Thirsty (for knowledge) Thursday: Why the First Mile is the Hardest

I recently came across an article that talks about why (physiologically) the first mile of a run can feel like the hardest.

First up is Sadi Raza: MD, FACC, and a board-certified cardiologist in Dallas, Texas. "The first mile is the hardest because it leads to a rapid increase in oxygen demand to your entire body. Your cardiac output is a direct product of your heart rate and stroke volume, where the stroke volume is the amount of blood pumped out by the heart in one contraction," explains Dr. Raza.

So, what’s going on during that first mile, exactly?

Early in a run, you'll feel your heart rush to meet the body's needs. "When you first start to exercise, your muscles' metabolic requirements may increase up to 50-fold," says Edo Paz, MD, a cardiologist and Vice President of Medical at K Health. To increase cardiac output during that first mile, the heart rate and stroke volume both increase quickly to better meet the new (and greater) oxygen demands.

As your heart pumps more blood (faster, stronger!) your blood vessels deliver more oxygen to your muscles. At the same time, blood flow to other organs, such as those in your gastrointestinal tract, decreases. As a result, the workout feels most challenging at first, before these organs have fully caught up. "Your lungs exchange more oxygen by increasing the rate of breathing, and exchanging more gas with each breath," says Dr. Paz. "In other words, your heart, lungs, blood vessels, and muscles work harder to support your exercise."

This is where cardiac output and stroke volume come in again. "The first mile is harder because of the mismatch," Dr. Raza says. "The heart rate and stroke volume haven't caught up to the cardiac output required by your muscles during that first mile."

I feel like people newer to the sport of running (or people just starting to or try to get into better shape) may throw in the towel here. But if you've been a runner for a while, you know that it's a feeling you get over:

You should feel better as you continue running.

A mile is an abstract thought — it’s just a distance. You can consider that first mile to be the toughest, rather than thinking in terms of how many minutes until you’ve adjusted. "The heart 'catches up' pretty quickly, but how quickly depends on your baseline level of conditioning," Dr. Raza says. In other words, a regular runner will acclimate sooner than someone just starting out. Most people, though, should feel adjusted by halfway into the first mile. Phew.

So, are there ways to make that "first mile fatigue" go away sooner, or maybe not show up at all?

A few warm-up tricks can make that first mile less grueling. "Make it easier by hydrating yourself well, which helps ensure a good stroke volume," says Dr. Raza, who recommends having a glass of water 30 minutes before you exercise.

You can also increase your heart rate ahead of time. Try raising your resting heart rate prior to that first mile through a warm-up such as stretching, flexing, or jogging in place.

They say the warm-up doesn't need to last long - even less than 5 minutes. And (as us... ahem... "older" athletes can tell you) this feeling of a rough first mile starts to go away over time. "Exercising consistently will help even more," says Dr. Paz. "As your body adapts over time, it is better able to meet the metabolic requirements of exercise."

For more "Thirsty Thursday" posts that highlight workouts, body science, and all kinds of interesting information, CLICK HERE. As always, check back for some "Friday Funnies" tomorrow!