# Changes

## Relative Running Economy

, 20:50, 26 December 2010
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</code>
</blockquote>

==What do the efficiency numbers mean?==
The number reflects how many times your heart beats when you run a mile. The higher the number, the more efficient you are running and the less often your heart is beating over the distance. Because the numbers are based around your heart beat, they are mostly useful for comparing your runs or comparing parts of the same run, rather than for comparing different runners' performance.
===Changes in efficiency ===
There are a number of reasons why your efficiency can change.
* Obviously changes in your running economy will change the efficiency numbers. For instance, a higher [Cadence] should improve your economy and increase your efficiency numbers.
* Running up hill or downhill will dramatically change the energy cost of running, so your efficiency numbers will change. If you want to compare you efficiency running uphill or downhill, it's best to compare numbers from the same slope.
* Dehydration will cause your heart rate to rise for the same work effort. Looking at changes in efficiency can be used to detect dehydration.
* If you look at your efficiency numbers for speed work, your heart rate will tend to lag behind your work effort. If you change from running at a 9 min/mile pace to a 6 min/mile pace, it will take time for your heart rate to rise up in respond to the extra demands. Likewise, dropping your pace will have a similar lag before your heart rate drops.
==A more impressive alternative==
The calculator below uses age, gender, and weight to calculate Calories consumed, and therefore the absolute efficiency. While this is more impressive and allows for comparison between runners, it makes quite a few assumptions in the calculations. If you know your VO<sub>2</sub>max, this calculation becomes somewhat more accurate, but should still be considered only a rough approximation.
<html>
<style type="text/css">
table.sample {
border-width: 1px;
border-spacing: 2px;
border-style: outset;
border-color: gray;
border-collapse: collapse;
background-color: rgb(255, 255, 240);
}
table.sample th {
border-width: 1px;
border-style: inset;
border-color: gray;
background-color: rgb(250, 240, 230);
-moz-border-radius: 0px 0px 0px 0px;
}
table.sample td {
border-width: 1px;
border-style: inset;
border-color: gray;
background-color: rgb(250, 240, 230);
-moz-border-radius: 0px 0px 0px 0px;
}
</style>
<form method="get" action="/fellrnr/efficiency_wrapper2.php" name="VDOT">
<table class="sample2" >
<tr>
<td>Time</td>
<td>
<table class="sample">
<tr>
<td><input maxlength="3" size="3" name="Hours" value="0"><br>
</td>
<td>Hours&nbsp;&nbsp;&nbsp;</td>
<td><input maxlength="3" size="3" name="Minutes" value="0"></td>
<td>Minutes&nbsp;&nbsp;&nbsp;</td>
<td><input maxlength="3" size="3" name="Seconds" value="0"></td>
<td>Seconds</td>
</tr>
</table>
</td>
</tr>
<tr> <td>VO2max (if known)</td> <td><input maxlength="3" size="3" name="VO2max"></td> </tr>
<tr> <td>Age</td> <td><input maxlength="3" size="3" name="Age"></td> </tr>
<tr>
<td>Body Weight</td>
<td>
<table style="text-align: left;" border="0" cellpadding="0" cellspacing="0">
<tr>
<td><input maxlength="3" size="3" name="Weight" value=""></td>
<td>
<select name="WeightUnits">
<option>Kg</option>
<option selected="selected">Pounds</option>
</select>
</td>
</tr>
</table>
</td>
</tr>
<tr>
<td>Gender</td>
<td>
<select name="Gender">
<option>Female</option>
<option selected="selected">Male</option>
</select>
</td>
</tr>
<tr><td>Average Heart Rate</td><td><input maxlength="3" size="3" name="AverageHeartRate" value="150"></td></tr>
<tr><td>Distance (miles)</td><td><input maxlength="3" size="3" name="Distance" value="1"></td></tr>
</table>
<button name="Calculate">Calculate</button><br>
</html>
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