Isometric Floor Press: A Valid, Reliable, and Practical Field-Based Assessment of Upper-Body Strength

Abstract

Kirk, BJC, Wills, JA, Glen, B, and Doyle, TLA. Isometric floor press: A valid, reliable, and practical field-based assessment of upper-body strength. J Strength Cond Res XX(X): 000–000, 2026—There is currently no standardized method for assessing upper-body isometric strength using portable field-based equipment, limiting practitioners' ability to monitor upper-body strength in applied environments. This study evaluated the validity and reliability of 4 novel tests performed using only a force plate system and isometric midthigh pull rack: the isometric push-up (IPU) on knees and feet, and the isometric floor press at 90° (IFP ₉₀ ) and 135° (IFP ₁₃₅ ) elbow angles. Twenty recreationally trained adults (16 men, 4 women) completed a 1 repetition maximum bench press and familiarization session, followed by 2 isometric testing sessions, each separated by 7 days. Validity was assessed using Pearson correlation with 1 repetition maximum bench press. Within-day and between-day reliability were evaluated using intraclass correlation coefficients (ICC) and coefficient of variation (CV%). IFP ₉₀ showed the strongest validity ( r = 0.887), followed by IFP ₁₃₅ ( r = 0.724), IPU on knees ( r = 0.711), and IPU on feet ( r = 0.692). All tests demonstrated excellent within-day reliability (ICC = 0.923–0.983; CV% = 5.3–7.7%) and between-day reliability (ICC = 0.912–0.955; CV% = 6.4–12.3%). Supine configurations (IFP) generally showed greater measurement stability than prone push-up variations (IPU), with lower variability and higher ICCs. Results were consistent across a broad strength range (bench press = 65–140 kg), supporting their applicability to both athletic and general populations. These findings suggest that IFP ₉₀ offers a valid, reliable, and practical field-based alternative to traditional upper-body strength testing. These tests may be especially useful in settings where safety, measurement sensitivity, and fatigue minimization are priorities.