the hot, humid summer morning air. He notices throughout his run that his heart rate is high but he is not running any faster than usual. Now, this example may be extreme, but it illustrates the many factors that can affect heart rate.

On the other hand, let’s go back to the original question. My athlete was running at the same pace, but noticing that his heart rate was lower. This can also be a good sign of adaptation. When this athlete is able to run faster at a lower heart rate, we call that efficiency. Now my athlete’s body is becoming more efficient, i.e. he is stressing his body less at the same running pace. Think of him as going from a gas guzzling SUV to a planet friendly hybrid.

Although, training with heart rate has its benefits, there are other tools an athlete can use to get the most out of their training. A GPS device that gives real-time pace is a great piece of technology athletes can use to maximize their training. So, now when you notice your heart rate lower, you can associate it with a pace and over time your coach can monitor how your efficiency improves. All for now.

SJI