Significant relationships were identified between LVL and RVL thickness and PF, PV, and jump height in the CMJ and SJ, as well as with PF in the IMTP (Table 3). Similarly, significant relationships were found between LLG pennation angle and PV in the CMJ, PF in the SJ, and PF and relative PF in the IMTP (Table 4). However, no significant relationships were identified between RLG pennation angle and any lower-body strength and power variable (Table 4). Furthermore, IMTP PF demonstrated a very large relationship with PF in the CMJ (r = 0.76, r2 = 0.57, p < 0.01) and SJ (r = 0.81, r2 = 0.65, p < 0.01), and large relationships with jump height in the CMJ and SJ (p < 0.01 and p = 0.02, respectively) (Figures 3 and 4). Additionally, lower-body MTC stiffness exhibited large relationships with DSD ratio (p < 0.01), RLG pennation angle (p < 0.01) (Figures 5 and 6), PF (r = 0.60, r2 = 0.36, p = 0.02), and jump height (r = 0.53, r2 = 0.28, p = 0.04) in the CMJ.
The purpose of this study was to determine whether any significant relationships were present between specific lower-body muscle structures and lower-body strength and power qualities, as well as within the strength and power qualities. The results of this study indicate that VL thickness of both the left and right leg was significantly related to performance in the CMJ, SJ and IMTP. Furthermore, LLG pennation angle exhibited significant relationships with SJ and IMTP PF, and IMTP rPF. Additionally, lower-body MTC stiffness was significantly related to DSD ratio, RLG pennation angle, and PF and jump height in the CMJ.
To the best of our knowledge, this is the first study to report on the relationships between lower-body muscle structure and performance in the IMTP. Although previous research has identified that VL thickness demonstrates significant relationships with lower-body strength, through performance in the squat, it is yet to be reported whether similar relationships were present with the IMTP (3,23). The results of this study indicate that increased thickness in the VL is related to greater PF and rPF production during the IMTP. It has been well established that the maximal force that can be produced by a muscle is determined by the activity of the subunits of the muscle, namely the muscle fibers, sarcomeres, and myofibrils (33). Therefore, it is proposed that larger thickness of the VL muscles reflects great hypertrophy of the extensors in general and thereby allows for a greater production of force, because of a potentially greater number of actin and myosin filaments within the muscle (33). This would allow for increased cross-bridging within the muscle fibers, and hence, it is apparent that larger muscles would be capable of producing greater forces when compared with smaller muscles (33).
Interestingly, VL thickness was also significantly related to all performance variables (PF, PV, jump height) of the CMJ and SJ. Furthermore, the results of this study identified that PF in the IMTP was significantly related to PF, PV, and jump height in the CMJ, as well as PF and jump height in the SJ. This suggests that the subjects with greater maximal lower-body strength, as measured with the IMTP, were capable of producing better performances in the CMJ and SJ. It appears likely that this is part due to increased muscle thickness, allowing for a greater production of force, directly influencing the isometric tests and underpinning performance in the dynamic tests of power. This is evidenced by VL thickness explaining approximately 30% of the variance in IMTP PF, and 35 and 58% of the variance in CMJ PF and SJ PF, respectively. These results are in agreement with previous research that suggests that lower-body strength underpins lower-body power in a range of sport relevant activities (6,24).
It has previously been reported that larger pennation angles within a muscle allow for a greater physiological cross-sectional area (PCSA) (17,19). Because of the higher PCSA, there is a greater concentration of muscle subunits, and hence an increase in the maximal magnitude of force that can be produced (8,19). In combination with the relationships identified between VL thickness and CMJ, SJ, and IMTP performance, this study suggests that the athletes with greater thickness in the VL and increased pennation in the LG exhibit higher levels of lower-body strength and power. These findings, in combination with the previous research that has shown that changes in VL thickness explains 64% of changes in speed performance in highly trained athletes (23), indicate that future research should determine whether increases in VL thickness and LG pennation angle can also transfer to associated improvements in CMJ, SJ, and IMTP performance.
Lower-body MTC stiffness was identified to exhibit significant relationships with DSD ratio, RLG pennation angle, and PF and jump height in the CMJ. Interestingly, this study is the first to identify significant relationships between lower-body MTC stiffness and DSD ratio. Furthermore, the data of this study suggest that 46% of the variance in DSD ratio is explained by lower-body MTC stiffness. This indicates that athletes with greater lower-body MTC stiffness have the ability to use a greater proportion of their maximal isometric force during a dynamic movement. In combination with the relationships identified between LG pennation angle and performance in the CMJ, this study provides further support to research that has suggested that the performance of dynamic lower-body activities are strongly related to the stiffness of the lower-body musculature (2). Although the concept that lower-body stiffness underpins performance in dynamic lower-body movements is not novel, to the best of our knowledge, this is the first study to report relationships between these variables using the equations presented in this study.
Although a limitation of this study is the small sample size, the identification of the muscle structures that are related to a greater expression of lower-body strength and power qualities in this study should still assist practitioners with talent identification and to provide a sound basis of for future training studies. Such training studies should investigate whether changes in these specific muscle structures are associated with a concomitant change in the strength and power qualities. Furthermore, as a result of the significant relationships between muscle structure variables and lower-body MTC stiffness, changes in DSD with training should be further investigated. These analyses would provide strength and conditioning practitioners with the ability to prescribe effective training programs and to evoke specific structural changes, as opposed to merely mimicking movement velocities and patterns (7).
The results of this study suggest that greater thickness in the VL and increased pennation in the LG muscles may be related to improved performance in the CMJ, SJ, and IMTP. It is proposed that together, these specific structures are the result of increased hypertrophy within the muscles, which improve the force producing capabilities. The stiffness of the lower-body MTC was related to DSD ratio, RLG pennation angle, and CMJ performance. This indicates that increased pennation in the RLG appears to be related to greater lower-body MTC stiffness, which allows the athlete to apply a greater magnitude of force in a dynamic movement, in relation to their maximal strength.
1. Blazevich AJ, Cannavan D, Coleman DR, Horne S. Influence of concentric and eccentric resistance training on architectural adaptation in human quadriceps muscles. J Appl Physiol (1985) 103: 1565–1575, 2007.
2. Bojsen-Moller J, Magnusson SP, Rasmussen LR, Kjaer M, Aagaard P. Muscle performance during maximal isometric and dynamic contractions is influenced by the stiffness of the tendinous structures. J Appl Physiol (1985) 99: 986–994, 2005.
3. Brechue WF, Abe T. The role of FFM accumulation and skeletal muscle architecture in powerlifting performance. Eur J Appl Physiol 86: 327–336, 2002.
4. Brughelli M, Cronin J, Nosaka K. Muscle architecture and optimum angle of the knee flexors and extensors: A comparison between cyclists and Australian Rules Football players. J Strength Cond Res 24: 717–721, 2010.
5. Comfort P, Jones PA, McMahon JJ, Newton RU. Effect of knee and trunk angle on kinetic variables during the isometric mid-thigh pull: Test-retest reliability. Int J Sports Physiol Perform 10: 58–63, 2015.
6. Comfort P, Stewart A, Bloom L, Clarkson B. Relationships between strength, sprint, and jump performance in well-trained youth soccer players. J Strength Cond Res 28: 173–177, 2014.
7. Earp JE, Kraemer WJ, Cormie P, Volek JS, Maresh CM, Joseph M, Newton RU. Influence of muscle-tendon unit structure on rate of force development during the squat, countermovement, and drop jumps. J Strength Cond Res 25: 340–347, 2011.
8. Earp JE, Kraemer WJ, Newton RU, Comstock BA, Fragala MS, Dunn-Lewis C, Solomon-Hill G, Penwell ZR, Powell MD, Volek JS, Denegar CR, Hakkinen K, Maresh CM. Lower-body muscle structure and its role in jump performance during squat, countermovement, and depth drop jumps. J Strength Cond Res 24: 722–729, 2010.
9. Farley CT, Gonzalez O. Leg stiffness and stride frequency in human running. J Biomech 29: 181–186, 1996.
10. Foure A, Nordez A, Cornu C. Plyometric training effects on Achilles tendon stiffness and dissipative properties. J Appl Physiol (1985) 109: 849–854, 2010.
11. Fukashiro S, Hay DC, Nagano A. Biomechanical behavior of muscle-tendon complex during dynamic human movements. J Appl Biomech 22: 131–147, 2006.
12. Fukunaga T, Ichinose Y, Ito M, Kawakami Y, Fukashiro S. Determination of fascicle length and pennation in a contracting human muscle in vivo. J Appl Physiol (1985) 82: 354–358, 1997.
13. Haff GG, Carlock JM, Hartman MJ, Kilgore JL, Kawamori N, Jackson JR, Morris RT, Sands WA, Stone MH. Force-time curve characteristics of dynamic and isometric muscle actions of elite women Olympic weightlifters. J Strength Cond Res 19: 741–748, 2005.
14. Haff GG, Stone M, O'Bryant HS, Harman E, Dinan C, Johnson R, Han KH. Force-time dependent characteristics of dynamic and isometric muscle actions. J Strength Cond Res 11: 269–272, 1997.
15. Hasson CJ, Dugan EL, Doyle TLA, Humphries B, Newton RU. Neuromechanical strategies employed to increase jump height during the initiation of the squat jump. J Electromyogr Kinesiol 14: 515–521, 2004.
17. Kawakami Y, Abe T, Fukunaga T. Muscle-fibre pennation angles are greater in hypertrophied than in normal muscles. J Appl Physiol (1985) 74: 2740–2744, 1993.
18. Kawakami Y, Abe T, Kuno S, Fukunaga T. Training-induced changes in muscle architecture and specific tension. Eur J Appl Physiol 72: 37–43, 1995.
19. Kawakami Y, Ichinose Y, Kubo K, Ito M, Imai M, Fukunaga T. Architecture of contracting human muscles and its functional significance. J Appl Biomech 16: 88–98, 2000.
20. Kraska JM, Ramsey MW, Haff GG, Fethke N, Sands WA, Stone ME, Stone MH. Relationship between strength characteristics and unweighted and weighted vertical jump height. Int J Sports Physiol Perform 4: 461–473, 2009.
21. Kubo K, Kanehisa H, Takeshita D, Kawakami Y, Fukashiro S, Fukunaga T. In vivo dynamics of human medial gastrocnemius muscle-tendon complex during stretch-shortening cycle exercise. Acta Physiol Scand 170: 127–135, 2000.
22. McGuigan MR, Doyle TA, Newton M, Edwards DJ, Nimphius S, Newton RU. Eccentric utilization ratio: Effects of sport and phase of training. J Strength Cond Res 20: 992–995, 2009.
23. Nimphius S, McGuigan MR, Newton RU. Changes in muscle architecture and performance during a competitive season in female softball players. J Strength Cond Res 26: 2655–2666, 2012.
24. Peterson MD, Alvar BA, Rhea MR. The contribution of maximal force production of explosive movement among collegiate athletes. J Strength Cond Res 20: 867–873, 2006.
25. Secomb JL, Farley ORL, Lundgren L, Tran TT, King A, Nimphius N, Sheppard JM. Associations between the performance of scoring manoeuvres and lower-body strength and power in elite surfers. Int J Sports Sci Coach In Press.
26. Secomb JL, Tran TT, Lundgren L, Farley ORL, Sheppard JM. Single-leg squat progressions. Strength Cond J 36: 68–71, 2014.
27. Sheppard JM, Chapman DW. An evaluation of a strength qualities assessment for the lower body. J Aus Strength Cond 19: 14–20, 2011.
28. Sheppard JM, Cronin J, Gabbett TJ, McGuigan MR, Extebarria N, Newton RU. Relative importance of strength and power qualities to jump performance in elite male volleyball players. J Strength Cond Res 22: 758–765, 2007.
29. Sheppard JM, Doyle TLA. Increasing compliance to instructions in the squat jump. J Strength Cond Res 22: 648–651, 2008.
30. Sheppard JM, Newton RU, McGuigan MR. The effects of depth-jumping
on vertical jump performance of elite volleyball players: An examination of the transfer of increased stretch-load tolerance to spike jump performance. J Aus Strength Cond 16: 3–10, 2008.
31. Sheppard JM, Nimphius S, Haff GG, Tran TT, Spiteri T, Brooks H, Slater G, Newton RU. Development of a comprehensive performance-testing protocol for competitive surfers. Int J Sports Physiol Perform 8: 490–495, 2013.
32. Young KP, Haff GG, Newton RU, Sheppard JM. Reliability of a novel testing protocol to assess upper body strength qualities in elite athletes. Int J Sports Physiol Perform 9: 871–875, 2014.
33. Zatsiorsky VM, Kraemer WJ. Science and Practice of Strength Training (2nd ed.). Champaign, IL: Human Kinetics, 2006.