In the fitness industry, few topics are as polarizing as the inclusion, prescription, and applicability of cardiovascular exercise. Cardiovascular exercise, or simply “cardio,” is defined as rhythmic and repetitive activity conducted by the body’s muscular system which elevates heart rate. Like a lane hogging, robustly muscled Shaquille O’Neal in his championship winning prime, cardio is the “go to" and has been an unquestioned recommendation by many health practitioners in the prevention of weight gain and hypokinetic disease.

The Shaq Analogy

Akin to a few NBA teams running their offenses for over the span of a decade through a behemoth specimen, cardio has long been championed by fitness organizations because its prescription largely involved no thought. I mean, why use other weapons on the court to splice through your opponent when you have a monster capable of single-handedly trouncing any opponent in his path?!

Throughout the latter part of the 20th century, jogging was advocated as a cure-all for ailing health and a way to zap away unwanted pounds. Regularly engaging in cardiovascular exercise elicits the following favorable adaptations:

  • Reduced resting systolic, diastolic, and mean arterial pressure values.
  • Streamlined myocardial functioning through collectively increasing stroke volume and lowering resting heart rate while also maintaining cardiac output.
  • Enlarged capillary structures which optimize the body’s transport of oxygen through the arterial system and subsequent extraction to working musculature.
  • Increased oxygen carrying capacity of the blood via erythrocytosis.
  • Proliferated mitochondrial content which increases the capacity to generate ATP.
  • Elevated maximal cardiac output and stroke volume values.
  • Lowered total cholesterol and elevated high density lipoprotein cholesterol.
  • Improved neurocognitive functioning.
  • Requires that a considerable amount of energy be expended, thereby making it ideal for individuals who desire weight loss.

Yes, cardiovascular exercise works...to a point. Kind of like Shaq...

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Until the 2000 NBA Western Conference Playoffs, Shaq, who was crowned the league’s MVP that year, was viewed as an indomitable force. Coaches of outmatched teams sought to exploit Shaq’s weakness as a free throw shooter by having their physically inferior players errantly swing their limbs at him and, in some cases, sacrificially use their bodies as speed bumps near the basketball. And alas, Shaq’s free throw shooting was epically woeful, much like extended cardio’s ability to offer anything positive.

The point of diminishing returns is reached far sooner with cardiovascular exercise than with resistance training, especially if is intended to improve body composition. A weight loss-centric individual who ignorantly locks himself into a one-dimensional approach consisting solely of cardio will usually morph into a smaller, weaker, skinny-fat version of his former self.

The Indoctrination of the Cardio Bunny

By virtue of ignorance, their physician’s suggested strategy to break free of statin drug dependency, or a cookie-cutter fitness website’s maligned interpretation of ACSM activity guidelines, many gym goers ascribe to a singular approach of only engaging in cardiovascular exercise. Deluded by their otherwise pedestrian feats on the trail, track, or treadmill (where more often than not heart rate is maintained in the lower end of 50-80% of maximum heart rate), some of these cardio bunnies decide to sign up for a local race, simultaneously feeding a frenzy of mediocrity characterized by suboptimal metabolic functioning and compromised vitality.

Off to the Races

Having experience as a spectator and as a participant in local runs (in my much younger years), I’d posit that only a handful of people are actually prepared to run a race in the first place. You’d swear genu valgum was a contagious disease, and you would be convinced that a number of the participants were newly birthed fawns donning race bibs as they shakily scamper through the run, looking as if their weedy legs will buckle at any moment. A majority of the participants keep coming back for pavement punishment which chews away at their joints with ground reaction forces their bodies aren’t capable of handling. Depending on the velocity, research has shown that ground reaction forces range from two to five times bodyweight during running gait.

Sport shoes running Close-up

Is it the surge of endorphins which keeps them coming back for more? Or is it the simplicity of lacing up the fluorescent colored, can-hardly-pronounce-the-brand of sneakers, and going out for a run that keeps them going? Perhaps it’s this site's readership who, in spite of possessing degrees and CSCS certifications, are viewed as Shrek-like creatures, emitting guttural noises from beneath a heavily loaded bar that isn’t in a Smith machine (oh my gosh!) and driving them away from the labyrinthine “free weight area”...driving them into an abyss of local runs, ill-advised half marathons, and thousands of miles on legs with the integrity of a decade or older Daewoo.

Running into Trouble

Not trying to sound alarmist here, especially since I have a few friends who are high up in the ACSM, but cardiovascular exercise, especially conducted in excessive volumes and at inappropriate intensities over a prolonged period, may be detrimental to one’s health as revealed in a landmark investigative review authored by O’Keefe and colleagues (4). WARNING: Showing the findings of this paper to avid runners may evoke a response similar to the time when you told your kids that Santa didn’t exist, as you will likely be met with skepticism or a deluge of tears.

O’Keefe and colleagues revealed the following:

  • Greater absolute mortality among marathoners, accounting for increased participation over 35 years and increased mortality rates among triathletes stemming from sudden cardiac death (SCD).
  • Greater presence of cardiac troponin, creatine kinase, B-type natriuretic peptide in the hearts of endurance-trained individuals.
  • Elevated urea nitrogen, serum creatinine, and cystatin, which are indicative of compromised renal functioning.
  • Propensity for arterioscelerosis, which is the loss of elasticity of the arteries the deposit of material along artery walls.
  • Elevated cytokytosis and monocytic activity, resulting in myocardial fibrosis.

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Exercise emits free radicals which damage the endolitheal cells lining the arteries. Based on our understanding of physiology, it stands to reason that the amount of damage incurred is correlative with the frequency, intensity, duration, and volume of exercise. Marathon runners were found to have elevated oxidative stress levels and chronic inflammation stemming from repeated stress (2, 4). Elevated oxidative stress can damage ATPase, thus limiting calcium uptake by the sarcoplasmic reticulum adversely affecting muscle’s excitation-contraction coupling properties, resulting in reduced contractility (6). Action potentials may also be inhibited and enzymatic processes may become overwhelmed by oxidative stress (6). Further, higher cortisol levels were noted among endurance-trained athletes, and prolonged endurance training among rat models (3) showed decreases in endogenous sex hormones, particularly testosterone.

Oxidative stress is only of great concern when the body’s antioxidative abilities are unable to combat it. Health, nutrition, training status, and supplementation impact the degree to which damage is incurred; however, it should be noted that many long distance runners may be in an athletic energy deficit, especially during competition or preceding preparation periods as greater amounts of oxidative stress is caused by exercise when it is exhaustive (2). Interestingly, resistance training has been shown to confer distinct protective effects against oxidative stress among healthy young men (1) and overweight and obese subjects (5).

The Verdict

Long duration, high frequency, and lower intensity cardiovascular exercise should be abstained from if it does not support preparation for a sport or activity. Further, it should not be utilized as a singular approach to address health needs or elicit improvements in body composition or athletic performance. If used as a standalone, expect to experience a point of diminishing returns considerably sooner than if used in conjunction with other modalities. Energy systems work, which includes aerobic training, and should be periodized and varied to prevent exercise-induced illness, injury, or burnout. If you are a coach or fitness professional, please advise your athletes or clients who engage in endurance training to incorporate strength training—unless they want to experience a demise in performance and health comparable to Shaq’s twilight years in the league.

References

  1. Cakir-Atabek, H., Demir, S., Pinarbasili, R.D., & Gunduz, N. (2010). Effects of different resistance training intensity on indices of oxidative stress. J Strength Cond Res, 24, 2491-2497.
  2. Gomez-Cabrera, M., Martinez, A., Santangelo, G., Pallardo, F.V., Sastre, J. & Vina, J. (2006). Oxidative stress in marathon runner: Interest of antioxidant supplementation. British Journal of Nutrition, 96, S31-33.
  3. Manna, I., Jana, K., Samanta, P. (2004). Intensive swimming exercise-induced oxidative stress and reproductive dysfunction in male wistar rats: protective role of alpha-tocopherol succinate. Canadian Journal of Applied Physiology, 29, 172-185.
  4. O’Keefe, J.H., Patil, H.R., Lavie, C.J., Magalski, A., Vogel, R.A., & McCullough, P.A. (2012). Potential adverse cardiovascular effects from excessive endurance exercise. Mayo Clin Proc, 87, 587-595.
  5. Vincent, H.K., Bourguignon, C., & Vincent, K.R. (2006). Resistance training lowers exercise-induced oxidative stress and homocysteine levels in overweight and obese older adults. Obesity, 14, 1921-1930.
  6. Vollaard, N.J.B., Shearman, J.P., & Cooper, E.C. (2005). Exercise-induced oxidative stress: Myths, realities, and physiological relevance. Sports Med, 35, 1045-1062