Can you tell me if the Rockport 1 mile walking test can be performed on a treadmill?
In a nutshell, yes, and it has been used in several scientific studies to increase reliability between assessments. There are some points to note, however. First, while exercise on a treadmill has been found to have a similar metabolic demand to that of hard surface exercise, there is less need to maintain a pace. And for those with a poor pacing ability, the treadmill (by providing an established pace) may provide a false reading. It does have the advantage of being able to be self tested regardless of outside weather and terrain (thus providing a more reliable measure for continuing assessments by limiting some diurnal variations). One key difference that must be catered for, however, is the establishment of an optimal pace setting. Unlike a hard surface test where the participant can go for a general walk as a warm up and then stop and commence the test, on the treadmill the warm up should be used to establish the pace and then the test should commence once the desired paced is obtained. If the participant needs to rest or remove clothing between the warm up and the test and the treadmill is stopped, the examiner should allow time for the treadmill to re-establish the pace to alleviate the lag created by the time taken for the treadmill belt speed to meet the target pace.
A final note is that some of my colleagues recommended the use of a one degree incline in the treadmill to simulate air resistance; however, I believe this is unnecessary as the true nature of outdoor diurnal variations could provide a variety of wind speeds from different directions, and these are not factored into the VO2 equations associated with the test.
The key is to take accurate detailed notes including: make and model of treadmill, belt speed, time of day, warm up and speed determination protocols, etc.