Biomechanics of the Vertical Jump, Part 2

“The Influence of the Biarticularity of the Gastrocnemius Muscle on Vertical-Jumping Achievement” was a study by Arthur J. Van Soest, Arend L. Schwab, Maarten F. Bobbert and Gerrit Jan Van Ingen Schenau. The researchers that biarticular muscles such as the gastrocnemius were especially suited for powerful movements like jumping hypothesized it. “Because the knee is extending, gastrocnemius length remains close to optimum and its contraction velocity remains relatively low, even when the ankle is extending fast.

As a result, it can generate a large force and a large power output around this joint.” (Van Soest, Schwab, Bobbert, and Van Ingen Schenau) Testing methods included two models, one with monoarticular gastrocnemius and the other with the biarticular gastrocnemius, and six elite male volleyball players. Their results show a 10mm decrease in vertical jump height of the monoarticular model, compared to the biarticular model. This would agree with the hypothesis and support the hypothesis of Bobbert and Van Ingen Schenau in a previous study in 1988. These results do contradict another previous study by Pandy and Zajac (1991). The authors of this study explained this contradiction in results by saying there were slight differences in models used. That fact leads to another result found in the study; “subtle differences in modeling methods can lead to diametrically opposite results when applied to design questions.” (Van Soest, Schwab, Bobbert and Van Ingen Schenau)

Marcus G. Pandy and Felix E. Zajac derived interesting conclusions in their study, “Optimal Muscular Coordination Strategies for Jumping.” Methods for this article were similar to those previously mentioned, five adult males and models performing squat jumps. The most interesting result of this study was their conclusion on the role of uni- and biarticular muscles, which is best described by the authors themselves. “Our results are in opposition to the notion that energy flows distally. For example, we found that energy production by musculotendon actuators is dominated by the uniarticular extensors VAS and GMAX, and that almost all of this energy is used to accelerate the center of mass of the trunk upwards. We have found no evidence to support the contention that power generated by the prime movers (i.e., VAS and GMAX) is transferred distally to the ankle joint.” (Pandy and Zajac) This statement is not consistent with the studies already mentioned. They go on to say: “We are opposed to the notion that jumping performance is increased by the unique biarticular action of GAS. Our results do not substantiate the claim that ankle power output is increased significantly as a result of power transferred by GAS form the knee to the ankle.” (Pandy and Zajac) They came to this conclusion by removing the biarticular part of their model, and adding another uniarticular ankle plantarflexor. Vertical jump increased in the second model.

In a study conducted by M. Ridgway (A Kinematic Comparison of the Block Jump and a Training Jump as Performed by Elite College and Recreational Female Volleyball Players) differences in the block jump and training jump were compared using female elite and non-elite players. Block jumps consisted of the blocking technique used by volleyball players during competition. This type of vertical jump is very sport specific because of the rules of the sport, which do not allow players to touch the net, (limiting arm swing) and not allowing players to cross the center line (effecting balance during landing).

Training jumps allowed for arm swing because the limitations (rules and net) were not there. Results show that the training jump heights were higher than the block jump heights. This suggested to the author that in jump training for volleyball players would be better suited to train using the block jump, because it is more specific to the sport. Major differences in the two techniques include; differences in arm movement (sagittal plane movement in the training jumps and frontal movement in the block jumps), and greater landing forces in the block jump, due to the players trying to maintain balance (shorter landing times and smaller ranges in motion).

The differences in the elite and recreational players were the jump heights for both the training jump and block jump, elite out-performing the recreational players, and the differences in the jumping style itself.

Velocity in the upper body of the elite players was significantly greater than the recreational players during the block jump. This fact supports the idea that “blocking with the arms enhances the transfer of momentum created in the arm swing to the body.

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