Come join us for a day of exploring weightlifting through the...
Come join us for a day of exploring weightlifting through the perspective of biomechanics and apply these concepts on top of your own lifting!
Check out: www.FuBarbell.com/Events (link in bio) for a location near you!
Lester Ho (@lesterhokw) and are back with another lesson in biomechanics. Ever wonder why you jump forward or back? Well, wonder no more!
In the photo above, using the lines of the platform as a reference, there is a clear jump-back. Today’s lesson isn’t about whether this is good or bad, but rather to explain why this is happening in the first place.
In the first pull (Frame 1 to frame 2), the centre of mass of both systems are relatively close to the vertical reference line which also represents the horizontal position of the CCOM (combined center of mass). More importantly, the CCOM still falls within the BOS (base of support which is the feet/shoes). As the lifter transitions into the power position, the BOS has slightly shortened from the balls of the feet to the toes and now the vertical reference line of the CCOM falls slightly behind but within the BOS. This means that the balance is starting to get shifted backwards.
As the second pull is executed, the vertical reference line falls just out of the BOS (past the balls of the feet). In real terms, the moment the COM falls out of the BOS, balance is lost and the object falls towards that direction. In this case, it means the entire weightlifter-barbell system is now falling backwards.
Thus, in the turnover phase, the feet come off the ground, meaning that in order to reestablish balance, the feet need to be repositioned to regain balance and have the systems stacked over each other over the BOS. For that to happen, the feet move back as the CCOM is already falling behind.
So basically, when a jump back or forward occurs during a lift, it means that the CCOM has started moving out of the BOS. This is also why it is critical to maintain the feeling of staying over the bar and feeling balanced through the feet in order to maintain the CCOM remaining constantly over the BOS through the lift.
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