Two of the most important variables of the training are the number of repetitions in each series and the amount of weight or tension used. Depending on the objectives you intend to achieve, you may want to do more repetitions with less weight or otherwise. Precor equipment has been designed to help you decide on one of the two methods or a combination of both.

In general, exercises with more repetitions are performed for the improvement of muscular endurance, while those with a higher weight and fewer repetitions are practiced to increase muscle size and strength. Here are some guidelines to start. You may want to work with a personal trainer or other professional to develop a program that allows you to achieve your goals.

The sets that extend beyond 15 repetitions have one major drawback: the amount of weight you can handle is not high enough to recruit fast-twitch type 2 muscle fibers. In short, type 2 fibers are where the growth potential resides, and they respond only to heavy weights, at least 75% of your 1RM (the largest amount of weight you can use to perform a single repetition).

However, it is an excellent means to increase muscular endurance, and therefore, can be very useful in many sports that have nothing to do with hypertrophy (muscle mass gain). However, if the essential thing is size, high repetitions are not a good idea: neither to grow, nor to define.

In weight training, something has withstood the test of time: to grow, you must be strong. Taking that to the extreme, many lifters adopt a heavy lifting approach with low repetitions. Take a look around your gym, and you're likely to find some aspiring bodybuilder who is struggling in squats or bench press near his 1RM.

It is a very safe method to build strength, and of course, there is more to see the size of some lifters like 'The Mountain', Game of Thrones. However, low repetition training has one major drawback: the stimulation of muscle fiber and, therefore, growth, which correlates closely with the amount of time a muscle is under tension. Short and intense sets of 15 seconds or less will develop strength, but are not as effective when hypertrophying.

Why is that critical range? Because when the series lasts more than a few seconds, the body is forced to rely on the glycolytic energy system, which leads to the formation of lactic acid. You can think of lactic acid as a bad thing, since it is mistakenly associated with the muscle pain that you feel days after a workout, but that pain is actually a very fleeting reaction that is vital to the production of new muscle tissue.

When lactic acid, or lactate, accumulates in large amounts, it induces an increase in the levels of anabolic hormones in the body, including growth hormone and the mother of muscle development, testosterone.

The range of moderate repetitions, when combined with a challenging weight, also causes a very desired condition: the muscular pumping. It is something like that feeling of tightness and fullness under the skin, caused by the accumulation of blood in the muscle. Studies have shown that the physiological conditions that lead to the muscular pumping activate the synthesis of proteins, and therefore, the muscular growth.

In the final analysis, substantial evidence holds that training in a range of moderate repetition (8-12 reps) is the best way to develop muscle mass. It increases the hormonal response, stimulates protein synthesis and provides the necessary time under tension to cause muscle damage.

Of course, to ensure that your body does not adapt to a particular regime and stagnate, you need variety. Perform low repetition training cycles to gain strength and use high repetition training to improve your endurance. Everything adds up, after all, and depends on your goals, but to gain muscle, it is best to keep in a moderate range of repetitions.