Reliability of Accelerometer Based Performance Measurements during Countermovement Vertical Jumps and the Influence of Sampling Frequency
The assessment of vertical jump performance is widely undertaken by coaches and sports scientists because of its strong relationship with sports performances including those in weightlifting, sprinting, and cycling. With the development of accelerometer based testing devices the traditional vertical jump field test may offer a more detailed evaluation of an athlete's performance capacity. However, little data are available on the reliability of this technology and the impact of sampling frequency on reliability. PURPOSE: To determine the reliability of accelerometer based performance measurements during countermovement vertical jumps and the influence of sampling frequency on reliability. METHODS: Ten college aged men (age = 23.6 ± 3.1 y; height = 180.1 ± 6.3 cm; mass = 85.0 ± 15.2kg; body fat = 14.2 ± 6.5%) performed two series of five restricted (no arm swing) zero load countermovement vertical jumps. During each jump a triaxial accelerometer that sampled at 500 Hz was used to assess acceleration, from which peak force (PF), rate of force development (RFD), peak power output (PP), peak velocity (PV), flight time (FT), and peak vertical displacement (VD) were derived and analyzed using a custom LabView Program. This program was used to re-sample the data collected at 500 Hz to 250Hz, 125 Hz and 50 Hz, which were then analyzed. The reliability of the accelerometer system was assessed with the use of intraclass correlations, while precision was determined with the use of the coefficient of variation (CV), and criterion validity was assessed via Pearsons correlation. RESULTS: At 500 Hz the accelerometer was reliable for PF (ICC = 0.94), RFD (ICC = 0.92), PP (ICC = 0.87), FT (ICC = 0.93), and VD (ICC = 0.93). Additionally, reliability was maintained at 250Hz for PF(0.95), RFD(0.92), PP(ICC = 0.86), FT(ICC = 0.93) and VD(ICC = 0.92). Good precision was determined for PF (CV = 7.3%), PV (CV = 7.6%), FT (CV = 2.3%), and VD(CV = 4.7%) at 500 Hz. Additionally precision was maintained at 250Hz for PF (CV = 6.8%), PV (CV = 7.7%), FT (CV = 2.4%), and VD(CV = 4.9%). Finally, criterion validity was high for PF(r = 0.96), RFD(r = 0.97), PP(r = 0.99), PV(r = 0.99), FT(r = 0.99) and VD(r = 0.99) when comparing the 250Hz data to the 500 Hz data. When sampling frequency was decreased below 250Hz reliability, precision and criterion validity all decreased. CONCLUSIONS: The accelerometer used in this investigation produced reliable, precise and valid for assessments of PF, PP, FT, and VD data at sampling frequencies ≥250Hz. PRACTICAL APPLICATIONS: For vertical jump applications it appears that accelerometers must have a minimum sampling frequency of 250Hz in order to maintain reliability, precision and validity. Therefore when assessing athlete performance, it is essential that the strength and conditioning professional consider sampling rate when utilizing this technology. ACKNOWLEDGMENTS: This investigation was partially supported by MyoTest Inc., which donated the accelerometer system used in this investigation.
Haff, G. Gregory; Ruben, R.; Saffel, H.; McCory, J.; Cormie, P.; Sands, William A.; and Stone, Michael H.. 2010. Reliability of Accelerometer Based Performance Measurements during Countermovement Vertical Jumps and the Influence of Sampling Frequency. NSCA, Orlando, FL.