For example, heavy resistance training can significantly increase the ability to generate peak force and the rate of force development when compared with untrained individuals (Figure 5) (51). Conversely, ballistic or explosive training can result in increases in the overall rate of force development that is greater than what can occur with heavy resistance training or during an untrained state. However, ballistic training cannot increase the overall maximal strength levels to the same extent as heavy resistance training. Therefore, a mixed training approach is often recommended when attempting to maximize the rate of force development and power output (31).
The optimal load is the load that elicits the maximal power output for a specific movement (19,42). It is suggested that the optimal load is an effective stimulus for improvements in power output (19,40,54,56,76,77,85). However, there are very few studies that have supported this contention (40,54,56,85). Conversely, several other studies suggest that training at the optimal load is not more effective than training with heavy loads (16,35) or with mixed-load models (76,77) when trying to maximize power development.
Theoretically, training at or around the optimal load may seem to be a better way to train for sports performance; the current body of knowledge does not convincingly justify this belief because many athletes require the ability to produce high power outputs under loaded conditions (4,5). For example, in Rugby League, one of the key differentiators between levels of play is the athlete’s overall strength and their ability to generate high power outputs under loaded conditions (4,5). Therefore, in these types of athletes, it is important to develop the ability to not only express high forces but also generate high power outputs under loaded conditions. Using loads that are higher than the optimal load increases the athlete’s ability to express high power outputs under loaded conditions (56). For example, Moss et al. (56) report training with higher loads seems (>80% 1RM) to result in superior power outputs under loaded conditions (>60% of 1RM) compared with training with moderate to low-load interventions (<30% of 1RM) (56). Because stronger athletes are better able to express higher power outputs under loaded conditions, it is evident that focusing on strength development is a key component of any strength training interventions that are preparing athletes in sports such as Rugby League, Rugby Union, and American Football.
When considering overall maximal strength development, the use of the optimal load for power development results in a muted ability to improve strength levels (16,35,54,76,77), which can have significant ramifications when working with athletes who must express high power outputs under loaded conditions. Furthermore, training at the optimal load has the inherent limitation of only maximizing power output at or near the load that is being trained (40,54). This may impact sports performance capacity by limiting the ability of an athlete to maximize power output under a variety of loaded conditions (56). This is a limitation because many athletes require the ability to produce power under both “unloaded” and “loaded” conditions. An unloaded condition involves activities such as sprinting or the squat jump, where an athlete primarily overcomes the inertia of their body mass (67). In comparison, a loaded condition may involve activities such as a collision in contact sports such as American football, rugby, and wrestling or an athlete changing direction where they must apply even greater forces to change the momentum of the system (mass × velocity). The scenarios of unloaded versus loaded demonstrate why power (force × velocity) is important to develop at many loads on the force-velocity spectrum. Although velocity will be compromised at higher loads (those above an individual's optimal load), the goal is always to produce the highest velocity (and therefore power) at any given load during competition or training. Ultimately, for many athletes, a continuum of loads are encountered during sporting play making it far more beneficial to develop the ability to maximize power output across a variety of loads. These loads should range from unloaded to load conditions in order to develop the entire force-velocity profile (39,67). One key area to accomplish this goal is with appropriate sequential periodization models as well as using warm-up sets that are performed at a variety of submaximal loads.
When examining the literature, unidimensional training approaches that only focuses on the development of strength or power do not maximize the development of power, strength (14,76,78), and overall sports performance capacity. Therefore, a mixed methods approach is recommended when attempting to maximize power output (19,58) (Figure 7).
The use of a mixed methods approach to optimize power-generating capacity allows for a superior increase in maximal power output and a greater transfer of training effect because of a more well-rounded development of the force-velocity relationship (20,76,77). Theoretically, the use of low-load high-velocity movements can impact the high-velocity area of the force-velocity relationship, while heavier loads enhance the high-force portion of this relationship. Thus, using combined methods of training allows for a more complete adaptation to occur across the entire force-velocity curve (19,20,76,77). Significant scientific support for the use of mixed methods is present in the contemporary literature (3,34,50,52,57,59,76,77), where superior enhancements in maximal power output and various markers of athletic performance are associated with mixed method training interventions. For example, Cormie et al. (14) reported that combined training results in improvements in power across a greater range of loaded activities and increased maximal strength to a greater degree compared with power or strength only training.
One strategy for employing a mixed training approach is to use a variety of training loads. For example, in the back squat, power development can occur between loads of 30–70% of 1RM, whereas higher loads (>75% of 1RM) would typically be employed for strength development (Figure 8) (15,44).
So, if athletes were performing sets at 80–85% of 1RM for the development of strength, they would perform submaximal back squats as part of their warm-up, which would effectively serve to develop power generating capacity if performed “explosively” (44). In this scenario, it is imperative that the athlete has the intent to move with high velocities (7). By lifting these submaximal warm-up loads “explosively” with the intent to move as quickly as possible, a greater potential for developing power across a variety of loads can be accomplished (21). Thus, with exercises that are used to target strength development, the warm-up sets actually become effective power training activities.
A second power development strategy is to use a mixed methods approach in which various portions of the force-velocity curve are targeted with the use of a variety of training exercises performed at different loading intensities. For example, unloaded jump squats, which are effectively plyometric exercises, would target power development of the low-force high-velocity portion of the force-velocity relationship when performed with loads between 0 and 30% of 1RM (Figure 9). Conversely, using moderate to high loads (70–90%) in the squat would target the development of power in the high-force portion of the force-velocity curve. While performing power cleans, either from the floor or hang, loads between 70 and 90% of 1RM have the potential to develop the wide range of force and velocity parameters.
A third power development strategy is to consider the various lifting activities available, such as strength training movements and their derivatives, jump squats, and traditional strength building exercises, and each of these exercise types have the ability to target the development of power under differing conditions. Each of these types of exercise can be related to portions of the force-velocity curve, thus allowing the strength and conditioning professional the ability to sequence various exercises into a mixed methods training session. For example, a variety of training methods could be used in the training program to capitalize on each type of exercises’ ability to develop power (Table 1). The back squat could be used to develop strength and the high-force low-velocity portion of the force-velocity relationship, whereas the power clean could be used to develop the high-force high-velocity portion of the curve. Incorporating the jump squat in the program could serve to maximize the low-force high-velocity portion of the curve.
Another approach would be to use strength training exercises such as the clean and snatch and their derivatives such as the pulling motions to more evenly develop all portions of the force-velocity curve (Table 2). Strength training exercises and their derivatives are particularly important when attempting to develop strength and power attributes and have been consistently shown to produce superior performance gains compared with other methods of power development (36,78). It is important that any program designed to maximize power output contain strength training movements because these exercises are considered superior to other training methods for their ability to develop power and translate training gains to sports performance capacity (12).
Regardless of the methods used for power development, it is essential that they are logically incorporated into a periodized training plan.
Periodization is the logical systematic structuring of training interventions in a sequential and integrative fashion to develop key attributes that results in the optimization of sports performance capacity at predetermined time points (10,11,29,37,38,62,79). To accomplish the primary goal of elevating performance, it is essential that the training program has structured variation that is designed to manage fatigue while stimulating physiological and performance adaptations. Typically, variation of training in the resistance training literature is considered in a very narrow scope with focus solely being on the loading paradigm used (22–24,46–48). A more comprehensive approach to variation must be used in which training foci, exercise selection, and density of training are considered in the context of the goals and structures contained in the periodized training plan (49,69,73,88). If variation is illogical, excessive, or unplanned, the overall effectiveness of the training plan will be limited and there will be an increased risk of overtraining responses.
Ultimately the training stimuli needs to be vertically integrated and horizontally sequenced to maximize the training-induced adaptations and performance outcomes (9,26). When training activities are vertically integrated, compatible training factors are paired allowing for the removal of interference effects (28,29). For example, if attempting to maximize the development of explosive strength and power one could vertically integrate the training plan by including activities to target maximal strength training, plyometric training, and sprint training (29). Additionally, from a power development perspective, vertical integration can allow for various parts of the force-velocity curve to be targeted through the selection of exercises and loads that target different parts of the curve (Figure 8).
The horizontal sequencing of training factors relates to the ordering of training foci (28,29,55,87). The sequential training approach can be applied to the development of power by initiating the training process with activities that target increases in muscle cross-sectional area followed by a period of training that maximizes muscular strength. Once muscular strength is developed, the training emphasis can then be shifted toward the maximization of power development (55,87) (Figure 9). Conceptually this type of training process is based upon the theory of phase potentiation, where the training adaptations stimulated by one period of training serve as the foundation for the subsequent phase (28,29). Support for this model of strength and power development can be found in the work of Harris et al. (34) where a sequenced training model in which combined training methods are employed resulted in greater improvements in back squat (11.6%⇑) and front squat (37.7%⇑) strength. Additionally, this model of training resulted in greater improvements in sprinting time across 9.14 m (2.3%⇓) and 30 m (1.4%⇓). Based upon the work of Minetti (55), Zamparo et al. (87), and Harris et al. (34) sequential periodization models are ideal for the optimal development of both strength and power.
While a complete discussion of the various periodization models needed for the development of power are out of the scope of this brief review, it is important to realize that there are a variety of programmatic models that can be used as part of a comprehensive periodized training plan. For further information on periodization, the reader is directed to the works of Stone et al. (72), Issurin (37,38), Bompa and Haff (9) and Verkoshansky (80,82,83).
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