Reliability of the reactive strength index, eccentric utilisation ratio, and pre-stretch augmentation in untrained, novice jumpers
Australian Strength and Conditioning Association
Faculty of Health, Engineering and Science
School of Exercise and Health Sciences / Centre for Exercise and Sports Science Research
Measures of readiness are often used as monitoring tools for athletes. Many of these measures aim to describe the status of the stretch-shortening cycle (SSC) to determine an athlete’s potential for explosive performance by using squat jump (SJ) and counter-movement jump (CMJ) variables. Greater jump heights observed during the CMJ, compared to the SJ, may be attributed to the ability to utilise the SSC. From SJ and CMJ tests, researchers have attempted to quantify the status, or readiness, of the SSC using different equations. Examples of these calculations include the reactive strength index (RSI), eccentric utilisation ratio (EUR), and the percentage of pre-stretch augmentation (PSA). The RSI is calculated by subtracting the SJ height from the CMJ height, which is considered to be a measure of the ability to utilise the SSC during the CMJ . The EUR is calculated by dividing the CMJ height by the SJ height, which is considered to be an indicator of SSC performance [2, 3]. The PSA is calculated by subtracting the SJ height from the CMJ height, dividing by SJH, then multiplying by 100, which is considered to be a measure of the ability to utilise the pre-stretch of the muscles during a CMJ [3-5]. The RSI, EUR, and PSA have all been used in trained populations [1, 3, 5], but have not been fully investigated in untrained individuals. Due to the novelty of specific jump instructions and techniques, describing the status of the SSC using the EUR, RSI, and PSA may not be warranted in untrained individuals. Therefore, the purpose of this study was to determine the reliability of the EUR, RSI, and PSA in untrained individuals.