Metabolic Boosting: Does A Super Slow Workout Really Hulk You Up? by Dr. Mauro DiPasquale

A training technique is generating lots of buzz among a segment of the training and fitness community. Super-slow resistance training, originally introduced in 1982 at the University of Florida by Ken Hutchins, is a form of strength training in which all movements are carried out in a very slow, careful and deliberate manner.

In super-slow training, the ‘concentric’ portion of each strengthening movement (in which muscles actually shorten as they are activated) take a full 10 seconds to complete, and the ‘eccentric’ portion (in which muscles are forced to elongate as they are activated) takes 4-5 seconds. For example, in a simple strengthening exercise such as the biceps curl, the lifting of the dumbbell to the shoulder (the concentric phase) would take 10 seconds, while the slow dropping of the dumbbell to the starting position (the eccentric phase) would take 4-5 seconds. By comparison, traditional strength training recommendations often involve a two-second concentric phase, a one-second pause and a four-second eccentric phase; and in practice many athletes abbreviate these phases to just one second each.

In super-slow technique, workout is in slow motion, focusing on coordination, form and control rather than speed. The objective is to create more tension in a muscle for a given workload. This is accomplished by decreasing the speed of movement. The amount of force or tension a muscle can develop during a muscle action is substantially affected by the rate of muscle shortening (concentric phase) or lengthening (eccentric phase). Proponents claim that the technique has more impact on strength and muscle size than traditional method. It also provides a a higher-quality aerobic workout than conventional weight work.

With lack of research studies on the matter, there are scant evidence to support these claims. Some physiologists pointed out, however, that energy expended (used) is a factor mainly of the amount of work performed during the session and the relative intensity (the percent of the one-repetition max) at which it is performed. Resting energy expenditure can increase after a strength workout, but the magnitude of this increase also seems to depend on the volume and intensity of the strength work carried out during the session. In a super-slow workout, both volume and intensity of work are likely to be fairly low.

Try bench pressing the maximum load you’re capable of and try holding and lifting this for 10 seconds and you’ll get an idea why super-slow training may not be such a metabolic booster.

Research on Metabolic Boosting Effect of Super-slow Training – To test the claims and counter arguments on super-slow training, scientists from the University of Alabama have conducted a study comparing the metabolic effects of super-slow and traditional strength training in seven young men who had been engaged in strength training for at least one year.

All of the subjects had stable body weights, averaging 79kg, and routinely carried out weight training with a combination of free weights and exercise machines. Their usual training involved 2-3 sets of various exercises, with 8-10 repetitions and an intensity of 65-70% of the one-repetition maximum (1RM) for each exercise. The athletes’ average 1RM for the bench press was 117kg, and it was 144kg for the squat.

Each athlete completed two workouts designed to train all of their major muscle groups, one using a traditional-training technique and the other the super-slow method. The workouts were separated by a three-day interval and the subjects were randomly assigned to a treatment order – either super-slow training first or traditional training first. The actual 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. On the morning after each workout (following a 12-hour overnight fast), the rate of resting energy expenditure was measured in each athlete.

The super-slow session involved one set of eight repetitions of each exercise, with 10 seconds of concentric and five seconds of eccentric action for each rep.

In the research work preceding the actual study, the researchers discovered limitation of super-slow training. In determining resistance to be used in the eight super-slow repetitions (reps), it was discovered none of the subjects could complete the required eight reps for any exercise with more than 30% of 1RM, so 25% of 1RM is chosen instead. This is considered very light resistance compared to the average 70% of 1RM for strength workouts.

In terms of actual exercise time, the amount between the two workouts differ even though workout duration was the same – 20 minutes (10 x8 x 15 seconds) for super-slow and 5:20 minutes (2 x 10 x8 x2 seconds) for traditional. Despite the shorter time, oxygen-consumption and heart rates were much higher during and after the traditional workout compared to the super-slow method. Average heart rate during the traditional workout was 143 beats per minute, compared with just 113 beats per minute during super-slow activity; average recovery heart rate with traditional training (recorded during the 15 minutes after the workout ended) was 119 beats per minute, compared with just 95 beats per minute with super-slow.

The same is true with respect to oxygen consumption. The net oxygen uptake during the traditional workout was 23 litres, compared with 15ltrs during super-slow effort. Similarly, during recovery after a traditional workout, the athletes burned 8.2ltrs of O2, compared with 6.7ltrs after super-slow training.

In terms of energy expenditure, super-slow lags behind the traditional workout. For the workout and 15-minute recovery period, traditional athletes expended a total of 172 calories compared with a paltry 107 kcals for the super-slow folks. Even post-exercise lactate levels favored traditional training, with lactate soaring to 7.9 millimoles per liter after traditional training, compared with just 4.0 after super-slow training. It is important to note that this lactate elevation would not increase the risk of muscle soreness in the traditional trainers since, contrary to popular belief, lactate is not linked with post-exercise muscular distress.

Metabolic Disadvantage – The research study also failed to support proponents claims of metabolic advantages for super-slow workout, and in fact present metabolic disadvantages. The amount of energy expended by the super-slow athletes during their 29-minute workouts was actually less than one would expect to burn during leisurely 20-minute-per-mile walking over the same time period, while oxygen consumption was too low to hike aerobic fitness.

In terms of intensity, 25-28% of 1RM in super-slow method is so meager that it is very difficult for this form of exercise to hoist metabolism in any significant way. In contrast, traditional workout’s 65-75% of 1RM is considerably higher, with greater consequent metabolic benefits.

In terms of actual benefit in muscular workout, the traditional method is ahead even though super-slow involve longer contraction times and more time spent lifting and lowering weight. Four times as much muscular work was performed during the traditional session than during the super-slow workout, even though the muscle-contraction time advantage favored super-slow effort by almost 4-1 (1200 seconds vs 320 seconds) .

Metabolic Boost or Bust – Does a workout where individual contractions are significantly extended provide strength benefits. To answer this question, 14 women, aged 19-45 years, were randomly assigned to either regular or super-slow groups. 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. The gains in strength for the 10 week study period for traditional resistance training and super-slow workout are compared.

The super-slow group used a 10-second-concentric and five-second-eccentric contraction sequence; the traditional exercisers employed two seconds of concentric and four seconds of eccentric action for each rep. Both groups completed one set of 8-12 reps for each exercise. The traditional athletes used an intensity of 80% of 1RM, while the super-slow athletes settled for 50%. Both groups took a 60-90-second rest between exercises and, as they grew stronger over the course of the study, resistance was increased in 2.5-5-% increments.

The results are (in terms of 1RM – in %):
metabolic boosting exercise

Both groups improved endurance, as measured on a cycle ergometer, to the same extent, and neither achieved a significant improvement in body composition.

Super-slow training proponents contend that super-slow promotes superior muscle hypertrophy (muscle size growth) better than traditional workout. Hypertrophy provide a one-two punch to fitness. One, muscle size growth is accompanied by gains in strength, Two, each 1lb gain in muscle tissue which accrues from strength training, there is usually a 10-20 kcal increase in daily energy expenditure, an effect which could enhance fat-burning and further magnify whole-body leanness. However, in super-slow training, there is a limitation. The intensity which is necessary to induce muscular hypertrophy is no less than 50% of 1RM, which is considered to be above the maximal intensity at which a great deal of super-slow training is carried out.

In summary, there is no evidence to suggest that super-slow training offers athletes much metabolic boosting. Super-slow training is, of course, better than no training at all, but there is no solid proof that it burns fat better, builds muscle more effectively, or provides a better ‘aerobic workout than conventional training.


Dr. Mauro Di Pasquale :: Dr. Mauro Di Pasquale :: is one of the most influential voices on diet, performance and athletic training in the world. His innovative work in finding safe nutritional alternatives to anabolic steroids and other performance-enhancing drugs has won him praise from athletes, trainers and fitness experts around the globe. Dr. Di Pasquale was a world-class athlete for over 15 years, winning the World Championships in powerlifting in 1976 and world games in 1981.

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