1) Here is a normal run for me, proceeded by a good 5-10 minute jogging warmup. Then I stop, reset my Garmin HRmonitor, and start my actual run. The actual run is then done at totally constant pace start-to-finish:
2) Here is a run where I decided to try a 6:1 Run:Walk set of cycles. Foolishly I only did a walking warmup, then started my normal run. You can see exactly the difference, the first cycle is not good and it takes until the second cycle to settle down, Third and other cycles are then fine. Good warmups and not over-doing the start of your run (start slow to finish strong) are really important.
I am not a really experienced nor long-distance runner, but I know about the importance of a good warmup and the recorded charts above capture and show it amazingly clearly
PS: Some coaches are strong believers in Run:Walk intervals (during training and races) to actually increase your overall speed and endurance while reducing the stress and strain on your body:
- Joe Henderson (10:1): http://www.running-world.net/walk_and_run_better_1.php
- Jeff Galloway (3:1 or 2:1 or 1:1): http://jeffgalloway.typepad.com/jeff_galloways_blog/2010/03/index.html