WHAT IS POST-ACTIVATION POTENTIATION?
Post-activation potentiation (PAP) is a phenomenon by which the force exerted by a muscle is increased due to its previous contraction. While we know that fatiguing muscle contractions can impair muscle performance (think of going way too hard on your warm up), PAP has taught us that non-fatiguing muscle contractions at high loads may enhance muscle performance of the following exercise.
For instance, a back squat. The acute excitation of a back squat has been shown to improve subsequent explosive performances such as a vertical jump due to an acute increase in muscular power (caused by PAP). This improvement is attributed to an excitation of the nervous system that produces an increase in the contractile function of a muscle due to a heavy load conditioning stimulus.
In other words, doing a movement to first “activate” your neuromuscular system, can help improve your performance of the following exercise.
Note: This typically only applies when the 1st exercise is bio-mechanically similar to the 2nd exercise. For instance, you wouldn’t necessarily want to perform a bench press in order to improve your sprint performance.
SO, HOW DOES PAP WORK? (THE SCIENCE)
The underlying mechanism responsible for PAP is a series of neurophysiological responses both intra and inter muscularly. While studies show there are multiple neurophysiological mechanisms that may contribute to the effects of PAP, the three that are thought to provide the largest effects are….
PHOSPHORYLATION OF THE REGULATORY LIGHT CHAINS
This theory suggests that there is an increase in the phosphorylation of the myosin regulatory light chains (RLC) after the first “activating” exercise. This increases the sensitivity of the myosin-actin interactions, which may lead to an increase in the cross-bridge cycling rate. This increase would then result in a shift of the force-velocity curve to the right, allowing for faster movements with higher loads.
POTENTIATED H-REFLEX RESPONSE
This theory is based on an excitation of several neurological mechanisms following the activation exercise. After the initial exercise, we see an excitation in H-reflex potentiation, an increase in motor unit synchronization, a desensitization of alpha motor neuron inputs, and a decrease in the reciprocal inhibition of the antagonistic muscles. However, of the aforementioned adaptations, H-reflex potentiation seems to be the most dominant of the neural mechanisms within the research.
Note: High H reflexes = higher excitability.
PENNATION ANGLE OF THE MUSCLE FIBERS
This theory suggests there is a decrease in the pennation angle of the muscle fibers following a conditioning exercise. A decrease in this pennation angle means that more force can be transmitted through the tendon and ultimately to the bone upon contraction. If we can have a more forceful contraction, we would technically elicit a better performance. But admittedly, more research is needed on this theory before we can assume its accuracy.
SO, LET’S SAY YOU WANT TO TRY PAP… WHAT TYPE OF LOAD/WEIGHT SHOULD YOU USE?
Welp, like most things in the exercise science world, the research is conflicting. While many studies have observed light loads vs heavy loads, it SEEMS that heavy-load intensities would be more effective than light loads.
Example: Performing a back squat at 90% of your 1RM would potentially elicit a greater PAP response than performing a back squat at 50% of your 1RM. The most significant potentiation response seems to be with loads over 80-85% of your 1RM.
OKAY, SO HEAVIER LOADS? GOT IT…
BUT HOW LONG SHOULD YOU REST BETWEEN THE TWO EXERCISES?
While several studies have shown that PAP can improve subsequent performance, it should be noted that adequate rest time between the two exercises is crucial. Without enough rest time, there is no improvement in performance (and could even be a detriment to the subsequent exercise). In other words, if fatigue is too high from the 1st exercise, no performance improvement in the subsequent exercise will take place.
However, the same holds true if the rest period between the two exercises is too long. If too much rest is provided, the potentiation may dissipate, which again, causes no improvement in the athlete’s performance. This is known as the “Fatigue Fitness Model” – seen below.
Note: It is when the fatigue dissipates, that the effects of PAP can be beneficial.
Needless to say, in order for PAP to best be utilized in a practical setting, we must first know what type of rest interval is most appropriate.
In this scenario, think of the rest interval as it relates to the Goldilocks Principle; too much rest isn’t good, but neither is not enough rest. Unfortunately, while many studies have directly investigated various rest times to identify which length is most effective there hasn’t been much of a unanimous decision made among researchers. That being said, there is a large body of research that suggests improvements with PAP utilizing anywhere from 3 minutes to 12 minutes, between exercises, though between 7 and 10 is probably optimal for most people.
One of the reasons it’s so hard to pinpoint a specific duration of optimal rest time (or any one specific set of guidelines for PAP), is due to the variances among the subjects. In other words, everyone is different!
For instance, trained individuals tend to be more sensitive to the effects of PAP than untrained individuals. In fact, athletes who have at least 3 years of resistance training under their belt seem to respond much more optimally to PAP than untrained individuals. Additionally, those with higher strength also typically have a higher sensitivity to PAP than weaker individuals. Needless to say, it’s tough to give specific training guidelines when it comes to PAP due to the individuality of the person that’s utilizing it.
SO, THIS LEADS US TO THE MOST COMMON QUESTION OF ALL … sHOULD YOU USE PAP? IS IT WORTH INCORPORATING INTO YOUR TRAINING?
Well, it depends…
Reasons you might want to use PAP:
You’re an experienced lifter and want to try to improve strength
It may improve performance (short term and long term)
It increases the work capacity during your workout session
Reasons you may want to avoid PAP:
You haven’t been lifting that long (under 1 year training experience has been shown to be less effective)
It’s super individualized and takes quite a bit of trial and error based on subject specific variables
It takes more time (long rest periods aren’t ideal for those who don’t have a ton of workout time)
A dynamic warm up has been proven to enhance muscle contractility and improve subsequent performance (without all the complicated fluff of PAP) so you’d see great results with a solid warm up anyway.
That being said, if you do want to go ahead and give PAP a try…Keep this summary in mind: (TLDR version)
Post-activation potentiation has been consistently proven to improve subsequent athletic performances
PAP is used by engaging in an activation type exercise to improve the performance of the next exercise
This improvement can only take place in the “window of opportunity” between the initial fatigue diminishing and the excitation of the muscle dissipating
Anywhere from 3-12 minutes rest is needed between exercises
High intensity/heavy-load (e.g. 90%RM) = longer rest time between exercises
Low intensity/ light-load (e.g. 30%RM squat jumps/ plyometrics) = shorter rest time between exercises
Higher volume sets = longer rest times are needed
Lower volume sets = shorter rest times are needed
Trained athletes = shorter rest times are needed
Untrained athletes = longer rest times are needed
Stronger athletes = shorter rest times are needed
Weaker athletes = longer rest times are needed
Hope ya learned something new! - Owner & Head Coach, Joelle