PURPOSE: Maximal strength and power capabilities are often trained to enhance maximal power output and sport-specific performance. Considerable research has focused on identifying the load which maximises peak concentric mechanical power (Pmax). Researchers have suggested power output at loads either side of Pmax are insubstantial and the preoccupation with identifying Pmax is unwarranted. The concept of adopting a ‘bandwidth’ approach for training prescription of loads is given prevalence, however, no research to date has quantified what a ‘substantial’ difference in power output across loads is for a lower-body incremental load-power profile. Therefore this research aimed to determine the load that maximises peak concentric mechanical power of the countermovement jump (CMJ), and to quantify the substantial difference in power output across a spectrum of loads. METHODS: 16 elite Australian Rules Football (ARF) and 20 highly trained Rugby Union (RU) players performed 3 CMJs across seven 10kg incremental loads (0-60kg). Measurement of force-time and displacement-time data was collected at a sampling frequency of 200Hz using a force plate and linear position transducer for calculation of power output. To estimate Pmax load, a quadratic equation was fitted to the log transformed power output (Watts) and load (kg) of each player. Goodness-of-fit of the correlation was expressed as an overall correlation coefficient (R). The substantial difference in concentric peak power across loads was quantified as 0.2 of the log transformed between-athlete SD of peak power at each load and then back-transformed and expressed as a percent. RESULTS: Mean Pmax for ARF players was 5151.0 ± 996.7 W and 6193.9 ± 1101.9 W for RU players (Fig. 1). For Australian Rules Football and Rugby Union players, an estimated load of 0.0kg, was found to maximise peak power (mean goodness-of-fit R = 0.99 and 0.98). The smallest substantial difference in power across loads was 4.2% (90% CI: 3.2-5.9%) and 3.5% (90% CI: 2.8-4.8%) for ARF and RU players respectively. CONCLUSIONS: The load that maximises peak concentric mechanical power in the CMJ of elite Australian Rules Football and highly trained Rugby Union players was 0.0kg (unloaded jump). Loads corresponding to peak powers that are within 4.2% and 3.5% of Pmax for Australian Rules Football and Rugby Union players are not substantially different from the Pmax. PRACTICAL APPLICATIONS: Practitioners should consider the smallest substantial difference in power output across loads when interpreting the incremental load-power profile for adequate prescription of training loads for the purpose of enhancing peak mechanical power production.