What does cardio fitness actually mean? How can it be determined? Which training is suitable for good cardio fitness? Prof. Dr. Theodor Stemper took an in-depth look at this topic for F&G.
The importance of good cardio fitness for overall cardiovascular health and life expectancy has been undisputed for decades (Blair et al., 1996). Although this realization is now gradually becoming noticeable in broad sections of the population - which is reflected, for example, in the decline in deaths from cardiovascular problems (heart attacks, strokes, etc.) in the USA in the new millennium and in the current slight improvement in activity levels in Germany (see DEGS1 results in Krug et al., 2013) - there is still a great need for action and understanding (see Wang, 2010, among others). There is also a need to understand what cardio fitness actually means and how it can be determined.
Cardio impact goals
A group of scientists recently developed new impact goals for the American Heart Association (AHA) for the USA for 2020 (U.S. "Impact Goals" for cardiovascular health and disease reduction) (Lloyd-Jones et al. 2010): "By 2020, the cardiovascular health of all Americans is improved by 20% and the death rate from heart disease and stroke is reduced by 20%."
But how can this goal be operationalized? What characterizes good, or even better, ideal cardiovascular health and what role does cardio fitness or, if applicable, physical activity play in this?
Relevance of physical activity
In addition to dietary habits, sufficient physical activity is particularly important. The comprehensive report makes it clear that cardiovascular health is clearly dependent on the amount and intensity of physical activity.
This expertise from the AHA fits very well with the fact that the resulting - or even genetically predetermined - cardio fitness is now understood as an independent protective factor alongside physical activity.
As shown in a review by Lee et al. (2010), low cardiorespiratory fitness (CRF) is a strong predictor of cardiovascular disease (CVD) and numerous other causes of early mortality. Poor cardio fitness is therefore a similarly high risk factor as the risk factors smoking, abdominal obesity ("belly fat"), high blood pressure and diabetes, which have been known for years.
Behavioral and health factors
The AHA working group has identified four health behaviors and three health factors:
4 behavioral factors
- Smoking abstinence
- BMI (body mass index) < 25 kg/m²
- Physical activity
(150 minutes per week of moderate or 75 minutes of strenuous activity or combination of both)
- Cardiovascular health-promoting diet
(Emphasis on low glycemic load; fiber-rich diet; high omega-3 fatty acid content from seafood; high polyunsaturated to saturated fat ratio; low trans fat content)
3 Health Factors
- Total cholesterol < 200 milligrams per deciliter (mg/dL)
- Fasting blood glucose < 100 mg/dL
- Blood pressure < 120/80 mm Hg.
Definition of cardio fitness
According to the authors Lee et al. (2010), cardio fitness is nothing more than the ability of the respiratory, circulatory and muscular systems to absorb, distribute and consume oxygen - which occurs in the aforementioned systems according to the demand in the muscle cells depending on the level of physical exertion. As a gross criterion for cardio fitness (CRF), the oxygen uptake in milliliters of oxygen per kilogram per minute (ml O2/kg/min) can be determined, which must be achieved over a longer period of time. A value dependent on this is MET, which denotes a person's resting metabolic rate and is usually quantified as 3.5 ml O2/kg/min, which in absolute terms results in a value of 3.5 x 70 = 245 ml O2 per minute for a person weighing 70 kg, for example.
If, for example, a person is able to achieve 8 times the resting metabolic rate (equivalent to jogging), then the O2 intake is 8 times the resting value, i.e. 3.5 x 8 = 28 ml O2/kg/min. It is important to know that, for all standard values, women generally achieve a value that is 2 METs lower, which can be explained primarily by relatively lower values for muscle mass, blood and stroke volume.
Influence on mortality rate
The aforementioned article by Lee et al. (2010) summarizes study results that convincingly demonstrate the connection between the level of cardio fitness and cardiovascular disease and mortality. The authors report results from the well-known Aerobics Center in Dallas, where the least fit were compared with the fittest. This resulted in a risk reduction of 43% and 53% for men and women respectively with regard to overall mortality and as much as 47% and 70% for cardiovascular mortality.
Survival of the Fittest?
The figures in the publication by Kodama et al. (2009) (so-called original meta-analysis, i.e. evaluation of the results of other studies) are also particularly impressive. Kodama et al. analyzed studies on the influence of cardio fitness on cardiovascular diseases and mortality on the basis of 33 large studies/investigations. They came to the conclusion that every 1-MET increase in cardio fitness (MET = metabolic unit for basal metabolic rate) reduces the risk of death and disease by 13% and 15% respectively. A similar value (12%) was already published in 2002 by Myers et al. and commented on with the bold slogan "Survival of the Fittest?".
Since these extensive data analyses at the latest, it is now undisputed that low cardio fitness is a strong risk factor for cardiovascular health, while high cardio fitness is a protective factor - and that this finding also persists with different age, gender, BMI (!) and even smoking habits (!).
The question now arises as to whether this connection between cardio fitness and health/disease/death is God-given, or whether it might not be possible to influence the risk of illness and death by changing cardio fitness as a result of training. An interesting question, especially for the fitness industry.
Cardio fitness against health risks
Based on all the data available to date, it can be rightly claimed that an improvement in cardio fitness is associated with a reduction in the risk of illness and mortality. Better cardio fitness means a healthier life. Lee et al. (2010), for example, used research to show that people who improved their cardio fitness from low levels to medium or even higher performance levels as a result of training had significantly reduced health risks, both in the cardiovascular area and in other areas. According to Erikssen et al. (1998), even slight improvements lead to significant risk reductions - a finding that should encourage untrained people in particular. Erikssen et al. (1998) prove this with a study of 2,014 healthy men (initially aged 40-60), whom they observed over 22 years. Above all, the improvement in cardio fitness in the first seven years explained the significant reductions in health risk.
Clear health benefits
According to Lee et al. (2010), there are various mechanisms that can explain why cardio fitness leads to risk reduction.
One of the most important adaptations to regular exercise and good cardio fitness is the reduction in insulin resistance, in which the body's cells no longer respond to insulin and absorb glucose from the blood. Cardio training, on the other hand, improves insulin sensitivity (again) so that muscle cells can absorb glucose, which can prevent the development of type 2 diabetes.
Secondly, good cardio fitness reduces the risk of all factors of the so-called metabolic syndrome, namely high abdominal circumference, fat metabolism disorder (increased triglycerides, increased cholesterol), high blood pressure, increased blood sugar (glucose).
And last but not least, the quality of cardio fitness also increases heart function itself. Better autonomic nervous supply, better blood circulation by lowering the resting pulse rate, strengthening the contractility of the heart muscle are just some of the cardiac-related adaptations.
All in all, cardio fitness correlates excellently with a wealth of important bodily functions that are desirable for health, so that it is essential to test them regularly with cardio tests and take them into account in health-oriented training programs in the gym. Cardio fitness is therefore an absolute "must" in health training.
Which training is recommended?
The following is recommended as standard by the well-known American College of Sports Medicine (ACSM) for significant improvements in cardio fitness (after excluding health risk factors):
- Training frequency: 3-5 days per week
- Training intensity: 64%-94% of maximum heart rate (e.g. Thompson, 2009).
- Exercise duration: 20 (beginners) to 60 (trained) minutes of continuous or extensive interval training (more on the topic of continuous training vs. HIIT in a future issue of F&G).
- Periodization through progressive increases in intensity and/or duration for the development of (even) higher cardio fitness and occasional changes and reductions in training loads are beneficial.
Prof. Dr. Theodor Stemper
Literature
Blair, S.N., Kampert, J.B., Kohl, H.W. III, et al. (1996). Influences of cardiorespiratory fitness and other precursors on cardiovascular disease and all-cause mortality in men and women. JAMA, 276 (3), 205-210
Erikssen, G., et al. (1998). Changes in physical fitness and changes in mortality. The Lancet, 352, 759-62.
Lee, D., et al. (2010). Mortality trends in the general population: The importance of cardiorespiratory fitness. Journal of Psychopharmacology, 24 (11), 27-35.
Lloyd-Jones, D.M., et al. (2010). Defining and setting national goals for cardiovascular health promotion and disease reduction: The American Heart Association's strategic Impact Goal through 2020 and beyond. Circulation, 121, 586-613. http://circ.ahajournals.org/content/121/4/586.full
Kodama, S., et al. (2009). Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women; a meta-analysis. Journal of the American Medical Association, 301 (19), 2024-35.
Krug ,S.,- Jordan, S., Mensink, G.B.M., Müters, S., Finger, J.D. & Lampert, - T. (2013). Physical activity. Results of the German Health Interview and Examination Survey for Adults (DEGS1). Bundesgesundheitsbl (56), 765-771. DOI 10.1007/s00103-012-1661-6.
Myers, J., Prakash, M., Froelicher, V., Do, D., Partington, S. & Atwood, JE (2002). Exercise capacity and mortality among men referred for exercise testing. N Engl J Med 346, 793-801.
Thompson, W.R. (Sen.Ed.) (2009). ACSM's Guidelines for Exercise Testing and Prescription (8th ed.). Philadelphia: Lippincott Williams & Wilkins.
Wang, C-Y., et al. (2010). Cardiorespiratory fitness levels among US adults 20-49 years of age: Findings from the 1999-2004 National Health and Nutrition Examination Survey. American Journal of Epidemiology, 171 (4), 426-35.
Source: F&G
Published on: 8 September 2014