Tag Archive: sport science

1. What is Dynamic Correspondence?

   22nd November 2012 12:25 pm 6 Comments

   Dynamic Correspondence: Is it misunderstood?

   The greatest challenge for any strength & conditioning/athletic development coach is to elicit specific adaptions on the athlete in order to gain an advantage on the field of play. Specificity can arise in the form of biomechanical, metabolic, or psychological adaptations¹. However, recent focus on specificity has taken on a new chapter, with the development of Siff & Verkhoshansky’s² dynamic correspondence model.

   Definition

   Dynamic Correspondence: This concept emphasises that all exercises for specific sports be chosen to enhance the required sport motor qualities/movement patterns in terms of several criteria which include:

   • the amplitude/direction of the movement 
   • the accentuated region of force production
   • the dynamics of effort
   • the rate and time of maximum force production
   • the regime of muscular work  

   Furthermore, the theory proposes that the strength displayed in the execution of a given movement be referred to only in the context of that given task.

   Sport movement tasks are specific and goal-directed and the enhancement in their execution should also be treated as such. Because of this, exercises should be evaluated based on the type of transfer that they may possess in relation to the degree of skill performance increase.

   After this is established, exercises and/or training techniques can further be classified into categories such as general physical preparation (GPP) or special physical preparation (SPP).

   Force Velocity Curve

   Evaluating the effectiveness of DC can only be decisive with the use of the force velocity curve alongside this argument. The force velocity curve (figure 1) shows an inverse relationship between force and velocity (e.g. the heavier the weight you lift (force), the slower you lift it (velocity); conversely, the lighter a weight, the faster you lift it).

   

   Figure 1: The force velocity curve and its suggested training values

   Therefore, different types of training occur on different parts of the force-velocity curve.  As you go from high force, low velocity to low force, high velocity, you go from max strength work all the way down to speed strength work on the other side of the spectrum.

   Force Velocity and Dynamic Correspondence

   So how does this help athletes and does the curve work in unison with DC? It is agreed that a desired effect of training is to produce greater force outputs at a higher velocity compared to pre-training values ³.

   Figure 2 shows what happens to the force velocity-curve after strength training (blue line) and speed training (green line).

   

   Figure 2: The force velocity curve and its relationship with strength (blue) and speed (green) training

   In advanced athletes, if you train at one end of the force velocity curve, you will improve that part of the curve, but the other will decrease. so can we train all the way along the force-velocity curve?

   The problem is your body can only adapt to so much. If you train all strength qualities at the same time, you won’t adapt optimally, hence why periodisation has taken on significant popularity amongst sports coaches.

   One principle of periodisation is to move from general training to more specific training ⁴. Strength is just general preparation whereas power and speed are more specific. So your periodisation plan should travel from left to right down the force-velocity curve .

   This concept, however is not new to the strength and conditioning world; Kurz⁵ highlights how the strength training year needs to be divided up into 3 phases:

   1. General strength.
   2. Functional strength.
   3. Specific strength.

   This seems to clash with DC’s suggestion on enhanced specificity.

   In conjunction with this, the main bulk of research into the DC theory seems to advocate Olympic lifting, a highly specific and technical exercise, as the main component to enhance sporting capacity.

   Olympic Lifting

   

   The snatch

   The use of DC alongside Olympic lifts in a programme seems to be the most popular training method when searching the current literature on the topic.

   According to Stone et al.,⁶ the hang power clean/snatch is a dynamic lift that is multi-jointed with a need for co-ordination and fluidity within the movement, which will increase power production and sports performance in an athlete.

   The argument being that this lift incorporates the triple extension with the force that is required, ensuring that the correct amplitude and direction of the force is apparent with many sporting movements, such as the engagement of the rugby scrum.

   However, on closer inspection of the scrum it seems the primary direction of force is horizontal rather than vertical!

   Hori and colleagues⁷ suggest that the rate of force development from the hang clean/snatch exercises in Olympic lifting also has a realistic transfer for rugby players. This part of the lift (2^nd pull) exhibits the most force, ensuring the lower limb contracts at speed to hold a dominant position during the engage of the scrum. This would seem to tick several of the boxes in the DC checklist.

   Limitations of the DC theory

   From all the information above it could be suggested that the use of Olympic lifts in the athletes programme will be a useful addition to rugby forwards. However, research needs to further its examination into the effect of Olympic lifting on other sports; as the bulk of work seems to come from heavy contact sports such as Rugby Union/League and American Football.

   Three notes of caution should be considered before assuming DC and Olympic lifting guarantees specific athletic training.

   Firstly, one could misinterpret the conditions of dynamic correspondence to mean that an athlete must literally copy the specific sport task during the training movement.

   This occurs quite often when you jump utilising a weighted vest, sprints towing a sled, or swings a bat representing a heavier load than the individual typically swings.

   These types of methods have been shown to be effective at times depending on the load being utilised but they also have their limitations. For example, larger loads often greatly alter the biomechanics of the movement which, in turn, will most likely force the athlete to alter finally rehearsed movements.

   Second, in an attempt to accelerate the progress of the athletes, many sports performance professionals will implement dynamic correspondence too early in the progression of an athlete’s mastery.

   An attempt to have certain athletes, especially young athletes, perform exercises of specific nature before they are fully ready will only inhibit the long-term athlete development of the given individual.

   The reason for this is he/she may not have attained sufficient levels of general physical qualities (such as strength or flexibility), optimized sporting skill technique, or perfected appropriate neuromuscular programs prior to performing exercise of a specific nature

   Finally, once incorporation of these training exercises are employed, one must address the all-important issue of just how much of the overall training volume is being consumed by DC type exercises versus those of more general nature in a structured training plan.

   Though the idea of periodisation has been studied extensively, this final point of caution has only been addressed on a limited basis and no clear recommendation can be made yet at this point.

   What about going sideways?

   Another difficulty with dynamic correspondence is its relationship with change of direction performance (COD or agility). In terms of the training studies, traditional strength and power training methods (i.e. Olympic-style weightlifting and plyometrics) have been shown to enhance functional performance^{8 9}.

   These training methods have been utilised in several training studies and are commonly used by strength and conditioning coaches. However, these traditional training methods have failed to improve COD performance.

   This failure can be due to the commonality in the design of these studies, which include bilateral movements in the vertical direction. Conversely, COD movements often occur unilaterally in the vertical-horizontal and/or lateral direction, and require anteriorposterior (braking and propulsive) and mediolateral force production¹⁰.

   Unfortunately, there is a distinct lack of research which investigates the correlations between unilateral horizontal jumping and COD performance. It could be speculated that since CODs require vertical-horizontal force production, horizontal jumping would be highly correlated with COD performance and could enhance COD performance with training.

   Furthermore, for those sports requiring lateral force production (squash and tennis), the effect of lateral-type jumps needs to be investigated ¹¹. Dynamic correspondence fails to highlight how a general to specific continuum, involving both bilateral and unilateral strength training can still have a great effect on performance while maintaining the sports specific qualities needed to succeed in the athletic arena.

   Jumping, sprinting and changing direction are all general motor skills which need a variety of training methods to consistently overload and progress the athlete.

   Conclusion

   • It should be noted that the principle of specificity will vary greatly according to the training status, physical preparation levels, maturation status, and overall level of sport mastery of the athlete².
   • Athletes that are at a lower level of sports mastery may benefit from nearly any training modality and in turn could see positive transfer of training to commonly executed sport tasks; most likely caused by the neural adaptations occurring².
   • Transfer will take place much easier in lower level athletes due to their high sensitivity levels to physical activity. Their room for adaptation is much larger than their more advanced counterparts.
   • As an athlete progresses in sport and training mastery, training methods must take on a greater emphasis of sports specificity in order to result in the desired adaptation¹.
   • This does not just mean Olympic lifting, you can use different overload variations.

   Brett Richmond

   Suggestions for future research

   Effects of DC on different classifications of sport, not just rugby union such as:

   • Track and field: Discus throwing
   • Invasion: Soccer
   • Racquet: Tennis

   A need to develop a testing procedure which measures DC effect on off balance sports such as the single leg hop and hold. It can also be used as a functional assessment looking at ankle, knee, hip rotation and technical stability on a grading score line.

   • Coaches: Come to our 1 day Coaching Athletic Development Course to see how to put theory into practice.

    References

   1. Gamble, P. (2006). Implications and applications of training specificity for coaches and athletes. Strength & Conditioning Journal, 28(3), 54-58.
   2. Siff, M., & Verkhoshansky, Y. (Eds.). (2009). Supertraining (6th ed.). Rome: Verkhoshansky.
   3. Zatsiorsky, V., & Kraemer, W. (Eds.). (2006). Science and Practice of Strength Training (2^nd ed.). Champaign, IL: Human Kinetics.
   4. Bompa, T, O., & Haff, G, G. (Eds.). (2009). Periodization: Theory and Methodology of Training (5^th ed.). Leeds: Human Kinetics.
   5. Kurz, T. (2001). Science of Sports Training: How to Plan and Control Training for Peak Performance. Island Pond, VT: Stadion Publishing Co.
   6. Stone, M. H., O’Bryant, H. S., Mccoy, L., Coglianese, R. & Lehmkuhl, M. (2003). Power and maximum strength relationship during performance of dynamic and static weighted jump. Journal of Strength and Conditioning Research,17, 140-147.
   7. Hori, N., Newton, R., Nosaka, K., & Stone, M. (2005). Weightlifting exercises enhance athletic performance that requires high-load speed strength. Strength and Conditioning Journal, 27, 34-40.
   8. Tricoli, V. A., Lamas, L., Carnevale, R., et al. (2005). Short-term effects on lower-body functional power development: weightlifting vs vertical jump training programs. Journal of Strength & Conditioning Research, 19(2), 433-437.
   9. Kotzamanidis, C., Chatzopoulos, D., & Michailidis, C., et al. (2005). The effect of a combined high-intensity strength and speed training program on the running and jumping ability of soccer players. Journal of Strength & Conditioning Research, 19(2), 369-375.
   10.   Brughelli, M., Cronin, J., Levin, G., & Chaouachi, A. (2008). Understanding Change of Direction Ability in Sport. Sports Medicine, 38(12), 1045-1063.
   11. Blazevich, A. J., & Jenkins, D. G. (2002). Effect of the movement speed of resistance training on sprint and strength performance in concurrently training elite junior sprinters. Journal of Sport Science, 20, 981-990.

2. 10 things Sports Science has taught us in the last decade

   13th July 2011 9:06 am Leave a Comment

   “Accurate observations of human nature hold true no matter their age.”

   Tom Kurz (in his guest blog about coach observation).

   I am of the view that pseudoscience is only repeating what we already know or suspect. However, conscious that I may be a luddite, I asked Matt Brookland to come up with 10 things it has taught us in the last decade:

   Sports science or should I say the science behind physical exercise can trace its origins to ancient Greece, where the physician Galen (131–201) wrote 87 detailed essays about improving health (proper nutrition), aerobic fitness, and strengthening muscles.

   Although it has been around for hundreds if not thousands of years, it has really only taken off recently.

   With regards to the question, it is an interesting one and therefore I should define exactly what I mean by the following comments. It is the facts and interventions that have improved the performance of athletes, be it technological or performance that I am detailing below:

   1 Altitude training doesn’t work –
   Physical de-conditioning can occur and sometimes adaptations can take months to take effect. It is actually better to live at altitude and train at sea level.

   2 Practical application by professional organisations –
   Sports Science is not thought of as a fad, there are real facts to back up what is being said. People do not now just listen to their body; they listen to hard quantitative facts as well.

   3 You can now tell when a player is more likely to get injured –
   Jack Wilshere having played so many games during the 2010-2011 season that he could not attend the under 21 European championships.

   4 Dynamic stretching before an event instead of static stretching –
   It has been shown to reduce power output in some studies although static stretching should still be carried out to increase flexibility.

   5 Use of inertial sensors to determine human movement –
   Instead of using cameras or researchers to look and analyse movements, these sensors can give measurements from inside joints for example.

   6 Video/ computer analysis –
   To see exactly where players move during performance and the use of statistics of opponents that were not available before. This technology can track individual players throughout an entire match.

   7 Eye vision technology –
   Athletes can now see exactly where they are looking. Research has also shown that teaching someone where to look and knowing where to look during certain competitions can determine the difference between experts and novices, this is prevalent within golf putting.

   8 Gold standards for testing –
   British Association of Sport and Exercise Sciences (BASES) has determined certain tests and brackets for certain levels of performance.

   9 Kinesiology tape to stabilize muscles and joints –
   Although tape has been around for decades, this new technique of stabilizing and pain relief is quite new, with some high profile users being noticeable for its use.

   10 3D tracking of a ball during play –
   Very apt as Wimbledon is taking place, but having the ability track a ball once hit by either a racket or a bat has enabled us to know exactly where it would land or end up. Hawk eye is in constant use in both tennis and cricket.

   There are some very interesting facts detailed above, whereas others may just be slightly common sense. Over the last decade sports science has given us both technical and performance innovation.

   Improving equipment, analysis as well as understanding for coaches alike has created this. I do wonder what this fast paced industry sector will enable us to talk about in another ten years?

   I have included the references below and so you can do a little more in depth reading. Please feel free to comment.

   References

   1.   http://physiotherapy.curtin.edu.au/resources/educational- resources/exphys/00/altitude.cfm.
   2.  http://news.bbc.co.uk/sport1/hi/football/13653177.stm
   3. Yamaguchi, T., Ishii, K. Effects of static stretching for 30 seconds and dynamic stretching on leg extension power. J. Strength Cond. Res. Aug; 19(3):677-83. 2005 3
   4.  http://www.mdpi.com/1424-8220/10/12/11556/pdf
   5.  http://www.prozonesports.com/index.html
   6. http://thedanplan.com
   7.   http://www.bases.org.uk/About
   8.  http://www.hawkeyeinnovations.co.uk/

3. How training the Central Nervous System helps you become a better athlete

   16th March 2011 10:00 am 6 Comments

   The Sporting Brain: Understanding how the mind helps us play sport

   Top cricket batsmen have been reported to hit balls within a time window of 2 to 3 milliseconds, that’s the same speed as a house fly’s wing flap! The Central Nervous System is an essential part of this skill.

   Have you ever wondered how they do this? More simply if someone throws you a ball, you catch it. But have you ever wondered how seeing that ball results in our body moving to catch it? How does what we see (visual stimuli) result in movement?

   Our brain process all the information we receive via sounds, sight and touch, but how does this result in movement? All of these systems, including the visual system, are part of the central nervous system.

   The Central Nervous System (CNS)

   The CNS is the brain’s first branch of the nervous system and consists of two parts:

   1. The brain
   2. The spinal cord

   The CNS is connected to the peripheral nervous system (PNS). The PNS is then connected to

   • Sensory organs (e.g. eyes and ears)
   • Muscles
   • Blood vessels
   • Glands
   • Other organs

   When we see something (stimulus), our eyes (receptor organ) collect information which is then relayed, to the CNS. The CNS then interprets this information and sends it back to effector organs (i.e. muscles) which then carry out the body’s response to the original stimuli.

   For example a cricket fielder sees a high ball coming towards them and their body reacts to catch it.

   

   Playing sport affects how the CNS controls muscle recruitment and action.

   Research that tested vertical jump performance in swimmers, jumpers and football players found that, not surprisingly, jumpers had the most powerful jumps (Eloranta, V. 2003).

   However using information gained directly from the muscles, they attributed this to the CNS influencing the firing and recruitment patterns of the muscle. Jumpers had optimum firing and recruitment for maximal jumps, whereas swimmers muscle firing and recruitment was more suited to kicking and therefore resulted in a poorer vertical jump.

   Eloranta (2003) concluded that ‘prolonged training in a specific sport will cause the central nervous system to program muscle coordination according to the demands of that sport’.

   They also found that this learned reflex could interfere in the performance of another task.

   A New Theory!

   A recently proposed theory for processing ultra fast events suggests after information is relayed to the CNS there are in fact two streams of processing what we see.

   1)     The ventral stream, providing information for perception

   Involved in object recognition

   2)     The dorsal stream, resulting in action. 

   • Involved in spatial awareness
   • Involved in guidance of objects

   These two systems work independently from each other and at different speeds!

   Visual stimuli results in electrical signals being sent to LGN (a sensory relay nucleus in the brain) where they are sorted and sent back to the visual cortex.

   Any signals that result in gross motor movement go through the dorsal stream with more sophisticated signals heading down ventral stream.

   The ventral system is tailored for situations where the movement times are longer and there is adequate time for cognitive processing to occur. The dorsal system is specialised for tasks performed when movement times are shorted and therefore affected by time constraints.

   More simply the ventral stream is used when you have time to think about your actions (assessing the situation when deciding to go for a conversion or a try during a penalty in rugby) and the dorsal stream is more automatic (catching a falling plate or returning a ping pong ball).

   How They Were Discovered

   These two pathways were discovered by Goodale et al., (1991) when a woman who suffered carbon monoxide poisoning was tested for visual defects. She was unable to identify common objects yet seemed to still be able to use her motor system to control her hand movements.

   A round disc (picture below) with a slot in it was placed 45cm away from her and she was asked to draw the angle of the slot. She was then asked to post a piece of card through the slot.

   The results showed that when asked to draw the angle of the slot she failed (ventral stream), however when asked to post the card through the slot (dorsal stream) she could orientate the card at the right angle every time.

   

   This showed damage to one system without affecting the other system, highlighting the evidence of two separate systems.

   Perception vs. Action

   Although there seems to be striking evidence that there are two separate systems, there is still much debate over how segregated these two streams really are.

   Research has suggested they work closely together and are heavily interconnected (Farivar, 2009).

   Much support comes from visual illusions such as the Ebbinghaus illusion and Müller-Lyer illusion (Pictured below). These illusions may distort judgments of a perceptual nature (ventral stream), but when the subject responds with an action (dorsal stream), such as grasping or pointing, studies have found no distortion occurs.

     Figure 1: Ebbinghauillusion

   

   Figure 2: Müller-Lyer illusion

   

   When asked to draw the diameter of the circles or the length of the line participants drew the right hand circle diameter and the bottom line longer. However when asked to show the diameter or length using their finger and thumb there was little difference between the two images.

   Illusions like the ones above seem to affect the perceptual (ventral) system but not the action (dorsal) system. Participants perceived the circle and line to be distorted but when using an action to illustrate it they were not fooled!

   It is important to note however, some contradictory research finding that these illusions can fool both the ventral and dorsal systems equally (Franz et al., 2000; Franz, Scharnowski, Gegenfurtner, 2005; Franze, Hesse & Kollath, 2008).

   How does the Central Nervous System relate to sport?

   We know that the dorsal system is used to visually guide movement execution. For instance, it controls the execution of a tennis stroke such that the ball will be hit at the right place, at the right time, with the right amount of force.

   The ventral system is involved in the perception of objects, events and places. As the ventral system obtains knowledge about what the environment offers for action, it can also contribute to action.

   It may, for instance, gather information whether a down-the-line or cross-court shot would be the most appropriate action (van der Kamp et al., 2008).

   It is important to be able to enhance both of these systems, not just one.

   ‘In most sports it is important to react quickly and decisively whilst also being able to evaluate what is going on and take in your surroundings’ (Morris, S, 2009). It is also important that these two systems don’t interfere with each other.

   When these two streams are working together in harmony, they make it possible for you to rapidly respond using the action process whilst simultaneously taking in the bigger picture with the perceptual process.

   The perceptual stream is conscious, and allows you to strategise and plan ahead while the action stream takes care of itself.

   

   Hockey skill under pressure

   For example a footballer or hockey player, whose two systems are enhanced and working together, can plan where there next pass or shot is going whilst receiving and dribbling the ball.

   Training these Systems

   You need to challenge both processes in a competition specific environment to develop and enhance them. Working both streams during training will help you to improve.

   Things as simple as listening to music or having a conversation about something irrelevant to training whilst practising specific skills, will work both systems.

   The aim is to be able to perform specific skills (i.e. throwing, catching, punching, and kicking) in a competition environment, using the dorsal (action) system, whilst using your ventral system to process other information.

   Therefore during a game or a competition you can perform these skills whilst assessing the environment and opposition.

   Conclusion

   • The CNS is the control centre for all information we need to process resulting in movement.
   • It is now believed that there are two systems that process visual information, the action (dorsal) and perception (ventral) systems.
   • It is important to train both of these systems in order to enhance them and improve sporting performance.

   A skilled athlete who can use these two systems effectively will be hard to beat!

   Skill development and rehearsal form an Integral part of our Training Programmes

   Information for Sports Coaches

   The skill development is one reason why we have restructured our strength and conditioning coaches and named them Athletic Development Coach

   Too much “S&C” work is gym based and lacks skill. We are only interested in what works on the pitch and court.

   References

   Eloranta, V. (2003). Influence of sports background on leg muscle co-ordination in vertical jumps. Electromyography Clinical Neurophysiology. 43(3):141-56

   Farivar R. (2009). Dorsal-ventral integration in object recognition.. Brain Res Rev. 61 (2): 144-53

   Franz, V. H., Gegenfurtner, K. R., Bülthoff, H. H., & Fahle, M. (2000). Grasping visual illusions: no evidence for a dissociation between perception and action.. Psychol Sci. 11 (1): 20–5.

   Franz, V. H., Hesse, C., & Kolath, S. (2008). Visual illusions, delayed grasping, and memory: No shift from dorsal to ventral control. Neuropsychologia, 47:6, 1518-1531.

   Franz, V. H., Scharnowski, F. & Gegenfurtner, K. R. (2005). Illusion effects on grasping are temporally constant not dynamic.. J Exp Psychol Hum Percept Perform. 31 (6): 1359–78.

   Goodale, M. A.,Milner, D., Jakobson, L. S., & Carey, D. P. (1991). A neurological dissociation between perceiving objects and grasping them. Nature. Vol 349.