The Influence of Countermovement Jump Protocol on Reactive Strength Index Modified and Flight Time: Contraction Time in Collegiate Basketball Players.

Aaron Heishman,Ryan Miller,Michael Bemben,Bryce Daub,Brady Brown,Eduardo Freitas

doi:10.3390/sports7020037

Abstract

The purpose of the present investigation was to evaluate differences in Reactive Strength Index Modified (RSIMod) and Flight Time to Contraction Time Ratio (FT:CT) during the countermovement jump (CMJ) performed without the arm swing (CMJNAS) compared to the CMJ with the arm swing (CMJAS), while exploring the relationship within each variable between jump protocols. A secondary purpose sought to explore the relationship between RSIMod and FT:CT during both jump protocols. Twenty-two collegiate basketball players performed both three CMJNAS and three CMJAS on a force plate, during two separate testing sessions. RSIMod was calculated by the flight-time (RSIModFT) and impulse-momentum methods (RSIModIMP). CMJ variables were significantly greater during the CMJAS compared to CMJNAS (p < 0.001). There were large to very large correlations within each variable between the CMJAS and CMJNAS. There were significant positive correlations among RSIModFT, RSIModIMP, and FT:CT during both the CMJAS (r ≥ 0.864, p < 0.001) and CMJNAS (r ≥ 0.960, p < 0.001). These findings identify an increase in RSIMod or FT:CT during the CMJAS, that may provide independent information from the CMJNAS. In addition, either RSIMod or FT:CT may be utilized to monitor changes in performance, but simultaneous inclusion may be unnecessary.

Highlights

The countermovement jump (CMJ) is routinely used by both practitioners and researchers to monitor acute and long-term changes in athlete performance
The CMJ involves the dynamic muscle action known as the stretch-shortening cycle (SSC), which is a key component in many sporting events [2]
Reactive Strength Index Modified (RSIMod) FT was calculated as jump height, determine by the conventional flight-time method (Jump HeightFT = 1/2 g(t/2)2, where g = gravitational acceleration and ft = flight time) divided by contraction time

Summary

Introduction

The countermovement jump (CMJ) is routinely used by both practitioners and researchers to monitor acute and long-term changes in athlete performance. The arm swing appears to positively influence performance during the CMJ, such as increasing jump height and velocity at take-off, when compared to the CMJ NAS [16,17,18,19]. These noted increases in performance may allude to an athlete’s absolute maximal capacities, which could provide pertinent information during an athlete’s needs analysis useful in directing a training program. The primary purpose of the present investigation was to evaluate differences in RSIMod FT , RSIMod IMP , and FT:CT during the CMJ NAS compared to the CMJ AS, while exploring the relationship within each variable between jump protocols. It was hypothesized RSIMod FT , RSIMod IMP , and FT:CT would demonstrate strong positive correlations during both CMJ NAS and CMJ AS, while the relationship between RSIMod FT and RSIMod IMP would produce enhanced limits of agreement during the CMJ NAS compared to the CMJ AS

Subjects

Procedures

Data Analysis

Statistical Analysis

Results

Bland-Altman Plot comparing