Reliability, Validity and Usefulness of 30-15 Intermittent Fitness Test in Female Soccer Players

Abstract

PURPOSE: The aim of this study was to examine the reliability, validity and usefulness of the 30-15_IFT in competitive female soccer players. METHODS: Seventeen elite female soccer players participated in the study. A within subject test-retest study design was utilized to assess the reliability of the 30-15 intermittent fitness test (IFT). Seven days prior to 30-15_IFT, subjects performed a continuous aerobic running test (CT) under laboratory conditions to assess the criterion validity of the 30-15_IFT. End running velocity (V_CT and V_IFT), peak heart rate (HRpeak) and maximal oxygen consumption (VO_2max) were collected and/or estimated for both tests. RESULTS: V_IFT (ICC = 0.91; CV = 1.8%), HRpeak (ICC = 0.94; CV = 1.2%), and VO_2max (ICC = 0.94; CV = 1.6%) obtained from the 30-15_IFT were all deemed highly reliable (p > 0.05). Pearson product moment correlations between the CT and 30-15_IFT for VO_2max, HRpeak and end running velocity were large (r = 0.67, p = 0.013), very large (r = 0.77, p = 0.02) and large (r = 0.57, p = 0.042), respectively. CONCLUSION: Current findings suggest that the 30-15_IFT is a valid and reliable intermittent aerobic fitness test of elite female soccer players. The findings have also provided practitioners with evidence to support the accurate detection of meaningful individual changes in V_IFT of 0.5 km/h (1 stage) and HRpeak of 2 bpm. This information may assist coaches in monitoring "real" aerobic fitness changes to better inform training of female intermittent team sport athletes. Lastly, coaches could use the 30-15_IFT as a practical alternative to laboratory based assessments to assess and monitor intermittent aerobic fitness changes in their athletes.

Keywords: 30–15 intermittent fitness test; aerobic; cardiorespiratory fitness; high intensity interval training; intermittent activity; soccer.

Figure 1

Relationship between 30–15_IFT end speed (V_IFT) and measured maximal oxygen consumption (VO_2max) obtained from the incremental continuous running treadmill test.

Figure 2

Linear dependence of estimated maximal oxygen consumption (VO₂max) based on 30–15_IFT end speed (V_IFT).

Figure 3

Differences between national selection and national league level players for the 30–15_IFT test–retest end speed (V_IFT), maximal heart rate (HRpeak) and maximal oxygen consumption (VO_2max) expressed as standardized units (Z-values).