Explosive Lifting Turns on Different Muscle Genes than Strength Training
by: Robbie Durand
Maximizing the hypertrophic response to resistance training is thought to be best achieved by proper manipulation of exercise program variables including exercise selection, exercise order, the length of rest intervals, intensity of maximal load, and training volume. If there ever was a controversial topic in the world of bodybuilding, it’s repetition speed. If you were involved in a sport like sprinting, it would be pretty easy to figure out that you have to train explosively because you need to teach your legs to move as fast as humanly possible. Also, if you’re involved in power sports such as Olympic lifting or football, then you know that there are no exercises that are performed slowly. All the exercises such as clean and jerks and power cleans are performed very explosively. Football wide receivers will often perform “over speed training” in which a slingshot type rubber tubing is attached to the player to train the muscles and nervous system faster than it’s used to.
With resistance exercise, it’s much harder to say which way to train is best for muscle mass. Some trainers swear by fast lifting for gaining muscle, whereas other were advocate slow and controlled lifting. A recent review article published by one of the top muscle growth experts in the world, Brad Schoenfeld recently published a great review on the topic titled, “Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis.”
Here is a breakdown of what researchers found in the collection of studies investigating repetition speed and muscle growth. A total of eight studies were identified that examined repetition duration in accordance with the criteria outlined. When they crunched all the data from the studies, they found that muscle hypertrophy outcomes are similar when training with repetition durations ranging from 0.5 to 8 seconds. What they did find was that “superslow training” (>10s per repetition) is inferior from a hypertrophy standpoint, although a lack of controlled studies on the topic makes it difficult to draw definitive conclusions.
Based on the recommendations of the author, he recommends a broad range of lifting speeds into a lifters workout. It seems logical that most of the workout should incorporate an explosive concentric based portions of the lift followed by a slow, controlled eccentric but not more than three seconds. You should never jeopardize an injury while trying to lift explosively, but the research tends to lean more to a faster tempo for muscle growth than a slow and controlled tempo.
The Science of Explosive Lifting
The interesting fact is that there is no research to validate what tempo of lifting speed is the optimal pace to increasing muscle hypertrophy. According to a study published in the European Journal of Applied Physiology, lowering the weight slowly may not be the best way to increase muscle mass and strength. In that study, male and female subjects were assigned to train for ten weeks to either two types of training: slow or fast velocity eccentric training. At the end of the study, the group that trained with fast eccentric contractions had the greatest increase in muscle hypertrophy. Muscle hypertrophy of the type IIB fibers (i.e. type IIB fibers are fast twitch fibers) increased from 6% to 13% in subjects. The slow group did not experience any gain in muscle mass. This is not the only study to document training with fast eccentric contractions are best for increasing muscle mass. For example, another study reported similar finding in that fast eccentric lowering was superior to slow eccentric lowering. Men and women trained the same number of reps and sets, but the only difference was the speed at which they performed the reps however the fast eccentric lowering group increased muscle hypertrophy by 13% whereas the slow eccentric group increased muscle hypertrophy by 7.8%.
In a follow-up study by Farthing and colleagues, compared fast and slow training, a group of 12 untrained men exercised both arms three days per week for eight weeks. The men trained one arm using a fast velocity while they did the same number of repetitions for the other arm at a slow speed. At the end of the study, Type I muscle fibers increased in size by an average of 9% with no significant differences between fast or slow training. The change in tissue area after training for the type II fibers was greater in the fast-trained versus the slow-trained arm. In addition to more significant increases in type IIb fibers, the fast eccentric contractions group increased strength to a greater extent than slow contractions.
The amount of weight lifted depends on the laws of physics. Simply, FORCE = MASS X ACCELERATION. This means the amount of force that you generate during weight lifting can be increased by either lifting more weight or lifting the same amount of weight at a faster speed. If you are performing the same number of reps with the same amount of weight but lifting it with more acceleration, you are producing more force- and this means larger central nervous system activation. This is not a new concept, in 1954, a study by Bigland-Ritchie and Lippold, demonstrated that the faster a weight is accelerated through a lift, the more nervous system activation is required for the movement. The more motor units or muscle fibers that are activated in a repetition, the greater the activation of the central nervous system. This represents an increase in training intensity. During muscle contraction, motor units or muscle fibers are recruited in relation to the force generated by the muscle. For example, during slow muscle contractions type I fibers are recruited, but as workload increases more type IIa and finally IIb, fibers are recruited. This is a basic tenet of motor unit recruitment. When examining the potential for hypertrophy between muscle fibers (i.e. slow type I and fast type II), there are differences. In general, Type IIb muscle fibers have the greatest potential for muscle hypertrophies yet are the last fibers to be recruited during a lift. This is a fundamental flaw in the SuperSlow training principles; with low force or slow activities, type I fibers are activated first then as the exercise becomes more fatiguing type IIa and then type IIb fibers are recruited later.
When using fast, explosive exercises, more fast twitch motor units are activated, and more hypertrophy can occur. Hypertrophy will only happen in those muscle fibers that are overloaded so that fast twitch fibers must be recruited during training for hypertrophy to occur. It was reported that an average of 25% increases in muscle hypertrophy across tissue types using an unloaded power training (i.e., plyometrics only). It has also been reported that lightweights performed explosively corresponding to the maximum power training intensity produced hypertrophy gains of 2.8%. Therefore, it appears that muscle hypertrophy occurs even when exercising with low loads if movement velocity is high. Indeed, there are a couple of studies showing that high movement speeds produce greater muscle hypertrophy than low movement speed when the workload is equalized between them.
Most bodybuilders do not train explosively and can benefit from incorporating explosive multi-component plyometric or speed resistance movements into their training regimen. For example, most bodybuilders have increases in type IIa fibers that occur during resistance training studies with no changes in type IIb fibers. This may be partially due to using high volume (i.e. 5-8 sets) and high repetition (i.e. 10-15 reps) training. However, incorporating plyometrics and other explosive lifts may cause additional muscle growth of IIb fibers. For example, there have been numerous studies that have documented increases in type IIb fibers after explosive weight training and plyometrics. For example, when male subjects performed plyometric training for three days a week for eight weeks resulted in significant increases in type IIb fiber hypertrophy and peak power production15. The plyometric training consisted of vertical jumping, bounding, and depth jumping. Other ways of performing explosive lifting are just trying to use a lighter weight and explode out of the eccentric part. Doing jump squats or smith bench press throws are two examples of lifts that can be performed explosively for type IIb motor recruitment.
Explosive Lifting Turns on Different Genes than Strength Training
In this month’s European Journal of Applied Physiology, researchers were interested in comparing two different types of training protocols and its effects on downstream regulators of genes for muscle hypertrophy. In particular, they were interested in a gene called wingless-type MMTV integration site family (WNT) that has recently been shown to be involved in adaptations to mechanical overload. For instance, this pathway was activated during skeletal muscle hypertrophy induced by an ablation protocol, which overloaded the leg muscle in mice. Greater increases in WNT production are associated with enhanced muscle hypertrophy. Also, previous research has reported that specific WNT-related genes are increased in myostatin knockout mice. Since it is well known that such animals exhibit marked muscle growth, this study also supports the hypothesis that WNT pathway activation may be associated with skeletal muscle hypertrophy. When WNT is activated, it turns on cell growth. The researchers assigned 25 subjects and were randomly assigned to strength training, power training, and a control group. The strength training (ST) and the power training or explosive lifting (PT) groups performed high and low-intensity squats, respectively, three times a week, for eight weeks. Muscle biopsies from the vastus lateralis muscle were collected before and after the training period. The strength training group trained with intensities between 10RM and 4RM, while the power training group trained with intensities varying from 30 to 60% of 1RM. Power training is performed using light loads and high movement velocities, examples of power training movements are jump squats and plyo-push ups while the ST regimen involves using high loads, which consequently lead to a greater time under tension and lower movement velocity. Both groups were instructed to perform each repetition as fast as possible and trained with a similar number of sets per week. However, training intensities and external movement velocity were different between them. Training intensities progressed through the 8-week period following a periodized model and were about 40% higher in the strength-training group compared with the power-training group. Load adjustments were performed every four weeks for both the strength training and power training groups. The strength training exercise load was based on the maximum load that could be supported to complete the desired number of repetitions while the power training exercise load was based on a percentage of the squat 1-RM. At the end of eight weeks, both groups experienced similar increases in muscle strength and muscle hypertrophy, but the researchers found that key genes related to the WNT pathway were up-regulated after 8 weeks of both groups; however it should be noted that the power training regimen was a much more potent stimulus to elevate the expression of WNT pathway genes compared to the strength training regimen. Remember, increased WNT levels are associated with muscle mass and hypertrophy although no differences were shown after eight weeks, long-term training may show different responses. The researchers suspected that the explosive lifting caused distinct molecular pathways to be activated. It could be that the high velocity of power training, which uses explosive force, caused the greater increases In the WNT pathway. For example, it has been shown that high-velocity eccentric muscle actions result in greater hypertrophy than low-velocity eccentric muscle actions, probably due to increased protein remodeling.
Besides, satellite cells are well known to participate in skeletal muscle repair; therefore, one can speculate that plyometric training, due to its high velocity/eccentric component, leads to a more intense recruitment of satellite cell activity. In conclusion, incorporating some fast, explosive training into your bodybuilding can increase fast twitch fibers and based on the new study reported this month can also upregulate genes for muscle hypertrophy. Try incorporating some explosive lifting into your routine and this may spur new muscle growth. The key to power training is lifting fast and explosively, so incorporating some explosive training would be a good way to shock your nervous system and enhance gains in muscle mass.