Dale's Cruise Intervals & "What's a LOADING RATE?"

I had been discussing some threshold paced workouts with Dale via his blog since Surf City. My thought was that he could use more threshold pace runs. He contacted me to meet on Tuesday morning, and he let me choose the workout! Bad idea Dale! I decided we would do a total volume of 4 miles at his T-pace which is 6:40 pace (based on his 68:14 10m PR). I let him choose between 4x1600m or 8x800m. The key to the workout is the short recovery 90 sec between 1600m or 45 sec between 800m. He chose the 1600s and we took off. The difficulty in this workout doesn't come until the last few sets, unless you run the first few too fast. We finished the first one in 6:50, jogged for 200m and then hit the next 2 in 6:38. You have just barely enough time to catch your breath and feel slightly ready before it is time to hit another one. The last set was getting tough so we split it into two 800s, but also cut the rest in half so we only took 45 seconds or 100m between and ran them each in 3:20. Dale nailed the workout! I would challenge Dale to progress these workouts by adding volume first (5x1600m or 10x800m and so on), then extending the length to 3x2mile with 3 min recovery jog. Once those workouts are completed then go back and try the workouts again at the same speeds but even less rest (30sec/800m and 60sec/1600m). Eventually running a 4-5 mile threshold run at 6:40 pace.

Afterward, Dale and I discussed running form a little bit as I have been jazzed about this recent blog post by Jay Dicharry, P.T. from the University of Virginia's SPEED Performance Clinic on optimal form to minimize loading rates. I got to meet Mr. Dicharry at the UVA running clinic I attended last April. He discussed some of this topic then and really summed it up well in his last two blog posts. They are both worth a read and reread.
Here is Part 1 and Part 2.

There is so much talk about heel striking vs midfoot striking vs forefoot striking when it comes to form. The conclusion most people make is that heel striking is BAD! They blame the running shoes for causing all the form changes and allowing a more comfortable heel strike and give runners something else to blame their injuries on. They may be partially correct, but what Mr. Dicharry has found in his lab is that foot contact style is not as important as contact position relative to center of mass when minimizing loading rates. This means that heel striking can be ok as long as the ground contact position is almost directly under the runner's center of mass (or almost directly under the hip). Loading rates are how quickly the body (bone, tendon, muscle) has to absorb the ground reaction forces with each step. The higher the loading rate the more force the body has to absorb in a short amount of time, thus increasing the likelihood of injury. The problem many runners have is over striding not heel striking (although many heel strikers are also over striders).

Mr. Dicharry used some great pictures on his post from subjects in his lab, but he also used a picture of Scott Jurek that I have seen and contemplated before. Here it is.

Look at the difference in foot position on the forward leg of Scott Jurek and the Tarahumaran runner. They are completely opposite. Scott has his toes pointed up (ready to heel strike) and the other has his toes pointed down (ready to forefoot strike). Both of these runners are very efficient but have completely different forms. The thing they both have in common is that when their lead leg hits the ground it will be almost right under the hip (under their center of mass) thus minimizing loading rates. Interestingly, Scott (a heel striker) is wearing running shoes and the Tarahumaran runner is wearing sandals...hmmmmm.

Optimal stride frequency has been found to be between 180 and 190 strides per minute. If you count your steps for 10 seconds and multiply by 6 you will have your stride frequency. If it is under 170 you may be over striding. This RunnersWorld.com article summed it up well.

There are some easy form drills and cues to help you increase your stride frequency and shorten stride length. Actual research has been done that shows decreased loading rates after runners modified their stride based on the cue, "run soft." That's it just "run soft." He also discusses the importance of lumbar posture when running and how an anterior tilt, or too much curve in the low back, can shift your center of mass back, thus causing a relative overstride. This is a sign of a weak core and can be remedied with core training and again form drills.

Take home points:
1. Increase your stride frequency to at least 180 strides/min without increasing your speed. Try it on an easy run day and play with it a little.
2. Barefoot running drills are a good way to work on form since it discourages over striding. I suggest 50-100m strides on grass to start.
3. "Run soft," I don't want to hear you coming up behind me on the roads, ok!
4. Just like the word "pronation," "heel striking" is not necessarily a BAD WORD.