The term ‘tempo’ is used to define the speed of movement of weight training exercises. More specifically, it is the rate of movement of the weight or limb involved in any strength training exercise. Most bodybuilders might change their exercise selection, sets, reps, and rest periods, but the one variable which has been largely overlooked, and which may significantly impact training results is the tempo of the exercises. For years, the standard repetition speed has been lift up or concentrically in two seconds and lower the weight slowly or eccentrically in four seconds, in a slow controlled manner for optimal muscle mass. Some top trainers have even taken this type of training a step further and developed what is known as SuperSlow training.
The interesting fact is that there is no research to validate that this tempo 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 10 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 (1).
This is not the only study to document training with fast eccentric contractions are best for increasing muscle mass. For example, Farthing et al. (25) 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. 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 (2). The men trained one arm using a fast velocity, while they did the same number of repetitions for the other arm at a slow velocity. 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 fiber area after training for the type II fibers was greater in the fast-trained versus the slow-trained arm. In addition to greater increases in type IIb fibers, the fast eccentric contractions group increased strength to a greater extent than slow contractions.
Why Lift Fast And Explosive for Muscle Hypertrophy?
In order to induce hypertrophy, either exercise intensity or volume must be increased: most bodybuilders perform enough sets but may find difficulty increasing training intensity to make additional gains in strength and size. However, the amount of weight used cannot be increased, and an alternative method to increase intensity must be achieved. Moving the weight at a higher speed implies using more power, as explained above, and more power translates directly to a higher level of intensity. Speed training provides an alternative path to the progressive resistance principle, which states that in order to induce muscle hypertrophy, one has to constantly keep increasing the weight used. Muscle hypertrophy is defined as an increase in muscle mass that is related to two factors: the amount of workload employed and the tension developed during muscle contraction (3). Most bodybuilders focus mainly on workload or the amount of sets utilized during their training routine to increase muscle hypertrophy, seldom changing repetition speed. Speed training may develop motor unit recruitment patterns different from traditional weight training, thus potentiating better gains with subsequent regular training cycles.
According to Dr. Verkhoshansky, the tempo of resistance exercise has a significant effect on the development of muscular strength (this is because of fast twitch fiber enhancement). Dr. Verkhoshansky reported that a combination of different movement tempos produce superior gains in strength compared to a set tempo. In that study, over a 10-week study, the group of men that trained with a combination of tempos produced a 22-kg increase in strength, however using a standard tempo pace resulted in only a 16.3 kg increase in strength (4). The results of the study demonstrate the importance of changing repetition speed during a training cycle.
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 (5). The more motor units or muscle fibers that are activated in a repetition, the greater the activation in 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.
What is unique about eccentric contractions is there is some evidence to suggest that the size principle could be altered or even reversed during certain types of movements-specifically those that contain an eccentric (muscle lengthening) component-such that fast-twitch motor units are recruited before slow- twitch motor units (24). It is possible that a preferential recruitment of fast-twitch motor units is influenced by the speed of the eccentric contraction, and can only occur using moderate to fast speeds.
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 hypertrophy yet are the last fibers to be recruited during a lift. This is a basic 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 occur in those muscle fibers that are overloaded, so that fast twitch fibers must be recruited during training in order for hypertrophy to occur (6). 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 (7). 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 (8, 9) and plyometrics (10, 11). 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 production. The plyometric training consisted of vertical jumping, bounding, and depth jumping (22).
Type IIb fibers are utilized during high force generating movements. Just remember, for any given speed, the force production by the muscle increases with the percentage of fast twitch fibers and, conversely, at any given force output, the velocity increases with the percentage of fast twitch fibers. For example, look at the thighs of 100m sprinters compared to distance runners. World-class sprinters have legs that would make some bodybuilders jealous. Sprinters train fast and explosively, utilizing a much greater percentage of type IIa, and type IIb fibers during training, compared to distance runners who rely mainly on type I fibers. Sprinters train in the gym the way they run; fast and explosive. A typical sprinter trains with explosive squatting, lots of plyometric jumps, and bounding exercises. Training specificity states that you should weight train like you perform in your competitions. For example, basketball players were assigned to either train with traditional weight training or traditional weight training plus explosive eccentric plyometrics for six weeks. While both groups experienced increases in their vertical jump at the end of the study, the group that trained with weight training and plyometrics increased their mean overall vertical jump by 8% (26). Thus, high force eccentric training can increase gains and muscle power possibly by increasing muscle size.
Why SuperSlow Training Does Not Work
SuperSlow Training (SST) involves performing reps very slowly, in a 4-1-10 tempo. That is a 10-second concentric movement per rep, a 1-second pause, and then a 10-second lowering movement. In SST, you take the momentum out of the movement and put all the tension on the muscle. Sounds good for muscle hypertrophy and metabolic responses right? It sounds good in theory but it just does not hold ground in research.
For example, researchers compared heart rate and oxygen consumption in seven young men who had been engaged in strength training for at least one year. In this study, each athlete completed two workouts designed to train all of their major muscle groups, one using a traditional-training technique and the other SST. The workouts were separated by a three-day interval and the subjects were randomly assigned to a treatment order – either SST first or traditional training first. The exercises performed included leg extensions, bench presses, biceps curls, leg curls, French curls, bent rows, reverse curls, military presses, upright rows and squats. Heart rates and minute-by-minute oxygen-consumption rates were recorded during each workout and for 15 minutes after the sessions as well; blood-lactate levels were measured immediately after the training ended. When researchers attempted to determine how much resistance could be used during the performance of eight super-slow repetitions of the exercises, they found that none of the subjects could complete the required eight repetitions for any exercise with more than 30% of 1RM.
As an astute reader, you can immediately see how SST has a remarkably limiting impact on the training intensity. Using 30% of 1RM is considered a very light resistance, and the average intensity used by most athletes during strength and muscle hypertrophy workouts is about 80 % of 1RM. Remember, a large load (80% of a 1-RM) will lead to rapid recruitment of fast twitch motor units which have high growth potential. At the end of the study, total net energy expenditure was about 45% higher for the traditional weight training compared to SST. The lactate responses post-exercise was almost 2 times greater following the traditional weight training compared to SST (12). So much for SST for increasing metabolism.
In another investigation, the gains in strength associated with 10 weeks of traditional resistance training were compared with those using SST (13). The subjects were 14 women, aged 19-45 years, who were randomly assigned to either regular or SST. Both groups trained three times a week during the study period, performing leg presses, leg curls, leg extensions, anterior lateral pull-downs, bench presses, seated rows, biceps curls, and triceps extensions. After 10 weeks, the traditional group had improved 1RM significantly more than the SST for the bench press (34% vs. 11%), the anterior lat pull-down (27% vs. 12%), the leg press (33% vs. 7%), leg extensions (56% vs. 24%) and leg curls (40% vs. 15%). The traditional group’s improvement in total weight lifted was significantly greater than that of the SST (39% vs. 15%). Although proponents of SST may feel lifting slowly is harder, the training responses do not add up to increased training gains.
Why Eccentric Contractions are Best for Muscle Hypertrophy
So why is so important to emphasize explosive eccentric (ECC) contractions in your training routine. When comparing the amount of force that can be exerted by muscle contractions, ECC contractions yield higher force production than concentric (CON) contractions. When comparing maximal ECC contractions to maximal CON contractions, you can generally handle about 30-40% greater workloads during ECC contractions. Additionally, it has been reported that type II b fibers are more susceptible to eccentric exercise induced muscle damage than type I fibers, which may explain how fast ECC contractions induce muscle hypertrophy (23). The greater force producing capacity and higher degree of muscle damage can stimulate hypertrophy thru numerous mechanisms.
ECC Contractions and Muscle Protein Synthetic Rates
Animal and human studies have documented that protein synthesis rates increase dramatically after ECC exercise, whereas protein synthesis rates after CON exercise are not elevated to the same extent. Wong and Boothe (14, 15) reported that ECC contractions induce muscle tissue hypertrophy through protein kinetics that are different from those of CON training. In their study, rats performed 24 electronically induced contractions of either plantar flexion (gastrocnemius) or extensions (tibialis anterior) every four days for 10 weeks. The goal of the study was to measure acute (12-17 hours) and post-exercise (36-41 hour’s) protein synthesis rates of identical contraction times for both CON and ECC training as well as tissue hypertrophy. Acute CON contractions increased gastrocnemius protein synthesis rates by 38 % but CON training failed to produce muscle hypertrophy despite an increase in protein synthesis. Contrary to CON training, acute ECC training resulted in a significantly higher protein synthesis rate 58% compared to 38%. Post-exercise protein synthesis rates from ECC but not CON exercise resulted in increased protein synthesis rates for 36-41 hours after exercise. ECC exercise produced muscle hypertrophy, whereas the similar CON protocol failed to produce muscle hypertrophy. Protein synthesis increased in the tibialis anterior (TA) after as little as 1 minute of total contraction duration (24 repetitions) by 30% and 8 minutes of total contraction time (192 repetitions) further increased TA protein synthesis by 45% above controls.
Taken together, when CON and ECC contractions are performed with the similar total contraction times the data suggest that ECC exercise may play a larger role in muscle hypertrophy than CON exercise due to greater myofibrilliar protein breakdown after exercise. It can therefore be hypothesized that ECC training could result in a more anabolic environment due to increased protein degradation that is followed by rapid increases in protein synthesis. The greater increase in protein synthetic rates is speculated to occur because ECC exercise causes more damage, which results in the turnover of proteins, which must be replaced by new proteins. It is the damage produced from ECC exercise that stimulates immunological mediators to remove damaged tissue and repair damaged tissues by the incorporation of new proteins.
ECC training and Muscle Hypertrophy
ECC contractions are not just important for muscle hypertrophy, but some research indicates that their role seems to be essential (18, 19). Cote et al. (19) tested sedentary subjects using maximal CON only training on an isokinetic strength training routine for 10 weeks. No significant changes in mean skeletal muscle fiber area (i.e. no muscle hypertrophy) were observed. Cote speculated that the reason isokinetic resistance equipment fail to produce tissue hypertrophy was due to the absence of ECC contractions in the training routine.
Hather et al. (17) documented that CON contractions without an ECC contraction failed to produce muscle tissue hypertrophy. Eight males trained unilateral leg extensions and leg press either with CON/ECC contractions or CON/CON (performed twice as many CON contractions) contractions for 4-5 sets and 6-12 reps two days a week for 19 weeks. Only the CON/ECC group showed an increase in mean fiber, whereas the group performing on CON contractions had no increase in muscle hypertrophy. Additionally, Hortobagyi et al. (20) had 15 males train either isokinetically CON or ECC for 12 weeks. Each subject trained with 4-6 sets of 8-12 reps; 3 times a week. At the end of 12 weeks, Type I fibers did not increase significantly in either group. The most interesting aspect of the study was that Type II fiber area increased 10 times more in the ECC group compared to the CON group.
In a similar study, Higbie et al. (21) had 16 women train isokinetically either CON or ECC. The subjects trained 3 times a week using 3 sets of 10 reps for 10 weeks. Quadriceps cross-sectional area measured by magnetic resonance imaging increased more in the ECC-training group (6.6%) than in the CON-training group (5.0%). One may speculate that ECC training produced greater hypertrophy because it produces greater torque; however, ECC training at low training intensities has also proven to stimulate muscle hypertrophy.
Incorporating Explosive Lifting Into Your Routine
Therefore, now that the science of explosive training has been presented, you are probably going to want to start incorporating some lifts into your routine. Plyometrics are a great for incorporating explosive eccentric exercise. An excellent reading resource for incorporating plyometrics into your training routine is Donald Chu’s, PhD. book, Jumping into Plyometrics. Plyometrics are an exercise technique that incorporates a rapid eccentric contraction followed by an explosive concentric contraction. I would suggest a 6 x 10 Method for hypertrophy and strength. That is 6 sets consisting of 10 explosive reps. This type of training will recruit the motor units that possess both Type IIB and Type IIA muscle fibers, respectively. This is very important since the aforementioned fibers have the greatest potential for growth. Emphasize explosive muscle actions (lifting) during the set, which maximally recruits the motor units mentioned above. Make the rest period short since you will be performing 10 reps per set, the total duration of the set is very short (~9 seconds). This is imperative since the force producing capabilities fast twitch motor decrease at any time longer than approximately 10 seconds. Rest periods should be approximately 1 minute between sets.
In conclusion, many bodybuilders and fitness oriented athletes alike would likely benefit from adding a few explosive type exercises to their training regimen such as plyometrics. In competitive athletics, when all other factors are equal, power is the deciding factor between winning and losing. The ability to generate concentric and eccentric force over a range of contraction velocities is often critical determinant of athletic success. For years, weight training was considered to slow an athlete down and make an athlete inflexible. Fifteen years ago, the University of Nebraska started training their football team using only the explosive Olympic lifts and the squat. Performing explosive lifts such as power cleans, jump squats, and depth jumps recruit entirely the fast twitch motor units. The training effect produced a stronger, faster, and more mobile athlete—and a winning record. Now, virtually all football teams incorporate Olympic lifts for explosive strength and power. Most bodybuilders never train with explosive eccentric contractions. The maximum force that a muscle can develop is attained during a rapid eccentric contraction. Incorporating these movements into your training routine will increase size and strength beyond traditional weight training.
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