What Do the Different Tests Tell us?
The CMJ is used to measure lower-body vertical power (Nuzzo 2008; Petrigna 2019). Athletes go from an eccentric downwards movement to a concentric vertical jump as quickly as possible, using the slow stretch-shortening cycle (SSC). The slow SSC has been defined as having a duration which is >0.25s (Schmidtbleicher 1992).
The SJ is also used to measure vertical lower-body vertical power (Nuzzo 2008; Petrigna 2019). Athletes start in a static, self-selected quarter position which is held for 3 seconds, with no further downward dipping allowed before jumping. This ensures any elastic energy is dissipated and eliminates the SSC effect on the vertical jump (Petrigna 2019), so we can measure an athlete’s lower-body vertical power as a concentric movement only, from a static position, with no SSC involved.
Eccentric Utilization Ratio
The EUR is simply the ratio between CMJ and SJ performance and provides insight into an athlete’s slow SSC ability. It has been suggested that an ideal EUR is ~1.1, in which the CMJ score should be 1.1x (10%) that of the SJ (McGuigan 2006). For example, if an athlete scores 45 cm on the CMJ and 39 cm on the SJ, they have a EUR of 1.15 (45 divided by 39).
This suggests that the athlete has an effective slow SSC in comparison to their lower-body vertical power from a static position. As such, power training which consists of no SSC, ballistic exercises, loaded plyometrics and maximum strength work would likely benefit this athlete. Ballistic exercises are defined as the explosive release of the body into the air, but the overall duration of the exercise is longer mainly due to an extended ground contact time, such as an SJ (Chandler 2018).
Incremental Drop Jump Test
The incremental DJ test measures reactive power, through the fast SSC. This has been defined through a ground contact time of <0.25 s (Flanagan 2007), which also defines the threshold for fast plyometric exercises Schmidtbleicher (1992). The scores from this test enable S&C coaches to calculate reactive strength index (RSI), which is an estimate of an athlete's ability to rapidly go from an eccentric muscular contraction to a concentric muscular contraction (Flanagan 2008).
According to Flanagan, the RSI can be used to decide which intensity of plyometric training is most appropriate depending on an athlete’s level. An RSI score of 2.0 – 2.5 suggests athletes are ready to perform high-intensity plyometrics (e.g. drop jumps), whereas a score of 1.5 – 2.0 makes moderate-intensity plyometrics (e.g. tuck jumps) and an athlete that scores <1.5 should perform the low intensity or extensive plyometrics (e.g. extensive pogo jumps).
From here on out, plyometrics refers to exercises which are characterized by a fast SSC activity, which a ‘shock’ component, where a GCT occurs with the floor that is < 0.25s (1992).
Force-velocity profiling provides a more detailed picture of an athlete’s specific strength and speed needs, through using a movement such as a Barbell Jump Squat with incremental loads (Jimenez-Reyes 2014). The equation used in the FVP has been validated for estimating an athlete´s different strength capacities and has high reliability (Samozino 2008).
By running an FVP-test, S&C Coaches can measure and plot an athlete’s force and velocity across the incremental loads and compare them to ideal and values, described as the force-velocity imbalance (Jimenez-Reyes 2014). This test can be conducted with a validated smartphone application that collects reliable FVP data for a low cost (Balsalobre-Fernandez 2015). Based on the acquired FVP, the S&C coach can see where the biggest potential for adaptation lies, across the athlete´s force-velocity curve (FV-curve).
In Figures 1 and 2 an athlete´s optimal force and velocity values (optimal profile) are presented in red, while the actual force and velocity values (actual profile) are presented in green. Figure 1 – This athlete requires training orientated towards force production (i.e. maximal strength and strength-speed).
This is based on where the deficiency is the biggest, between the optimal and actual values (i.e. biggest gap between the red and green line). Figure 2 – This athlete requires training orientated towards velocity (i.e. speed-strength and plyometrics). This is because the deficiency is biggest between the optimal and actual values (i.e. the biggest gap between the red and green line) at high velocity, low force.