A number of studies have investigated the relationship between vertical jump performance (VJ), both in the squat jump (SJ) and countermovement jump (CMJ) to strength and power in single-joint isometric tests (Baker et al., 1994), multi-joint isometric tests (Haff et al., 1997; Haff et al., 2005; Kawamori et al., 2006), and multi-joint dynamic tests (Wisloff et al., 1998; Young et al., 1999).
Strength is often associated with superior performance in sport (Stone et al., 2003). Several of the characteristics associated with strength (e.g., peak force, RFD, velocity, and power-generating capacity) have been identified as underlying mechanisms related to sports performance, particularly in the VJ (Stone et al., 2003; Peterson et al., 2006). According to several authors, success in sport depends upon the development of strength as well as power, both of which contribute to VJ performance (Baker et al., 1994; Stone et al., 2003; McGuigan and Winchester, 2008). Furthermore, training-induced increases in measures of maximum strength have been shown to result in VJ height increases (Stone et al., 1979; Stone et al., 2003).
Explosiveness is an important aspect of physical performance, and may be defined as requiring one to produce as much force as possible within a limited time window (usually < 200 ms). It could be hypothesized that if you are more explosive, one should jump higher, sprint faster, change direction quicker, for example. Vertical jumping ability has been shown to have a strong correlation with many other fundamental explosive movements including sprint performance (Peterson et al., 2006), ability to change direction (Brughelli et al., 2008), baseball bat velocity (Szymanski et al., 2010), weightlifting performance (Carlock et al., 2004), and sprint cycling (Stone et al., 2004).
Here is a table detailing studies looking at the relationship between maximal strength and VJ performance.
Although a correlation does not determine a cause-and-effect relationship, a few factors can in part explain the reported relationships.
To optimize VJ performance, produced force should be directed as vertically to the ground as possible. If produced force is not directed vertically, the resulting jump will contain horizontal displacement proportional to the magnitude of force (Hall, 2007). However, in other horizontal movements, vertical force has still been reported to be a key factor in performance. Weyand et al., (2000) reported that vertical force production is as important, if not more, as horizontal force for achieving greater running speeds in sprinting. Previous data has also suggested that stronger athletes (back squat ≥ 2 kg/kg) may have advantages in exhibiting a potentiation effect in a horizontal plyometric activity after performing an ascending back squat protocol (Ruben et al., 2010).
Neuromuscular activation patterns in dynamic explosive movements (performed with maximum effort to accelerate) have been shown to be different from non-explosive movements (non-ballistic movements without maximum effort to accelerate) (Cormie et al., 2011b; Cormie et al., 2011a). In particular, firing frequency and synchronization of motor units have been reported to be greater in explosive movements (Komi, 1992). In addition, if effective, many training modalities have shown to improve VJ height; including conventional resistance training, ballistic and semi-ballistic resistance training, and plyometric training.
Stronger athletes manage the eccentric load during SSC movements more efficiently as they are able to increase concentric force as a result, which should result in higher jump heights. The ability to increase force at a given eccentric velocity & increase velocity of the descent, allows the use of the eccentric phase in SSC movements more efficiently to generate an increase in power during sporting movements. Stronger athletes are able to increase unloading, and by tolerating high stretch loads they generate during quick eccentric actions, they use this to translate momentum into force, resulting in an increased stiffness, eccentric force, rate of force development, and power during explosive movements.