In the study, researchers wanted to see what played a bigger role in arterial stiffness (an indicator of heart health) for women: cardiorespiratory (heart and lung) fitness or body composition.
The study analyzed 146 women between the ages of 16 and 58. Participants’ cardiorespiratory fitness was measured using an exercise test and researchers also collected their body fat percentage, fat-free mass index (a measure of fat-free tissue—like bone, muscle, and fluid), and mean arterial pressure (i.e., blood pressure in the arteries).
Next, these findings were analyzed alongside the participants’ arterial stiffness to see what associations (if any) stood out.
The two biggest factors associated with arterial stiffness were fat-free mass index and mean arterial pressure. Specifically, a higher fat-free mass and a lower mean arterial pressure were both linked to lower arterial stiffness.
This held firm in the study regardless of body fat percentage, but older age was linked to arterial stiffness. That means the amount of fat-free mass (like muscle) you carry may play a bigger role in heart health than body fat or total body weight, but age plays a factor as well (something to keep in mind, as women tend to lose muscle mass as they age).
Building muscle through targeted lifestyle changes—e.g., weight training and eating more protein—is a reliable way to increase your fat-free mass.
However, it’s important to remember that this study was observational, so we can’t know for sure that improving muscle mass will always result in better heart health.