This study examined the effect of negative and positive stereotypes on the strength produced by older adults at different perceived effort intensities, reflecting different levels of task difficulty. Fifty older women were randomly assigned to a positive stereotype, a negative stereotype, or a control condition. Before (T1) and after (T2) the stereotype manipulation, they were asked to perform a voluntary isometric contraction at a level of muscular effort that corresponded to four perceived effort intensities (“easy,” “moderate,” hard” and “very hard”). Results showed that participants attained greater strength during the easy and hard tasks after exposure to both positive and negative stereotypes. At the moderate and very hard intensities, stereotype induction did not significantly change the strength from the baseline performance. While these results are not fully in line with the stereotype threat theory, they provide evidence that task difficulty could modulate the effect of aging stereotypes during physical tasks.