Athletic Power Development


Athletic Power Development

Athletic Power Development

Sport Australia (formerly Australian Sports Commission) 14024-01

Prepared by: Kym Williams, Strength and Conditioning, Australian Institute of Sport
Evaluated by: Ross Smith, Manager Strength and Conditioning Operations, Australian Institute of Sport (July 2015)
Last Updated: July 2015 

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Introduction

Understanding athletic performance and factors contributing to its generation is invaluable to sports scientist, alike. The very nature of human movement and athletic performance, involves the interaction between the nervous system and the mechanical properties of the muscles (1, 7, 11, 12, 32, 34). A by-product of the unique interaction is the development mechanical force.

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In the year, 1687, Sir Isaac Newton initiated the concept of mechanical force and its importance to human movement. Newton’s stated that: “in order for motion to occur, a force must act upon the object to change its state of being and in the direction of its purpose”. In other words: the magnitude of force is equal to the mass of an object times the rate of acceleration and in the direction of that applied of force (F=Ma). In the field of sports science, the importance of force can be seen when the muscles and tendon generate both mechanical and elastic force to accelerate a limb; and the magnitude of this movement is directly proportionate to the rate in which one can develop mechanical force (21).

Hill, 1922 to 1949, was the first researcher to delve into the mechanics of the human body and understand how the muscles produce movement through the development of force. During examination, Hill realised that a muscle behaves in a predictable manner when contracted. Hill stated that: “the heat energy generating capability of the neuromuscular system under maximal activation (force) is dependent upon the contractile shortening velocity of the muscle”, as illustrated by Hill’s force-velocity relationship” (28) (figure 1)

The force-velocity relationship    

Figure 1 - The force/Velocity relationship (13) 

The inverse relationship that force and velocity share in muscular contractions is a hyperbolic curve, that inherently represents that a muscles ability to generate mechanical force is inversely dependent upon the shortening velocity of an individual muscle fibril, and vice versa (13, 22, 25, 32, 38) (Figure 1). This observation have since been verified and observed at a micro (mechanical) level by Wilki (36) who provided a practical explanation for Hill’s model by stating that: “because it takes time for cross-bridge to attach and detach during a single contractile cycle, the total number of cross-bridges that can be attached to generate and transfer ATP into mechanical force is inversely limited by an increase in contractile shortening velocity”. (36). 

Since the generation of Hill’s model, a cohort of authors (2, 3, 4, 15, 16, 17, 22, 25, 31) have since badged the term “power” to encompass the force/velocity relationship, and then applied the term to dynamic (multi-directional) movements. As such, “power” - in anaerobic explosive events - is the product of force and contractile shortening velocity. This relationship is, therefore, optimized at a compromised level of both force and velocity.

Strength and Conditioning Coaches find the F/V relationship appealing as all dynamic movement is seen an integration of force and velocity; that is, most sporting movements involve a mixture of activation that span the full length of the force and velocity capability of the muscle. For example: High jumpers and Powerlifters require a high level of strength to perform their respective tasks; however, they primary train at opposite ends of the force/velocity spectrum to achieve the optimal contractile characteristics to maximise sports specific performance. To inherently enhance sporting performance, one must always aim to improve specific parts of the force/velocity curve to match the mechanical power demands of a sports specific task. Nonetheless, an increase in one side of the curve will positively alter the shape of the force/velocity curve with a diminishing influence the further the adaptation moves along the curve (17).

Like the aforementioned example, the force/velocity theory allows practitioners the opportunity to analysis, classify, and diagnosis various sporting movements to particular axis along the force/velocity spectrum. Using this information, strength and conditioning coaches can target various physiology traits with a particular stimulus to cause a positive performance shift in either force or velocity. However, an athlete cannot be powerful without first being strong (2, 32). Therefore, one’s level of strength (otherwise known, as magnitude of force production) is fundamentally what underpins power output, and intern sporting performance (31).

Length-tension relationship of sarcomeres presented in a graphical form. 

Figure 2: Length-tension relationship of sarcomeres presented in a graphical form.
[source: http://slidingfilament.webnode.com


 14022-04What influences the F/V relationship?  

To understand the characteristics that shape power output, one must understand a muscle’s architecture and the mechanics that underpin the force & velocity relationship. First and foremost, muscular power applied for a given movement is determined by a complex range of mechanical interactions within the skeletal muscle, between muscle and tendon, and between muscles and the machines of the skeleton (13). A muscle generates tension through a process called the sliding filament theory (SFT) - a biological process where myosin and actin filaments (proteins that drive muscular contractions) interact to drive the magnitude of contraction for a specific movement. The number of active bridging sites determines the amount of energy-released, and thus, the extent of force derived through an individual muscle fascicle. Therefore, for the SFT to optimize its contractile capacity, it must be operating in a zone that maximizes the number of active actin and myosin bridging sites. This is a product of the length-tension relationship, which is a U shaped relationship where the greatest tension is generated at or near resting length; whilst less contractile tension can be obtained when the muscle is stretched or shortened above or below this length (Figure 2) (13). If a muscle is slightly outside the optimal contractile zone, it will affect the magnitude and rate of one’s mechanical force production.

Over the years, empirical evidence has constantly pointed to the impact that ones’ strength level has on power output. Strength can be defined as the ability of musculature to produce force against the mechanical construct of the skeleton (12). Therefore, an individual's level of strength determines theirs upper limit of force production, and thus, impacts of the force velocity relationship. 

Currently, the literature clearly demonstrates a strong link between strength and power. Cormie (6) demonstrated that stronger individuals have consistently been shown to display superior power output than individuals with a lower level of strength. This is due to a wide variety of integrated physiological factors (muscle fiber composition, cross-sectional area, fascicle length, pennation angle and tendon compliance) and neuromuscular factors (motor unit recruitment, firing frequency, synchronisation and inter-muscular coordination) that accompany strength training. (1, 23, 24, 25 15, 16). Fry (8) further supported Cormie’s observation by demonstrating that stronger athletes had greater vertical jump heights and sprint times compared to relatively weaker athletes. This suggests a strong practical relationship between maximal strength and power related measures. However, the reported finding may be in part, due to, the mechanical, physiological and neurological advantages that strength training may acquire over a continuum of training. 

Therefore, as the strength level of an athlete improves, the level of force output should follow in a linear fashion. Subsequently, as force shares an inverse relationship with power; a fundamental relationship exist between strength and power, which dictates that an individual cannot obtain a high level of power without first being relatively strong (2, 32). Therefore, enhancing maximal strength is essential when considering the long-term development of the magnitude power (16, 32) and its effectiveness in the coordination of motor tasks, which are fundamental to athletic performance. 


14024-02Rate of Force Development

Resistance training is not just limited by its ability to magnify the muscle capacity to apply force, but also, the rate in which force can be applied to the ground or an object. Rate of force development (RFD) is a change in force divided by a change in time, and is directly related to the increase rate of muscle activation by the nervous system (34). Although the magnitude of force applied is directly responsible for the acceleration of an object, one may argue that the faster a given force is attained, the more rapid the corresponding acceleration of a mass. As such, RFD is critical for sports that are required to generate force explosively within restricted period’s time (e.g., 100m Sprint, Shotput, High Jump etc.,). Data compiled by Ward (35) from Olympic caliber throwers supported the aforementioned observation by stating that throwing ability was significantly related to maximal explosive strength (RFD) obtained in lifts, which is consider to enhance not only maximal force, but the rate in which force is applied. Hori also agreed with wards observation by reporting that maximal explosive strength (like those seen in Olympic weightlifting or plyometric activities) improved the up-regulation, and synchronisation of the neurological system, that inherently enhances the RFD in dynamic athletic movements. For explosive movements such as sprints, throws, and jumps in which force needs to be produced within minuet time periods of time (100ms - 300 ms), RFD is strongly related to performance (37).

To amplify the rate of force developed, an athlete must over stimulate the neurological system in training to react explosively. The characteristics that drive the level of adaption from a stimulus are determined by the type of contraction (or activity), the rate of muscle activation, and the degree of muscle activation (15). Explosive training modalities, such as ballistic training, and plyometric training, are equivocally responsible for over-stimulating the neurological system by up-regulating the transfer of force into an athletic outcome. It would come as no surprise that sprint athletes are required to have a mix of high force (strength) and high RFD (explosive strength) to perform the necessary mechanics for successful performance. It should be noted that an athlete cannot attain a high RFD without first being relatively strong. Therefore, coaches must take a stepwise approach by periodising their athletes training program to maximise the athletic (physical) development phase. A combination of technique, strength, and RFD are critical for sports that require various elements of explosive ability. However, strength is the underlying characteristic that determines sporting success.


Further Resources and Reading

References

  1. Aagaard, P., et al. (2001). "A mechanism for increased contractile strength of human pennate muscle in response to strength training: changes in muscle architecture." The journal of physiology 534(2): 613-623.
  2. Argus, C. K., N. D. Gill, et al. (2013). "Assessing the variation in the load that produces maximal upper-body power." Journal of strength and conditioning research/National Strength & Conditioning Association.
  3. Baker, D. and S. Nance (1999). "The relation between running speed and measures of strength and power in professional rugby league players." The Journal of Strength & Conditioning Research 13(3): 230-235.
  4. Baker, D., S. Nance, et al. (2001). "The load that maximizes the average mechanical power output during jump squats in power-trained athletes." The Journal of Strength & Conditioning Research 15(1): 92-97.
  5. Baker, D. G. and R. U. Newton (2008). "Comparison of lower body strength, power, acceleration, speed, agility, and sprint momentum to describe and compare playing rank among professional rugby league players." The Journal of Strength & Conditioning Research 22(1): 153-158.
  6. Blazevich, A. J. and N. C. Sharp (2006). "Understanding muscle architectural adaptation: macro-and micro-level research." Cells Tissues Organs 181(1): 1-10.
  7. Bondarchuk, A. and M. Yessis (2010). Transfer of Training in Sports II, Ultimate Athlete Concepts.
  8. Bottinelli, R., et al. (1999). "Specific contributions of various muscle fibre types to human muscle performance: an in vitro study." Journal of Electromyography and Kinesiology 9(2): 87-95.
  9. Bourque, P. J. (2003). Determinants of load at peak power during maximal effort squat jumps in endurance-and power-trained athletes, University of New Brunswick (Canada).
  10. Campos, G. E., T. J. Luecke, et al. (2002). "Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones." European journal of applied physiology 88(1-2): 50-60.
  11. Carlock, J. M., et al. (2004). "The relationship between vertical jump power estimates and weightlifting ability: a field-test approach." The Journal of Strength & Conditioning Research 18(3): 534-539.
  12. Cormie, P., R. Deane, et al. (2007). "Methodological concerns for determining power output in the jump squat." The Journal of Strength & Conditioning Research 21(2): 424-430.
  13. Cormie, P. and S. P. Flanagan (2008). "Does an Optimal load exist for power training?" Strength & Conditioning Journal 30(2): 67-69.
  14. Cormie, P., J. M. McBride, et al. (2008). "Power-time, force-time, and velocity-time curve analysis during the jump squat: impact of load." Journal of applied biomechanics 24(2): 112.
  15. Cormie, P., J. M. McBride, et al. (2009). "Power-time, force-time, and velocity-time curve analysis of the countermovement jump: impact of training." The Journal of Strength & Conditioning Research 23(1): 177-186.
  16. Cormie, P., M. R. McGuigan, et al. (2010). "Influence of strength on magnitude and mechanisms of adaptation to power training." Med Sci Sports Exerc 42(8): 1566-1581.
  17. Cormie, P., M. R. McGuigan, et al. (2011). "Developing maximal neuromuscular power." Sports medicine 41(1): 17-38.
  18. Friden, J. and R. Lieber (2001). "Eccentric exercise‚Äêinduced injuries to contractile and cytoskeletal muscle fibre components." Acta Physiologica Scandinavica 171(3): 321-326.
  19. Fry, A. C. and W. J. Kraemer (1991). "Physical performance characteristics of American collegiate football players." The Journal of Strength & Conditioning Research 5(3): 126-138.
  20. Gollhofer, A., V. Strojnik, et al. (1992). "Behaviour of triceps surae muscle-tendon complex in different jump conditions." European journal of applied physiology and occupational physiology 64(4): 283-291.
  21. Hill, A. (1938). "The heat of shortening and the dynamic constants of muscle." Proceedings of the Royal Society of London. Series B, Biological Sciences: 136-195.
  22. Hori, N., Newton, R. U., Andrews, W. A., Kawamori, N., McGuigan, M. R., & Nosaka, K. (2007). Comparison of four different methods to measure power output during the hang power clean and the weighted jump squat. Journal of Strength and Conditioning Research, 21(2), 314-325.
  23. Kawamori, N. and G. G. Haff (2004). "The optimal training load for the development of muscular power." The Journal of Strength & Conditioning Research 18(3): 675-684.
  24. Kraemer, W. J., S. J. Fleck, et al. (1996). "Strength and power training: physiological mechanisms of adaptation." Exercise and sport sciences reviews 24: 363.
  25. McBride, J. M., et al. (1999). "A comparison of strength and power characteristics between power lifters, Olympic lifters, and sprinters." The Journal of Strength & Conditioning Research 13(1): 58.
  26. Marco C., N. R., Nosaka K., Ed. (2011). Strength and conditioning. "Biological Principles and Practical Application". West Sussex, Wiley-Blackwell.
  27. Roger Bartlett, (2007). Introduction to sports biomechanics. “Analysing human movement patterns” London, England, Taylor & Francis group
  28. Schilling, B. K., et al. (2008). "Force-velocity, impulse-momentum relationships: Implications for efficacy of purposefully slow resistance training." Journal of sports science & medicine 7(2): 299.
  29. Sleivert, G., & Taingahue, M. (2004). The relationship between maximal jump-squat power and sprint acceleration in athletes. European journal of applied physiology, 91(1), 46-52.
  30. Smilios, I., et al. (2005). "Short-term effects of selected exercise and load in contrast training on vertical jump performance." The Journal of Strength & Conditioning Research 19(1): 135-139.
  31. Stone, M. H., G. Moir, et al. (2002). "How much strength is necessary?" Physical Therapy in Sport 3(2): 88-96.
  32. Stone, M. H., H. S. O'Bryant, et al. (2003). "Power and maximum strength relationships during performance of dynamic and static weighted jumps." The Journal of Strength & Conditioning Research 17(1): 140-147.
  33. Tricoli, V., et al. (2005). "Short-term effects on lower-body functional power development: weightlifting vs. vertical jump training programs." The Journal of Strength & Conditioning Research 19(2): 433-437.
  34. Viitasalo, J. and P. Komi (1978). "Force-time characteristics and fiber composition in human leg extensor muscles." European journal of applied physiology and occupational physiology 40(1): 7-15.
  35. Ward, G., et al. (1982). "Activation by exercise of human skeletal muscle pyruvate dehydrogenase in vivo." Clin Sci (Lond) 63: 87-92.
  36. Wilkie, D. (1956). "Measurement of the series elastic component at various times during a single muscle twitch." The Journal of physiology 134(3): 527-530.
  37. Wilson, G. J., et al. (1995). "Assessing dynamic performance: A comparison of rate of force development tests." The Journal of Strength & Conditioning Research 9(3): 176-181.
  38. Widrick, J. J., et al. (2002). "Functional properties of human muscle fibers after short-term resistance exercise training." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 283(2): R408-R416. 

 



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