PAP: A Simple Strategy to Unlock Strength and Size Gains?

Post-activation potentiation (PAP) refers to an acute improvement in force or power production. The strategy utilized to elicit this response involves performing 2 distinct exercises back-to-back. The first of which is known as the conditioning activity (CA). The CA typically includes exercises commonly used in resistance training such as the barbell bench press and barbell back squat. Such exercises are generally performed for 1-5 repetitions (reps) at 80-90% of a 1 repetition maximum (1RM). 

Following the CA, a rest interval (usually a few minutes) is taken before transitioning into a second exercise. The second exercise is a similar movement pattern to the CA that requires a rapid expression of force or power. For example, performing a vertical jump test after barbell back squats, or throwing a shot put following a set of barbell bench presses. 

Without getting into the nuances of the mechanisms at play, some of the many theories behind the efficacy of this approach include the ability of a CA to facilitate excitation of the nervous system, increase recruitment of motor units, and/or enhance myosin light chain phosphorylation. 

Indeed, the research has consistently shown that implementing some sort of CA can enhance subsequent performance in a variety of tasks. In a trial on Collegiate Division II athletes, 4 separate studies were conducted examining the effect of a CA on vertical and horizontal jump performance, shot put performance, and sprint performance. 

The researchers found that performing 3 reps of a parallel back squat at 85% 1RM, followed by 8 minutes of rest, significantly improved vertical and horizontal jump performance. In conjunction, performing a 3RM of a parallel back squat, followed by 8 minutes of rest, resulted in significantly lower times for a sprint test, but did not improve performance in the shot put. In contrast, a 3RM bench press did have a positive impact on the following shot put performance.

Similar outcomes have been reported for other CA interventions as well. For example, 5 sets of 1 rep of a barbell half-squat performed to a bench at 90% 1RM, followed by a 5 minute rest interval was shown to improve sprint performance in elite handball players

When it comes to improving metrics of sports performance, the benefits of incorporating training methods to elicit PAP is clear, but do these findings translate to resistance exercise? Can the inclusion of a couple heavy sets of squats or bench press improve our performance in succeeding sets? 

While PAP is not exactly a new phenomenon, there has been a dearth of trials examining the ability of a CA to improve resistance exercise performance. Fortunately, this has changed in recent times. Due to the practicality and ease of implementation, significant interest has accumulated in the use of CAs to improve resistance training outcomes. 

This largely stems from an increasingly convincing link between the amount of training volume performed and the results obtained from resistance exercise. If including some sort of CA can increase the amount of volume load (load x sets x reps) achieved in subsequent sets, it would make sense that this would lead to superior long-term outcomes. Now, let’s dive into the literature on this topic.

PAP and Resistance Training: The Research

In a randomized crossover design, participants performed 3 sets of bench press to muscular failure at 60% 1RM with and without a CA. 

The subjects included in this trial were strength trained men with an average of 6.3 years of resistance training experience and a bench press 1RM of at least 120% of body weight. The average subject was ~202 lbs with a bench press 1RM of ~283 lbs.

During the CA intervention, subjects completed 3 sets of 3 reps at 85% 1RM before completing the reps to failure assignment. The rest taken between the CA and the reps to failure protocol was assigned based on a test that sought to determine the optimal intra-complex rest interval for the individual. This resulted in a 4 minute rest interval for 7 participants, an 8 minute rest interval for 3 participants, and a 12 minute rest interval for 2 participants.

In the end, there were no significant differences in total reps performed between the control and CA intervention (17.4 ± 7.0 and 17.8 ± 6.8 reps, respectively). The only significant difference in reps appeared on set 3 and favored the CA group (10.9 ± 2.5 and 10.0 ± 2.3 reps, respectively).

In another randomized crossover trial examining the effects of a CA on total number of reps performed in the bench press, subjects performed 3 sets of bench press to muscular failure at 75% 1RM with 1.5 minute rest intervals between sets.

The participants in this study were required to have at least 1 year of uninterrupted resistance training practice and had been performing the bench press for the past 6 months. The average subject weighed ~198 lbs and had a bench press 1RM of ~219 lbs.

In the CA group, subjects preceded the reps to failure assignment with 1 set of 3 reps at 90% 1RM, followed by 10 minutes of recovery.

The results showed a significantly greater amount of total work performed in the CA intervention. Across 3 sets to failure, subjects were able to complete an average of 22 total reps after the CA and 19 reps without it. 

Interestingly, this increase in total reps was attributed to increased performance on sets 1 and 2, with no significant difference in reps performed on set 3.

Continuing with this theme of the bench press, let’s examine the impact of a much different CA on the number of reps to failure with a moderate load. 

In this study, 2 different testing sessions were utilized. In the first testing session, both the control and CA groups worked up to 1 set of 2 reps at 85% 1RM on the smith machine bench press. Following this heavy double, subjects rested 3 minutes and then performed a maximum repetition test at 65% 1RM.

In the second testing session, the control group performed the same protocol utilized in the first testing session. The CA group performed a supra-maximal eccentric loading protocol which called for a 4 second eccentric with 120% of their 1RM.

For this trial, subjects were required to have at least 1 year of resistance training experience and an exercise frequency of at least 3 times per week. The average body weight of the participants was ~171.6 lbs and their average smith machine bench press 1RM was ~226 lbs. 

The researchers found that the supra-maximal eccentric loading protocol resulted in slightly better performance in the muscular endurance test (18.28 ± 4.11 vs. 17.25 ± 3.93 reps, respectively).

In the last study for this research review, we’ll be transitioning away from the bench press and taking a look at the squat. 

In a randomized crossover design, this trial looked at the effects of a CA on total reps performed in the back squat. Subjects performed 4 sets of back squats to failure at 70% 1RM, with 2 minute rest intervals between sets. 

Subjects were required to have at least 1 year of resistance training experience at a frequency of 3 days per week. Participants had an average body weight of ~179 lbs and an average back squat 1RM of ~230 lbs.

In the CA intervention, 1 set of 2 reps at 90% 1RM was performed, followed by a 5 minute rest interval.

The results showed a clear advantage for the CA intervention. In comparison to the control, significantly more reps were performed when the reps to failure protocol followed the CA (56.2 ± 17.3 vs 48.8 ± 14.5 reps, respectively). 

Despite this significant difference in total reps performed, there was only a significant difference in total reps performed on the first set. There were no significant differences in total reps performed for sets 2,3, and 4.

Variability in Response and Protocols 

Increases in muscle performance after a CA depend on the net balance between fatigue and potentiation. Muscle performance may improve if potentiation dominates and fatigue is reduced, remain unchanged if fatigue and potentiation are at similar levels, or decrease if fatigue dominates. The resulting potentiation and fatigue generated is influenced by the volume and intensity of the CA, as well as the recovery period between the CA and the subsequent exercise.

In addition to this, the characteristics of the individual utilizing the protocol must be considered. Variables such as training age, fitness level, and fiber type distribution may ultimately impact the potentiation and fatigue generated by a particular strategy. 

This notion of individuality has been evidenced by research in Division I volleyball players. In this study, the effect of performing a power exercise (hang clean) or strength exercise (back squat) on subsequent performance in a vertical jump test was measured. 

The results showed some participants had better improvements in vertical jump performance following the clean while other participants had better performance following the squat.

Concerning the heterogeneity of the studies from the previous section, it can be pretty difficult to draw strong conclusions about the effectiveness of a CA for resistance training performance. Fortunately, a systematic review and meta-analysis has been conducted which provides some insight into the factors which affect the response to a specific CA. 

It was found that stronger and more trained (minimum of 2 years of training experience) individuals experienced a greater PAP effect. Also, greater levels of potentiation were generally observed when 5-7 minute rest intervals were taken after the CA. 

In addition, stronger individuals exhibited a greater PAP effect after a single set of a CA, while weaker individuals showed a greater PAP effect following multiple sets of a CA. Furthermore, stronger individuals displayed a larger PAP effect when a rep-max load was used, while weaker counterparts experienced a larger effect with a submaximal load.  

Concerning these findings, I’d like to shift our attention to the first study mentioned in our research round-up. This was the only study that failed to find any meaningful impact from performing a CA prior to moderate-repetition work. This trial also included the most well-trained subjects of the 4 studies analyzed.

Theoretically, considering these individuals were the most well-trained, both in terms of strength levels and training experience, you would expect them to undergo a notable performance increase following a CA. My hunch is that the lack of success stems from the strategy utilized, which was 3 sets of 3 reps at 85% 1RM. This may have been a lackluster strategy for the population tested due to the amount of volume (9 total reps) generating excessive fatigue. Also, it is possible the intensity may not have been sufficient.

In line with the findings from the review paper, we could speculate that if these subjects performed 1 set of 3 reps at 90% 1RM, or more simply, a 3RM, they may have been able to perform more total reps in the subsequent 3 sets to failure.

Practical Takeaway

In general, it appears that utilizing a CA has the ability to improve resistance exercise performance through eliciting PAP. With that being said, the particular method implemented needs to be tailored to the individual in order to obtain the best outcomes (or any positive outcomes at all). 

Considering the ease of implementation, I definitely think it’s worth experimenting with a CA before performing lighter volume work in your training regimen. 

Using the broad recommendations from the previously cited review article as a starting point, I suggest incorporating 1-3 heavy sets (~80-90% 1RM) on your main movement before moving on to higher-rep work. If you’re a relatively stronger, more experienced lifter, maybe test out 1 set at 90% 1RM. If you’re a relatively weaker, inexperienced lifter (<2 years of hard structured training), try 3 sets at 80-85% 1RM.  

If you find that you are able to accumulate more total reps for a given number of sets following a CA, then you might have found a simple strategy to bolster strength and hypertrophy adaptations. If it doesn’t, try manipulating the number of sets and the intensity (% 1RM) of the protocol. For example, if you feel a bit fatigued transitioning into your volume work, try removing a set and shaving 2.5-5% off the load and see if there are any improvements in your performance.

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