Genetics significantly influence physical fitness levels by determining factors like muscle composition, metabolism, and overall body structure. Genetic predispositions can affect how individuals respond to exercise, including potential for strength gain and endurance. Some people may have a natural advantage in activities such as sprinting or endurance running, while others may find it easier to build muscle. However, despite genetic factors, lifestyle choices and consistent training can greatly impact fitness outcomes, enabling individuals to improve their physical abilities regardless of genetic background.