Fitness Blog

January, 29 2014

Physical Activity vs. High Intensity Training

Physical Activity vs. High Intensity Training

Executive Summary:

  1. žYou can be physically active without being “fit”.

  2. Improving cardiorespiratory fitness is important for actual changes in all-cause mortality risk reduction.

  3. Exercise must be strenuous if it is to be effective in improving health, fitness, longevity, aesthetics and performance.


If your primary fitness goal is to lose body fat and/or improve muscle mass/tone, then it would behoove you to prioritize the investment of your time in high intensity training over physical activity.  Don’t get me wrong, physical activity certainly has merits, however, unless you are hitting physiological thresholds, such as:  peak heart rate, lactic acid surges, neuromuscular fatigue, systemic/cardiovascular fatigue, etc., you may be playing an inefficient game of quantity vs. quality.  Avoidance or failure to reach physiological thresholds during physical activity will likely NOT induce significant changes in fitness and fatness, unless you spend 6-10 hours per week doing it (or more, depending on the intensity).  For years, I have observed this phenomenon in anecdotal settings (IE: “cardio junkies” at the gym), and recently, I serendipitously discovered some critical science substantiating this phenomenon.

In my Junior year at USC, I registered for an overseas program that enabled me to study a semester of Kinesiology at the University of Queensland, Brisbane, Australia.  At UQ,  I enrolled in an Advanced Exercise Physiology course. As part of our curriculum for the semester, all students were required to disseminate a published research paper and subsequently conduct a presentation for the class.  Students were able to choose from a series of categories, ranging from ‘ergogenic effects of caffeine’ to ‘bone mineralization during developmental years’; a quite diverse array of categories indeed.  Being one of the last groups to pick, my partner and I were stuck with the “Fitness vs. Fatness” category, which at first glance, seemed a bit dry/boring.

Our paper, entitled “Comparisons of leisure-time physical activity and cardiorespiratory fitness as predictors of all-cause mortality in men and women”, didn’t seem particularly interesting.  The paper was an 30-year “observational study” (meaning, they did not control any variables) that measured the effect of self-reported physical activity and cardiorespiratory fitness (CRF) on health outcomes/mortality risk factors.  I know… exciting, huh?  However, the more I read, the more I realized that I was sitting on a gold mine of valuable information!

The paper articulated the difference between physical activity and cardiorespiratory fitness (another term for cardiovascular fitness).  Essentially, physical activity is “a behaviour, defined as any body movement that increases energy expenditure, including leisure-time activities and sports, whereas CRF is a physiologic attribute, usually measured by a maximal or submaximal exercise test.”  The basis for their research was apparently attributed to several cross-sectional studies that demonstrated a low correlation between self-reported physical activity and CRF. These findings supported the authors’ hypothesis that physical activity and CRF are independent in relation to health outcomes.  Meaning, you can be physically active, without actually improving your health and fitness!

The study followed 10 physical activity categories:  cycling, stationary cycling, swimming, racquet sports, aerobic dance, walking, jogging, running, treadmill exercise, and other sports (basketball, soccer, etc.).  Volume of physical activity was reported according to the relative speed/intensity, duration, and frequency of the activity.  Values were then calculated into total MET-minutes/week.  Cardiorespiratory fitness was assessed via “modified Balke protocol”, a maximal treadmill test that is highly correlated with maximal oxygen uptake (r≥0.92).

Here is a brief summary of the research:

  1. Mortality risk reduction (decreased likelihood of dying – a good thing!) is correlated with cardiorespiratory fitness.
  2. Physical activity does not appear to be associated with reducing risk of mortality.

  3. Individuals that demonstrated a higher level of cardiorespiratory fitness, but reported less physical activity (IE: sedentary outside of exercise), actually had a lower risk of all-cause mortality.

  4. Individuals who met physical activity recommendations but demonstrated low cardiorespiratory fitness (IE: no strenuous exercise), had no significant decrease in all-cause mortality over the reference group.


Cumulatively, the research showed that regardless of the level of physical activity that was reported, the only thing that positively affected health outcomes was cardiorespiratory fitness.  It was concluded that:

“…healthcare providers should encourage their patients to become more fit by participating in regular PA that is sufficient to improve CRF to reduce risk of mortality. In addition, increasing CRF should be considered in the development of future PA guidelines.”

Like many research articles, the conclusion – although sound – is devoid of practical tips/application, which is often due to the scope and limitations of the study.  Regardless, allow me to fill in the blanks.

From my professional perspective – and as previously indicated – I believe that health and fitness outcomes will likely NOT improve unless individuals participate in strenuous activity that stimulates physiological thresholds (lactic acid surges, peak heart rate, local muscular fatigue, etc.).  Although physical activity does indeed burn calories, if it is not challenging enough, it may not contribute to drastic changes in fitness, longevity, aesthetics, and/or performance.

These concepts especially resonate with me in regards to my own personal experiences.  I actually spend the majority of my time sitting in front of a computer, doing research, writing, nutrition coaching, etc.  I am actually quite sedentary.  However, when I workout, I exercise like a beast! And typically for only 30-40 minutes per workout, approximately 3-4 hours per week in total (now that’s efficiency!).   My fitness is great and my biometrics are spot on! This is precisely attributed to training at a very high intensity (complimented by a holistic fitness plan) that stimulates either Metabolic or Mechanical Stress – requisite stimuli that affect surges in fat burning and muscle building hormones.  Although my workouts are purely resistance training based (weights, plyometrics, sprinting, etc.), I take very short rest intervals, which drastically elicits a substantial cardiovascular response.  Respectively, my workouts signifcantly improve my cardiorespiratory fitness as well.

So what to do with this information?  Well for starters, the 2008 Physical Activity Guidelines for Americans (also cited in the study) needs to be updated.  The recommended minimum of “150 minutes a week of moderate-intensity” or “75 minutes a week of vigorous-intensity aerobic physical activity” for “substantial health benefits” needs to be modified to include variables that actually induce changes to cardiorespiratory fitness, and thus affect health.  Examples may include:  heart rate ranges specific to age, ratings of perceived exertion using the Borg scale, or physical descriptions of local fatigue – IE: perform exercise to produce “burning” sensation (lactic acid fatigue), etc.

If you are not hitting thresholds during your workouts, up your game.  Yes, it will be more difficult, but the results will be well worth it.  If you believe that walking 6-9 hours/week will help you lose body fat, think again.  Even though the duration is high, the intensity is not where it needs to be.  Try doing interval training instead:  perform an interval to fatigue (local muscle fatigue or cardiovascular fatigue) followed by 2-4 minutes of rest (depending on your fitness level).

High intensity training is a beautiful recipe for success and training efficiency.  And if your workouts are efficient, then your fitness will be that much more sustainable.



Lee, D-C, X Sui, F B Ortega, et al. “Comparison of leisure-time physical activity and cardiorespiratory fitness as predictors of all-cause mortality in men and women.”Br J Sports Med. (2010)

“Physical Activity Guidelines for Americans.” U.S. Department of Health & Human Services. N.p., 16 10 2008. Web. 29 Jan  2014.


Leave a Reply