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Cardiorespiratory fitness (CRF), or cardiovascular endurance, is the body’s ability to absorb and use oxygen during exertion. Thanks to smart devices, you can monitor your level in real-time and influence it as well. However, to achieve this, you will have to sweat, quite literally.
Although the promising connection between cardiorespiratory fitness and health outcomes has been studied in many reviews, no single study has compiled all the evidence. Gaps in the literature persist, particularly limited research involving women. Scientists from the USA, Canada, Australia, and Spain decided to fill these gaps and analyzed 199 existing studies on this topic. The results of their work were published in the British Journal of Sports Medicine.
Cardiorespiratory Fitness: Pros and Cons
The link between cardiorespiratory fitness and all-cause mortality, along with cardiovascular diseases and cancer, has been studied since the 1980s. The results demonstrate that low cardiovascular endurance is associated with an increased risk of these issues. Additionally, it is linked to a higher likelihood of developing type 2 diabetes, metabolic syndrome, stroke, and depression.
But low endurance isn’t the only problem. Postmenopausal women with a normal level of cardiorespiratory fitness are 55% less likely to suffer hip fractures and have denser bones than their inactive peers. The risk of death after such an injury ranges from 8% in the first month to 53% over three years.
Men with good levels of CRF are 40% less likely to develop nine types of cancer, according to a large-scale study last year, including lung cancer and gastrointestinal tract cancers.
Better CRF positively impacts health even in the presence of chronic and severe diseases such as cancer, chronic kidney disorder, and peripheral artery disease. Just last week, a new study presented at the scientific congress of the European Society of Cardiology showed that even light yoga significantly improved heart indicators in patients with heart failure.
Measuring Cardiorespiratory Fitness
CRF is measured using the VO₂ max indicator – this is the maximum rate of oxygen consumption per kilogram of body weight (ml/kg/min). It can also be measured in metabolic equivalent tasks (MET), which is the ratio of energy expended during an activity to the energy expended at rest. The higher the level of cardiorespiratory fitness, the better the body’s condition, and the more efficiently it operates.
VO₂ max can be measured with the help of specialized personnel using specialized equipment in a specialized environment, or by wearing a fitness tracker. The tracker calculates a predicted VO₂ max based on heart rate and movement data. Factors such as gender, age, and certain cardiovascular medications can also influence VO₂ max.
20.9 Million Observations
The authors aimed to review studies on cardiovascular fitness and verify the reliability of the reported health outcomes. Their analysis included 26 systematic reviews, 199 unique cohort studies, and a cumulative sample size of 20.9 million observations over 20 years.
The observations considered data from conditionally healthy adult participants as well as those diagnosed with chronic diseases. Professional athletes, individuals post-surgery, pregnant women, and lifelong patients were excluded.
Health outcomes included: all-cause or cause-specific mortality; events related to physical risk factors; chronic diseases or mental health issues. For patients with diagnosed chronic diseases, the scientists included evidence regarding outcomes such as mortality or disease severity.
A Single Indicator for Diagnosing Overall Health
Cardiorespiratory fitness turned out to be a reliable predictor of all-cause or cause-specific mortality. These included cardiovascular diseases, sudden cardiac arrest, all types of cancer, and lung cancer. Overall, individuals with high CRF had a 41-52% lower risk of premature death compared to those with low CRF.
Low CRF was a key risk factor for the development of stroke, hypertension, heart failure, type 2 diabetes, kidney diseases, dementia, and depression. Conversely, higher CRF was associated with better prognosis in patients with chronic diseases, including heart failure and cancer.
A major limitation of all these studies is the extremely low representation of women. For instance, there were 1,858,274 male participants compared to 180,202 female participants in all-cause mortality metrics. Only two studies reported results separately for women. High CRF provided greater protection against stroke and type 2 diabetes for women compared to men.
Therefore, while the authors agree that high CRF significantly reduces the risk of serious diseases and death, they emphasize the need for additional high-quality studies and greater representation of women. They also recommend considering the inclusion of cardiorespiratory fitness in clinical and diagnostic practice.
Improving Cardiorespiratory Fitness
Physiologically: your heart rate and breathing are to speed up. Practically: this means aerobic exercises and all cardio workouts – running, high-intensity interval training (HIIT), or fast cycling. Even a faster pace and more challenging route during your daily walk can push your cardiorespiratory fitness upward.
Modern smartphones can display trends in your CRF, allowing you to track your progress. Improving your fitness is a gradual and fairly slow process, but the results are worth it.
