Among the most common energy-wasting stride errors is failure to properly activate the deep abdominal muscles that are responsible for maintaining pelvic stability during running. According to Michael Fredericson, Ph.D., a running biomechanics expert at Stanford University, 90 percent of runners exhibit this flaw.
The deep abdominal muscles -- the transverse abdominis and the internal obliques, to be specific -- wrap around the abdominal area like a corset. When these muscles contract, your navel moves toward your spine and your pelvis rotates backward. The deep abs have an important role to play during the thrust phase of the running stride -- when your foot is planted on the ground and your buttock muscles and hamstrings are contracting forcefully to pull your body forward in relation to your foot.
Because these thrusting muscles attach to the back and bottom of the pelvis, their forceful contraction tends to tilt the pelvis forward. If the pelvis is actually allowed to tilt forward, some of the energy that your thrusting muscles are trying to transfer to the ground for forward movement winds up wasted in stretching your deep abs.
However, if you activate your deep abs to hold the pelvis neutral, more of the force generated by the thrusting muscles is indeed transferred to the ground. The end result is that you cover more ground with each stride.
If you're having trouble picturing these actions, consider the following analogy. Imagine you're trying to push a heavy trunk forward on a tile floor. The trouble is that you're standing on a small rug that starts to slide backward every time you try to push the trunk forward. Removing the rug allows your feet to get a more stable grip on the floor, so that more of your muscle energy is transferred to the trunk.
In this analogy, the slipping rug is like deep abs that are not properly activated. Removing the rug is like tightening your deep abs so that your pelvis is stable, allowing more of your muscle work to translate into forward movement.
The good news is that this common stride flaw is correctible, and correcting it will boost the efficiency of your running stride significantly. Learning to properly activate your deep abs consistently throughout every run takes time and effort. These muscles are so seldom used by most of us that the brain's motor centers literally have trouble finding them. Getting the job done requires a three-step process.
Step one: Sit up straight
One of the major reasons the brain and the deep abs are not on speaking terms in most of us is that we spend so much time sitting, and sitting is a position in which the deep abs are typically inactive. But they don't have to be.
As you're sitting, think about drawing your bellybutton toward your spine. Make sure you continue breathing normally. You'll feel more stable in your sitting and you'll sit taller. When you stand up, do the same thing. When you're waiting in line at the grocery store or the bank, pull your bellybutton toward your spine and pull your pelvis upward. If you conscientiously counteract your automatic postural tendencies in this way whenever you think of it, properly engaging your deep abs will eventually become natural.
Step two: Condition your deep abs
There are various exercises you can do to learn how to engage your deep abs and to condition these muscles so they are able to remain active throughout a run. Here are two such exercises:
Cook Hip Lift
Lie face up with your legs sharply bent. Place your left foot flat on the floor and draw the right leg up against your torso, holding it in place with pressure from your hands. Now contract the hamstrings and glutes of the left leg to lift your butt off the floor two or three inches. Concentrate hard on keeping your deep abs contracted and your pelvis neutral. Hold this position for five seconds and relax. Repeat 5 times and then switch legs.
Lying Draw-In with Hip Flexion
Lie face up with your head supported by a large pillow or foam roller. Begin with your legs bent 90 degrees and your thighs perpendicular to the floor, feet together. Engage your deep abs by drawing your navel toward your spine. While holding this contraction, slowly lower your right foot to the floor, return immediately to the start position, and then lower the left foot. If you find this easy, you are failing to hold the contraction of your deep abs. Lower each foot to the floor eight to 10 times.
Step three: Run mindfully
A moment before you start your next run, pull your navel gently towards your spine and roll your pelvis slightly backward. As you start running, concentrate hard on maintaining this posture. During the thrust phase of each stride, you will feel a tug on the bottom of your pelvis and a strain on your deep abs. Sometimes you may even lose the battle and feel your pelvis rotate forward despite your efforts to prevent it. This is OK, because it only enhances your feel for the difference between running with and without pelvic stability. Just try to win the next battle.
You can further improve your feel for running with pelvic stability by running 12 to 24 hours after doing the core exercises described above. Your deep abs will be a little sore, and you will be especially aware of this soreness when you engage your deep abs to resist forward tilting of the pelvis while running, which will help you distinguish when you are and are not using them.
Most of us are accustomed to letting our thoughts wander aimlessly while we run. While learning to activate your deep abs, it's important that you fight this habit and keep your attention squarely focused on your deep abs and pelvis. As soon as you let your thoughts wander off, you will revert to old patterns. A few weeks of focused attention should suffice to ingrain the new pattern to the point where it's completely natural.
Matt Fitzgerald is the author of several books on triathlon and running, including Runner's World Performance Nutrition for Runners (Rodale, 2005).