USEFULNESS OF REACTIVE STRENGTH. INDEX DERIVED FROM THE TEN TO. FIVE REPEATED JUMP TEST. 1Biomechanics Research Unit, University of ...
INTERDAY RELIABILITY AND USEFULNESS OF REACTIVE STRENGTH INDEX DERIVED FROM THE TEN TO FIVE REPEATED JUMP TEST. Thomas Comyns1,Eamonn P. Flanagan2, Damian Harper3, Sean Fleming1, & Evan Fitzgerald1 1Biomechanics
Research Unit, University of Limerick, Limerick, Ireland. 2Sport Ireland Institute, National Sports Campus, Dublin 15, Ireland. 3School of Sport, York St John University, York, UK. Ireland
Introduction • Reactive strength index (RSI) = ability to change quickly from an eccentric to concentric contraction (Young, 1995). Height Jumped (m)
RSI = Contact time (s)
• Numerous tests to assess RSI, including 10/5 RJT. • Purpose: Assess the interday reliability and usefulness of this 10/5 RJT.
Methods • 15 female participants from field-based sports (mean age: 21.1 ± 0.9 years; stature: 1.65 ± 0.73 m; body mass: 62.0 ± 5.1 kg). S1
• Familiarisation of the 10/5 RJT technique. Players told to minimise ground contact time and maximise jump height
S2
• Testing session 1: 2 x 10/5 RJT trials with 60 s rest were completed and RSI derived via OptojumpTM (Microgate, Italy)
S3
• Testing session 2: 48 hours later players performed 2 x 10/5 RJT trials with 60 s rest. Data collected via OptojumpTM
• RSI calculated for each trial and best was used for interday reliability (ICC, CV%) and usefulness analysis (TE compared to SWC).
Results ICC
CV%
TE (m.s)
SWC (m.s)
Rating
0.91
7.3%
0.14
0.09
marginal
• Acceptable reliability was determined at an ICC ≥ 0.8 and a CV ≤ 10% (Hopkins, 2000) • 10/5 RJT demonstrated good interday reliability. • According to criteria from Hopkins (2004) usefulness of the test to detect meaningful change was rated as ‘marginal’ (TE ˃ SWC).
Implications 1. 10/5 RJT can be considered a reliable test to derive RSI for a female field-based sporting population. 2. Test may be limited in detecting the smallest meaningful change for RSI.
References • Hopkins, W.G. (2000) Measures of reliability in sports medicine and science. Sports Medicine, 30(1),1-15. • Hopkins, W.G. (2004). How to interpret changes in an athletic performance test. Sportscience, 8(1),1-7. • Young, W (1995). Laboratory strength assessment of athletes. New Studies in Athletics, 10, 88–96.
