Many advanced bodybuilders can be seen performing their reps in the gym with far less than full range of motion. They consider it beneficial to keep their reps somewhere in the mid-range of most exercises, utilizing just 30 % to 75 % of the total exercise-specific range of motion, often avoiding full joint lock-outs, and with some exercises also the “easier” bottom positions. Performing partial reps sometimes permits to use less weight, but often also allows to handle more weight as compared to executing full reps, depending on the exercise and the actual portion of the movement used to target a certain muscle; either the mid-position, the stretched position, or the shortened position of the muscle can selectively be hit. With partials, a full exercise movement is shortened in order to maximally isolate the target muscle, to produce more adaptive stress and to stimulate greater development of the respective area. The method serves to keep the target muscle under constant tension and generates an amazing pump, accompanied by an intense “lactic acid burn”, which makes the lift more difficult. Proponents of partials are convinced that maintaining constant tension on a muscle and thereby increasing “time under tension” generates more “metabolic stress”, one of the three major mechanism of hypertrophy, thereby prompting more muscle gains than working through full range of motion. Accordingly, they often perform the majority of their exercises in this way. The question is, whether this type of training technique truly has any merits, and whether YOU should incorporate this method into your work-outs ?

Let’s be clear, when discussing partial reps, we are NOT talking about those crazies, who load up the sled of an Incline Press with so many weight-plates that they just manage to perform a few knee bends with wobbly legs, at the most spanning a range of 4 to 6 inch near the movement’s top position. The same goes for those “athletes”, who load up their squat-bar with much more weight that they can handle for just one single full squat, then hardly manage to stagger a step back from the rack with the bar on their shoulders, before beginning to perform shaky knee bends that resemble quarter reps at the most. This is just mere foolishness, endangers the lifter, and is to be attributed to an ill- conceived attempt at “showing off” or just mere stupidity, which doesn’t need to be further discussed.

True partials, in the sense of an advanced bodybuilding tool, are based on the science that all exercises have their specific strength curve: in the course of performing a full-range lift, the targeted muscle often has to work hardest just during a certain portion of the movement, while the load on the target muscle often drops off near the top and/or when approaching the bottom of a lift.

When, for example, performing a biceps curl, we note that the lowest 30 % of the range of motion feels fairly easy, before the curl gets more difficult in mid-range, and eventually gets easier again, once the elbows have passed the 90 degree angle and the bar approaches top position. Staying in the mid-range of the motion where the lift is most difficult, and performing as many reps as possible between approximately 45 and 135 degrees of elbow flexion will serve to keep constant tension on the biceps. Wouldn’t it seem reasonable to assume that exclusively focusing on the hardest portion of the movement may generate better muscle development than performing each rep through full range of motion, granting the biceps a short reprieve in every bottom position ?

With dumbbell lateral raises, there is no load placed on the deltoids, when the arms are down next to the thighs; slowly raising the dumbbells out to the sides, the tension on the medial deltoids gradually increases and reaches its peak, when the arms arrive parallel to the floor. Executing partials by repeatedly raising the dumbbells up to shoulder level and then lowering them just halfway before raising them up again keeps constant tension on the medial deltoids and generates more “time under tension” and metabolic stress than allowing the dumbbells to come down all the way to the thighs with each rep, which would grant the deltoids a brief rest between reps. Doesn’t it seem to be a good idea to cut out the unproductive range and concentrate on the most productive range of the motion ?

When performing a full-range compound exercise, the movement usually ends with a full joint lock-out in top position where the weight- load is mainly supported by the skeletal system which grants the target muscle a short reprieve. With the bench press, each time the elbows lock out in top position, the weight load is stabilized by the joints and bones of shoulders and arms as well as the contracted triceps muscles, while the pecs get a short break. At the bottom position of the bench press, the front deltoids seem to take the brunt of the weight-load; the same applies to all other chest press movements. Keeping the reps in the mid- range of motion where the pecs are doing most of the work while eliminating those portions of the range, where the triceps and deltoids strongly assist, maintains maximum tension and focus on the pecs.

By cutting out the “easier portions” as well as the full joint-lock-outs of a lift, focusing on moving the load up and down in a controlled manner within the the most difficult range of an exercise, the target muscle stays constantly and maximally engaged and doesn’t have any chance to rest at any point during the set; this allows to best isolate the muscle, which many theorize to elicit superior muscle gains.

Performing exercises in the described manner will indeed serve to generate a great pump, which specifically applies to advanced bodybuilders; it is well known that it is far easier to achieve a tremendous pump when muscles are already well-developed. Utilizing partial reps quickly engorges the targeted muscle with more blood than can leave, and the experience of the burn that accompanies the accumulation of acidic waste products in that muscle, prompting cellular swelling by increased inflow of plasma into the muscle cells, suggests a highly beneficial work-out to bodybuilders, who often swear by this technique. Their prior extensive work-out-experience generally served to establish the proper control and a great mind-muscle connection, which is vital to successfully apply this advanced training method; they “feel” that this way of training works best for them in stimulating the hypertrophy they are striving to achieve, and the results appear to prove them right.

But when it comes to available scientific research into the effectiveness of “partial reps” or “constant tension” training, things tend to look less favorable. The vast majority of scientific studies has found that full repetitions are not only superior to partial reps for promoting power and strength across the entire movement, which could be expected, but, quite surprisingly, partials don’t even seem to truly outperform full reps in promoting muscle growth in most exercises.

When performing partials with a given weight, a lifter can generally perform more reps per set to failure than full reps with the same weight, which results in more “metabolic stress”, known to be one of three factors that contribute to hypertrophy. However, scientific research suggests that hypertrophy is even better stimulated, when muscles are forced to work against a heavy load at angles where they are in their most stretched position, an essential stimulus that is missing in partials where fully stretched positions are eliminated. As opposed to partial reps, full reps do not only contract a muscle completely, but also stretch it out entirely. At the start of each new concentric repetition, the muscle is forced to contract against the load when it is most lengthened, which appears to promote maximum muscle growth. When “time under tension” is extended by prolonging the eccentric phase of full repetitions so that the weight-load is lowered twice as slowly as it is lifted, muscle growth appears to be even more positively effected.

Another issue with partial reps is related to volume or work-load. When performing sets of “partials”, lifters often end up performing less total work as compared to performing sets of full reps, thus apparently shortchanging themselves, even though partials often allow to handle more weight and/or to perform more repetitions per set. Muscle growth is related to training volume, and volume-load per set refers to how much weight is lifted for how many reps and over what distance. Shortening the motion to just half its range tends to reduce the amount of total work and training volume per set when compared to performing sets of full reps to failure. After all, lifting 300 pounds over a distance of 8 inches involves just half the work than lifting those 300 LBS over a distance of 16 inches. The consideration that more volume equals a larger dose of training, which in turn stimulates more hypertrophy, suggests that partial reps should fail to promote more muscle growth than full rep sets, even when heavier weights are used, more (half) reps per set are executed, and good control and constant tension are employed.

Despite all the research and considerations in favor of performing repetitions through a full exercise-specific range of motion, one can’t sensibly argue that all those huge pro-builders, who heavily rely on partial reps in their training, might even be bigger and better developed, if they would just stick to full reps instead. One can not fail to acknowledge that for some individuals and in many instances, partial reps produce as good or even better results than full range repetitions. Fact is, that many advanced and professional bodybuilders have become experts at what what they do; throughout years of amassing extensive training experience – initially with full rep training ! – , they generally established high levels of intramuscular and inter-muscular control, and also a great mind-muscle connection and instinct, which guides them in figuring out what works best for them. Advanced bodybuilders are not concerned with performing all their exercises with what is deemed “perfect technique” and through a complete range of motion, but their focus is exclusively on stimulating their muscles in the way that works best for them. When strategically used, partials can serve to push for improvement in stubborn areas that may not be responding optimally to normal training. Partial reps lend themselves as an ideal tool for this purpose as they are so versatile: they can be done anywhere in an exercise’s range of motion and thereby allow to concentrate the focus on any particular portion of a movement which needs special attention.

With some exercises, the use of partials also seems to reduce stress on involved joints, may decrease the incidence of acute joint- and tendon- related injuries, and may diminish the deterioration of joints, which is a common consequence of long-term wear and tear sustained from executing countless repetitions of multiple exercises with full joint-lock- out under extreme weight-stress. Occasionally and strategically utilizing partial rep sets, where they are most effective, instead of exclusively performing full reps, may contribute to keeping joints intact and pain- free. This eliminates the set-backs and training-breaks required to recover from injuries, which usually engender the loss of plenty of hard- gained muscle.

When severe joint damage already exists, as it is often the case with older lifters, partial reps can prove an invaluable tool to still enable working muscles that would otherwise not receive any training. Controlled partial movements may provide an option to keep effectively working a muscle or body-part, when a joint issue causes too much pain to work through full range of motion. Partials can also be extremely useful in the rehabilitation of a joint-injury when full range of motion of the affected joint is physically not yet possible.

Partial repetitions can also be great when incorporating them into full repetition sets. A good example is adding partials at the end of a set performed with full repetitions, when momentary muscle failure makes performing any further complete reps impossible. Extending such a set by cranking out as many partial reps as still manageable excellently overloads the muscle in its stretched position and results in utmost fiber recruitment; enduring the resulting “lactic acid burn” for as long as

bearable, exercise intensity, “time under tension” and metabolic stress increase significantly, stimulating more hypertrophy.

Another example for effectively integrating partial repetitions with full rep sets is an old school bodybuilding technique called “21s”. “21s” involve to first perform seven repetitions of an exercise in the lower half range of the motion, followed by performing seven repetitions in the upper half range of the motion, before finally executing seven repetitions throughout the full range of motion. This is yet another time-proven method to maximize “time under tension”. Exercises that are particularly suitable for this method are biceps curls, straight-arm pull downs, Bulgarian split-squats, etc.

The so-called “one-and-a-half-technique” is yet another interesting way of integrating partials with full rep-sets; it can be highly beneficial to improve the sticking points of compound movements such as squats, bench presses, etc.

All the above explanations should suffice to point out that the partial- reps-method in its various forms can be a valuable bodybuilding tool, when strategically and intelligently utilized as a complement to full repetition training. However, partials are not indispensable to grow muscle and should not be relied upon as the predominant training method. Full repetition training still remains the bread and butter of weight-training, as it has proven most effective to improve overall functional strength and achieve maximum muscle development. Only when executing full range of motion, the highest possible percentage of motor units of a muscle will get properly activated, exposed to high levels of mechanical load, and optimally stimulated to grow.

On the other hand, partials aren’t always inferior, and not every repetition of every set needs to be performed through full exercise- specific range of motion.

In fact, the best path forward for most advanced bodybuilders may be to judiciously combine full and partial range of motion. Performing most of their exercises with full repetitions, but to sensibly add some partial rep training to their program when this seems most advantageous and in line with their individual goals may well turn out to be the perfect strategy.

Beginners and early intermediate bodybuilders do not need advanced training tools like partials, or other intensity techniques; in fact, these would prove counterproductive at this early stage of their training endeavors. During their initial two or three years of training, beginners and early intermediate lifters must focus on learning proper exercise techniques and build up a solid foundation; correctly applying progressive resistance and training all exercises through full range of motion is the proper way to best achieve this. Only once good intramuscular and inter-muscular coordination has been acquired, sufficient training experience has been gained, and a good mind-muscle connection has been established, the requirements for successfully including advanced training tools like partials or other intensity techniques are met.

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