This study examined the validity of 6 1-repetition maximum (1RM) repetitions-to-fatigue prediction equations on 11 machine lifts for 51 older adults (70.7 +/- 6.1 years). In the first session, subjects selected a weight that they could lift for 7-10 repetitions on each machine exercise, and a 1RM was predicted using 6 different equations. In session 2, subjects completed an actual 1RM by selecting the maximum load that they could safely lift once (1-3 reps). Correlations between the actual and the 6 predicted 1RM scores demonstrated a moderate to strong relationship for all exercises (upper extremity: r = 0.77-0.90; lower extremity: r = 0.60-0.80). The average predicted 1RM value was lower than the actual 1RM for all exercises and all prediction equations (p <= 0.001). The use of a prediction equation for older adults appears to be a valid measure of 1RM within a range of 1-10 kg, depending on the machine lift. In all cases, the prediction equation underestimated the actual 1RM.
(C) 1999 National Strength and Conditioning Association