<p>The run/walk approach will also likely produce some signficant fitness and fat loss results, too. Here’s a very interesting study:</p>
<p>[Two</a> weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women](<a href=“http://jap.physiology.org/content/102/4/1439.full]Two”>http://jap.physiology.org/content/102/4/1439.full)</p>
<p>They took 8 physically active (3 to 4 days per week) 22 year old women, stresss tested them to determine their V02max, and had them do a base line 60 minute cycling test at 60% of their VO2 max while hooked up to all kinds of monitoring stuff.</p>
<p>Then, they had them do 7 sessions of high intensity interval training, every other day for thirteen days. These sessions were constant RPM at 90% of V02max for 4 minutes (brutal) alternating with 2 minutes of slow speed rest. So, like walk/run training with 4 minutes of hard running and 2 minutes of walking.</p>
<p>At the end of these fourteen days of training, they had them do another 60 minute test at 60% of VO2max on the cycles.</p>
<p>In the second test, after just two weeks of training, their average heart rates in the later stages of the 60 minute test had fallen dramatically – from 160 bpm to 150 bpm:</p>
<p><a href=“http://jap.physiology.org/content/102/4/1439/F4.large.jpg[/url]”>http://jap.physiology.org/content/102/4/1439/F4.large.jpg</a></p>
<p>Their VO2max, after just two weeks of training, had increased an average of 13%.</p>
<p>And, here’s the really interesting part from a fat loss standpoint. In the second 60-minute test, after two weeks of interval training, their metabolism had changed. They were burning signficantly more fat and significantly less carbohydrate than during the first test.</p>
<p><a href=“http://jap.physiology.org/content/102/4/1439/F3.large.jpg[/url]”>http://jap.physiology.org/content/102/4/1439/F3.large.jpg</a></p>
<p>So, the interval training increased their fat burning, even during long, slow cardio sessions (60 minutes on an exercise bike). Combine this with the fact that high intensity intervals cause increases in testosterone and human growth hormone, and it’s pretty clear how this approach can result in actual physioligical changes that help with fat loss. The shifting of fuel from carb burning to fat burning has implications for race day and “bonking”.</p>
<p>All things considered, it looks like there is good reason to do run hard then walk training.</p>