Muscle myths abound: Don't want those big muscles? Lift heavy

Different people have different goals when it comes to resistance training. Whether your goal is strength, increasing muscle size, or overall fitness, there are a lot of myths when it comes to how much weight you should be lifting. Unfortunately, and we hear this a lot from our female athletes, people think that heavy resistance exercise always makes your muscles bigger.

Muscle growth, or hypertrophy, is caused by the increase in size of the individual fibers that make up the larger muscle. When you apply stress to a muscle fiber or group of fibers, they respond with growth to accommodate the new stress. The question that many sports scientists have tried to solve is; how much stress causes the most amount of muscle growth? To understand this question and research surrounding it you have to understand the idea of the 1 rep max (1RM). The 1 rep max is the maximum amount of weight a person can complete one (and only one) repetition of in a given exercise. Overall loading of muscles in weight training is then determined in relation to the 1RM, so you can control and monitor intensity. For example, if your 1RM in the bench press was 100 pounds, and I instructed you to do 10 repetitions at 60%, you would do 10 reps on bench press with 60 pounds.

Now that we understand 1RM, lets investigate what intensity of weight training elicits the greatest muscle growth. The American College of Sports Medicine suggests that for muscle hypertrophy, moderate intensity loads be used, and that training focus on high volume of exercise. High volume training uses moderate (medium-high intensity) loads for a large number of repetitions and sets, with a small amount of rest between sets and exercises. In addition research has shown that the rest time between sets has a large impact on the growth of muscles. Research from Eastern Illinois University showed that not letting your muscles recover between sets, using 30-60 seconds of rest, acutely increased the release of growth hormone prompting greater muscle hypertrophy (growth). Research from the University of Connecticut corroborated, showing that high volume weight training with short rest periods produced the greatest hormone elevations (e.g. testosterone, growth hormone), a critical factor in muscle growth.

In addition to hormone increases, other factors contribute to the overall growth of a muscle. On a basic level, muscles are made up of two types of fibers, slow and fast-twitch. Research from the Human Performance Laboratory at The University of Memphis compared different types of weight training. Olympic and Power lifters, who generally work with heavy loads (80-95% of 1RM), low amounts of repetitions, and lots of rest showed the greatest hypertrophy in fast twitch fibers. Body builders on the other hand, whose training sessions generally involve a larger amount of repetition at a lower relative weight, showed hypertrophy of both slow, and fast twitch fibers, which would contribute to a greater overall muscle growth.

So why don’t athletes always train at moderate intensities to get their muscles as big and strong as possible? Muscle size isn’t the only factor affecting the strength of a muscle. A lot of the strength a muscle can exert has to do with how many of the individual fibers are contracting at once, which is a function of your central nervous system (your body’s control room). For example, research from Arizona State University showed that the greatest strength gains on collegiate athletes were made training with 85% of their 1 rep max. In addition, this training load did not increase muscle size, showing that the strength gains could mostly be attributed to neurological (central nervous system) factors.

Our athletes train at a variety of intensities, emphasizing strength, speed and sometimes muscle growth. Weights lifted are calculated off the athletes’ body weight (instead of 1RM) to get a more accurate idea of the overall intensity of the workouts. Rest periods are carefully monitored and changed to emphasize different performance goals. The human body is very complex, and one training stimulus never tells the whole story. Heavy weights don’t always make muscles bigger, in the same way that the biggest muscles aren’t always the strongest.