Test-Retest Reliability of the Digijump Machine

Repetitive jumping has been identified as a possible exercise modality able to provide sufficient stimulus to improve bone health. However, it is necessary to establish whether repetitive jumping can elicit a consistent physiological response with the ablity to monitor work rate. The purpose of this investigation was to determine the stability reliability of the Digijump device for the commonly used laboratory measures of oxygen uptake (VO2), heart rate (HR), and rate of perceived exertion (RPE). College-aged individuals (N = 17) completed two 3-min repetitive jumping bouts on the Digijump machine (120 jumps per minute, jump height = 1.27 cm) at least seven days apart. Stability reliability was calculated using the intraclass correlation coefficient derived from 1-way ANOVA. Absolute VO2 displayed the highest test-retest reliability (0.95), while the coefficient for relative VO2 was also acceptable (0.71). The test-retest reliability coefficients for HR (0.89), and RPE (0.75) were determined to be within acceptable limits. Coefficients for all variables compared well with the stability reliability reported for other ergometers such as the Stairmaster, treadmill, and cycle. This data represent an important step in determining the validity of the Digijump machine for physiological testing.