Post Activation Potentiation (PAP) is a theory that muscle force and rate of force development (RFD) will increase as the result of a previous muscle contraction. Meaning that after a heavy, or moderately heavy lift, the performance of an explosive movement that is biomechanically similar to that lift will acutely improve.
How Does This Happen?
The heavy loading leading to an acute increase in performance of explosive movements is thought to occur as a result of two main mechanisms; phosphorylation of myosin regulatory light chains and recruitment of higher order motor units. A change in pennation angle is also thought to contribute to PAP (Tillin and Bishop, 2009). Phosphorylation, the addition of a phosphate group, is an important mechanism by which cells can alter the activity of proteins after they have been formed. With regards to PAP, phosphorylation of the regulatory light chains of myosin is thought to alter physical structure of the myosin protein moving it away from the thick filament backbone, thereby potentiating subsequent contractions. Myosin phosphorylation has also been shown to increase the sensitivity of the actin-myosin interaction to its signaling molecule, calcium ions (Tillin and Bishop, 2009). The second mechanism involves higher order motor units, groups of muscle fibers innervated by the same motor neuron, which involve type II muscle fibers (fast twitch) and are responsible for more powerful muscle contractions. Motor units are recruited in order of smallest to largest, i.e. slow twitch to fast twitch, because the body wants to be as efficient as possible. Type I fibers are less powerful than type II, but they are more fatigue resistant, so they’re activated first. Since heavy weights require greater force, type II fibers will be recruited based on their greater force production capabilities. Therefore, after you lift something heavy your nervous system is ramped up to a greater extent than usual, and this allows your body to produce more force with greater RFD, which helps you throw, jump, or sprint at a higher level than you’d otherwise be able to.
Loading
So, how heavy should you load your lift?
A meta analysis by Wilson et al. found that moderate loads (60-84% 1RM) on the strength movement resulted in the greatest power output during the explosive movement (Wilson et al., 2012). This seems to confirm Dr. Fred Hatfield’s findings that loads near 78% 1RM have the greatest effect on power-moving a given weight fast over a given distance. Weights below 55% 1RM are too light to produce enough force (mass x acceleration) to improve power, and heavy weights; above 85% 1RM, move too slowly.
Rest
The rest required between sets is a significant factor in PAP training due to the physical and energy demands of PAP training. The energy system that is primarily used, the phosphagen energy system, requires a work to rest ratio of at least 1:10.
Aside from rest between sets, there needs to be rest between the lift and the explosive movement. A study by Golas et al. found 6 minutes to be the optimal rest period between the lifting movement and the explosive movement, but the rest period should be individualized to the athlete and their training level. In this study they tried rest periods as short as 2 minutes, and as long as 8 minutes, and found 6 minutes to be optimal across the training groups. But, training experience and strength level do affect the rest required.
For example, in a 2014 study by Seitz et al., elite junior rugby players divided into two groups based on strength levels, showed differences in not only their ideal rest period, but the overall effectiveness of PAP training. The “strong” group, players with a back squat of at least 2x bodyweight, demonstrated maximum PAP effect 3 to 12 minutes after their lift, while the “weak” group, players with a back squat less than 2x bodyweight, demonstrated maximum PAP effect 6 to 12 minutes after their lift. Additionally, the “strong” group displayed a greater maximum PAP response (Seitz et al., 2014).
While there is no perfect answer in terms of rest between the lift and explosive movement, 6 minutes seems to be the “ideal” rest for strong athletes, while a longer rest period, such as 9 minutes, is a better option for weaker less experienced individuals. The key with rest is to find a happy medium between enough rest that you’ve recovered from the lift but not too much that you’ve lost the benefit of PAP.
How to Utilize PAP
Pick a movement that you can load relatively heavy and for which you know your 1RM, such as a bench press, squat, or deadlift and pair it with an explosive movement using the same general movement pattern. For example, load a bench press variation moderately heavy (64-80%), then perform a medicine ball chest pass variation at maximum effort. Or, load a squat and then perform a vertical jump variation. Being vector specific, moving in the same direction, makes sense when possible, but it won’t always be an option. If you want to use a lateral bound as your explosive movement, as it has a strong correlation with throwing velocity, a lateral lunge would seem like a good choice because it is a vector specific lift. However, a lateral lunge can’t be loaded as heavy as a squat as the movement is a more complex and unilateral movement.
Overall, if you choose to use PAP, keep it simple. Use bilateral movements that can be loaded heavy and pick explosive movements that don’t require extensive skill. The focus should be on moving fast, not on overthinking technique.
What Phase of Training
This form of training works best in power and peaking/preseason blocks. Athletes who have built a solid base of strength and work capacity will be able to handle the demands of PAP training. Also, the volume and high intensity of PAP is ideal for peak/preseason phases of traiing.
PAP is not the end-all-be-all, but it can be a useful tool for strong and experienced athletes looking to improve their power.
Resources
Seitz LB, de Villareal ES, Haff GG (2014) The temporal profile of postactivation potentiation is related to strength level. Journal of Strength and Conditioning Research
Golas A, Masszczyk A, Zajac A, Mikolajec K, Stastny P (2016) Optimizing post activation potentiation for explosive activities in competitive sports. Journal of Human Kinetics.
Wilson J, Duncan N, Marin P, Brown L (2012) Post Activation Potentiation: A Meta Analysis Examining The Effects Of Volume, Rest Period Length, And Conditioning Mode On Power. Journal of Strength and Conditioning Research.
Tillin NA, Bishop D (2009) Factors modulating post-activation potentiation and its effect on performance of subsequent explosive activities. Journal of Sports Medicine.