For 1997 forward, interviewers began the inquiry into adult leisure-time physical activity by stating, "The next questions are about physical activities (exercise, sports, physically active hobbies ...) that you may do in your leisure time." "Exercise, sports, [and] physically active hobbies" were to be respondent defined.

For each year, beginning in 1997, the survey collected information about sample adults' leisure time spent in "vigorous," "light or moderate," and "strengthening" physical activities. (See MOD10FNO and STRONGFNO for definitions of "light or moderate activity" and "strengthening activity".) In 2001, information was also collected on leisure time spent by sample adults in "stretching" activities. (See STRETCHFNO.) Strengthening and stretching exercises can be done at a pace that is either "vigorous" or "moderate," so exercise sessions involving strengthening and stretching overlap with vigorous and moderate exercise sessions.

For VIG10FNO, beginning in quarter 3 of 1997, sample adults were asked, "How often do you do vigorous leisure-time physical activities for at least 10 minutes that cause heavy sweating or large increases in breathing or heart rate?" The Field Representative's Manual provided examples of vigorous activities, although these examples were not routinely shared with respondents. These examples include fast walking, fast bicycling, jogging, strenuous swimming or sports play, vigorous aerobic dance, and strenuous gardening.

The Field Representative's Manuals for 2001 forward noted that information about general health behaviors, including physical activity, "helps researchers measure how a person's daily habits affect his/her overall health." More specifically, according to the Manuals for 2002 forward, responses to the questions about leisure-time physical activity were used "for tracking Healthy People Objectives (22.1-22.4)."

For example, one such objective framed in terms of vigorous activity is increasing the proportion of adults who "engage in vigorous physical activity that promotes the development and maintenance of cardio respiratory fitness 3 or more days per week for 20 or more minutes per occasion."

Beginning in 2005, NHIS data on physical activity were also used in Health, United States to classify adults as "inactive," "with some leisure time activity," or "with regular leisure-time activity." This classification system is described in the Appendix of Health, United States for 2005 as follows:

The National Health Interview Series first collected information on physical activity beginning in 1975. Prior to 1997, these inquiries generally focused on specific activities, such walking or playing baseball. (See the National Health Interview Survey's summary website on Adult Physical Activity Information in the NHIS for full details.)

The Survey Descriptions for 1997-2000 note that the physical activity questions included in the sample adult (core) module were "substantially different from those included in pre-1997 NHIS questionnaires."

The aforementioned website on "Adult Physical Activity Information in the NHIS" supplies the following background information on the development of these questions:

For all years from 1997 forward, the survey section on physical activity began with the statement, "The next questions are about physical activities (exercise, sports, physically active hobbies ...) that you may do in your leisure time." Beginning in 2004, the question about the frequency of vigorous activities reiterated the point that respondents were only to report leisure-time activities. From 1997 through 2003, interviewers asked, "How often do you do vigorous activities ..."; for 2004 forward, they asked, "How often do you do vigorous leisure-time physical activities ..." Thus, beginning in 2004, the question wording made explicit what had previously been implicit and had been specified in the introductory statement only.

However, while these directions were missing from the survey questionnaire before 1999, they were included in the Field Representative's Manuals for 1997-2000, which directed, "Prompt with 'How many times per day, per week, per month, or per year do you do these activities?'" Furthermore, the 1997-2000 Manuals stated, "Always probe for an exact number. If the Sample Adult reports a range or interval, assist the Sample Adult in making an estimate by probing. For example, you might ask 'Could you give me a more exact number?'"

Prior to 2020, the question stated, "How often do you do vigorous leisure-time physical activities for at least 10 minutes that cause heavy sweating or large increases in breathing or heart rate?" Beginning in 2020, the question simply asks, "How often do you do vigorous-intensity leisure-time physical activities?" The question is preceded by a definition of vigorous intensity activities as those that "cause large increases in breathing or heart rate."