Effort is the Secret

I recently read two Internet postings that got me thinking about the significance of activating high threshold motor units, not just to increase strength and muscle hypertrophy, which is usually the focus of such discussions, but to burn fat and increase cardiovascular fitness as well. Is this the real secret?



The first of these postings appeared on the "Sweat Science" Blog at the on-line Runners World site. It describes a study conducted by Dr. Steven Boutcher at the University of New South Wales, Australia, and published in the The Journal of Obesity.  The study looked at High Intensity Interval Training (HIIT) and it's effect on both cardiovascular fitness and positive changes to body composition, something that has actually been been looked at and replicated repeatedly. What was interesting, and somewhat new, about this study was the speculation about what caused the cross-the-board positive effects.

"Fast sprinting caused the body to release high levels of a specific group of hormones, called catecholamines, which drive the release of fat, especially abdominal and visceral fat, from fat stores so it can be burned by working muscles.

''We don't know why, but moving limbs very fast generates high levels of catecholamine"

Very fast movement, as well as very heavy or very effortful lifting, is usually attributed to type II muscle fibers, the high threshold motor units. Thus the linkage between high threshold motor units and catecholomine release.

Catecholomines are are the category name for specific stress (fight or flight) hormones, most commonly epinephrine, norepinephrine, and dopamine.

Days later, I was reading the monthly updates on the Clarence Bass Web Site (one of my favorites by the way/ full of great information) where he described a study conducted by Southampton Solvent University (UK) doctoral candidate James Steele, published online in the June 2012 Journal of Exercise Physiology (JEP). This study presented evidence that essentially said that resistance training, if carried out at high intensity (meaning at or close to failure, ip.e. great effort) made separate cardiovascular exercise unnecessary.

That is, if weight training is carried to failure, you don't need to do separate aerobic exercise to get the same positive bodily adaptations.  You don't need to run, cycle, swim or do other forms of cardiovascular exercise.

The key is working to failure.  And, as recent studies done at McMaster University in Ontario have shown, whether it's heavy weights and low reps, or lighter weights and high reps, if you work to failure, you are  activating those high threshold motor  units.


Although more studies certainly need to be conducted, the conclusion you should be able to draw is this:

• High intensity work (aerobically or weight training) is going to activate high threshold motor units.
• Doing so releases catecholomines.
•  You burn fat, get stronger, and your cardiovascular system and lungs get healthier.

I look forward to additional research into high effort cardio and strength training and the specific mechanisms that produce positive results in health and performance.