From the study[0][1-pdf], the exercise routine was walking on a treadmill with adjustable gradient. The objective was to keep participants in the 50-60% heart rate range for 30 minutes, which was done by altering the gradient and speed. Including the 10 minutes warm-up and 10 minutes cool-down, this gave 4x weekly workouts of 50 minutes to the mostly 75+ year old patients.

Given that the participants were screened to be low-exercise individuals beforehand, this gives some evidence that "exercise more" is a reasonable treatment for low-activity seniors experiencing cognitive decline.

Because it stood out as weird to me, I want to remark that the study's participation requirements explicitly filtered out depressed patients, day-to-day impaired patients, and anyone left-handed (???).

[0] https://content.iospress.com/articles/journal-of-alzheimers-... [1-pdf] https://content.iospress.com/download/journal-of-alzheimers-...