PRACTICAL APPLICATIONS: The portable force plates provide a reliable and economical method of obtaining accurate measures of jump height. It is therefore suggested that practitioners interested in measuring and monitoring jump height calculated from center of mass takeoff velocity, but do not have access to laboratory standard force plates, can use the relatively inexpensive portable force plates interchangeably.
REFERENCES 1. Reeve, TC & Tyler, CJ. The validity of the Smartjump contact mat. J Strength Cond Res 27(6): 1597-1601, 2013.
METHODS (cont.) Reliability was assessed from 10 returning subjects. Before assessing reliability and validity, normality, uniform distribution and linearity were checked. Ordinary least-products regression was used to assess fixed and proportional bias between data from the two testing sessions and the portable and laboratory force plates. If the 95% confidence interval for the intercept did not include 0, then fixed bias was present. If the 95% confidence interval for the slope did not include 1.0, then proportional bias was present.
The mean and standard deviation of the differences between the data from the two testing sessions and the portable and laboratory force plates and the 95% Limits of Agreement (LOA: mean of the differences ± 1.96 s) were calculated. Practically unacceptable LOA were determined a priori as greater than 0.05 m. RESULTS Mean Kistler jump height was 0.33 ± 0.06 m and 0.33 ± 0.06 m for days one and two, respectively. Similarly, mean Pasco jump height was 0.33 ± 0.07 m and 0.33 ± 0.06 m for days one and two, respectively.
These were not significantly different, showed no fixed or proportional bias, and LOA results were practically acceptable. The results of the validity analysis revealed the presence of proportional and fixed bias. However, validity limits of agreement were practically acceptable.
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