By analyzing reported physical activity levels over time in more than 11 000 American adults, Johns Hopkins Medicine researchers conclude that increasing physical activity to recommended levels over as few as six years in middle age is associated with a significantly decreased risk of heart failure, a condition that affects an estimated 5 million to 6 million Americans.

The same analysis found that as little as six years without physical activity in middle age was linked to an increased risk of the disorder.

Unlike a heart attack, in which heart muscle dies, heart failure is marked by a long-term, chronic inability of the heart to pump enough blood, or pump it hard enough, to bring needed oxygen to the body. The leading cause of hospitalizations in those over 65, the disorder’s risk factors include high blood pressure, high cholesterol, diabetes, smoking and family history.

Think state-of-the-art shoes, performance diets and well-thought-out racing strategies are only for elite runners?

Think again.

In reality, the slower you are, the more such measures improve your finish times, suggests new University of Colorado Boulder research.

The study, published in the journal¬†Frontiers in Physiology, takes a mathematical approach to answer a question that has perplexed exercise physiologists for years: How much does improving your body’s “running economy” – or the number of calories burned per second at an aerobic pace – really improve your speed?

The question has piqued the interest of the broader running community since July, 2017 when Nike introduced its Zoom Vaporfly 4% – a shoe that, according to previous CU research, improves running economy by 4 percent on average.

Members of the media, recreational athletes and some researchers have since assumed that meant runners wearing the shoes could cross the finish line 4 percent faster. With such savings, many predicted, a sub-2-hour marathon was well within reach.

But, according to the new study, the math is more complicated than that.

For the paper, the researchers re-examined treadmill studies of runners dating back decades, re-crunching the numbers to account for things like air resistance and oxygen uptake velocity (which both increase the faster you run).

They concluded that for runners moving slower than 9 minutes per mile, any percent improvement in running economy (due to better footwear, nutritional supplements, a tailwind, drafting or other measures) translates to an even higher percentage improvement in pace.

For instance, a 1 percent improvement in running economy for a 4:30:00 marathoner would make him or her 1.17 percent faster, dropping a significant 3 minutes and 7 seconds off their finish time.

On the flip side, for those who run faster than 9 minutes per mile, each percent improvement in the body’s gas mileage results in less than that percentage improvement in pace. For instance, that same 1 percent improvement in a 2:03:00 marathoner would enable him to run only .65 percent faster, a mere 47 second improvement.

All this is good news for recreational runners, say the authors.

A lot of times recreational runners assume these things are just going to benefit elite athletes when the reality is they can benefit even more than the elites.

A slower runner, slipping on a pair of shoes which improve running economy by 4 percent could actually translate to as much as a 5 percent improvement in finish times. Meanwhile, other measures to boost metabolic efficiency, such as drinking beet juice, drafting behind another runner, or doing plyometric exercises can also add up to boost speed.

For those at the upper end of the competitive spectrum however, the new paper elucidates something many intuitively know already: The faster you are, the harder it is to get faster.

Since the introduction of the 4% shoe, the authors note, the marathon world record has only improved by a relatively small 1.03 percent.

Shalaya Kipp, left, conducts a treadmill test in the Locomotion Lab at the University of Colorado Boulder. (photo: CU Boulder)