How to Select the Right Sets and Tempo for Your Clients

The principle of progression states that if an exercise program is to produce the desired outcome, the intensity should gradually become more challenging to apply an effective overload. This tells us that an individual needs to work harder, but that the changes to a program should be incremental and not occur all at once. Progression and overload are closely related—the intensity of the overload should increase gradually, 5 percent or less at a time, to allow the body to receive and adapt to the new stimulus.

A set is defined as a group of repetitions before taking a rest interval to allow recovery. According to the American College of Sports Medicine (ACSM) Guidelines for Resistance Training, one set of 10 to 12 repetitions to momentary muscle fatigue is sufficient to create initial strength improvements in clients with little-to-no training experience.  However, once a client experiences initial strength gains as a result of improved recruitment of involved muscle fibers, the number of sets needs to be progressed to apply an overload and create the desired training effect. This is why clients can seem to make strength gains relatively quickly when they are consistently training—the nervous system becomes more effective at recruiting and using the involved muscle fibers to generate the necessary force.

Tempo is the program design variable referencing the speed of movement for an exercise. A different consideration of tempo is the time under tension (TUT), which is the length of time that muscle fibers are under mechanical tension from a resistance-training exercise. Along with intensity, TUT is critical for creating the desired stimulus for increasing muscle definition or size. Mechanical strain on muscle fibers signal the mechanisms responsible for repairing structural damage to existing fibers and laying down the foundation for new muscle cells.

To review, a repetition is compromised of three distinct phases of muscle action: 

• Eccentric: The muscle is lengthening, yielding to the force of the applied resistance while storing mechanical (potential) energy, which is then released during the concentric phase of muscle action. Depending on the skill level and training goal of a client, this phase can last from a very brief instant to a number of seconds.

• Isometric: The muscle is developing tension and contracting, but no joint movement occurs. During an exercise, this is the transition from lengthening (storing potential energy) to shortening (the release of kinetic energy). The technical term for this action is the amortization phase, and it can last from milliseconds during an explosive exercise to an extended period of time for an isometric exercise.

• Concentric: The muscle is shortening, releasing the mechanical (kinetic) energy to generate the force required to overcome an applied resistance. This phase can last from a brief instant during an explosive exercise to a period of 15 seconds or longer during a slow-tempo exercise. <