Watch this video, you have likely seen it already but did you notice it ? You will have to fast forward to 1:40 to see the video that applies to this screenshot here today.
How much knee flexion should occur during the initial loading response ? In this walking gait video, if you look closely enough, her high heeled shoes are forcing her to load in a what is technically a midfoot stride (because of the high heel) when in fact she is truly loading initially in a forefoot load, ie. plantarflexion. This abrupt load is forcing her to dampen the load with a quadriceps eccentric (if you watch closely enough, the knee flexes every time during loading, more than it should). Normally, in flat-er shoes, this knee eccentric is basically hidden (it is almost an isometric), it should never be this obvious unless one's quads are truly too weak. To be fair, the shoes are propping her into anterior pelvis tilt, as these high heeled shoes always do, which promotes lower abdominal challenges and premature quad loading, and delayed glute loading (don't believe us? stand up, dump into an anterior pelvic tilt and increased lordosis and try to engage your glutes. Nadda ! So the loading shifts into the quads).
Welcome to another ramification of high heeled shoes, again.
Admittedly, this lady does a great job. Her belt line stays pretty neutral and doesn't dip on each loading response and she is in good control. Ivo and Shawn on the other hand are terrible in their pumps :)
Sprinters, and those who forefoot load during running, are you surprised with anterior knee pain when it comes on, or achilles pain or calf tightness when the calf fatigues and can no longer hold you in adequate plantarflexion ? How about low back pain or tightness after runs ? No, you should not be surprised is the correct answer (unless you have enough durability in the quad and calf, and lower abdominals to sustain the length of your workouts, over and over and over.