Scientists have a pretty clear picture of what happens when summer sunlight, high air temperatures and/or humidity increase both skin and core temperatures in runners who increase their mileage training for a fall marathon or cyclists and triathletes preparing for autumn events. They bake. Muscles in motion generate enormous amounts of energy, only about 25 percent of which is used in contractions. The other 75 percent or so becomes body heat. Yet why someone has more difficulty dissipating body heat on one hot afternoon’s run than on another is still mysterious.
Who doesn’t want a healthy flow of energy coursing through their pelvis, stomach and spine? Who doesn’t want a strong, resilient backbone, ready and able to engage life fully? The term “trunk” might seem outdated, but it holds the key to developing natural, resilient running — and to cultivating our innermost powers of coping with healthful, stimulating kinds of stress.
Your trunk is actually a vital part of your “spring system”: its massive muscle groups and powerful ligaments contain a surprising number of elastic fibers which, along with the arches of your feet and the flexing of your knees, absorb the impact of your feet hitting the ground and then spring it back to propel you forward. Using the trunk muscles in the torso to gently tip the pelvis from side to side like a seesaw returns elastic energy to the arch and spring ligaments in the feet; this allows everything to rebound reflexively, pushing you off the ground towards floating, flying and weightlessness. (1)
Sound idealistic? Remember that your mental images, ideas, and beliefs about your body can affect performance, sometimes just as powerfully as your physical fitness.
Trunk Training gives you an experiential sense, of how to harness your spring system to increase your stride length — without over-striding — by making it much easier to swing your legs upward and forward in a series of reciprocal, circular movements. The brilliant Feldenkrais disciple, Jae Gruenke, founder of The Balanced Runner in Edinburgh, Scotland, uses the words “core action” to describe this. Joe Pilates might have called it, “running from the powerhouse.” But let’s not quibble over semantics. Any way you slice it, a well-trained trunk has a soothing effect on your legs, it helps to adjust your foot-strike naturally and eliminates the continuous pounding on your knees from over-striding/heel-striking and iliotibial band syndrome. (2) Once you feel the power of a harmonized spring system, you’ll see why training regimens that “blast your core” without incorporating the legs and feet are missing the mark.
It’s widely speculated that the trunk should remain constantly still, in a permanent state of contraction throughout the running cycle. At first glance, it might appear this way when the bare torso of an international athlete is on display. It certainly looks as if their trunk barely moves. But if you look deeper you can observe the fact that their years of practice and focusing on technique have made them adept at coordinating the muscles around their trunk and pelvis, so they contract and relax in perfect rhythm with the muscles producing force in their legs.
Before the London Marathon in April, Eliud Kipchoge promised a “beautiful race.” He delivered, as he always does. What I love about Eliud (besides his magnanimous smile) is that he clearly understands the importance of trunk training: he uses almost all pelvic rhythm to quicken his leg rate, like revolutions per minute. He runs from the belly, which tapers the muscular effort in his legs and feet. It’s something to see.
Of course, it’s a rarity to find an ordinary runner with a specialized, functional physique resembling a world class runner, but people with normal, everyday bodies can still benefit from their genius.