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Transfer of Energy
The ability to maximize transfer of energy in sport is typically what sets the elite athletes apart from the rest. Not only does it allow them to jump higher, run faster, and move more efficiently, it also allows them to save valuable energy so that they are not burnt out at the end of the game. In the long run, efficient transfer of energy may also prevent the risk of injury. It is well established that fatigue masks fitness, and injuries typically present themselves at the end of the game when the athletes are in a high state of fatigue. If transfer of energy is optimized, that athlete might never reach that level of fatigue that puts them at a risk for injury.
What are the two assessments?
The two assessments that can be used to assess energy and power transfer in jumping are the Eccentric Utilization Ratio (EUR) and Stretch-Shortening Cycle % difference (SSC%). Both assessments help find deficiencies in jumping performance and can help practitioners create a more “optimal” jumping profile going into competition (i.e. when all of your training matters most).
Eccentric Utilization Ratio (EUR)
EUR takes an average of 3 countermovement jumps (CMJ) and 3 squat jumps (SJ). This ratio can then be used to assess the transfer of energy and power in your athletes by simply dividing CMJ by SJ.
If you are unsure of what a CMJ and SJ are, the SJ begins at a depth around 90 degrees knee flexion (varies on the athlete’s preferred jumping depth). It does not use a “countermovement”, rather a static pause is held for 3 seconds at the bottom before thrusting vertically. On the contrary, CMJ uses a “countermovement” and typically yields a higher value than the SJ because of the usage of the SCC. However, this is not always the case. Best practice of both jumps is completed “akimbo”, or hands on hips.
EUR = CMJ/SJ
Stretch-Shortening Cycle % Difference (SSC%)
The stretch-shortening cycle (SCC) forms the foundation of all dynamic movement. It is composed of three muscle action, an eccentric, isometric, and concentric phase (i.e. Triphasic).
SSC% aims to quantify the efficiency of the SCC. This assessment takes the percent difference between the CMJ and SJ. Research suggests that a 10% difference (CMJ higher) is “optimal” for performance. This is especially true in sports that require effective use of the SSC (i.e. vertical jumping sports). In “Isometrics for Performance”, Matt Van Dyke expresses that he uses this 10% difference in his athletes. The guidelines are shown below:
SSC% = (CMJ-SJ) / SJ
10% difference → “optimal” difference, the athlete is in a good place to begin the season
<10% difference → plyometric/reactive/explosive training emphasis
>10% difference → strength training emphasis
Making sense of the guidelines
(<10% athlete) “Force abilities of a truck, springs of a Prius.”
This athlete bleeds power. They are relatively strong but have weak tendons. The primary focus should be on developing proper usage of the SCC, this can be accomplished by incorporating more plyometric/reactive work than strength training. This ratio may vary greatly, however a 2:1 plyometric to strength can be used. Coaching cues should be used such as stiff ankles, popping of the ground, and low ground contact time. Examples of exercises that can be used are pogo jumps, drop jumps, continuous hurdle jumps, and continuous bounding. Progression should move on a continuum from extensive to intensive in nature.
(>10% athlete) “Force abilities of a Prius, springs of a monster truck.”
This type of athlete may be leaving a huge amount of energy on the table. This is your “springy” athlete, probably very long and lengthy. As the case for many athletes, this athlete will benefit greatly by incorporating true strength work. These exercises should include low rep sets with adequate rest between each. Maximal force should also be applied into each rep, ensuring high quality work is completed.
(10% athlete) “Force abilities of a monster truck, springs of a monster truck.”
This is the “optimal” athlete. The springs (tendons) match the capabilities of the engine (force). This athlete is in good shape for the season. They have a good transfer of energy and power efficiency. However, one should consider that just because the athlete is “optimal”, both the springs (tendons) and the engine (force) can be built to a higher level. The off-season should be the time you build your athletes base.
What sports are these assessments useful for?
These two assessments can ultimately be used in any sport but might be more beneficial for sports that involve some type of vertical jumping component (i.e. basketball, volleyball) because power is specific to the plane of movement used.
How often should I test?
These two assessments are not tests that need to be tracked every single day. It would be a good idea to use these assessments at the beginning of an off-season training plan, and then again at the end of each training phase to objectively see how your athletes are adapting to the training.
There may be points in time of your annual training plan that you know power is not the primary objective, and strength work is the goal. In this case, you may have many athletes on your team that produce a SCC% of 2-3%. Looking back at the guidelines, this would tell you that plyometric/reactive work should be emphasized in training. However, this is not a red flag to say you should incorporate 500 depth jumps a week into your athletes training plan. Rather you should consider where you are at in the annual training plan, and what quality you are looking to gain at that specific time point.
For someone that is doing a Westside program, it may be a good idea to keep that SCC% around 10% the entire program. This can ensure that you are not overkilling one quality over the other (i.e. max strength is going way up, and power work is not keeping up). The closer you can keep this value to 10% all while increasing max strength and vertical jump height (i.e. power), the better prepared your athlete will be.
Again, these are all just considerations and it is ultimately up to the coach to decide the parameters as to when they want their athletes to be peaking for competition.
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