Jumping 101
If we want to improve our jumping skills we need to understand what actually happens with our bodies when we jump and what mechanisms are at play.
Image: @Dzonikor wearing Purple Performance Shorts
Plyometrics nowadays describe almost every jumping event, from rope skipping to high drop jumps. The term was coined as a western translation of “Shock Method” developed by Yurii Verhoshensky.1 The term changed over time resulting in plyometric activity being sinonymous with “stretch-shrotening cycle”.
In various movements like running, jumping, throwing, etc. muscle shortening (propulsion phase) is preceded by muscle lengthening (wind up phase). When trying to jump, everyone naturally does a quick squat just before. If you stayed at the bottom of that squat for let’s say 5 seconds, you would jump less. The mechanism called “stretch shortening cycle” is responsible for that sudden increase in power after a fast “countermovement”.2
The stretch shortening cycle has 3 phases:
1. Eccentric – where the muscles and tendons are lengthening
2. Isometric – the transitional static phase
3. Concetric – muscle-tendon shortening phase.
Image 1 – Three phases of stretch shortening cycle: Eccentric – Loading phase (1), Isometric – Transitional phase (2), Concentric – Unloading phase (3)
The arrows indicate moving body parts during each phase.
During the lengthening, tendons store potential elastic energy so they can release it in concentric phase. Just like rubber bands, stretching them stores elastic energy which is released when you let go.3 However unlike rubber bands, tendons loose elasticity as the time they spend under stretch passes.4
This all means that the faster the SSC overall, the more elastic energy will be utilized. If you squat slowly before a jump, it wouldn’t be as effective.
The amount of energy stored and released by the tendon depends on how much a tendon can stretch. 5,6 The more compliant (elastic) the tendon, the more it stretches and more energy it can store but it can’t witstand high forces as they would stretch it too much to a point of failure (injury).7
To maximize this tendon action muscles need to be really stiff in isometric position during transitional phase to enable tendon lengthening. 8 If we go back to the rubber band example, the hand that is holding the band needs to be still, because if it moves back with the force that stretches the band not a lot of stretching will happen and energy will be lost. That is one of the reasons muscle strength is highly important, it helps keep the static position to enable tendons to fully stretch and utilize elastic energy.
Strength is also the foundation of any movement, and the higher force you can produce when jumping the greater the jump will be.9,10,11
This often leads to parkour practitioners training strength excessively, which if they don’t train in parallel with jumping, leads to loss of coordination.12
“Strength training should be only complimentary and the main focus should be on parkour.”
Because jumping several times consecutively, especially on different surfaces and heights is quite challenging to coordinate properly, it can be only achieved by training those type of movements specifically.13,14
When trying a new training regime or you’re coming back to training, I would say that most of your early gains in plyometrics (like for the first 1-2 months) can be contributed primarily to coordination, that’s how important it is.
@Gagi_pkfr wearing Purple Performance shorts
In conclusion
There are many mechanisms behind plyometrics but I think these are the most important ones.
• Tendon function – storage and release of elastic energy,
• Muscle function – generate force and allow tendons to do their job,
• Coordination – microadjust muscle contractions to optimize this chain of events.
I go into a bit more detail in the video version, which you definitely need to check out as well!
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References:
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Verkhoshansky Y. Shock Method. Verkhoshansky SSTM; 2018.
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Edman KA, Elzinga G, Noble MI. Residual force enhancement after stretch of contracting frog single muscle fibers. J Gen Physiol. 1982;80(5):769-784. doi:10.1085/jgp.80.5.769
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Cavagna GA. Storage and utilization of elastic energy in skeletal muscle. Exerc Sport Sci Rev. 1977;5:89-129.
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Cohen RE, Hooley CJ, McCrum NG. Mechanism of the viscoelastic deformation of collagenous tissue. Nature. 1974;247(5435):59-61. doi:10.1038/247059a0
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Anderson FC, Pandy MG. Storage and utilization of elastic strain energy during jumping. J Biomech. 1993;26(12):1413-1427. doi:10.1016/0021-9290(93)90092-s
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Mendoza E, Azizi E. Tuned muscle and spring properties increase elastic energy storage. J Exp Biol. 2021;224(24):jeb243180. doi:10.1242/jeb.243180
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LaCroix AS, Duenwald-Kuehl SE, Lakes RS, Vanderby R. Relationship between tendon stiffness and failure: a metaanalysis. J Appl Physiol. 2013;115(1):43-51. doi:10.1152/japplphysiol.01449.2012
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Morgan DL, Proske U, Warren D. Measurements of muscle stiffness and the mechanism of elastic storage of energy in hopping kangaroos. J Physiol. 1978;282:253-261.
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McLellan CP, Lovell DI, Gass GC. The role of rate of force development on vertical jump performance. J Strength Cond Res. 2011;25(2):379-385. doi:10.1519/JSC.0b013e3181be305c
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Perez-Gomez J, Calbet J a. L. Training methods to improve vertical jump performance. J Sports Med Phys Fitness. 2013;53(4):339-357.
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Grosprêtre S, Ufland P, Jecker D. The adaptation to standing long jump distance in parkour is performed by the modulation of specific variables prior and during take-off. Mov Sport Sci – Sci Mot. 2018;(100):27-37. doi:10.1051/sm/2017022
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Kyrölänen H, Komi PV, Kim DH. Effects of power training on neuromuscular performance and mechanical efficiency. Scand J Med Sci Sports. 1991;1(2):78-87. doi:10.1111/j.1600-0838.1991.tb00275.x
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Trecroci A, Cavaggioni L, Caccia R, Alberti G. Jump Rope Training: Balance and Motor Coordination in Preadolescent Soccer Players. J Sports Sci Med. 2015;14(4):792-798.
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Almeida MB de, Leandro CG, Queiroz D da R, et al. Plyometric training increases gross motor coordination and associated components of physical fitness in children. Eur J Sport Sci. 2021;21(9):1263-1272. doi:10.1080/17461391.2020.1838620
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Komi PV, Fukashiro S, Järvinen M. Biomechanical loading of Achilles tendon during normal locomotion. Clin Sports Med. 1992;11(3):521-531.
