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Does elastic resistance enhance traditional cable column exercises?

Recently, strength and conditioning professionals have been adding elastic resistance to traditional isotonic resistance exercises such as the bench press and squat in an effort to improve strength outcomes. In theory, so-called “variable” resistance (in the form of elastic bands or weighted chains) provides increasing resistance toward the end of the range of motion and helps facilitate power development. A study in the Journal of Strength and Conditioning Research found that adding elastic bands and chains to traditional free-weight barbell exercises may increase maximal strength levels and increase power input.

Adding elastic bands to the ends of barbells produces resistance in ‘parallel’ to the direction of gravity. Researchers in Spain wanted to see if they could produce similar results by adding elastic resistance in ‘series’ with the direction of exercise using a cable column exercise machine. They noted that the combination of elastic resistance with the constant load of the pulley cable should decrease the need for deceleration at the end of the movement, thus enhancing muscle tension throughout the range of motion.

The researchers began by connecting an elastic resistance device in-series with the pulley cable and handle. The resistance of the band was equivalent to the load of the pulley weight stack, representing 70% of one repetition maximum (RM). 21 healthy undergraduate students performed a standing biceps curl exercise to fatigue with 2 conditions: traditional pulley resistance and elastic resistance in series with the pulley. The conditions were counterbalanced with a week in between testing. Data were collected on the number of repetitions to failure, velocity, and rating of perceived exertion (RPE).

 Subjects were able to complete 1.5 more repetitions with the traditional isotonic resistance compared to the series elastic condition (average 12.4 versus 10.9 repetitions, respectively) at similar RPE levels (7.9 and 8.2 on the OMNI scale). In addition, there was more decrease in acceleration in the traditional pulley resistance compared to the elastic resistance-enhanced condition, suggesting decreased deceleration as the researchers had postulated.

The researchers concluded that the elastic resistance applied in series to a cable pulley resulted in a smoother and consistent decline in acceleration during the biceps curl exercise. They suggested that a greater average muscle tension could have been achieved throughout the range of motion, leading to earlier fatigue during the elastic condition. Unfortunately, the researchers did not assess muscle activity levels through EMG analysis, which could help confirm this assumption.

In summary, elastic resistance in series with traditional isotonic resistance may enhance muscle stimulus, resulting in a smoother and more consistent contraction. The elastic resistance helps avoid deceleration at the end of the range of motion, which is thought to enhance the benefits of the exercise, and may provide greater increases in muscular hypertrophy according to the authors.

REFERENCE García-López D, Herrero AJ, González-Calvo G, Rhea MR, Marín PJ. Influence of “in series” elastic resistance on muscular performance during a biceps-curl set on the cable machine. J Strength Cond Res. 2010 Sep;24(9):2449-55.

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