Different types of strength training affect muscle fibers by targeting various muscle groups and eliciting specific adaptations. For instance, high-repetition training typically focuses on endurance and can lead to an increase in the number of capillaries and mitochondria within muscle fibers. Conversely, low-repetition training with heavier weights emphasizes strength and size, promoting hypertrophy in fast-twitch muscle fibers. Combining both types effectively enhances overall performance and ensures well-rounded muscle development, addressing both endurance and strength capabilities in the muscles.