Changes in eccentric utilization ratio, reactive strength index and leg stiffness in highly trained sprinters between training phases

Changes in jump parameters in sprinters

Abstract

Purpose: To determine changes in eccentric utilization ratio (EUR), reactive strength index (RSI), squat jump (SJ) and
countermovement jump (CMJ) parameters in elite sprinters from the preparation phase to the competition (indoor) phase.
Methods: Ten elite-level sprinters (n=10) were examined. All sprinters performed the SJ, CMJ and 10/5 rebound jump (RJ) tests.
Body composition analysis was assessed using dual X-ray absorptiometry (DXA) method. A paired t-test was performed to determine
statistical significance.
Results: SJ height and relative peak power increased significantly from 43.10 ± 6.1 cm to 46.30 ± 5.7 cm (P= .013, Cohen’s d=
.98) and from 52.62 ± 4.5 W·kg BM-1 to 55.55 ± 4.5 W·kg BM-1 (P= .017, d= .92) respectively. CMJ height and relative peak power
increased significantly from 46.78 ± 6.1 cm to 49.18 ± 5.5 cm (P= .039, d= .76) and from 55.53 ± 4.1 W·kg BM-1 to 57.92 ± 4.0
W·kg BM-1 (P= .024, d= .86) respectively. No significant differences were observed in RJ performance parameters.
Conclusions: SJ and CMJ height, flight time and peak power output per body mass increased in elite sprinters from the preparation
to the competition phase while RSI, EUR and leg stiffness (LS) values did not. SJ and CMJ performance can be used as markers
of training phase changes in elite sprinters. EUR should be used cautiously to determine training status in elite sprinters since
sprint training encompasses reactive strength training all year round. Reactive strength levels via RSI and stiffness levels should
be assessed individually in each training phase to determine whether the measured value of these parameters is satisfactory to
optimize competition readiness. LS levels should not be compared to general guidelines but rather individually to the athletes’ sprint
performance and then training should be adjusted accordingly.