 During each intervention session, the researchers will measure performance on one or more of the following tasks: a five trials of generative naming given a unique category and one-minute response period per trial, b distance traveled using an exercise machine for five minutes, c generative naming given unique categories and one-minute response periods and distance traveled using an exercise machine when performing both tasks simultaneously for five minutes, d number of words generated in five minutes in response to conversational topic prompts, e distance traveled when walking for five minutes, and f number of words generated in response to conversational topic prompts and distance traveled when walking when performing both tasks simultaneously for five minutes. The first three measures comprise intervention tasks, and the remaining three are generalization measures. 