Swing Blocking is much like the long hair look on guys; it comes and it goes in popularity and when it is done right it looks good, but all too often looks bad.
The basic explanation for Swing Blocking is an attempt to gain more vertical on the block, to elevate the height of block by using an approach sequence. Remember that hitters take an aggressive approach and generally jump higher on their attack than the block. Just look at stats players give - Approach jump 9'10", block jump 9'6". A swing block incorporates an approach sequence into the blocking skill. The middle blockers have always used a certain footwork pattern when moving to outside to close the block, but this movement was just to close, not to jump.
As the swing blockers concentrate on using footwork to gain higher elevation, they also include an arm swing movement (much like an attack approach). The combination of a footwork sequence (also by the end blockers who start more toward the middle of the net to allow for space to engage in a footwork sequence) and the arm drive, does result in a higher jump on the block. In my observations, a swing block can lead to many more touches by the block - But, not all touches are good.
I don't believe in the swing block technique for blocking and let me tell you why:
1. The blockers are moving at the time of attack by the hitter. Even though proponents of swing blocking say the blockers should be stationary (not drifting laterally), that is not the live competition case. If a block is drifting (because the blockers did not plant their outside foot to such a degree to stop the momentum of their movement while jumping), then the hitter has the advantage because body of the blocker can easily move or direct the ball out of bounds with their lateral drift.
2. If the block is drifting, it makes the read/react by the defense very tough. Back row defense is based on filling avenues or zones which the block is not covering - I call it being in the light or being in the shadow of the block. If the hitter were to have a giant spot light attached to their head and the blockers created shadows by their arms on their own side of the court, the defenders want to stay in the light, not in the shadows. When the block drifts, the shadows are always changing, which means the defense must always change. I have found that the more movement by a defense, the less successful it is. This is why offensive systems do more that just set high balls to the antennas; they run combination plays, move the attack points around, have different tempos on each attack; all to make the defense move as much as possible.
3. The arms of the blocker, while they may reach higher, are in the blocking zone for a smaller amount of time. This is why the swing block looks so great when it actually blocks a ball, because the blocker is higher and for that split second of time, the arms were in a prime position and blocked the ball. But, because of the movement of the body and shoulders, the blocker's arms rotate through the block zone, instead of holding in the block zone. Remember that the swing blocker's shoulders are perpendicular to the net when starting the jump, then the blocker rotates their shoulders parallel to the net to block; but, the rotation movement will naturally continue and the shoulders will rotate off the net. This rotation movement creates less time in block zone, as opposed to a stationary blocker penetrating the net, holding the block form and then landing in the same spot.
4. The outside hitters can easily defeat a swing block by hitting down the line. Once again, because of the body drift and shoulder rotation of the blocker, when the attacker hits line, they are attacking the weakest point of the block scheme. Many times the block does not fully close off the line because they are moving out towards the antennae and making a quick guess about ball position at point of contact, along with the actual inward swing of the blocker's arm allows for an easy tool or using of the outside block arm/hand by the hitter.
5. A fast offensive system creates havoc for a swing block. The end swing blocker needs time to move outward and gain elevation, but a fast set to the antennae does not allow for this needed time. Also, combination plays work well because they do not allow for the block to load and swing their arms because the offense has compressed the net space (please, please, please remember that you should set the first option in a combination play a few times before setting the second option/combination attacker).
The above reasons are mine for not using a swing block technique with my defensive strategy. I would rather have a stationary, static block that concentrates on proper body position and maximizing hands in the blocking zone (which means penetrating the net), so they either block the ball onto the other court or direct it into my defenders and we transition.
Swing Blocking, like the jump serve and the back row attack, came to us via the Men's game, but I think these other two imports will stay with us, while the Swing Block will fade away, only to return with 80's music.