Final answer:
The statement is true; individual differences, rooted in genetics, influence how people adapt to training. These differences are a fundamental part of evolutionary theory, which states that individuals most adapted to their surroundings survive and reproduce.
Step-by-step explanation:
The principle of individual differences does indeed state that the rate and magnitude of adaptations to training can be limited by our differing genetics, making the statement True. This concept is closely related to the broader principles of evolution and natural selection, which suggest that individuals most adapted to their environment are more likely to survive and pass their traits on to the next generation. Genetic variation, including the proportion of slow-twitch to fast-twitch muscle fibers, varies from person to person, influencing how individuals respond to physical training and other environmental demands. It is a misconception to think that natural selection produces certain beneficial adaptations, such as better running speed, simply because individuals run more frequently. Rather, these adaptations are a result of genetic variation and the survival of traits that are favorable in a given environment over time.