Beginning exercisers who performed strrength training repetitions more slowly experienced significantly greater strength gains.
A few years ago, another researcher and I published the results of a study featuring beginning exercisers who performed strength training at either a faster repetition speed (7 seconds each) or a slower repetition speed (14 seconds each). We found that the subjects who performed their repetitions more slowly experienced significantly greater strength gains.1
We concluded that slower repetition speeds were preferable to faster repetition speeds for strength development, presumably due to less momentum and more muscle stimulus. While this may be true, it is possible that other factors influenced our findings. First let's examine the similarities and differences between the two training protocols.
Protocol similaritiesSimilarity No. 1. Both exercise protocols required the same time under load for completion of the exercise set. Group 1 performed an average of 10 repetitions (ranging from eight to 12) in seven seconds each for a 70-second exercise set. Group 2 performed an average of five repetitions (ranging from four to six) in 14 seconds each for a 70-second exercise set.
Similarity No. 2. Both exercise protocols used a four-second eccentric muscle action on each repetition. Group 1 performed a two-second lifting (concentric) movement, paused one second in the position of full muscle contraction, and then performed a four-second lowering (eccentric) movement. Group 2 performed a 10-second lifting (concentric) movement followed by a four-second lowering (eccentric) movement.
Protocol differencesDifference No. 1. The subjects in Group 1 spent less time in each concentric muscle action than Group 2. As noted above, Group 1 executed two-second lifting (concentric) movements, whereas Group 2 performed 10-second lifting (concentric) movements.
Difference No. 2. The subjects who performed 10-second lifting movements reported more training discomfort than the subjects who executed two-second lifting movements. In fact, only two of the 147 study subjects chose to train with 14-second repetitions after the study was completed, even though the slower repetition speed produced superior results.
It is notable that the Group 1 subjects spent approximately 30 percent of each repetition in concentric muscle action, whereas the Group 2 subjects, who attained greater strength gains, spent approximately 70 percent of each repetition in concentric muscle action. Based on this observation, I decided to take a closer look at the concentric action time versus the eccentric action time in repetitions of equal duration. Because beginning exercisers appear to be more comfortable with moderate-speed repetitions compared to slow-speed repetitions, I chose a six-second repetition speed for this study.
Study particularsFor this study, 54 women were randomly assigned to one of two training protocols. All of the subjects performed eight to 12 arm curls to the point of muscle fatigue on a Nautilus biceps curl machine equipped with a Fitness Advisor computer. The computer provided visual and audible guidance for each lifting (concentric) and lowering (eccentric) movement. Twenty-eight women performed six-second repetitions with a shorter concentric muscle action (two seconds lifting and four seconds lowering). They spent approximately 33 percent of each repetition in concentric muscle action. Twenty-six women performed six-second repetitions with a longer concentric muscle action (four seconds lifting and two seconds lowering). They spent approximately 66 percent of each repetition in concentric muscle action.
All of the subjects were assessed isometrically (via Microfit computer) for maximum biceps strength (90 degrees elbow flexion) before and after the 10-week training program. On average, the women who executed two-second concentric muscle actions increased their biceps strength by 9 pounds, and the women who executed four-second concentric muscle actions increased their biceps strength by 12 pounds (see Figure 1). Although data analyses fell slightly short of statistical significance (p<0.06), six-second repetitions performed with longer (four-second) concentric muscle actions compared favorably with six-second repetitions performed with shorter (two-second) concentric muscle actions, and may prove to be more effective for strength development over longer training periods.
Study resultsWhile our preliminary research project requires replication studies, there appear to be advantages to spending a higher percentage of each repetition on the concentric muscle action. First, consider that muscles can produce more force output during eccentric actions than during concentric actions. That is, with a given weightload, the lifting movement is more difficult than the lowering movement. Second, consider that muscles can produce more force output during slower speeds than during faster speeds (see Figure 2). Consequently, it may make sense to use a slower speed during the more difficult lifting (concentric) action, and to use a faster speed during the easier lowering (eccentric) action.
Although our research has not shown six-second repetitions to be more effective than other controlled movement speeds, most people find this to be a comfortable repetition cadence.2 Of course, six-second repetitions have been widely used in fitness facilities since Arthur Jones recommended this exercise speed in 1970. Let me suggest that instead of always asking clients to perform six-second repetitions in a two seconds up and four seconds down format, you occasionally have them perform six-second repetitions in a four seconds up and two seconds down format. You may find, as did our study subjects, that this is a highly productive strength training protocol. Clients will still complete 10 repetitions in 60 seconds, but 40 seconds (rather than 20 seconds) will be used for the more challenging concentric muscle actions.
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Body Bar Systems Inc.
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Iron Grip Barbell Company
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Matrix Fitness Systems
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