Hughes, JD, Massiah, RG, and Clarke, RD. The potentiating effect of an accentuated eccentric load on countermovement jump performance. J Strength Cond Res 30(12): 3450-3455, 2016-Postactivation potentiation (PAP) following a bout of high-intensity exercise of short duration is known to produce both a fatigued and a potentiated state. There has been much research in the effectiveness of various PAP protocols, yet the type of dynamic muscle action utilized has seldom been investigated. Therefore, the present study aimed to assess whether an accentuated eccentric load (AE) could enhance subsequent performance. Eleven men (21 ± 2 years, 179.1 ± 6.9 cm, 83.2 ± 10.1 kg) performed 3 countermovement jumps (CMJs) before and 6 minutes after an AE and a back squat (BSq) PAP protocol. The participant's maximum CMJ height (cm) was determined before and after both protocol. A 2-way repeated measures analysis of variance was conducted to evaluate the effect of PAP condition and time on vertical jumping performance. A significant condition × time interaction was found (p = 0.02). Post hoc tests revealed that AE PAP had a significant (p = 0.03) potentiating effect on CMJ jump height. Whereas, the BSq PAP revealed no significant differences (p = 0.32). In conclusion, this study has shown that jump performance can be enhanced by eccentric muscle action when compared with a traditional BSq PAP protocol. This may provide a more practical method for coaches to enhance short-term explosive movements in athletic populations.