On a single knee bend pull, the knees of the lifter do NOT re bend a second time. However, many lifters hold a bent knee position until their last split second before extending on a second pull, and it is that holding of that bent knee position that has confused many lifters into thinking such a style is a double knee bend pull.
On a double knee bend pull, the knees of the lifter must "re bend" slightly more from the original slightly bent leg or straight leg position, when the bar reaches the top of the thighs. This can NOT happen unless a shrug with traps is initiated a split second before the rebending of the knees.
Essentially, on a double knee bend, or knee re bending style, the lifter is pulling themself slightly under the bar. Then with those legs in the bent position the weight is shifted from the heels to the toes in a jumping action. The shrug part of the second pull is initiated a split second before the knee re bend and jump.
ALL double knee bend lifters are jumpers. However, NOT ALL single knee bend lifters jump! Some just pull and drop, with the only foot movement being a slight foot slide laterally.
I would recommend, to all athletes serious about Olympic lifting, that you support Denis' publication. For more information, write Denis at: 30 Cambria Rd, West Newton, MA. 02465.
America's Shane Hamman, uses the double knee bend style.
Although these are not the best sequence pictures to show a double knee
bend, still note the middle picture where Shane's knees are quite forward
and under the bar. Also notice that his feet are flat with the weight
on his heels before he initiates a jump extension on his second pull. Although
close, this attempt with 190kg/ 418lbs failed. Finally, note the full shrug
of his traps as he extends. Shane's coach, Steve Miller has taught him
well,
China's Tang Weifang DOES NOT use a double knee bend style!
Instead she holds her knees in a slightly bent position all the way while
the bar brushes up her thighs. Note that in the first and second pictures
that her knee positions are virtually bent the same. This was a successful
world record with 110.5kg/ 243.6lbs
Ansel Ozgur of Turkey shows a sloppy double knee bend. This
failed attempt, with 112.5kg/ 248lbs, was doomed from the start!!! First
note that her shins are slanted forward. Then, because of weak hamstrings,
her butt comes up and her legs straighten... This in turn then forces the
bar to swing out away from her. She then initates a rebending of her legs
under the bar while off balance.
Note: When doing the double knee bend style, it is imperative,
that while re bending your legs, the weight be back on your heels with
your feet flat on the floor. This is important on all jump style lifts!
Simply because a person can not effectively initate a jump if they are
already up on their toes.
Alexei Kurlovich of Russia. IMO, the consummate technician.
Contrary to what many people might think, Kurly did NOT use a double knee
bend style! Like Weifang above, he just kept his knees bent as the bar
brushed up his thighs. He then straightened his legs while simultaneously
shrugging. This was a successful 205kg/ 450lb attempt. Kurlovich's best
snatch was 215kg/ 473lbs done Sept 23, 1989. The second highest official
snatch ever.
Finally, it is not important that a lifter use the double or single knee bend style. What is important is, that on all Olympic style pulls, you get a full extension on your second pull.
All the best with your training. JVA