Validity of Formulas Used to Estimate One Repetition Maximum Strength of Upper and Lower Extremities

This study aimed to assess the validity of 15 formulas used to estimate one repetition maximum (1RM) bench press and deep squat strength in male and female university students who are recreationally active in sports. Forty-eight students (age = 22.4 ± 2 years, height = 169.8 ± 10.2 cm, weight = 66.5 ± 17.6 kg, BMI = 22.8 ± 4.3 kg/m2) from the Faculty of Sport Sciences participated. The participants’ 1RM values in the bench press and deep squat tests were compared with 15 different formulas. Levene’s test was used to test the homogeneity of variance, and a paired t-test was employed to evaluate the agreement of repeated paired measurements. Additionally, Bland-Altman plots, Intraclass Correlation Coefficient (ICC), and Concordance Correlation Coefficient (CCC) were utilized to assess the agreement of measurements. Results indicated that some formulas provided predictions close to the measured 1RM values, while others showed deviations. Specifically, in the bench press test, the P2 (Berger) and P6 (Kemmler) formulas provided more accurate predictions for female participants, while P5 (Cummings & Finn) and P10 (Mayhew) were successful for males. In the deep squat test, P3 (Brown) and P4 (Brzycki) provided the best predictions for females, while P1 (Adams) and P12 (O'Connor) showed high agreement for males. The findings suggest that selecting suitable formulas for 1RM estimation by gender and exercise type is essential for enhancing the effectiveness of strength training in sports sciences.