1575 Muscle fatigue alters lower extremity function during gait and jumping resulting in impaired performance and altered loading characteristics. Landing immediately following stretch shortening cycle (SSC) exercise fatigue has been shown to result in decreased lower extremity stiffness and impact magnitudes. PURPOSE: To determine the effects of other methods of fatigue on landing impact characteristics and to compare the effects of different fatiguing activities. METHODS: Ten male subjects (23.5 +/− 1.58 yr; 1.78 +/− 0.07 m; 74.5 +/− 9.96 kg) performed 10 non-fatigued and 5 fatigued landings (0.6 m) per session on two separate testing days (10 d to 6 mo apart). The testing sessions were identical except for the method of fatigue. A series of repeated maximum effort isometric squats (knee angle = 60 deg of flexion) was used to induce fatigue (50% of maximum voluntary contraction, MVC) on the first day. A sub-max protocol consisting of cycle ergometer exercise at 60% of peak work rate (cadence of 60–80 rpm) was used to induce fatigue (cadence < 40 rpm) on the second day. MVC isometric squat measurements were taken before fatigue and after fatigued landings on each day. All bilateral landings were performed with the right limb landing on a force plate while knee angular kinematics were simultaneously recorded using an elgon (1000 Hz). MVC, ground reaction force peak, rate, and impulse values, and knee angular position at contact, range of motion (ROM), and max velocity values were compared (ANOVA) pre- and post-fatigue and between fatiguing activities. RESULTS: Fatigue resulted in significant (P < 0.05) decreases in MVC (2012 +/− 199.2 to 1842 +/− 164.9 N; M +/− SE), peak (42.8 +/− 5.14 to 33.8 +/− 3.92 N/kg), and impulse (1.54 +/− 0.10 to 1.38 +/− 0.08 N*s/kg). Significant (P < 0.05) increases were observed in knee ROM (54.5 +/− 5.45 to 61.6 +/− 4.00 deg) and knee angular velocity (572.7 +/− 38.05 to 625 +/− 36.70 deg/s). No significant differences were found between fatiguing activities. CONCLUSIONS: There were no differences between methods of fatigue, but post-fatigue alterations were similar to those previously observed during SSC exercise. The state of fatigue may be more important than the method of fatigue in determining landing impact characteristics.