One of the biggest exercise myths is that a designated number of repetitions need to be performed in order to get specific results. For example, if you perform 1-3 reps of an exercise you are working on power, 3-5 is for strength, 8-12 is for building muscle, and 15+ is for endurance. As a personal trainer in Schaumburg, I am often debunking this myth.
The biggest issue with the above logic is that not all repetitions are created equal. There are drastic differences between leveraging the inertial properties of a mass to move it over a given distance versus attempting to minimize the inertial effects while moving a mass.
Think about a baseball pitcher throwing a ball. In order for the pitcher to get the ball to the catcher, he does not have to be in contact with the ball the entire time it travels to the catcher’s glove. Essentially, he puts a large amount of force into the ball during the initial stages of the pitch. Then he releases the ball and there is no longer a challenge for his system to overcome in order to move the ball.
This same series of events can be seen by many gym-goers who are focused on simply moving the weight in order to accomplish a magical number of repetitions instead of focusing on actually challenging their muscular system. We often think that flinging the weights around for a predetermined number of times is enough to get the results we want, but we forget that our body does not count reps, it just responds to the challenges and stresses placed upon it.
Another logical example of why the number of repetitions is not what causes our body to adapt is a “plank”. How many reps of are ever performed? Zero? One? Either way, if we are bought into the idea that the number of reps determines the adaptation then we would have to also believe that planks, or any isometric exercises for that matter, are only useful for “developing power”. Hmm.
So if the number of reps is not determining factor, what is?
Time under tension. In other words, the duration of time you generate tension with the challenged muscles while performing an exercise. In fact, time under tension was what initially brought about the entire repetition scheme in the first place. The part that is often left out of the story, however, is the tempo or time taken to complete each stage of a repetition.
Without that tempo piece, what started out as an effective means by which to strategically challenge the muscular system has turned into a new sport of moving weights through space, with the emphasis being on the weight getting from point A to point B versus how it gets there.
And to bring this all back around to the conversation of building muscle, Burd et al. (2010) found that a minimum of 43 seconds of time under tension stimulated greater muscle protein synthesis than performing exercises for less time.
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