How do advanced techniques affect hypertrophy?
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Bodybuilders often make use of a range of advanced techniques, including back off sets, drop sets, rest pause training, forced repetitions, pre-exhaustion training, antagonist supersets, and stretching between sets. The research investigating these techniques is minimal, but we can make predictions about their effectiveness (and their limitations) based on our understanding of how hypertrophy works.
Back off sets
Back off sets involve performing additional sets with a lighter weight immediately (or shortly) after a main sequence of heavier sets. Since heavy loads are used in the main part of the workout, this technique is more often used by strength athletes, than by bodybuilders.
Even so, the long-term research that has been performed into back off sets suggests that they are effective for increasing hypertrophy, most likely because they increase the total number of stimulating reps in the workout.
Such beneficial effects are likely only going to be apparent when the main sets are performed with heavy loads (and therefore involve little aerobic demand, minimal afferent feedback associated with metabolite accumulation, and few stimulating reps per set), such that the addition of a set with a light or moderate load to failure causes a large increase in the number of stimulating reps for the workout. Adding a back off set with a light load on the end of a workout involving multiple sets to failure with a moderate load may not have the same incrementally beneficial effect.
Drop sets are probably the most well-researched advanced technique. The method involves doing multiple sets to failure immediately after one another, without taking any rest between sets. This is accomplished by reducing the weight on the bar for each set.
Research investigating the long-term effects of training with drop sets has been done, but is conflicting. Some studies indicate that the additional drop sets provide no additional benefits beyond the first set. However, other studies indicate that drop sets involving a total of three sets produce just as much hypertrophy as three conventional sets to failure.
On balance, it seems that a drop set workout comprising a total of three sets to failure (with two drops in weight from the first set) produces essentially the same amount of hypertrophy as three sets to failure with the same weight, with moderate (90-second to 3-minute) rests between sets. The studies in the literature have taken a varied approach to the rest period duration used by the comparison group, which is a bit problematic given that rest period duration does affect muscle growth, but even so.
Since drop sets are normally performed with moderate loads, each set should involve a similar number of stimulating reps, regardless of the weight on the bar. Therefore, we should perhaps not be too surprised that a drop set with three total sets produces similar muscle growth to three conventional sets to failure. However, drop sets involve performing multiple sets immediately after one another, with little rest, and we know that longer rests are superior for hypertrophy from both long-term training studies and also assessments of muscle protein synthesis rates.
Short rest periods probably reduce hypertrophy by either (1) allowing lifters to do subsequent sets before central nervous system fatigue has dissipated, or by (2) triggering greater central nervous system fatigue through either greater aerobic demand or afferent feedback. Since all of these factors are likely also produced by drop sets, it remains mysterious why they are not less effective than the same number of conventional sets to failure.
Ultimately, it seems that drop sets allow the same number of stimulating reps to be accomplished in a shorter amount of time. This may be advantageous for advanced bodybuilders who struggle to fit their target training volume into a workout.
Forced repetitions involve a spotter providing assistance to the lifter to perform additional reps after reaching muscular failure.
Although they look very different, forced repetitions are essentially identical to drop sets, except it is the spotter that reduces the effective external resistance of the barbell weight by providing an upward force, instead of the external resistance being reduced by taking weight from the bar.
Currently, there is very limited research into the effects of forced repetitions, and such research has only assessed changes in maximum strength and not muscle size. Even so, based on the essentially identical nature of forced repetitions and drop sets, it seems likely that they will have similar effects, with the main downside being the inability to quantify the magnitude of the force being exerted during the forced repetitions, which makes tracking progressive overload practically impossible.
Rest pause training
Rest pause training involves performing one main set, followed by additional sets with very short (20-second) rests. Since the weight on the bar is not altered, these additional sets tend to involve only a small number of reps compared to the first set. Moreover, rest pause training often targets a total number of reps for the workout, with the number of additional sets being varied to reach this target.
Rest pause training has shown promising results in the research that has been performed to date. Even so, this research is limited insofar as the comparison group probably did not do each of their multiple sets to failure. Even so, it is likely that rest pause training simply allows lifters to perform additional stimulating reps, with the added benefit that each rep in the later sets is a stimulating rep, which makes the approach quite efficient.
While rest pause training has attracted adherents because of its efficiency, it does have a downside compared to conventional sets to failure or drop sets. Unless carefully calibrated, each additional set after the first main set will involve fewer than five reps, which means that quite a few additional sets are required to reach a meaningful number of stimulating reps for the workout. This requires training to failure many times, and this may delay recovery.
Ultimately, rest pause training likely allows the same number of stimulating reps to be achieved in a shorter amount of time, due to the very short rest periods between additional sets that can be used without negative effects. This may be advantageous for advanced bodybuilders who struggle to fit their target training volume into a workout.
Antagonist supersets involve performing alternating sets of two exercises for opposing muscle groups. For example, the bench press is often supersetted with a row variation.
By targeting completely different muscle groups, each exercise can be trained with a fairly long rest period, while alternating exercises are performed with much shorter rest periods. Sometimes, the exercises are done immediately after one another, followed by a moderately long rest. At other times, the exercises are equally spaced with short rest periods between them. Either approach allows workouts of a given volume to be accomplished much more quickly, or larger volume workouts to be done in the same period of time.
To date, no long-term studies have compared the effects of training with a normal sequence of exercises and with antagonist supersets.
However, research has shown that supersetting the chest press and seated row exercises allows a greater number of reps to be performed in each exercise in the later sets. These extra reps are likely the result of the fatigued antagonist muscle producing less force during the subsequent agonist exercise, and this is unlikely to be particularly helpful for hypertrophy. Yet, it does suggest that there is no negative effect of supersets on training volume, which might be expected if there was increased central nervous system fatigue secondary to either a greater aerobic demand or afferent feedback, as with using short rest periods between sets of the same exercise.
Therefore, it seems likely that antagonist supersets allow the same number of stimulating reps to be accomplished in a shorter amount of time, and this may well be advantageous for advanced bodybuilders who struggle to fit their target training volume into a workout.
Pre-exhaustion involves performing a single-joint exercise before a multi-joint exercise that involves the same muscle group as a prime mover. For example, the knee extension might be used before the leg press, or the triceps extension or dumbbell fly might be used before the bench press.
By performing a single-joint exercise prior to a multi-joint exercise that involves the same muscle group as a prime mover, this alters the effects of the multi-joint exercise on all of the prime movers, although the extent of the effects differ depending on which muscle group is pre-exhausted and the muscles loaded by the single-joint and multi-joint exercises.
This is most easily appreciated by considering worked examples.
#1. Knee extension/leg press
When the quadriceps are trained first with a single-joint knee extension exercise prior to the multi-joint squat or leg press exercises, both the two-joint rectus femoris and the single-joint vastus lateralis, medialis, and intermedius muscles are worked, although the rectus femoris is developed to a greater extent, as shown by long-term training studies.
Consequently, it is possible that only the rectus femoris achieves full motor unit recruitment in the knee extension, although all of the quadriceps will be fatigued (both peripherally and centrally).
When doing the leg press after the knee extension, the quadriceps are already fatigued (both peripherally and centrally). Since the leg press is limited by our ability to produce force with the single-joint vastus lateralis, medialis, and intermedius muscles (and less by the ability to produce force with the hip extensors), while the rectus femoris is minimally involved, this has two effects. Firstly, it reduces the load we can lift for a given number of reps (which reduces the training effect on the unfatigued hip extensors). Secondly, single-joint vastus lateralis, medialis, and intermedius muscles may not reach full motor unit recruitment, due to the presence of central fatigue.
Therefore, the use of pre-exhaustion with the knee extension and leg press (or squat) is unlikely to be as effective as the reverse order, in which the single-joint vastus lateralis, medialis, and intermedius muscles are trained very effectively by the squat, with a higher loading on the hip extensors as well, while the rectus femoris is left largely untouched. Subsequently, in the knee extension exercise, the single-joint vastus lateralis, medialis, and intermedius muscles are already fatigued, but the rectus femoris is the limiting factor and it receives the largest stimulus from the exercise.
#2. Triceps extension/bench press
When the triceps brachii are trained first with a single-joint elbow extension exercise prior to the multi-joint bench press exercise, which head of the triceps brachii is worked most will depend on the exact exercise. Even so, elbow extension exercises are very effective for loading all heads of this muscle, so they likely achieve full motor unit recruitment, although they are fatigued afterwards.
When doing the bench press after the elbow extension, the triceps brachii are already fatigued (both peripherally and centrally). Since the bench press is limited by our ability to produce force with the pectoralis major (clavicular and sternocostal heads), anterior deltoid, and triceps brachii working together, there is a degree of load sharing between these muscle groups. Consequently, when the triceps brachii are already fatigued, a greater load is likely placed upon the other prime movers. We might expect a pre-exhaustion approach to training the triceps brachii before the bench press to produce greater gains in triceps muscle size as well as (probably) pectoralis major (sternocostal head) size.
Stretching between sets
Either form of mechanical loading causes hypertrophy, and this phenomenon has been observed in training studies involving both animals and humans. Also, when fibers are subjected to both active and passive force production at the same time, this leads to enhanced anabolic signaling, which suggests that the two types of mechanical loading are additive, although the effects of passive loading alone are much smaller than the effects of active force production alone, which indicates that strength training should always be prioritized over stretching for muscle growth.
Indeed, stretching the prime mover (agonist) muscle between sets of an exercise reduces the number of reps that can be performed, and this reduces hypertrophy over the long-term. This most likely happens because the stretching is fatiguing the muscle without producing quite as much stimulus for hypertrophy. Conversely, stretching the antagonist muscle between sets seems to increase the number of reps, most likely because the opposing force is reduced during the subsequent set with the prime mover, although this probably does not enhance hypertrophy.
Moreover, strength training using an exercise where the forces are greatest while the muscle is in a stretched position (such as the quadriceps in the squat) is likely a better method for applying stretch loading to a muscle than passively stretching, since the external load is an easy way to provide a large force to stretch the muscle, and the muscle is simultaneously contracting, which produces the additive effects at the same time as strength training, rather than afterwards.
Additionally, it is worth noting that not all muscle groups are likely to be affected in the same way by using an exercise where the forces are greatest while the muscle is in a stretched position. Those muscles whose muscle fibers operate on the descending limb of the length-tension relationship (such as the quadriceps, and particularly the vastus medialis) will likely be substantially affected by using such exercises, but those that do not (such as the triceps brachii) will not.
What does this mean in practice?
In practice, drop sets, forced reps, rest pause training, and antagonist supersets are ways in which the number of stimulating reps in a workout can be increased without similarly increasing the length of time spent in the gym. Each approach has slightly different advantages, disadvantages, and limitations, but ultimately they are way to increase training volume without simultaneously triggering the problems that reducing rest period duration causes. Back off sets involve fractionally greater time commitments, but are probably only really useful when training with heavier loads.
Each of these methods introduces a greater degree of complexity into the workout (some more than others), and this presents a challenge for monitoring progressive overload, which is essential to long-term muscle growth. Forced reps are essentially impossible to monitor in the gym, and lifters using this method could easily spin their wheels for months without realizing that they were not moving forwards with an exercise. Drop sets, rest pause methods, and supersets are more straightforward to track, so long as the short rest periods between drops, additional sets, or supersets are maintained the same length. Even so, without following the clock very closely, it is easy to allow these short rest periods to increase by a couple of seconds, which can improve strength recovery, and make it appear like progressive overload has been achieved when it has not.
Pre-exhaustion is a completely different method, which requires an understanding of how the fatigue produced by the single-joint exercise is affecting the stimulating effects of the multi-joint exercise.
Stretching muscles between sets is unlikely to have as beneficial an effect as conventional strength training, so time spent stretching is probably best spent resting or performing an exercise instead.
What is the takeaway?
Most advanced techniques used by bodybuilders are methods that seem to allow a larger number of stimulating reps to be performed in a shorter period of time but without the reduced stimulus that is associated with using shorter rest period durations. The main drawback with such approaches is that it can be more challenging to track progressive overload over time, and this is essential to ensure that progress is being made.
If you enjoyed this article, you will like my second book (see on Amazon).