BACKGROUND: The Five Times Sit-to-Stand Test (FTSST) has been found reliable, safe and valid for measuring healthy adults' lower limb muscle strength and for determining balance control, fall risk, and exercise capacity among older examinees. We believe that the FTSST has the potential to be a straightforward, low cost and valuable tool for identifying muscle disability and functional status following critical illness. The aim of our study was to establish the applicability, safety, and psychometric qualities of FTSST in patients at Intensive Care Unit (ICU) discharge. METHODS: In our study applicability was determined by assessing the percentage of patients who could perform the test at ICU discharge. Safety was assessed by examining data regarding any exacerbated haemodynamic and respiratory responses or adverse events associated with the test. For assessing FTSST reliability, intraclass correlation coefficients (ICCs), standard error of measurement (SEM) and Bland-Altman plot were used. For assessing concurrent validity handgrip strength, ICU length of stay, duration of invasive ventilation, Simplified Acute Physiology Score 3 (SAPS3) and age variables were used. For investigating predictive validity, correlations between the FTSST and measures of hospital length of stay and functional independence were evaluated. RESULTS: Only 30% of ICU survivors (n = 261 out of 817) were eligible to perform the FTSST and 7% of patients who performed the test (n = 10 out of 142) presented adverse events. Both inter (ICC 0.92 CI95% 0.89-0.94) and intra-rater (ICC 0.95 CI95% 0.93-0.96) reliability were excellent and higher scores were associated with lower muscle strength, longer hospital stay and greater functional impairment at hospital discharge in adult survivors of critical diseases. CONCLUSION: Our results suggest that the FTSST may be applicable only to high-functioning critical care survivors. In this specifical population, FTSST is a safe, easy to perform, valid and reliable measure that can be applied to fall risk and functional recovery management.