The 75 Hard Challenge can help improve flexibility and mobility by encouraging participants to incorporate stretching and mobility exercises into their daily routine. The program's structure requires two daily workouts, which can include flexibility and mobility work to enhance overall physical function and reduce the risk of injury. By focusing on these aspects of fitness, participants can improve their range of motion, reduce muscle stiffness, and enhance athletic performance. The challenge's emphasis on discipline and consistency helps individuals make stretching and mobility exercises a regular part of their routine, leading to long-term benefits for their physical health.