Reply To: Front crawl kick is non-propulsive
You’re probably right. I doubt anyone will research “bad” kicking at this point in time. It’s also possible, for backward kickers, that the knee is leading the kick and the thigh is pushing water forward with very little backward propulsion from the lower leg. In this case, the lower leg is just following the knee rather than performing its own powerful movement. This would be hip flexion without any effort towards leg extension.
As for propulsive kicking, one debate point I’ve used is that when a coach requires a swimmer to get to the other side of the pool by only kicking then the swimmer must figure out a way to get there (or face the wrath of the coach). This in no way indicates that flutter kicking is propulsive in full freestyle. It is easy to see how much velocity is generated by kicking alone: have a swimmer start off the wall and begin kicking. Acceleration is minimal and they will probably purposely kick down and back harder to get their body moving. This is very much different than pushing off the wall and using the kick to maintain a velocity to the other side. And very much different than balancing pitch and roll of the body during arm swimming.
In terms of power and drag, the thigh may create drag but if the thigh moves into the drag position relatively slowly the energy loss will be minimal. If the lower leg and ankle/foot generate a powerful downbeat kick then forward propulsion will occur. This would be hip flexion coordinated with powerful leg extension and ankle dorsiflexion. I’m not sure how much the bottom of the foot will contribute to this on the upbeat during hip extension and ankle plantarflexion. The anatomical angles don’t seem right.