A few months back a new forum poster asked what I believed to be a harmless question:
Do partial reps build muscle more effectively than full range of motion reps?
Being the grumpy old school lifter that I am, I responded with a resounding no. I really don't know any lifter than relies on partial reps as a muscle building staple, so therefore I consider them to be a non-essential practice.
Before even doing research and writing this article, I will tell you unequivocally that I will still feel the same way no matter what information I find. While some tools may work as muscle builders, that does not make them essential tools.
Partial reps. Drop sets. Rest-pause training. On and on. All of these tools can hold value, but that does not make them essential. You do not need them in any way to build muscle. That doesn't mean they can't provide benefit. They simply aren't needed.
The war FOR partial reps
Now, remember how I started this article by stating that I "believed" this was a harmless question? Wow, was I completely wrong. My answer was met with a full-scale forum war retaliation.
Posters were crawling out of the wood work to tell me that bodybuilder "so and so" uses only partial reps, and that bodybuilding writer "so and so" preaches about them as if they were magic. Fair enough. Like I said, all tools can be useful. Let's not forget the likely reality that both of these individuals made the majority of their gains before ever considering the use of partial reps.
So, that aside, and my dogmatic view on partial reps aside, let's take a deeper look at what they are, and if they do indeed provide some benefit.
What are partial reps?
Partial reps are performed pretty much as you would expect. You move the resistance for a given exercise only over a portion of the total range of motion.
Though they can be used in many ways, the majority of training videos I have seen featuring partial reps utilize them over a 50 to 75% range of motion. I have also seen bodybuilders use mini-partials at the end of sets at a 30 to 50% range of motion.
A key aspect of the partial rep (in the bodybuilding realm) has to do with the avoidance of the lockout position. In fact, in my research this is why more and more bodybuilders are advocating partial reps. The theory is that by performing partial reps and avoiding the lockout position, a greater degree of stress is placed upon a muscle (or muscles involved), lending itself to a greater amount of gains.
Strength training and partial reps
Avoiding the lockout does it increase the stress placed upon a muscle?
Yes. You will most certainly experience a greater degree of lactic acid buildup. This is primarily due to no longer having a reprieve (lockout) between reps.
Lactic acid buildup almost always makes a set more difficult. You are trying to perform each additional rep while experiencing increasing amounts of pain. This will lead to an amplification of other various forces and variables, such as greater shakiness, which places greater demands on both the muscles, joints and connective tissue.
But with this increase in stress placed upon a muscle, tradeoffs are made. Though a muscle will be under a "burn" for a higher percentage of time during a set, you will not be able to maintain as much time under tension because of this burn. You will also be forced to use an overall lighter weight.
Does lactic acid build muscle?
Then there is the whole issue of lactic acid burn and muscle building. Lactic acid makes a set feel more intense, but this is not a guarantee that muscle is being built. You can hold a pencil over your head, and eventually the lactic acid buildup will force you to lower your hand. Is this building muscle? No.
Lactic acid buildup is an indicator of lactic acid buildup. The pain associated with lactic acid is your body's method of telling you to stop exercising. While it does indicate that a muscle is being placed under an unusual stress, lactic acid itself has no tie in with the muscle building process.
One might argue that lactic acid production lends itself to more IGF-1 and HGH release. While this might be true, natural lifters still can't "pump through the pain" and create inhuman amounts of muscle size that transcend natural physiological limits.
If muscle building was as simple as this, we would have found out long ago that lifters don't need steroids - they would only need to push through the pain. This simply isn't reality. The muscle size of natural bodybuilding champions hasn't changed one bit over the last 60 years. (See: Your Maximum Muscular Bodyweight and Measurements by Casey Butt, Ph.D.)
If pumping through the pain yielded inhuman amounts of mucle size for naturals, someone would have found out long ago and the world of natural bodybuilding would have changed. It hasn't.
In the short term partial reps will certainly feel more difficult. They will place a higher degree of stress upon the body. Much of this stress is smoke and mirrors, in my opinion. Lactic acid will make a set feel more intense, and can continue to do so in the absence of progressive resistance. This alone signals that it's impact is highly deceptive.
At the end of the day, and as with most things in the muscle building realm, we are forced to return our focus back upon progressive resistance. So partial reps or not, whatever you do much involve greater degrees of resistance.
Can this increase in stress be a good thing?
For some exercises, partial range of motion may be better for the body. For others, not so much.
Let's look at squats, for example. If you fail to reach parallel during barbell squats the emphasis of the lift remains on the anterior chain, or muscles in the front of the body. This results in an unbalancing of the forces placed upon the knee, and can lead to knee issues.
When you squat to parallel, balance is restored as the posterior chain comes more into play. The squat immediately becomes a more knee-friendly lift.
If one were to squat from parallel to, say, a half squat position, the knee might be safer but the weight used would have to be dramatically decreased and it would be more difficult to maintain tightness throughout the lift.
If you were to squat just shy of lockout, but to parallel as you descend, the lift would be rather safe, but there's a good chance you would experience an increase in lower back fatigue as the reps mounted.
The point here being...weight causes stress. This is an unavoidable reality. If you take the stress off one area, it will be placed upon another area. If you do not lockout a lift, you are maintaining a continuous amount of stress, and perpetuating an increase in overall set stress.
This could impact joints, connective tissue, and some muscle groups that weren't normally targeted during an exercise's execution.
Do we know for certain which exercises become more dangerous due to the discontinuance of the lockout? Probably not. These are likely to be different for each lifter. Therefore, when utilizing partials make sure to listen to your body and what it's trying to tell you regarding a specific exercise.
In what other ways might a partial rep increase training effectiveness?
More Reps Per Set. Partial reps can help you perform more reps per set, as sets are typically performed in a burst - or machine gun style. While this is an effective short term tactic to 'shock" a muscle, or groups of muscles, the body will adapt to the unique demands of this protocol rather quickly.
Progressive resistance will need to be introduced at some point. Because of this, the introduction of partial reps as a method to perform more reps has limited impact. It is a good tactic to try every now and then as a finisher or one off workout, but is not inherently better than full range reps simply because it can temporarily increase total rep output.
More Weight Per Set? Or Less? It is unlikely that partial reps that avoid lockouts will allow for the use of more weight. In most cases, the opposite will be true. Take the lockout out of the equation, along with the short break that a lockout provides, and you are making a lift more difficult.
For this reason, partial reps come with a small, and generally unnoticeable tradeoff. Any benefits that might come from partial rep usage will be counteracted by the requirement to use a slightly lighter resistance.
To further complicate this topic, we can look at one of the major studies performed on partial reps, "Specificity of limited range of motion variable resistance training" (Graves, 1989). This research revealed that partial rep training had a carry over of up to an additional 20 degrees above the training angle.
In the real world this means that whatever angle you are working your joints up to, they are building an equivalent amount of strength of up to 20 additional degrees. So it you were curling only to the halfway point of a rep, or up to 45 degrees, you should be able to curl that same amount of weight up to 65 degrees.
So, partial rep sets that are performed closest to the lockout state have the greatest impact on near-lockout to lockout strength. Half reps, on the other hand, did not increase lockout strength.
Does this matter when it comes to muscle building? Not really. Again, we are pulled back to the need for progressive resistance, regardless of the technique or angle used. If you keep doing the same thing over and over again, the body acclimates. Add in a tougher demand, the body responds and tries to adapt.
Powerlifting-style partials do indeed allow for greater weight used, but again, they are a completely different beast because they involve lockouts.
But I heard some studies say partials were good?
Partials that involve overloading the portion of a lift where force production is maximal have been shown to be beneficial. Unfortunately for the bodybuilding realm, this typically involves the last 2 to 5 inches of a lift - or the lockout a movement.
So while bodybuilders are training partials shy of locking out a movement, with no imminent guarantee that this is any more effective than conventional training, they may in fact benefit from the opposite - overloading the top end of a lift.
A Bloomberg University study (Mookerjee and Ratamess) found that trainees who worked partials in this manner increase not only their one rep max strength, but also their 5 rep max strength. The potential carryover to muscle building is simple: greater demands and strength increases could provoke a greater degree of muscle building.
Simply stated, using partials that involve lockouts, in conjunction with your existing muscle building workout system, may be just as useful or a tool, if not more useful than working non-lockout partials.
The verdict on partials - lockouts, no lockouts, or avoid partials?
Here is what we know about partial reps shy of lockout.
- Partial reps shy of lockout can be a useful "shock" tool.
- Partial reps can be a good technique to assist with the muscle building process if used in conjunction with progressive resistance.
- Partial reps increase lactic acid buildup which isn't necessarily indicative of effectiveness.
- Partial reps generally reduce time under tension potential due to more rapid tactic acid buildup, but can increase the number of reps per set performed if done in burst fashion.
- Partial reps generally reduce the amount of resistance utilized, which isn't important if progressive overload is in the mix.
- Partial reps may place unwanted stress on some joints, while relieving stress on other joints. This is very much lift specific.
Here is what we know about partial reps that are worked in maximal force areas (that involve lockouts):
- Lockout partial reps can increase strength in the 1 to 5 rep max range.
- These strength increases, in conjunction with a muscle building workout, have the potential to work hand in hand to yield more rapid muscle gains. More overload creates a potential for more rapid gains.
- Lockout partial reps can create unwanted joint stress for certain movements (Squats not to parallel, for example).
Here is what we know about lockouts, and normal sets in general:
- Lockouts create a temporary reprieve for the muscle, extending set time by create a slight amount of time for a muscle to recover intra-set. This reduces the rate of cumulative lactic acid buildup, allowing for the potential to perform more reps with a given weight.
- Full range reps involve an equal, or balanced amount of force. All things considered, this may be the best thing for the body and joints as a whole.
So the conclusion is...
The best way to build muscle is progressive resistance using a full range of motion. This is the bread and butter of training, and will yield consistent results.
Tools such as partial reps, in any form, can have value.
You are best focusing on the basics during your first year or two of training. Learn form, don't miss workouts, use a good exercise selection and focus on progressive resistance. It is inadvisable that a beginning training utilize partial reps, especially before they have a proven grasp of exercise form.
At some point advanced training techniques can offer a mental and physical break from the demands of constant ultra-heavy training. For this reason, they carry inherent value. This does not mean they are needed, but merely that they can assist with the muscle building process should a lifter find them valuable.
Experiment for yourself. You will likely find that partials might be of value to you on some exercises, but not for others.
Monitor the impact partials have on your joints. Take extensive notes and determine if their usage comes with risks and rewards. Consider using non-lockout partials as finishers or as shock workouts rather than staples.
Some of you will likely enjoy partial rep usage. If so, by all means use them. Even if they become an effective tool, understand that what works best for you will not be a requirement for the next lifter.
Each of us is mechanically and physiologically unique. What feels good for you will feel awful for the next guy. Therefore, while partial reps on certain exercises might be a boon for you, another lifter might benefit more during their intermediate years from the inclusion of tools such as burn sets or supersets.
Understand that one bodybuilder might find them to be effective for several lifts. This does not mean they will be effective for all lifts at all time, nor that they are even needed.
Try things yourself, always knowing that the basics work just fine and most of you will never have to worry about any advanced techniques to reach your goals.