Final answer:
The statement that speed play only works for individuals at an optimal level of physical fitness is false. Speed play can benefit various fitness levels, and the proportion of muscle fiber types varies among people. Additionally, other true/false statements related to muscle fibers, the heart's tissue, and physiological adaptation were addressed.
Step-by-step explanation:
True or False: Speed play only works with individuals who are at an optimal level of physical fitness. This statement is False. Speed play, or fartlek training, is a form of interval training that can benefit individuals at various levels of physical fitness. It involves varying pace and intensity, which can be adjusted according to an individual's fitness level. Also, all people do not have the same proportion of slow-twitch to fast-twitch muscle fibers; this varies from person to person and can determine how one might respond to different types of physical activity like endurance training or sprinting, which is an anaerobic exercise.
As for the other true/false statements, the position vs time graph of an object that is speeding up would not be a straight line - it would be a curve, indicating acceleration. Hence, the statement is False. The heart is made up of cardiac muscle, not smooth muscle tissue, so this statement is also False. Lastly, the claim that 'the fittest are the strongest, largest, fastest' is an oversimplification. While strength and speed are advantages, evolutionary fitness also includes other factors such as the ability to adapt to the environment, reproductive success, and sometimes even smaller or average-sized organisms thrive better than larger ones.
Genetic differences do cause variations in the results people obtain from physical exercise. Those with more slow-twitch fibers might develop greater endurance as they have more capillaries, mitochondria, and myoglobin, enabling them to sustain aerobic activity longer than those with a higher proportion of fast-twitch fibers.