What is MVPA?
The term "MVPA" refers to "Moderate to Vigorous Physical Activity." This term is often used when referring to the amount of time a subject/patient spends above a "Moderate" cut point level, thus indicating "significant' activity. The popularity of MVPA has likely come from the U.S. Government's Center for Disease Control paper on entitled 2008 Physical Activity Guidelines for Americans (discussed here on the CDC website) in which the authors call for adults to perform at least 150 minutes of moderate aerobic activity each week in order to receive significant health benefits.
How is MVPA calculated in ActiLife?
MVPA is calculated along with Cut Points in ActiLife (see "How are cut points calculated?"). MVPA counts are actually an additional cut point with a lower-limit threshold equal to the Moderate level of a given Cut Point set. An example of the MVPA level for Freedson Adult 1998 Cut Points is shown below.
By default, the minimum Counts per Minute (CPM) for all Cut Point levels labeled "Moderate" are used as the minimum CPM level for the MVPA.
ActiLife calculates MVPA and other Cut Points similarly. The following values are calculated in the Scoring tab:
Summary level output
At the summary level (in the summary screen), ActiLife will display Time in MVPA, % in MVPA and Average MVPA per Day. An example screenshot of the summary data is shown below. Important: Each of these values will exclude non-wear times if the "Exclude non-wear times from analysis" box is checked.
- Time in MVPA - The total amount of time with activity with corresponding count levels equivalent to the MVPA cut point level or higher. (See "How are cut points calculated?" for details about handling of 60-sec and sub-60-sec epoch files)
- % in MVPA - The percentage of total time (wear-time only if "exclude non-wear.." is checked) spent at or above the MVPA cut point level
- Average MVPA per Day - The Time in MVPA divided by Calendar Days of valid days (show the "Calendar Days" column to see that number).
Day and Hour MVPA Breakdown
Clicking the "Details" button after calculating data in the Data Scoring tab will reveal the Days, Hour and Epoch-level MVPA results. An example screenshot is shown below.
Daily MVPA output
- Total MVPA - Total time spent at or above the MVPA cut point level for the given day
- % in MVPA - The percentage of wear time spent at or above the cut point level for the given day
- Average MVPA per Hour - The total MVPA divided by the number of hours with at least one valid (wear time) epoch. Hours with 0 wear epochs are ignored
Hourly MVPA output
- Total MVPA - The total time spent at or above the MVPA level for the given hour
- % in MVPA - The Total MVPA (per hour) divided by the total number of wear minutes for that hour.
What is the MVPA cut point level?
The MVPA cut point level is fixed for the built-in cut point sets. To see that level, click on the "edit" option to the right of "Cut Points and MVPA" in the Scoring tab and select the cut point set of interest. The MVPA Minimum at the bottom right-hand side of the screen reveals the MVPA level. An example is shown below.
Custom MVPA Settings
To set an MVPA level in a custom cut point, simply create a custom cut point set (as shown in "How are Cut Points Calculated?") and select the desired MVPA level. By default, any level with the word "Moderate" will be selected as the MVPA level.