Do braking and amortisation forces in countermovement jumps contribute to jump height?

Increasing the braking and amortisation forces during a countermovement jump (CMJ) increases the early-half concentric mean force (EMF) which can enhance muscle contraction velocity in the latter half of the concentric phase. This may negatively affect exertion force, owing to the force-velocity relationship and not increase the jump height. This study aimed to investigate the associations of the braking and amortisation forces during the CMJ with the latter-half concentric mean force (LMF). Twenty-seven men (age: 20 ± 1 years, body mass: 76.2 ± 8.3 kg, height: 173.5 ± 4.7 cm) with training experience who performed body mass CMJs and five loaded CMJs were included. We calculated the braking rate of force development (B-RFD), amortisation force (AmF), EMF, and LMF, as well as the theoretical maximum force (F0) and velocity (V0) of the force-velocity profile. Correlation analyses per variable identified significant negative correlations of B-RFD and AmF with the LMF, but not of B-RFD and AmF with the jump height. Additionally, V0 was significantly correlated with the LMF. Therefore, increasing the initial concentric force by increasing the braking and amortisation forces may not contribute to jump height owing to a decrease in the latter-half concentric force due to the force-velocity relationship.