Jumping movements in athletics require powerful contractions of the lower body to elevate an athlete to maximal or near maximal heights. Muscular power during jumping movements can be expressed as a function of force application and movement velocity. Improving force output and movement velocity, either singularly (given the other component of power remains constant) or in combination, will increase muscular power. The loaded jump squat (JS) has become an increasingly popular method for developing lower-body power.
Research has demonstrated that JS training at low to moderate intensities (approximately 0-30% of 1 repetition maximum back squat) can improve muscular power during jumping activities (1,6,10). Furthermore, it has been shown that JS training can offer greater gains in lower-body power output when compared with lower-body resistance training or plyometric training alone (10) and may be equally as effective as combined resistance and plyometric training at improving jumping ability (6). A recent review examining optimal training loads for lower-body resistance exercises (e.g., JS, squat) indicated that power improvements after moderate-intensity JS training were most attributable to increased force production as velocity showed a smaller degree of change (3). Improvements in lower-body force production and power output after JS training may be beneficial for improving vertical jumping ability with less transference to activities such as sprinting.
Currently, there is no standard definition of the JS movement. One interpretation, shown in Figures 1-4, describes the movement as a maximum vertical leap initiated after a controlled eccentric descent until the thighs are parallel to the floor (2). Another interpretation defines the movement as a countermovement vertical jump (CMJ) with an additional external load. The 2 JS technique variations also differ in regard to the depth and speed of eccentric lowering as the latter uses a much shallower (quarter squat depth) and faster eccentric dip when initiating the movement. Regardless of which JS variation is used, an external loading tool for the JS can take many forms (e.g., free weight barbell, Smith machine barbell, dumbbells, and weight vest). More recently, elastic banding, specialized jump training equipment, and weight-releasing devices have been used to externally load JS movements. Choosing an appropriate tool to load the JS is an important decision that athletes and coaches should be aware of before incorporating this technique into their training programs. Individual technique choices should be based on what research suggests is the best approach. The purpose of this article is to educate athletes and coaches so that they can make an informed decision regarding which loading tool to use when performing the JS.
JS LOADING TOOLS
As previously stated, athletes and coaches implementing JSs into their training programs may choose a variety of different methods to load the movement. Using a barbell, dumbbells, or a weighted vest to load the JS are commonplace methods used in strength and conditioning programs and require little in terms of equipment and setup. At the time of this writing, only one published investigation has directly compared separate JS loading methods while all other variables were kept constant. Sheppard et al. (7) indicated that JSs with a free weight barbell elicited greater values in mean power in comparison to the same technique performed in a Smith machine. The authors suggested that individuals should perform free weight barbell JSs to maximize the benefits of training.
As previously mentioned, a number of methods for loading the JS have been recently developed. These loading methods usually restrict the JS movement pattern (i.e. eliminate arm swing) or manipulate the resistive load in some manner. One novel method, using an additional eccentric load in the form of dumbbells or weight plates, has shown promising results in current research (8,9). This technique can be thought of as a CMJ with dumbbells or weight plates in the hands. The movement begins with an initial countermovement dip, whereby the dumbbells or weight plates are dropped at the bottom of the countermovement and immediately followed by the concentric portion of a vertical jump. Other novel JS loading methods have been developed using specialized jump trainers, which tend to lock athletes into a more restricted jumping pattern. Several of these specialized jump trainers can decrease the eccentric load during landing; however, it remains unclear if this reduction in eccentric loading can increase the effectiveness of the JS (4,5).
SPECIFICITY AND SAFETY CONSIDERATIONS
When incorporating the JS technique into training programs, athletes and coaches should choose variations that most closely replicate the movement patterns encountered in their sport. This will ensure that athletes receive the best possible training adaptations as a result of the exercise. Weighted vests offer a great option for maintaining movement patterns while performing the JS. Variations using a barbell, dumbbells, or a specialized jump training device tend to restrict arm motion during the JS and may be less preferable. However, the loading limitations of weighted vests may make using a barbell, dumbbells, or some other JS loading method a more desirable option depending on the needs of the sport.
As noted, specificity to normal jumping patterns is critical for achieving the best possible performance adaptations. However, safety while performing this exercise should supersede any specificity needs. Regardless of the loading tool, JS training should follow a thorough warm-up and be completed at the beginning of a resistance training session to maximize the benefits of ballistic exercise and reduce injury potential because of fatigue. In addition, coaches and athletes should be aware that barbell or Smith machine JS variations may be inherently more dangerous than variations using dumbbells, weighted vests, or specialized equipment because of the positioning of the external load on the upper back. To further minimize injuries, athletes must constantly keep the bar in contact with their upper back and shoulders while using this technique. This will eliminate “crashing” of the bar onto the back during the landing and initial eccentric dip. This can be accomplished by instructing athletes to forcefully pull down and hold the bar across the upper back and shoulders throughout the movement.
Presently, there is no singular JS loading tool that research supports as being superior. Free weight variations have been shown to be more favorable than machine variations at improving acute performance measures and may be preferred over other methods (7). Specialized jump training devices have not been extensively studied by peer-reviewed research. Currently, there is no basis to suggest that these devices are more effective than using a simple barbell, dumbbells, or a weighted vest when performing the JS. In addition, the high cost and space considerations for these jump trainers may preclude them as viable options in many weight rooms and training facilities. Nonetheless, the restricted movement patterns, padded shoulder rests, and decreased eccentric loading options available on many of these devices may be a more suitable option for athletes with a limited training background. Above all else, safety considerations should play the largest role in determining which JS loading tool that athletes and coaches choose to use.
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