8th November, 2022 updated 19th November, 2022

Strength training variables

I hope this post can help you understand which variables you can manipulate in order to plan and manage your strength training, whether your objective is sport-specific or aesthetic. I hope with this knowledge you can focus on the things that matter most, and put aside the things that matter less, so that you don't waste your time trying to optimize factors that are only marginally effective.

The three variables

These are the factors that a coach or trainee can directly modify in order to overload the tissues involved in the expression of strength.


Often mistaken for Intensity as explained in the post discussing progressive overload, is the amount of weight lifted at any given time. Whether it is the weight on the stack of a selectorized machine or the weight of the barbell and the plates, load is the weight measured in Kg or Lbs.

Load can be used as a measure of intensity in the case of the 1-RM, which represent 100% intensity. However, when using percentages of 1-RM (or similar measurements of load) coupled with multiple repetitions, load does not represent a measure of intensity because other variables are at play (e.g. inter-repetition rest time).


Is the total work performed. It generally is equal to the number of repetitions multiplied by the load. When discussing a single set, volume is the number of repetitions in that set. Assuming a constant load (heavy enough for anaerobic work), a higher volume in a single set brings the trainee closer to failure.

Volume can be manipulated by increasing or decreasing the total number of repetitions in the considered time frame. Typically the total number of repetitions are increased either in the same number of sets that is being performed or by adding sets to the program.

The most up-to-date evidence indicates that, in the context of resistance training, volume can be measured with the number of sets terminated in close proximity to failure. This proximity to failure is a measure of intensity and it can be measured with the RBF scale.

According to this definition of volume, volume manipulation can be achieved by increasing or decreasing the total number of sets terminated in close proximity to failure in the considered time frame.


Is the distance in time between training sessions. This is usually primarily the result of the selection of load and volume. High loads require lower frequencies to allow the body to recover, and high volumes can be spread across multiple sessions.

Within a single training session, frequency is the rest period between sets. Assuming constant load and volume, a lower frequency brings a trainee closer to failure. This is how frequency influences intensity.

Rarely, frequency is used to describe the inter-repetition rest time in the context of a single set. This should be considered together with exercise selection and the objective of the training program.

Manipulating frequency is done by splitting or combining training sessions, shortening or lengthening the rest between sets within a training session, and/or the inter-repetition rest time within a single set.

Other variables

All other variables are either derivative or less important than these three. You may have noticed that there is no velocity among the variables above. This is because velocity is a factor that depends on load.

One could imagine intensity as a function that maps one value of load to one value of velocity, higher values of load map to lower values of velocity, while lower values of load map to higher values of velocity. Purposely slowing down the concentric movement does not lead to better strength training outcomes (González-Badillo et al., 2014)

Typically, intensity is considered to be one of the training variables. Often this is because the word intensity is used as synonym of load. While it is possible to manipulate intensity, it cannot be manipulated independently from load, volume and/or frequency. Additionally, being relative to the individual, intensity can and will change independently of these three variables were these kept constant.

In the next post I will explain how these variables can be manipulated according to your objectives.