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Dynamic Strength Index

The Dynamic Strength Index (DSI) is the ratio of ballistic peak force to isometric peak force. In other words, the DSI measures the difference between an athlete's ability to produce force during a dynamic or isometric test, versus their ability to produce force during a ballistic exercise.

purpose: to get a measure of the explosive strength potential of athletes, and to use this information to design appropriate strength training programs.

equipment required: weight training equipment, force plate and/or strength dynamometer.

pre-test: Explain the test procedures to the subject. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender and test conditions. Calibrate, test and adjust the equipment if necessary. See more details of pre-test procedures.

procedure: any two measures of peak from a ballistic and isometric exercise can be used to determine the index, though commonly a counter-movement jump or squat jump (ballistic test) and an isometric mid-thigh pull (isometric test) is used to calculate an athlete's DSI. Another exercise combination that has been used is the Ballistic Bench Throw and Isometric Bench Press exercises.

scoring: the DSI is the ratio - ballistic peak force / isometric peak force. A low DSI (<0.6) indicates the athlete should work on ballistic exercises, and high DSI (>0.8) indicates the athlete should concentrate of maximal strength training.

interpretation: The DSI allows the strength and conditioning coach to identify the athlete's "strength potential" - how much of their peak isometric peak force they use during a high-speed ballistic movement.

variations: an alternative measure is the delta dynamic strength index (ΔDSI), which reduces the maximum force measures by the bodyweight of the athlete.

advantages: creates a single index that is easy to interpret and can be used for exercise prescription.

disadvantages: requires the equipment necessary to measure peak forces during exercise.

comments: the DIS is also has been known as Dynamic Strength Deficit or the Explosive Strength Deficit.

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