SenseWear these are
estimated MET values.</td>
</tr>
<tr class="even">
<td>ExtSleep</td>
<td>Externally derived classification of sleep, used as if it was
derived from an external function for sleep detection.</td>
</tr>
<tr class="odd">
<td>ExtStep</td>
<td>Externally derived step count, used as if it was derived from an
external function for event detection.</td>
</tr>
<tr class="even">
<td>ExtHeartRate</td>
<td>Externally derived measure of hear rate in beats per minute.
Currently used as indicator of ac