A growing number of studies have begun to employ neuroimaging methods to better understand the impact of exercise on the brain both longitudinally and acutely. For example, Smith and colleagues [37] conducted fMRI scans pre and post an exercise training program in older adults with mild cognitive impairment and found that exercise improved neural efficiency during cognitive tasks post-intervention. Structural MRI has also been used to show the neuroprotective effects of regular exercise in older adults with respect to preservation of brain volume[38]. In contrast to using neuroimaging to track changes in the brain over time, neuroimaging during and immediately following exercise presents some unique challenges due to artifacts associated with movement and the physiological underpinnings of many neuroimaging methods (e.g. BOLD response). EEG has been used most extensively to explore the effects of exercise on cortical activity [39]. PET and fMRI have also been used, though to a much lesser extent. For example, Boecker and colleagues used PET to demonstrate the effects of a long-distance run on opioid release in the brain and Janse Van Rensberg and colleagues used fMRI to examine brain responses to nicotine craving following 10 minutes of moderate intensity cycling. Our study adds to this important body of literature by using fMRI to show that an acute bout of moderate intensity exercise improved brain mechanisms underlying pain modulation in patients with chronic pain and further highlights the potential benefits of utilizing neuroimaging technology to better understand the more immediate effects of exercise on the human brain.
We have addressed each concern below and made changes in the manuscript accordingly.