The purpose of this study was to measure power values generated in elite karate fighters during brief high intensity cycle ergometry when resistive forces were derived from total - body mass (TBM) or fat - free mass (FFM). Male international karate practitioners volunteered as participants (n = 11). Body density was calculated using hydrostatic weighing procedures with fat mass ascertained from body density values. Participants were required to pedal maximally on a cycle ergometer (Monark 864) against randomly assigned loads ranging from 70 g·kg^-1 - 95 g·kg^-1 (using a TBM or FFM protocol) for 8 seconds. The resistive force that produced the highest peak power output (PPO) for each protocol was considered optimal. Differences (p < 0.05) in peak power outputs were found between the TBM and FFM experimental condition (1164 ± 137 W vs. 1289 ± 145 W respectively). Differences were also recorded (p < 0.01) between pedal velocity and applied resistive forces (127 ± 8 rpm vs. 142 ± 7 rpm; 6.6 ± 1 kg vs. 5.5 ± 1 kg, respectively). No differences (p > 0.05) were observed between time to PPO, or heart rate when the TBM and FFM protocols were compared. The findings of this study suggest that when high intensity cycle ergometer resistive forces are derived from FFM, greater peak powers can be obtained consistently in karate athletes. Resistive forces that relate to the active muscle tissue utilised during this type of exercise may need to be explored in preference to protocols that include both lean and fat masses. The findings have implications for both exercise prescription and the evaluation of experimental results concerning karate athletes.

• Methods for quantifying and measuring high intensity performance using high intensity cycle ergometry have received considerable attention in recent years.

• The assumption has been that the relationship between total - body mass (TBM) and fat - free mass (FFM) is the same.

• However, variations in body composition between participants may under or over estimate cradle resistive forces used in high intensity cycle ergometry power assessment.

• This may lead to spurious calculations of power.

• The findings of this study demonstrate that the total capacity, power and relative contribution of the energy systems involved during experimental high intensity cycle ergometer exercise need re - evaluating.