Deadlifts help you jump higher
At least according to a study published in the Journal of Strength and Conditioning research:
Barbell Deadlift Training Increases the Rate of Torque Development and Vertical Jump Performance in Novices
Abstract: Thompson, BJ, Stock, MS, Shields, JE, Luera, MJ, Munayer, IK, Mota, JA, Carrillo, EC, and Olinghouse, KD. Barbell deadlift training increases the rate of torque development and vertical jump performance in novices. J Strength Cond Res 29(1): 1–10, 2015—The primary purpose of this study was to examine the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors. A secondary aim was to analyze the relationships between training-induced changes in rapid torque and vertical jump performance. Fifty-four subjects (age, mean ± SD = 23 ± 3 years) were randomly assigned to a control (n = 20) or training group (n = 34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and after the intervention. Torque-time curves were used to calculate rate of torque development (RTD) values at peak and at 50 and 200 milliseconds from torque onset. Barbell deadlift training induced significant pre- to post-increases of 18.8–49.0% for all rapid torque variables (p < 0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm (7.4%; p < 0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r = 0.30–0.37, p < 0.01–0.03). These findings showed that a 10-week barbell deadlift training program was effective at enhancing rapid torque capacities in both the knee extensors and flexors. Changes in rapid torque were associated with improvements in vertical jump height, suggesting a transfer of adaptations from deadlift training to an explosive, performance-based task. Professionals may use these findings when attempting to design effective, time-efficient resistance training programs to improve explosive strength capacities in novices.
Some topics of discussion from this study. Participants were considered "novice," so many of them did not complete pre-study max testing. I believe that many of the study participants may have actually improved their torque and vertical jump even more if they had started the program with a better understanding of form and their physical limitations (max testing), although that is just speculative at this point.
Another aspect of the study that I found interesting; the participants were not instructed on how to powerfully lift the bar. Instead, they were basically instructed on how to lift the bar up and put it back down (with correct form). The deadlift should be considered a power exercise that promotes powerful hip drive during the last phase of the lift to complete the ascent of the bar. When you think of an athlete jumping, the power for an explosive jump is initiated and driven from the hips, primarily.
5 repetitions over 5 sets, or 25 "working repetitions" were used for every set (2 warm-up sets). The lifters completed deadlifts twice a week, either on Monday/Thursday or Tuesday/Friday. If a lifter could compete all of their repetitions with a certain weight then they would increase in weight anywhere from 0.45-2.2kg (progressive overload). If, on the other hand, participants failed to achieve all repetitions of a specific weight, 0.45-2.2kg was removed from the bar and a sixth set was added in order to complete 25 "working repetitions" during every workout. Rest periods were 3 minutes between sets - all pretty standard strength training protocols.
I personally love to use deadlifts with clients, especially those who do not have the proper flexibility and/or mobility to complete a full range of motion squat. I still maintain that squats are a fantastic lower body exercise to increase power and strength, however for those individuals who lack the flexibility and mobility to complete a heavy squat safely and effectively can work on developing power and strength with deadlifts as they are generally less of a "technical" move to master and can be completed with less range of motion.
The basketball players I train are a prime example of this as many of them have very unique limb lengths and joint angles making squats relatively awkward and uncomfortable. Rather than just saying, "You need to do a proper squat," I would much rather them work on exercises that can improve their lower body strength and power safely than forcing them to do something, at least right away, that they are incapable of doing safely and effectively.