The 30-15 Intermittent Fitness Test (30-15IFT) has become a common on-field method to assess the level of cardiorespiratory performance in sports. Although literature has suggested excellent reliability properties, the validity against objective measures has been mainly conducted in individual sports, while findings in team sport athletes like futsal are lacking. Therefore, the main purpose of the study was to examine the reliability and validity of the 30-15IFT. Fifty-eight U21 male futsal players (age = 20.10 ± 0.90 years; height = 177.14 ± 5.72 cm; weight = 67.31 ± 7.33 kg) were recruited. A within-subject test-retest with seven days apart between trials was conducted to examine the reliability of the 30-15IFT, while the criterion validity included estimated VO₂max derived from the 30–15IFT and laboratory measured VO₂max obtained from the continuous running test in laboratory conditions performed seven days prior the 30-15IFT.Results indicated very high reliability of the 30-15IFT for Vmax (ICC = 0.95; CV = 1.00%, p < 0.001), peak heart rate (HRpeak; ICC = 0.94; CV = 1.12%, p < 0.001) and maximal oxygen uptake (VO2max; ICC = 0.95; CV = 1.10%, p < 0.001). Correlations between the 30-15IFT outcomes and a graded incremental treadmill test protocol were large for Vmax (r = 0.75), HRpeak (r = 0.73) and VO2max (r = 0.78). This study shows that the 30-15IFT is a reliable and valid intermittent field-based test to assess the level of cardiorespiratory fitness in male futsal players.
Li et al. (Mon,) studied this question.