Category Archives: Sprint Training

Mechanisms of the stretch shortening cycle during plyometric exercise

Plyometric training (PT) has been introduced to the training program of the female rugby team because it will improve the speed, power and strength of individual players which will enhance the ability and performance level of the entire team.  This short article will explain PT, demonstrate the benefits of using PT within a training program and how it can be implemented within the structure of rugby training and development to both compliment skills training and enhance athletic ability.

Plyometric training utilises the stretch shortening cycle (SSC) (Komi, 2000.  Nicol, Avela, & Komi, 2012.  Turner & Jeffreys, 2010) each time the body uses one movement to drive an opposite movement such as a dip down before a high jump, also known as a countermovement jump (CMJ) (video 1).

The body uses an eccentric contraction, which is when the muscle is stretched as seen in the downward movement, followed by a moment of no movement (isometric) leading to the muscle reducing in length (concentric) which is seen as the jump up section (video 2).

SSC utilises the body’s reflex responses to the fast countermovement.  When the muscle spindles, which are the muscles monitoring systems, are triggered they send an electrical pulse to the control centre of the muscle to cause a contraction (Komi, 2000. Komi, 2008).  The spindles also send a signal to the opposing (antagonist) muscle of the joint to ensure it relaxes to avoid injury (Chimera, Swanik, Swanik, & Straub, 2004).  Plyometrics also use elastic energy (EE) that is stored in the muscle tendon, the attachment of muscle to bone, in short movements  (Cavanagh & Komi, 1979).  The human skeletal muscle is more inclined to stretch and contract then the tendons, so to utilise the EE we have to restrict movement in the muscle by stiffening the joint  (Turner & Jeffreys 2010), for example the reduced movement in the ankle during the landing and shorter ground contact time (GCT) (Video 3).

When used effectively, plyometric training can:

  • improve the coordination between muscles (Swanik et al., 2002),
  • improved stability of the joints (Chimera et al., 2004.  Hewett, Stroupe, Nance, & Noyes, 1996),
  • reduce ground contact time leading to enhanced agility (Dymond, Flanagan, & Turner. 2011.  Miller, Herniman, Ricard, Cheatham, & Michael, 2006),
  • improve the tendons ability to store and transfer EE (Komi, 2000).

Research indicates that plyometric training programs can improve countermovement jump performance by nearly 9% (Markovic, 2007) and shows significant improvements in sports actions, such as sprinting and change of direction, even after short term plyometric training (Meylan & Malatesta, 2009) with improvements in both leg strength and power demonstrated when a blend of PT and strength training is implemented (Blakeyl & Southard, 1987.  Deutsch & Lloyd, 2008.  Ebben & Watts, 1998).

PT has shown similar improvements on performance for both men and women as well as various fitness levels (Chimera, Swanik, Swanik, & Straub, 2004.  Sáez-Sáez de Villarreal, Requena, & Newton.  2010).  Although Turner, Owings, & Schwane, (2003) demonstrated that a 6 week plyometric program improved the efficiency of amateur but not elite runners, the program was based on 1 session per week and the only variability was increasing the volume of training per week.  However, three 30 minute sessions of plyometric training per week can improve highly trained runners by reducing the energy required to move and improving the mechanics they use to run (Saunders et al., 2006).

It is recommended to follow an introductory training of 6 weeks (Hedrick. 1994) as a basic level of strength will be required to prepare the muscles for high impact movements and prevent injuries, with a subsequent training volume of two sessions per week consisting of 40 jumps per session for 8 weeks. (Sáez-Sáez de Villarreal, Requena, & Newton, 2010).  It is also recommended that linear sprint training is not included in any blended training program that includes strength and PT (Deutsch & Lloyd, 2008).  Upper body (UB) PT has been shown to benefit the health of the shoulder joint as well as reaction speed and muscle performance (Swanik et al., 2002).  This is a key factor in rugby players as shoulder joint health is key due to the impacting nature of the sport.

Grouping a rugby team during training sessions in to their general sporting characteristics has been shown to ensure specific performance goals are achieved (Meir, Newton, Curtis, Fardell, & Butler, 2001) with the emphasis being applied on the back line for speed and power and the forwards for strength (Brewer & Davis, 1995).  PT has been shown to be effective in a 4 week microcycle when implemented in to a rugby training program (Pienaar & Coetzee, 2013).

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Applying this to a female rugby team will ensure the time spent on athletic ability will be specific to the role each person plays in the team.  Each week plyometric training specific to position played, such as back line or forward pack, has been implemented with a separation of abilities within these groups.  This season will see a balancing out of abilities to further enhance training sessions, by reducing learning times and unifying training groups, as well as result in increased linear speed, power and strength in game situations.

REFERENCES

Blakeyl, J. B., & Southard, D. (1987). The Combined Effects of Weight Training and Plyometrics on Dynamic Leg Strength and Leg Power. Journal of Strength, 1(1), 14–16.

Brewer, M. J., & Davis, J. (1995). Applied Physiology of Rugby League. Sports Medicine, 20(3), 129–135. doi:10.2165/00007256-199520030-00001

Cavanagh, P. R., & Komi, P. V. (1979). Electromechanical delay in human skeletal muscle under concentric and eccentric contractions. European Journal of Applied Physiology and Occupational Physiology, 42(3), 159–163. doi:10.1007/BF00431022

Chimera, N. J., Swanik, K. A., Swanik, C. B., & Straub, S. J. (2004). Effects of Plyometric Training on Muscle-Activation Strategies and Performance in Female Athletes. Journal of Athletic Training, 39(1), 24–31.

Deutsch, M., & Lloyd, R. (2008). Effect of order of exercise on performance during a complex training session in rugby players. Journal of Sports Sciences, 26(8), 803–809. doi:10.1080/02640410801942130

Dymond, C., Flanagan, E. P., & Turner, A. P. (2011). The relationship between maximal strength and plyometric ability in Rugby players. ISBS – Conference Proceedings Archive, 1(1). Retrieved from https://ojs.ub.uni-konstanz.de/cpa/article/view/4777

Ebben, W. P. M., & Watts, P. B. (1998). A Review of Combined Weight Training and Plyometric Training Modes: Complex Training. Strength & Conditioning, 20(5), 18–27.

Flanagan, E. P., Ebben, W. P., & Jensen, R. L. (2008). Reliability of the Reactive Strength Index and Time to Stabilization During Depth Jumps: Journal of Strength and Conditioning Research, 22(5), 1677–1682. doi:10.1519/JSC.0b013e318182034b

Hedrick, A. M. (1994). Strength/Power Training for the National Speed Skating Team. Strength & Conditioning, 16(5), 33–39.

Hewett, T. E., Stroupe, A. L., Nance, T. A., & Noyes, F. R. (1996). Plyometric Training in Female Athletes Decreased Impact Forces and Increased Hamstring Torques. The American Journal of Sports Medicine, 24(6), 765–773. doi:10.1177/036354659602400611

Komi, P. (2008). The Encyclopaedia of Sports Medicine: An IOC Medical Commission Publication, Strength and Power in Sport. John Wiley & Sons.

Komi, P. V. (2000). Stretch-shortening cycle: a powerful model to study normal and fatigued muscle. Journal of Biomechanics, 33(10), 1197–1206. doi:10.1016/S0021-9290(00)00064-6

Markovic, G. (2007). Does plyometric training improve vertical jump height? A meta-analytical review. British Journal of Sports Medicine, 41(6), 349–355. doi:10.1136/bjsm.2007.035113

Meir, R., Newton, R., Curtis, E., Fardell, M., & Butler, B. (2001). Physical Fitness Qualities of Professional Rugby League Football Players: Determination of Positional Differences. Journal of Strength, 15(4), 450–458.

Meylan, C., & Malatesta, D. (2009). Effects of In-Season Plyometric Training Within Soccer Practice on Explosive Actions of Young Players: Journal of Strength and Conditioning Research, 23(9), 2605–2613. doi:10.1519/JSC.0b013e3181b1f330

Miller, M. G., Herniman, J. J., Ricard, M. D., Cheatham, C. C., & Michael, T. J. (2006). The Effects of a 6-Week Plyometric Training Program on Agility. Journal of Sports Science & Medicine, 5(3), 459–465.

Nicol, C., Avela, J., & Komi, P. P. V. (2012). The Stretch-Shortening Cycle. Sports Medicine, 36(11), 977–999. doi:10.2165/00007256-200636110-00004

Meir, R., Newton, R., Curtis, E., Fardell, M., & Butler, B. (2001). Physical Fitness Qualities of Professional Rugby League Football Players: Determination of Positional Differences. Journal of Strength, 15(4), 450–458.

Pienaar, C., & Coetzee, B. (2013). Changes in Selected Physical, Motor Performance and Anthropometric Components of University-Level Rugby Players After One Microcycle of a Combined Rugby Conditioning and Plyometric Training Program: Journal of Strength and Conditioning Research, 27(2), 398–415. doi:10.1519/JSC.0b013e31825770ea

Sáez-Sáez de Villarreal, E., Requena, B., & Newton, R. U. (2010). Does plyometric training improve strength performance? A meta-analysis. Journal of Science and Medicine in Sport, 13(5), 513–522. doi:10.1016/j.jsams.2009.08.005

Saunders, P. U., Telford, R. D., Pyne, D. B., Peltola, E. M., Cunningham, R. B., Gore, C. J., & Hawley, J. A. (2006). Short-term plyometric training improves running economy in highly trained middle and long distance runners. Journal of Strength, 20(4), 947–954.

Swanik, K. A., Lephart, S. M., Swanik, C. B., Lephart, S. P., Stone, D. A., & Fu, F. H. (2002). The effects of shoulder plyometric training on proprioception and selected muscle performance characteristics. Journal of Shoulder and Elbow Surgery, 11(6), 579–586. doi:10.1067/mse.2002.127303

Turner, A. M., Owings, M., & Schwane, J. A. (2003). Improvement in Running Economy After 6 Weeks of Plyometric Training. Journal of Strength, 17(1), 60–67.

Turner, A. N., & Jeffreys, I. (2010). The Stretch-Shortening Cycle: Proposed Mechanisms and Methods for Enhancement: Strength and Conditioning Journal, 32(4), 87–99. doi:10.1519/SSC.0b013e3181e928f9


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