Research Spotlight: The combination of cardiorespiratory fitness and muscle strength, and mortality risk
Little is known about the relationship between cardio fitness and hand grip strength with mortality in general adult populations. However, a recent study in the European Journal of Epidemiology concluded that improving both cardio fitness and muscle strength, as opposed to either of the two alone, may be the most effective behavioral strategy to reduce mortality risk.
Significant research has shown that high cardiorespiratory fitness is closely connected to positive health outcomes. In addition, there is significant research that shows that muscle strength is an important marker in reducing mortality rate, as well as reducing the risk of sarcopenia. However, little historical research has been done to show the combined impacts of cardio fitness and muscle strength in relation to mortality risk.
The current public health guidelines recommend the population engage in both aerobic and muscle-strengthening activities, thus it is important to understand the clinical impacts of these activities on the mortality rate.
In 2018 researchers from the UK embarked on a large study to show the relationship between cardiorespiratory fitness, muscle strength and mortality. Researchers had access to a large sample of over 70,000 UK adults aged between 40-69 years. Cardiorespiratory fitness was measured through sub-maximal bike tests. Muscle strength was measured using a hand-held dynamometer to test grip strength. Grip strength was chosen as the method to measure muscle strength as grip strength measures have good reliability and reproducibility. Mortality data was gathered over a six year follow-up and was categorised by "all-cause mortality", "cardiovascular disease" and "cancer".
The researchers found that compared to those with low cardio fitness, those with high cardio fitness reduced their risk of all cause mortality by 35%. Compared to those with low grip strength, those high grip strength reduced their risk of all cause mortality by 21%. When combined, compared to those with low cardio fitness and low grip strength, those with high cardio fitness and high grip strength reduced the risk of all cause mortality by 47%.
Overall, the study is significant in that it analysed such a large sample size and is one of the one studies looking at the synergistic effects of combining resistance training and aerobic exercise among the general popluation. Other simliar studies have been conducted, however they have focussed on subsects of the population, such as older adults, those with type 2 diabetes or those were who overweight.
Overall, individuals in the study with higher cardiorespiratory fitness showed lower risks of all-cause, cardiovascular disease and cancer mortality. Those with higher grip strength had lower all-cause mortality. All-cause and cardiovascular disease mortality risk was lowest in adults with both higher cardiorespiratory fitness and higher grip strength. Finally, improving both cardiorespiratory fitness and muscle strength, as opposed to either of the two alone, may be the most effective behavioral strategy to reduce all-cause and cardiovascular mortality risk.
Kim Y, White T, Wijndaele K, Westgate K, Sharp SJ, Helge JW, Wareham NJ, Brage S. The combination of cardiorespiratory fitness and muscle strength, and mortality risk. Eur J Epidemiol. 2018 Oct;33(10):953-964. doi: 10.1007/s10654-018-0384-x. Epub 2018 Mar 28. PMID: 29594847; PMCID: PMC6153509.