Repeated by trainers and other self-proclaimed exercise pundits in the fitness industry is the fallacy that high-rep training does not develop strength, only endurance. However, data from clinical studies refute the notion that low reps produce the greatest strength gains. Studies indicate that high-rep training, between 12 and 20 reps per set, produces muscle mass faster than low-rep sets of 10 or less.

Muscle Mass Equals Contraction Force Equals Strength

Using your skeletal system as leverage, muscles are capable of producing two movements: pushing and pulling. The force with which a muscle contracts is the measure of strength. The more muscle mass you have, the more strength. Muscle mass development is a product of protein synthesis.

The correlation between high-rep training and strength gains is a manifestation of how muscles grow, or protein synthesis.

Catabolism, Anabolism, and Hypertrophy

In the beginning of the metabolic process, the body breaks down foods into usable molecules through a metabolic process called catabolism. Once a person’s metabolism reduces food down to carbohydrates, sugars, amino acids, vitamins and minerals via catabolism, the body can then use the nutrients to repair damaged muscle fibers.

Damage to the muscle fibers is the desired result of exercise, because the damage prompts the body to begin repairing itself and protect muscle fibers from future damage by increasing muscle mass, otherwise known as strength.

The metabolic process responsible for the repair and construction of muscle is called anabolism. The anabolic process specific to the muscle mass production is hypertrophy. Hypertrophy is growth, and thus is equivalent with increases in strength.

The Effects of Endurance Training on Hypertrophy and Strength

The satellite cell theory of hypertrophy explains the process of building muscle mass. Hypertrophy can be thought of as the anabolic process of building strength. It is with respect to the growth-promoting damage that endurance training is critical. Endurance training increases the “good” muscle tissue damage, which means endurance training promotes hypertrophy, the development of muscle mass, hence strength.

The reason endurance training must be implemented into a strength training regimen in conjunction with heavy-weight, low-rep sets is because low-rep sets fail to stress the entirety of a muscle sufficiently to spread micro-tears throughout it. The higher the number of reps, the more widespread the “good” damage to a muscle.

It is understood by even neophytes that if the weight pulled or pressed is not sufficient, strength gains will not occur. But, it is equally important to understand that endurance training is a critical aspect of increasing muscular hypertrophy.

Sources:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404827/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2918506/