If you lift weights to build muscle, then you know that one of the holy grails of weight training is muscle hypertrophy, which is simply an increase in size of skeletal muscle through a growth in the size of its cells.

One commonly held belief is that a muscle must be worked to fatigue if you really want it to experience seriously significant hypertrophy. The idea is that a muscle is induced to grow after the muscle damage, metabolic stress, and mechanical tension, which happens as a result of muscular failure during a weight training set. To learn about the science behind this response, you should check out “How To Build Muscle.”

I’ve certainly visited this topic before. For example in “How to Get Better Results from Weightlifting”, Tip #8 is to do forced repetitions, which are exercises that are assisted by a training partner, or spotter. These are typically performed with a much heavier weight than you could normally lift on your own, or significantly more repetitions than you could do by yourself. As you reach failure, your spotter helps you, or forces you, to complete the set.

But is this really true? Do you really need to do forced repetitions or work a muscle to absolute and complete failure and fatigue to get it to grow larger? In this episode, you’ll discover the truth.

The Latest Research on Building Muscle

Surprisingly, at this point, only one forced repetition study has ever been done. In it, 12 basketball and 10 volleyball players trained three times per week for six weeks using the bench press. The participants were split into three groups, each of which performed a different number of forced repetitions. All groups experienced a significant increase in chest circumference and muscle mass. But the study also found that the group who was performing more forced repetitions (e.g., doing every single set to failure then going past that point and using a spotter to get final 25-50% of repetitions) didn’t experience any greater improvements in muscle hypertrophy than the groups performing fewer sets to failure. In other words, by simply working to forced repetitions on the very last set of a weight training routine for a specific body part, you can achieve muscle building results that are just as good as if you had performed every set with a spotter or to complete fatigue.

In contrast to forced repetitions, another style of training is called momentary muscular failure (MMF). With this style of training, you simply work a muscle to the point where it’s too tired to keep going, but you have no help from a spotter or partner to help you crank out just a few more repetitions. This is the more common style of training that you’d do if you were working out by yourself. While the muscle building response to this style of training hasn’t been compared to forced repetition training, it has been found that MMF training results in a similar increase in testosterone and free testosterone as forced repetitions. But the forced repetition approach causes a greater decrease in muscle force production, electrical muscle activity, and a great increase in growth hormone and cortisol—all signs that the forced repetition approach could potentially result in greater increases in fitness and muscle strength and endurance (also known as an “anabolic response”), even if it doesn’t necessarily make the muscle grow bigger any better than MMF style training. However, at the same time, elevations in anabolic hormones have been linked to hypertrophy, so when you consider the fact that only one study has looked into the effect of forced repetitions on hypertrophy, you could hazard a guess that if you really want to build muscle as fast as possible, you could hedge your bets by performing at least one set (e.g., the final set of a series of sets) to failure and complete fatigue, with the help of a spotter or training partner.

Three Quick And Dirty Tips

There are three final considerations here:

• 1.) A constant surge in cortisol can potentially lead to overreaching or overtraining, so it would be prudent to allow for 48-72 hours minimum recovery between sets that you perform to failure.
• 2.) As you learn in “Why Bigger Muscles Aren’t Always Better,” a pursuit of muscle hypertrophy may not be quite as good for long-term health and longevity as a pursuit of muscle function, coordination, and power.
• 3.) As I discuss in this episode about muscle-building myths, you can theoretically achieve “forced repetitions” by doing lighter or body weight repetitions to complete failure (e.g., push-ups until your chest hits the ground and you can’t do another push-up to save your life!).

If you have more questions or comments about whether you need to fatigue your muscles to make them bigger, then head over to Facebook.com/GetFitGuy and join the conversation there! 

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