Reliability of phase-specific outcome measurements in change of direction tests using a motorized resistance device

Abstract

The aim of this study was to determine reliability of phase specific information during the initial acceleration to deceleration (phase 1a) and re-acceleration phase (phase 1b), of different change of direction (CoD) tests using a motorized resistance device (MRD). A total of 21 participants (16 males and 5 females and (age 22.3 ± 3.9 years, body mass 75.2 ± 6.9 kg, height 177.9 ± 6.8 cm) completed the modified 505 (m505), 10-0-5 (105) and 15-0-5 (155) test on four different test sessions while exposed to an external load (3 kg) provided by the MRD. Outcome variables included overall and phase specific time as well as average and peak velocity of phase 1a and 1b. Then, the deceleration part of phase 1a was identified (from max velocity to velocity changed direction), which in turn was divided into early (max velocity to 50% reduction of max velocity) and late deceleration (from 50% reduction of max velocity to velocity changed direction). Also, the same approach was used for the re-acceleration phase with early re-acceleration (from velocity changed direction to 50% of max velocity) and late re-acceleration (from 50% of max velocity to max velocity). For both early and late deceleration and reacceleration peak and average deceleration/acceleration, horizontal force, impulse, and power where measured or calculated. Reliability was assessed using intraclass correlation coefficient (ICC), coefficient of variation (CV), typical error (TE) and minimal detectable change (MDC). Mainly good to excellent ICC values (> 0.75), and acceptable (< 10%) to good (< 5%) CV values were observed for all outcome measurements. Specifically, 80.1 % (822 out of 1026) of all variables showed good or better relative reliability, while 96.98 % (995 out of 1026) of all variables showed acceptable or better absolute reliability. In conclusion, the present study shows that the MRD can obtain mainly reliable phase specific outcome measurements of different CoD tests, which provides coaches and researchers with new opportunities to advance our understanding CoD ability.