Final answer:
The idea that speed play is only effective for individuals at an optimal level of physical fitness is false. Speed play can be adapted for different fitness levels, and it helps improve an individual's speed and endurance over time, regardless of their starting fitness level.
Step-by-step explanation:
The statement 'Speed play only works with individuals who are at an optimal level of physical fitness' is false. Speed play, or interval training, is a versatile training method that can be beneficial for a variety of fitness levels. It involves short bursts of intense effort followed by periods of lower-intensity recovery. This type of training can be tailored to meet the needs of individuals at different stages of physical fitness and is not exclusive to elite athletes or those at peak fitness levels.
Moreover, natural selection and the adaptation of traits such as better running speed are long-term evolutionary concepts and do not directly apply to the improvements one might see in an individual's speed from a training regimen. It's also not accurate to state that all people have the same proportion of slow-twitch to fast-twitch muscle fibers, as there is considerable variation among individuals. Also, the concept of fitness in biological terms involves more than just strength and speed; rather, fitness refers to the ability to survive and reproduce, with many factors at play.