I used to run 5-7 miles per day, 4-6 days per week depending on how much time I could allot and whether it was enough of a priority.
The truth was that every day I missed a workout, it bugged me. No doubt consistency was important to me, but I couldn’t put it before my husband, my work, my family.
Then I heard about high intensity interval training (HIIT), which brags better results with 20-30 minutes of anaerobic exercise than with my 75+ minutes of slow going cardio.
Somewhat begrudgingly I gave HIIT a try and have never since looked back.
Here are a few reasons it may be a good idea for you to switch from 45 minutes – 1 hour+ on the elliptical, bike or the hard pavement, to short burst interval training.
Study Discovers Heart Damage in Marathon Runners
40 elite athletes were examined after completing an endurance race lasting from 3-11 hours. Researchers looked at their hearts and noted any markers for heart injury immediately following and then one week after the marathon.
They found that even the fittest runners showed markers of heart damage. They also suffered acute dysfunction of the right ventricle (RV). This condition may be the reason healthy marathon runners have suddenly dropped dead. The heart is continually undergoing stress, releasing free radicals, becoming increasingly inflamed and diminishing in its ability to efficiently pump blood.
The authors concluded:
“Intense endurance exercise causes acute dysfunction of the RV, but not the LV. Although short-term recovery appears complete, chronic structural changes and reduced RV function are evident in some of the most practiced athletes, the long-term clinical significance of which warrants further study.”
Upper Limits Even For the Fittest
Other research has revealed that running too fast for too long on a consistent basis actually eliminates the heart healthy benefits, canceling the runners’ mortality advantage. Overdoing it may cause coronary heart calcification in the athlete equivalent to that of the sedentary.
In this case, overdoing it means running more than 20 miles every week at or above a pace of 8mph.
The healthier approach is going to be a little less distance with a little less speed. Our bodies are designed for a lot of motion and activity, but not constant stress.
Increased Cortisol Increases Fat Storage
Speaking of stress, long-duration cardio increases production of cortisol, the stress hormone.  Excess cortisol is associated with:
- heart disease
- suppressed immune function
- autoimmune disorders including arthritis, asthma and allergies
- accumulation of visceral fat
It also increases hunger and sugar cravings and disrupts sleep. When we are deprived of even one hour of sleep, especially over time, our bodies become insulin resistant. Insulin resistance is the precursor to diabetes and obesity.
Slow Cardio Insufficient for Fat Loss
Expert voices today are mounting with evidence and argument that endurance exercise is NOT the most efficient way to burn fat, although it can actually increase insulin resistance and fat storage.
Fitness expert Shaun Hadsall recently cited a study that found in women a decrease of T3/thyroid hormone production after doing “traditional cardio.” T3 plays a key role in metabolism. The body slows or stops this hormone in order to maintain fat for later energy needs. The authors concluded that the fat conservation response:
“…is related to the decreased leptin concentrations, and could represent a possible means of energy conservation in these exercising women.”
For the Long Haul
Even amidst all of the alarming information about endurance exercise, going for long walks is extremely beneficial. Enjoying a “nice” jog is great for you. Dancing to your heart’s content is life giving. Being out and about and on your feet is a good thing, as long it’s not continuously stressing your bod out.
Light to moderate activity such as a daily brisk walk or leisurely swim may not be your ultimate fat burning regimen, but it’s great for your off-days from intense training. We’re not just working out to achieve physical benefits, but because it’s a natural and vital part of being alive.
You and I are designed to live active lives doing low-impact work throughout the day. Ideally we’ll walk from one place to the next rather than drive everywhere. We’ll get up and move at some point during every hour of every day and we’ll supplement regular movement with high intensity workouts that increase human growth hormone (HGH), improve sleep, reduce stress, regulate blood sugar, increase insulin sensitivity and, as a result, burn fat and build muscle.
High intensity interval training does just that; it trains your body to be fit, accomplishing much in little time so that you can spend the rest of your days playing.
To learn more about HIIT see 6 Surprising Benefits Of High Intensity Interval Training (HIIT).
Make sure to check out Shawn Stevenson’s Fat Loss Code Program. He is the best!
 Nadine Skoluda, Lucia Dettenborn, et al. “Elevated hair cortisol concentrations in endurance Athletes.” (2011)