Why is the Dynamic Strength Index important?
The DSI provides the strength and conditioning coach with valuable information regarding how forceful (i.e. strong) the athlete is, and how much of that strength they can use during fast movements. This information allows the coach to design a more specific training programme focussed on developing an athlete’s strength and/or power capacities (6).
The Importance of Maximal Strength
High muscular strength is considered a vital element of athletic performance. Greater muscular strength has been shown to enhance the ability to perform general sports skills such as jumping, sprinting, and change of direction tasks, improve overall performance, allow athletes to potentiate earlier and to a greater extent, and even reduce the risk of injury (8). To add to this, maximal strength is strongly related to power output (r = 0.77-0.94 ) for both the lower- (10-13) and upper-body (10, 14-17). Therefore an athlete’s ability to produce power is largely dependent on their maximal force capacity (i.e. strength) (18-20). As a result, the “first box to be checked” so to speak when performing a strength diagnosis, is perhaps an athlete’s maximal strength.
The importance of being able to produce high-force in a short timeframe
Kawamori et al., (7) observed that it took approximately 260-ms to achieve peak force during the IMTP and 400-ms during the CMJ. Other research has shown time to peak force during the CMJ to take approximately 240-ms (21). So whilst the time to achieve peak force during the IMTP (260-ms) can be somewhat similar to the CMJ (240-400-ms), it is in fact how ‘much’ force is developed which separates the two exercises. Table 1 provides a clear example of how the peak force differs between the IMTP and the CMJ. Thus, the important factor is to determine how much force an athlete can produce under no time constraints (e.g. IMTP) versus how much force they can produce under short time constraints (e.g. CMJ).