When writing a training program there are many variables that can be manipulated in order to assist a client with reaching their goals. 

Whether the trainer selects to change sets, repetitions, rest intervals, training frequency, load, complexity, or tempo, each variable will yield different results.

Due to all of these factors that have the potential to be changed, one may wonder how the trainer determines which variable to manipulate.  That is where experience and education come into play, and the use of science takes over for the creation and implementation of the program.



When analyzing how to cause muscular adaptation through resistance training, one variable that is widely discussed is tempo.

Tempo is the rate of movement for any particular exercise, or, in other words, the amount of time it takes to perform the concentric and eccentric phase of a movement.

The time it takes to complete a movement can be changed to be slower or faster; the debated question is which speed is more effective for muscle growth and adaptation.

We are going to specifically discuss the rate of movement at which a person performs the exercise with an external load.

It is important to note that “rate of movement” for this article does not refer to the contractile speed of muscle fibers, but rather the speed at which an external weight is lifted.

It’s about the repetitions

Slow speed of movement  or slow muscle movements refer to low repetitions with heavy external loads (LRHL) or max effort lifts, whereas fast speed of movement refers to training with high repetitions using a light load (HRLL).

When speed of movement is fast, the tendency for joints, ligaments, and tendons to become stressed out is caused by the momentum of both the weight of the external load and the speed at which the load is travelling.

In contrast, with heavy loads, the stress on joints and ligaments is increased solely due to the external force of the weight by itself.

But is the stress on the body that is created just by the external load in LRHL movements greater than the stress caused when forcibly moving a joint quickly through a range of motion when doing HRLL movements?

It has been argued both ways, and I am here to tell you it doesn’t matter!

slow muscle movements_2Low repetition vs high repetition

Whether you are using LRHL or HRLL the main principle at work is stressing the body, or, the overload principle. The overload principle states that in order to create a change on the human body, a greater-than-normal stress needs to be placed on the body in order to stimulate an adaptation.

To increase muscular strength, it must be gradually stressed over time, therefore, muscular strength can happen with either LRHL or HRLL. 

According to the American Council of Sports Medicine, the most effective way to stimulate muscle growth (hypertrophy) is by stressing the body with heavy loads and completing a low number of reps.

However, if achieving strength by increasing muscular endurance is your priority, one would need to use lighter external loads at higher number of reps.

You will achieve

Regardless, in either case whether you are looking to create strength through either an increase in muscular size or muscular endurance, the requisite overload can be achieved with either LRHL or LRHL movements; it simply depends on your training goal.

In other words, if your goal is an increase in muscular growth or stamina, the stimulus just needs to stress the body with loads that are greater than normal.

Therefore, it does not matter if the weight is 1000 lbs. lifted 1 time or 100 lbs. lifted 100 times.

Training at both tempos will give you the best ability to overload the body completely and the best way to increase overall muscular strength whether you are in the size-building or endurance-building phase of your program.

Whatever type of exercises you choose, just remember to complete them at both tempos in order to be the most well rounded athlete possible. 

Connect with Expert Frank Cosenza

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