Ze wrote:Your initial assumption that impact forces are inherently bad is wrong to begin with. They're not automatically bad. In fact, for proper bone density, you want some of them. Cyclists sometimes have problems with bone density, but not runners. Special treadmills have been designed for astronauts to force them to get more impact forces than they would without gravity, or else their bones would weaken.
The human body is pretty awesome at adapting, as long as you give it sufficient time to scale and don't go overboard. Body dealing with impact forces is like dealing with altitude - gradually build up and the body will be able to handle high loads - but go straight to 26,000 ft or jump off a building and your body won't ever handle it.
When you run to avoid impact forces / high rate loading, you are going to bend your knees and hips more to compensate and absorb the energy. This can have negative consequences as well. Instead of impact force overloading, you can have more patellafemoral pain (aggravation of cartilage under kneecap) and achilles tendonitis as these areas will get loaded more than more upright loading.
Landing on the balls of your feet is not more efficient. It's less.
In general I would think the "safest" approach for any person is to land midfoot, as it is not at one extreme. More important is to pick a running style that doesn't hurt and combining that with a proper routine that increases mileage gradually, along with many rest days to allow tendons to get back to full strength, and foam rolling / stretching / strengthening.
I do love to run, though right now I've been doing more cycling as my intense endurance, and running 2-3 miles 2 times a week. Had some plantar fascitis / achilles tendonitis issues that had gotten better but then reaggravated playing too much basketball. Has gotten better again so I hope to do a bit more trail running soon.
Thanks for sharing about your current running regimen. I agree that a moderate amount of impact is not only good but is necessary for bone/tendon health. I believe it's exaclty that moderate amount of impact that's allowed me to continue running for so many years without any major, long term injuries. I'm also familiar with the NASA study conclusions regarding bone density loss when bodies are deprived of stimulus provided through normal, regular impact. I know everyone is different and I respect each persons freedom to pursue their own form of exercise, running, etc. However I stand by my assertion that heel-striking is not good and is not a natural form of running. Aside from a very small portion of the population, humans would not run with a stride that included landing on their heels if they had to run barefoot like our ancestors did prior to the invention of evo-foam padded air-cushion running shoes. I challenge anyone who thinks heel-striking is natural to take off their shoes and run on pavment or trail (not grass or carpet) and see if landing on your heels feels right. the bottoms of our feet are highly sensitive and most people will avoid contacting their heels and arches on hard, rough surfaces. I understand the foot-strike topic is hotly debated in the track-n-field, marathon, and triathalon communities. Their are doctors and physical therapists on both sides of the debate. We unfortunately don't know which experts are paid by running shoe companies. Maybe a mid-foot or full-foot strike is a good compromise? What I've offered here is my opinion as an exchange of ideas and information, I'm not a doctor, physical therapist, or expert on anyone's running style except maybe my own.