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This is one of the most common misconceived and misunderstood myths in all of exercise. The orgins of this myth are probably from misplaced perceptions and false cause and effect logic. It is my hope I can help you understand the truth behind this truly debilitating myth. Before we get too deep into this discussion we need to provide clarity on two items:

  •  What is considered "heavy" weight?
  • What does "bulky" really mean?

What does "heavy" mean to you in terms of the weight room or strength training? For many folks "heavy" is simply an arbitrary number made up in their head or their perception of something appearing to be heavy. For purposes of clarity let's quickly talk about intensity and how it relates to "heaviness" of a weight. In strength training intensity refers to a certain percentage of one's maximum strength. For example let's say someone can perform a maximal squat of 200 pounds one time. Two hundred pounds would be their 100% intensity, so for them it would be accurate to say 200 pounds would be a very "heavy" weight. But what about the person squatting next to them who can perform a maximal squat at 100% intensity of 400 pounds? For this person 200 pounds would only be 50% of their maximum intensity and obviously would not be considered "heavy."

On that basis I hope you can start to see that "heaviness" is always relative to someone's maximum strength levels, it has no bearing on what the number actually is or how big the dumbbell looks. For the sake of our discussion we will consider anything over 85% of someone's maximal intensity "heavy."

We'll make this second part really short. "Bulk" or "bulkiness" simply refers to muscle hypertrophy, which is simply the increase in size of the muscles. So someone who is deemed "bulky" probably has a large amount of muscle mass which is evident simply by their physique.

*Before I get into the myth itself let's make sure we understand that without modifications in the diet you will not gain any "bulk." There must be a consistent calorie surplus to build muscle. This is a fact which cannot be overlooked. If you aren't eating to "bulk" you won't, no matter how light or heavy the weights you exercise with happen to be. Cool? Okay here we go...

So with that said which set and rep scheme would be more appropriate for building "bulkiness" using the person we used earlier who has a maximal squat of 200 pounds?

A. Squatting "heavy" with weights at 90% of maximal intensity for sets of 3
B. Squatting "lighter" with weights at 65% maximum intensity for sets of 12

If you believe that lifting heavier weights makes you bulky then obviously who would pick the heavier weight, but what actually causes muscles to grow in the first place?

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When it comes to building muscle (muscular hypertrophy) or "bulk" research has proven to us that there are three primary mechanisms which allow this to happen.

  1. Mechanical tension
  2. Metabolic stress
  3. Muscle damage

Mechanical tension is what you feel when a muscle contracts. Flex your bicep; that is mechanical tension. The higher the level of tension that is created throughout a full range of motion is one factor effecting muscle gain. The longer that tension is held (known as time under tension or TUT) the larger effect on muscular hypertrophy. This is why bodybuilders typically stress the importance of TUT during an exercise.

Metabolic stress can be related to the "burning" sensation you feel when trying to isolate a muscle or when you perform a high number of repetitions. The accumulation of metabolic stress (muscle hypoxia, occlusion of veins, build-up of metabolic byproducts, pooling of blood) is a factor effecting muscle hypertrophy. This is why bodybuilders use techniques and methods such as partial repetitions and 1.5 reps to cause more metabolic stress.

Muscular damage relates to the delayed-onset muscle soreness you feel after training. Muscle damage occurs when excessive strain accumulates through the use of new methods and exercises, increases in overall volume or targeted methods to actually increase the overall damage of the muscles being trained. This is why bodybuilders use methods like controlled eccentrics to slowly lower the weights to produce more overall muscular damage.

It is the combination of all three of these factors that will cause someone to gain "bulk." This is why body builders commonly train the way they do, using submaximal weights (50-85% of maximal intensities) for higher repetitions to accumulate tension, stress and muscular damage. And there-in lays the irony of it all. Many folks are unknowingly training for muscular hypertrophy in attempts to avoid it. The only reason they aren't looking more bulky is like I mentioned earlier, nutritional interventions.

This also explains why strongmen, powerlifters and other folks in the know train with higher intensities and lower reps when attempting to build strength. Although the size of the muscle plays a factor, the majority of gains in strength are actually neural (from the neuro-muscular system) as opposed to the muscular system. Without getting too geeky most strength is developed by nervous system adaptations that take place (increased level of muscular activation, speed of activation, order of activation, etc.) My point here is the use of higher weights is mainly strength related which isn't muscular. Meaning heavy weights = increased strength not increased bulk.

Personally I love to train for strength and muscle using lower and higher rep ranges but that is because I want to build both size and strength. If you don't want size do not train as I described and if you don't want strength (God help you) then don't train for it, but please do not from this point forward make the statement that heavy weightlifting makes you bulky!

Takeaways:

  •  Strength is mostly produced from neurological adaptations, not muscular.
  •  Strength is best trained using heavy weights (85-100% maximal intensities) for 1-5 reps.
  •  "Bulking" or muscular hypertrophy is best trained using a mixed approach of higher reps and lower training intensites.
  •  Gaining significant amounts of muscle is really hard, remember there are plenty of folks out there that are purposefully eating for it and training for it yet still struggle to have that 'bulky" look they are trying to get.
  •  Whether training with lower intensities or higher intensities it is always critical you learn how to perform the exercise safely and efficiently before adding any weight.