A Review of Research on SuperSlow® High Intensity Strength Training
Published Studies on SuperSlow
Several published studies have compared the effectiveness of SuperSlow and traditional strength training protocols. These include 1993 and 1999 studies by Westcott et al, a 2001 study by Keeler et al, and a 2003 study by Hunter et al.
The 1993 and 1999 studies by Westcott et al concluded SuperSlow increases muscular strength more effectively than the traditional two-second positive and four-second negative repetition speed. The study by Keeler et al concluded the opposite. Keeler et al also compared the effects on body composition and aerobic capacity (VO2 max), finding no significant improvements in either group. The Hunter et al study compared the effects of SuperSlow and a traditional protocol on metabolism and heart rate response, finding the traditional protocol resulted in greater heart rate increases and energy expenditure.
Keeler et al
In the Keeler study, fourteen previously untrained women were divided into SuperSlow and traditional groups, each performing one set of eight exercises three times weekly for ten weeks.
The SuperSlow group used a ten second positive and five second negative speed and a repetition range of eight to twelve, starting with 50% of their one repetition maximum (1RM). The traditional group used a two second positive and four second negative speed and a repetition range of eight to twelve, starting with 80% of their 1RM. Subjects were timed with stopwatches. When subjects were capable of performing twelve repetitions in good form the resistance was increased by 2.5% for the leg press and 5% for all other exercises. The average time to failure or time to finish (TTF) for the SuperSlow group was 120 to 180 seconds, while the average TTF for the traditional group was only 48 to 72 seconds.
Subjects were tested for their 1RM with no speed limitations on all exercises before and after ten weeks. At the completion of the study, the SuperSlow group only increased their 1RM loads by an average of 8.2 pounds, compared to an average of 19 pounds for the traditional group.
Critics of the Keeler study claim the lack of standardization of training loads and set duration obviates fair comparison of the protocols. However, the 1RM percentages used reflect the initial resistance selection recommendations in the second edition of the SuperSlow technical manual, page 132 of “70% of the suggestion for the standard 2/4 protocol”. The 50% of 1RM used by the SuperSlow group is approximately 70% of the 80% of 1RM used by the traditional group.
Although TTF was not standardized, the 120 to 180 second TTF resulting from the 10/5 repetition cadence and eight to twelve repetition range is within the 100 to 180 second TTF currently recommended for SuperSlow.
Keeler: One set of 8 exercises, 3 times per week for 10 weeks. N=14
SuperSlow Group: N=6, 10/5 rep speed, 8 to 12 repetitions, 120 to 180 second TTF
Average 1RM for all exercises increased by an average of 15% or 8.2 lbs
Traditional Group: N=8, 2/4 rep speed, 8 to 12 repetitions, 48 to 72 second TTF
Average 1RM for all exercises increased by an average of 39% or 19 lbs
Westcott et al
In both of Westcott’s studies, the SuperSlow group used a ten second positive and four second negative speed and a repetition range of four to six. The traditional group used a two second positive, one second pause, and a four second negative speed and a repetition range of eight to twelve. Subjects were supervised by instructors who provided a cadence count, but were not timed with stopwatches. When subjects were capable of performing the upper repetition guide number in good form the resistance was increased by 5%. The TTF for both groups was 56 to 84 seconds per exercise, with an average TTF of 70 seconds.
In the 1993 study 74 previously untrained men and women were divided into SuperSlow and traditional groups, each performing one set of 13 exercises, three times weekly for eight weeks. The SuperSlow group was tested for their five repetition maximum in all exercises using a 10/4 cadence (70 seconds TTF) and the traditional group was tested for their ten repetition maximum in all exercises using a 2/1/4 cadence (70 seconds TTF) at two and eight weeks. The SuperSlow group increased their exercise weight loads by an average of 26.5 pounds, compared to only 17.5 pounds for the traditional group.
In the 1999 study 73 previously untrained men and women were divided into SuperSlow and traditional groups, each performing one set of 13 exercises, two or three times weekly for ten weeks. The SuperSlow group was tested for their five repetition maximum in all exercises using a 10/4 cadence (70 seconds TTF), and the traditional group was tested for their ten repetition maximum in all exercises using a 2/1/4 speed (70 seconds TTF) at two and ten weeks. The SuperSlow group increased their 5RM chest press weight loads by an average of 24.0 pounds, compared to only 16.3 pounds for the traditional group.
In both studies by Westcott et al the SuperSlow groups’ exercise weight loads increased on average 50% more than the traditional groups’, while Keeler’s SuperSlow group’s average weight load increases were over 50% lower than those of the traditional group.
Critics of Westcott’s studies claim since repetition speeds were not timed during training or testing, any conclusions should be regarded as questionable. Westcott stated although stopwatches were not used, all workouts and tests were supervised by instructors who provided a cadence count.
Westcott 1: One set of 13 exercises, 3 days per week for 8 weeks. N=74
SuperSlow Group: N=37, 10/4 rep speed, 4 to 6 repetitions, 56 to 84 second TTF
Exercise 5RMs increased by an average of 26.5 lbs
Traditional Group: N=37, 2/1/4 rep speed, 8 to 12 repetitions, 56 to 84 second TTF
Exercise 10RMs increased by an average of 17.5 lbs
Westcott 2: One set of 13 exercises, 2 or 3 days per week for 10 weeks. N=73
SuperSlow Group: N=30, 10/4 rep speed, 4 to 6 repetitions, 56 to 84 second TTF
Chest press 5RM increased by an average of 24.0 lbs
Traditional Group: N=43, 2/1/4 rep speed, 8 to 12 repetitions, 56 to 84 second TTF
Chest press 10RM increased by an average of 16.3 lbs
Due to differences in study design and lack of standardized testing methods it is difficult to directly compare the effect of TTF between the SuperSlow groups in the Westcott and Keeler studies. However, a shorter TTF appears to be more effective for increasing muscular strength in previously untrained subjects when using the SuperSlow protocol. Westcott’s ten-week SuperSlow group’s average 5RM chest press loads increased by an average of 200% more than the 1RM chest press weight loads of Keeler’s SuperSlow group.
Comparison of Westcott 1999 and Keeler SuperSlow Groups
Westcott 2: N=30, 10/4 rep speed, 4 to 6 repetitions, 56 to 84 second TTF, 13 exercises 2 or 3 times per week
Chest press 5RM increased by an average of 24.0 lbs
Keeler: N=6, 10/5 rep speed, 8 to 12 repetitions, 120 to 180 second TTF, 8 exercises 3 times per week
Chest press 1RM increased by an average of 9 lbs
The significantly greater strength increases achieved by Westcott’s SuperSlow groups compared to Keeler’s reflect the experiences of a number of SuperSlow instructors and trainees currently using TTF averaging 40 to 80 seconds who report greater muscular strength and size increases than with the recommended 100 to 180 seconds.
The issue of effectiveness of shorter versus longer TTF has been the subject of debate among SuperSlow instructors for several years now. Objections to shorter TTF include the belief it may increase risk of injury or instances and severity of form discrepancies. Experienced SuperSlow instructors using shorter TTF with clients have reported neither problem.
Although the majority of published research shows no significant difference in the effectiveness of different repetition ranges (within a reasonable range of three to twenty) for increasing muscular strength, even the higher repetition counts used (up to 25) result in a set duration well under 90 seconds at typical, unrestricted repetition speeds. Additionally, lower repetition ranges with heavier loads may be required to increase bone density.
Hunter et al
In the Hunter study, seven previously trained men were measured for heart rate during and energy expenditure during, immediately following, and 22 hours after both SuperSlow and traditional strength training workouts. Subjects were measured for resting energy expenditure after a twelve-hour overnight fast using a Delta Trac II, and for 1RM in each of ten exercises, then randomly assigned to a protocol order group, either SuperSlow followed by traditional strength training, or traditional followed by SuperSlow. Each group was tested using both protocols, with the second workout performed three days afterwards.
The SuperSlow group performed one set of eight repetitions (120 seconds TTF) of ten exercises, using a 10/5 cadence and 25% of their 1RM. The percentage was determined by preliminary tests for the amount subjects could use for eight repetitions. Rest intervals were limited to one minute, and total workout times averaged twenty nine minutes.
The traditional group performed two sets of eight repetitions (approximately 30 seconds TTF) of ten exercises, using an unspecified speed of movement and 65% of their 1RM. Rest intervals were limited to one minute, and total workout times also averaged twenty nine minutes. The paper states “the cadence between repetitions was controlled so each set took thirty seconds”. It is not clear whether this refers to the actual repetition speed or a rest period between repetitions. The speed of each repetition for the traditional group averaged slightly faster than four seconds.
The energy expenditure for the SuperSlow workouts was substantially lower than for the traditional workouts during, immediately following, and twenty two hours later, and the heart rates during the workouts were much lower for the SuperSlow group. This is not surprising considering the SuperSlow group used significantly less resistance than the traditional group.
It is important to consider that claims regarding the fat-loss benefits of SuperSlow are based on increases in resting energy expenditure resulting from increases in muscle tissue, rather than increases in energy expenditure during and after the workouts. Studies comparing the effectiveness of strength training protocols for fat loss should focus on increases in lean mass and resting energy expenditure over time, rather than energy expenditure during and immediately following exercise.
General Criticism of Published Studies on SuperSlow
Both the Westcott and Keeler studies were of insufficient duration to rule out motor learning as a significant factor in improved test performance. Clinical studies on exercise should last significantly longer than six to eight weeks, generally considered the duration over which motor learning has a significant effect on performance improvements.
Static strength testing protocols should be used in any study comparing the effects of repetition speeds for standardization and to rule out potential speed-specific improvements as a factor in test performance.
Some claim the results of these studies are questionable because subjects were not trained by certified SuperSlow instructors. However, the purpose of these studies was to compare exercise protocols, not instructional ability, so this is not a valid criticism.
Force Gauge Experiments
Advocates claim SuperSlow strength training is safer than traditional, faster repetition protocols because it exposes the body to lower levels of force. However, force gauge experiments by Brian Johnston have shown no significant difference between peak forces during exercises performed with 10/10, 5/5, and 2/4 repetition cadences.
Using a Quantrol AFTI digital force gauge and WinWedge software to plot data points, Johnston measured the forces during one repetition of cable shoulder presses using a resistance of thirty four pounds, including the weight of the force gauge hardware and cable handle. The subject positioned himself at the end point of the range of motion then performed the negative and positive phases of the exercise using ten second negative and positive movements, five second negative and positive movements, and four second negative and two second positive movements.
Both the 10/10 and 5/5 protocols resulted in peak force measurements of 34.7 pounds. The 2/4 protocol only produced a slightly higher peak force measurement of 36.3 pounds. Although there was no significant difference between the 10/10, 5/5, and 2/4, all of these produced significantly lower peak forces than the “explosive” protocols tested, which resulted in measurements of 54.3 and 63.1 pounds.
The graph below shows the force gauge measurements of the 5/5 and SuperSlow 10/10 repetition cadences superimposed over the measurement of the traditional Nautilus 2/4 repetition cadence. The width of the lines from the original 5/5 and 10/10 graphs have been adjusted so the start and end points line up with those of the 2/4 graph, but the heights of the lines has not been changed. Although the 2/4 line is easily identifiable due to the different ratio of time spent performing the negative to the positive, the measurements for the 5/5 and SuperSlow 10/10 repetition cadences are nearly impossible to tell apart.
Since the greatest acceleration typically occurs during the reversal of direction (turnaround) at the start and end of the range of motion rather than during the concentric or eccentric portion of an exercise, peak forces are affected significantly more by turnaround performance than repetition speed.
Although no significant reduction in peak force may be achieved by using repetition cadences slower than 5/5, slower repetition speeds may be safer for some trainees due to improved ability to maintain proper form and greater ease of observation and correction of form discrepancies by instructors. Individuals with poor kinesthetic sense or “body awareness” may also find it easier to focus on the target musculature when moving more slowly during exercise.
There is no conclusive research showing SuperSlow or other very slow repetition protocols are more effective for increasing muscular strength and size than traditional repetition speeds. Force gauge studies suggest there is no significant difference in peak forces or quality of muscular loading between traditional repetition speeds and slower repetitions.
Ken Hutchins, the developer of the SuperSlow protocol currently recommends a TTF of 100 to 180 seconds and routines consisting of as few as three or four exercises performed once or twice per week. While this may be appropriate for some individuals, a repetition cadence and range resulting in a TTF similar to the traditional Nautilus protocol would be a better starting point for most (around 60 to 90 seconds). Since response to exercise varies experimentation is necessary to determine the appropriate set duration, volume and frequency for any individual.
Carpinelli RN, Otto RM, Winett RA. A Critical Analysis of the ACSM Position Stand on Resistance Training: Insufficient Evidence to Support Recommended Training Protocols. Journal of Exercise Physiology Online 2004;7(3):1-60
Hunter GR, Seelhorst D, Snyder S. Comparison of Metabolic and Heart Rate Responses to Super Slow Vs. Traditional Resistance Training. Journal of Strength and Conditioning Research: Vol. 17, No. 1, pp. 76–81
Hutchins, Ken. SuperSlow: The Ultimate Exercise Protocol, 2nd Edition. 1992
Hutchins, Ken. SuperSlow: The Ultimate Exercise Protocol, Supplement to the 2nd Edition. 2001
Johnston BD. The Effects of Momentum on Muscle Loading, Synergy 2005
Keeler, L. K., Finkelstein, L. H., Miller, W., & Fernhall, B. (2001). Early-phase adaptations of traditional-speed vs. SuperSlow resistance training on strength and aerobic capacity in sedentary individuals. Journal of Strength and Conditioning Research, Vol 15, No. 1, pp. 309-314
Kerr D, Morton A, Dick I, Prince R. Exercise effects on bone mass in postmenopausal women are site-specific and load-dependent. J Bone Min Res 1996; 11: 218-25
McGuff MD. Rep Cadence and Force: A Personal Anecdote. http://www.ultimate-exercise.com/repcadence.html
Taaffe DR, Pruitt L, Pyka G, Guido D, Marcus R. Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women. Clin Physiol 1996; 16: 381-92
Westcott WL, Winett RA, Anderson ES, Wojcik JR, Loud RL, Cleggett E, Glover S. Effects of regular and slow speed resistance training on muscle strength. Journal of Sports Medicine and Physical Fitness. 2001 Jun;41(2):154-8
Phone discussion with Wayne Westcott, PhD., March 15, 2005
Informal surveys and interviews of SuperSlow instructors and trainees conducted during summer and fall 2004