INTRODUCTION
Many aspects of a strength and conditioning program center on power development with complex training being commonly used. Complex training involves maximal or high-intensity dynamic exercises before performing a lighter-resistance ballistic movement with similar biomechanical characteristics (7). Recent research has shown that maximal or high-intensity dynamic exercises (e.g., heavy squats, weighted countermovement jumps and drop jumps) can enhance the rate of force development and jump height of both vertical and horizontal jump performance (5,16,29). This training technique takes advantage of postactivation potentiation (PAP) which is defined as the enhanced neuromuscular condition observed in the skeletal muscle after an initial bout of heavy resistance exercise (27).
The short-term increases in power after maximal or high-intensity dynamic exercises are thought to result from a combination of 2 physiological phenomena. The first theory focuses within the localized muscle where the increased recruitment of high threshold motor units (7,18,24,28) and phosphorylation of myosin regulatory light chains makes the actin and myosin more sensitive to Ca2+ released from the sarcoplasmic reticulum (23). This increases the rate of binding of actin and myosin resulting in faster muscle contraction (13). The second theory focuses on the spinal level where the potentiated muscular state is attributed to an increase in α-motoneuron excitability as reflected by changes in the H-reflex (6,25). The H-reflex is a reflexive neural signal, which when superimposed on voluntary muscle activation, increases the strength of the electrical impulse, thus activating more motor units (6).
PAP has been shown to increase the rate of force development of the affected muscle groups which leads to an increase in acceleration and velocity (26). Both acute and chronic increases in muscular strength and power may be further enhanced by performing an explosive power exercise while the affected muscle groups are in this potentiated state (27).
INTRACOMPLEX RECOVERY
One of the major factors affecting PAP utilization is the optimal intracomplex recovery (i.e., rest interval between maximal or high-intensity dynamic exercise and ballistic exercise) (7,18,24,28). A muscular contraction produces both PAP and fatigue and it is the next balance between these 2 variables that determines whether the subsequent performance response is enhanced, reduced, or unchanged (Figure) (14). During the rest interval, muscle performance may improve if potentiation dominates and fatigue is reduced, decrease if fatigue dominates over potentiation and remain unchanged if both fatigue and potentiation are at similar levels.
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Figure.: A model of the relationship between postactivation potentiation (PAP) and fatigue after a previous conditioning stimulus (Adapted from Tillin and Bishop, 2009). PAP can be achieved earlier after a low-volume conditioning stimulus (window 1) or later after a high-volume conditioning stimulus (window 2).
Since PAP coexists with fatigue, it is vital to identify the optimal rest interval whereby the muscle has partially recovered from fatigue but is still in a potentiated state (3). Previous reviews in the assessment of the temporal profile of PAP had reported a lack of consensus regarding the optimal intracomplex recovery with the recovery interval ranging from 3 to 10 minutes (19,28). To implement complex training in a training cycle, a shorter recovery interval of ∼3–4 minutes would be ideal for strength and conditioning coaches to execute an effective, yet practical training program when performing and incorporating PAP.
TRAINING STATUS AND STRENGTH LEVELS
Other major contributing factors affecting PAP utilization are an athlete's training status, resistance training experience, and strength level (7,18,24,28). To adhere to the recommended ∼3–4 minutes intracomplex recovery, it is recommended to implement complex training in training cycles of moderately highly trained athletes with high relative 1 repetition maximum (1RM) strength levels (training status = club, professional and elite athletes; resistance training experience ≥2 years; lower body strength levels ≥1.8 relative 1RM; upper body strength levels ≥1.4 relative 1RM) (15,18–20). The ability of stronger individuals to express their greatest PAP effect earlier may be explained by the fact that they develop fatigue resistance to heavier loads after a near-maximal effort (1). Given the interplay between strength, fatigue, and potentiation, stronger and experienced individuals may be able to dissipate fatigue quicker after the maximal or high-intensity dynamic exercise because of their greater capacity to resist fatigue and therefore may be able to achieve their maximal PAP response earlier than weaker individuals (1). Stronger individuals may have a higher percentage of type II muscle fibers and therefore likely exhibit greater increases in myosin RLC phosphorylation in response to dynamic exercise or respond more to increases in the ability to recruit type II muscle fibers resulting in a greater voluntary PAP response (21).
In contrast, moderately trained athletes may incorporate the use of plyometric exercises to induce the effect of PAP for complex training within a training cycle. Plyometric exercises are associated with the preferential recruitment of type II motor units which is one central level mechanism underpinning PAP (6). One study directly compared the effect of a plyometric versus traditional resistance exercise and reported a greater PAP effect after the former (16). Twelve trained volleyball players performed a variety of specific warm-up stimuli (unloaded and loaded countermovement jumps and drop jumps) after baseline measurements on randomized separate occasions. Jump height and maximal power output significantly improved by 2–5% and 2–11%, respectively.
A recent meta-analysis has also shown that a plyometric exercise may produce less fatigue than a loaded traditional resistance exercise as a conditioning stimulus, thus allowing a greater potentiation effect to be achieved and reducing the time necessary to achieve the maximal PAP effect (19). Given the relationship between fatigue and PAP, a plyometric exercise may produce less fatigue than a loaded traditional resistance exercise, thus allowing a greater potentiation effect to be achieved and reducing the intracomplex recovery needed to achieve the maximal PAP effect (19).
CHRONIC ADAPTATIONS OF POSTACTIVATION POTENTIATION IN A TRAINING CYCLE
Only a handful of studies have investigated the effectiveness of complex training within a training cycle of 6–10 weeks (4,8–11,17,22) (Table 1). The majority of studies showed that club and elite level athletes taking part in a periodized complex training cycle showed significant improvements in lower body power production (i.e., vertical jump height). These studies show how with the ideal combination of moderately highly trained athletes and adequate intracomplex recovery it is possible to effectively implement complex training for power development in a training cycle.
Table 1: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-A: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-B: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-C: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-D: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-E: Studies investigating chronic adaptations of postactivation potentiation on performance measures
Table 1-F: Studies investigating chronic adaptations of postactivation potentiation on performance measures
One concern is how to effectively use the rest interval between both the complex pairs and exercise sets (intracomplex recovery: ∼3–4 minutes; intercomplex recovery: ∼5 minutes). A possible solution is to cater mobility and/or stability drills for the unaffected limbs (i.e., upper body/core corrective exercises for lower body complex exercise sets), with the aim of addressing dysfunctional movement patterns that can cause a decrease in performance and an increase in injuries (2).
Basic movement pattern limitation, due to asymmetrical function of joint mobility and stability, is thought to reduce the effects and benefits of functional training and physical conditioning. If the asymmetrical dysfunction is unattended to, compensatory movement patterns develop during training and the individual creates a dysfunctional movement pattern that is used subconsciously whenever executing an exercise movement (2). This may lead to greater mobility and stability imbalances and deficiencies, which increase the potential for injury (12).
These corrective exercises are implemented during the rest periods (intracomplex recovery) between the conditioning stimulus and ballistic exercise. This may effectively address other injury management concerns of the athletes during training. This prehabilitation training approach can be supplemented into a complex training protocol without unnecessarily extending the total training time. All these are factored into program design to cater to an effective, yet practical training program (see Table 2 for sample program templates tailored for both a highly and moderatelytrained athlete).
Table 2: Sample complex training programs for a highly trained and moderately trained athlete
SUMMARY
The majority of the studies investigating the effectiveness of complex training within a training cycle showed significant improvements in lower body power production. The major factors affecting PAP utilization are the optimal intracomplex recovery, training status, and strength levels of the athletes. This shows that with the ideal combination of moderately highly trained athletes and adequate intracomplex recovery, it is possible to effectively implement complex training for power development in a training cycle. The key to successfully using PAP into a training cycle is, taking all the above considerations and implementing them in an effective, yet practical training program. The programming of mobility and/or stability drills within the intracomplex and intercomplex recovery interval may be a solution to address other injury management concerns of the athletes during training, without unnecessarily extending the total training time.
PRACTICAL APPLICATION
Guidelines for using PAP within a training program.
- Ideal subject characteristics
- Training status = moderately to highly trained athletes
- Resistance training experience ≥2 years
- Strength levels ≥1.8 relative lower body 1RM
- Strength levels ≥1.4 relative upper body 1RM
- Effective rest interval
- Intracomplex recovery (between complex pairs) = ∼3–4 minutes
- Intercomplex recovery (between exercise sets) = ∼5 minutes
- Programming mobility and/or stability drills within the intracomplex and intercomplex recovery interval.
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