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Dynamic Strength Index - When to switch between strength and power training?

When injured athletes go through rehabilitation, the recovery journey (figure 1.) usually goes from pain reduction to core activation, re-learning motor control or movement pattern then eventually returning back to play through the strength and conditioning program. However, it is often not clear on the part when one should move from strength to power training, implementing the element of time and explosive intent in their workout. This is where Dynamic Strength Index (DSI) comes in.

A table showing the rehab journey from pain reduction to muscle activation to better movement, then training for strength and sports performance

In professional sports, profiling and monitoring adaptation and fatigue in athletes are of utmost importance. This monitoring allows the strength and conditioning coach and the physiotherapist to make decisions on game time, resting period, deload week and even dosages for the exercise program.

Dynamic Strength Index (DSI) is one of those indicators to help determine where the athlete is sitting along the force-velocity continuum (figure 2.). All athletes sit somewhere along the force-velocity continuum and they can shift along the curve based on their specific training.


A graph showing the force-velocity continuum with force on the vertical axis and velocity on the horizontal axis.

DSI is essentially a ratio and comparison between absolute concentric/ eccentric force and isometric force.


Common tests used are counter-movement jump (CMJ figure 3.) which is able to demonstrate functional peak power and landing force in terms of stretch-shortening cycle (between concentric and eccentric phase), and isometric mid-thigh pull (IMTP figure 4.) which demonstrates peak vertical force and rate of force development (how quickly the athlete can generate such force). DSI calculation is not limited to these two tests as long as the alternative tests involve ballistic and isometric components.


A person demonstrating the counter movement jump and the isometric mid thigh pull on VALD Forcedecks

Why DSI?


DSI provides us with important information such as:

  1. Determining the maximal amount of force an athlete can produce

  2. How much total force they can produce ballistically

A table showing various dynamic strength index and training recommendations

To further our understanding of DSI score, when athletes have a high DSI score i.e. >0.80 they may benefit from additional maximal strength training since they are close to producing their maximal isometric force during the jump. In comparison to athletes with lower DSI score, they will gain more value from additional ballistic training since they are only capable of producing 60% of their maximal isometric force during a dynamic movement such as a jump.


Example

A table showing VALD forcedeck results from the counter movement jump and isometric mid thigh pull tests.

Above is an example athlete who scored 0.90 on DSI with a CMJ Peak Force of 2094N and IMTP Peak Force of 2339N. Based on this athlete’s performance measure, this suggests that the athlete can effectively utilise dynamic force capacity relative to maximal force capacity. Thus, you would recommend the program should be more tailored to maximal strength training and incorporate strength-focused exercises such as trap bar deadlift, back squat, etc.


DSI is a vital tool to allow coaches and physiotherapists to determine when to implement strength or plyometric blocks into their training program. If you have been training as an athlete or even just a casual gym goer and would like to know where you sit in the force-velocity continuum and find out our training recommendations, feel free to book a consult with us as we will be able to assist you with profiling and monitoring through our VALD Forcedecks.




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