With the growing popularity of large-screen smartphones, the time older adults spend using these devices continues to increase. However, age-related declines in hand muscle function make older adults more susceptible to significant fatigue during touchscreen operations. Therefore, understanding how to measure and mitigate this touch fatigue is essential for developing age-appropriate smartphone interaction designs. This study investigated the measurement of touch fatigue in older adults during smartphone interactions through a literature review, focusing on muscle fatigue and related theories. A database search yielded 25 relevant papers that examined hand fatigue during touch interactions and explored potential mechanisms of fatigue development. Based on this literature, the study identified two approaches to measuring hand muscle fatigue: subjective and objective. Using these measures, it was determined that factors such as screen size, thumb orientation, and the size and location of touch targets influence fatigue development. Based on these findings, this study offers design recommendations to reduce touch interaction fatigue in older adults: i) Touch interactions that require extensive thumb flexion and extension should be minimized. ii) Touch targets should be enlarged. Iii) Smartphone aspect ratios should be reduced. iv) Commonly used touch controls should be placed outside the lower-right and upper-left corners of the screen. This study summarizes the methods and metrics for measuring hand fatigue, providing a foundation for future academic research. Moreover, practitioners can apply these design recommendations to better accommodate the needs of older users.