Physical fitness is not a single quality but a spectrum of capabilities, including cardiovascular endurance, muscular strength, and body composition, according to exercise scientists. Aerobic fitness — the ability to sustain prolonged activity using oxygen, measured by VO₂max scores — is linked to reduced risk of heart disease, type 2 diabetes, dementia, and premature death, while anaerobic fitness, which governs short bursts of high-intensity effort, helps build the muscle strength and explosive power that keep older adults mobile and independent. Experts recommend following World Health Organization guidelines of at least 150 minutes of moderate aerobic activity per week combined with two days of strength training, noting that genetics, sleep, and nutrition all influence results, but that consistency remains the most important factor regardless of the chosen activity.