Exercise selection and program design are proficiencies that personal trainers must possess to successfully perform their defined job tasks. The training methods and the exercises selected by a personal trainer for their respective clientele should be based on evaluative criteria defining the best approach to meet the needs of the client. Depending on the client-specific needs, a personal trainer should match the exercise selection and program design applications to the skills and abilities of the client, the availability of time, as well as their client’s goals. Although specific goals may be the emphasis of the exercise selection, program decisions should promote a well-rounded distribution of physical fitness components to ensure each area of health and performance is adequately maintained over a lifespan.

One area where many programs are deficient is in the realm of training for power. Progressive training models are encouraging clients of varying age and backgrounds to engage in activities that promote power for improved performance and to prevent the onset of premature functional decline. To safely implement power-based exercise in a program, the variables that require adjustment to create the stress for adaptations must be identified and appropriately managed. It is the dynamics of these variables that make the exercise effective, but consequently, also increase the risk of potential injury with participation. Identifying the ideal balance of power-related variables is necessary to maximize the efficiency of the adaptation process. A key factor in establishing the combination of movement-appropriate training efficiency with appropriate resistance-speed intensity is analyzing the relationship between the contraction velocity and both the force production and power output capabilities of a muscle. In order to fully understand this relationship, one must first understand some basic underlying components that drive the system.

There is a notable difference between power and strength. Power is a product of force and distance, divided by time (How much, how far, and how fast?), whereas strength is simply a measure of absolute force (How much?). The personal trainer must be aware of these differences and be capable of exploiting them through different training modalities to optimize the combination of force-rate and time. Muscle fiber type plays a large role in determining peak power output. Across all contraction velocities, muscles with predominantly more type II fibers will produce more power than muscles with predominantly type I fibers at the same velocity. This is due to certain intrinsic qualities associated with each respective fiber type. Type II fibers possess higher concentrations of ATPase, allowing ATP to be broken down more quickly and efficiently than type I fibers, while the increased rate of calcium release from a more organized and developed sarcoplasmic reticulum increases contractile stimulation.

Strength (force) and power are different, but related, components of muscle physiology. From a training standpoint, optimizing power outputs necessitates finding the point where the most amount of weight can be moved through a given distance over shortest duration of time. Remember, power is the product of force and distance, divided by time. Graphing the relationship between power and muscular velocity will result in the shape of an inverted U, with velocity across the horizontal axis and muscle power along the vertical axis. Muscle power is lowest at both very slow and very fast speeds. The peak power region generally occurs at approximately 40-60% of maximal angular velocity of the muscle. Each muscle group, depending on its specific biomechanical makeup will have an optimum movement speed, but most muscle groups will fall within this peak power region. Looking at this from a training standpoint, it is important for trainers to choose activities that will elicit the most appropriate responses for each client using the correct combination of movement speed and resistance.

Utilizing certain equipment in the gym such as a medicine ball or thera-band will help these adaptations to occur. The incorporation of medicine ball throws into an exercise program will increase the power gains of any client, if programmed appropriately. Medicine ball chest passes, an exercise that requires the client to forcefully contract the muscles of the chest, shoulders, and triceps resulting in a full extension and throw of the ball, should take place in that peak power region (~40-60% max velocity). Trainers should be conscious to not use too heavy a weight where the exercise becomes too slow, or too light a weight where the velocity is near maximal, as both cases will result in decreased power output. Maximizing power gains will be dependent on the selection of the appropriate resistance and the muscles employed during the performance. For instance medicine ball throws with forward step or trunk/hip flexion increase the power output capabilities and are more functional, whereas single joint movements are less powerful and less beneficial overall unless improvements of specific muscles or actions are the goal. In most cases of human performance, whether getting up from a chair or shooting a basketball, power is applied through purposeful angular momentum generated from the rotational inertia supported by several force couples and muscle group interaction. Combining movements best influences power output, particularly when the hip movements are employed. Obviously, things such as professional judgment and exercise testing will help determine the best choice for each client.

Another key concept is the understanding of the relationship between force production capabilities and the velocity of movement. The three types of muscle contractions; concentric, eccentric, and isometric, are employed at varying speeds in power exercises compared to traditional strength training. Concentric contractions occur for acceleration and may not be combined with eccentric movements under the same demands. Eccentric contractions are only used when the length of the muscle increases, therefore, unless deceleration is required (catch, receive, or landing) eccentric movements will be limited. Isometric contractions are those that stabilize the joint actions, but also contribute to body control when the high velocity movements act to offset dynamic or static equilibrium. An individual’s maximal isometric force production capabilities will often be a limiting factor in performance efficiency in power.

With regard to force production capabilities related to the velocity of movement there is an inverse relationship that exists. As the speed of the contraction increases, force production will decrease. Analyzing a traditional exercise such as the bench press it becomes obvious that the heaviest lifts are performed at a generally slow, controlled pace allowing the stabilizers to enhance the prime movers effectiveness. Consider completing a maximal squat repetition (1RM); how fast will one be able to lower and raise the weight? Not very quickly, but the amount of force the muscles are generating is maximal during the concentric phase. Now, consider using a weight that is 30% 1RM in the same exercise. The repetitions will be able to be performed much more rapidly due to the reduced force production requirements as well as the reduced contribution to deceleration. The closer the resistance comes to the 1RM the slower the movement will be. This exemplifies the relationship between speed and force production. A good trainer will match the speed of the movement and force production requirements with the training goals. If an athlete is being trained for a sport where speed or power defines performance outcomes, high speed movements should be incorporated into the exercise program. Whereas if a different client’s training goal is to maximize strength gains and increase force production, the exercise program should include slower repetition ranges using higher loads. In absolute terms, maximum force production is attained using heavy loads at controlled speed while maximal power is attained when the product of velocity and force production are correctly synergized or the maximum speed of movement attained within the range of approximately 45-60% 1RM. A common error in exercise programming is thinking heavy weight lifting effectively increases power. Based on the principle of specificity, power training would best increase power, whereas strength training would optimally improve strength. Although a relationship between the two exists it is not strong enough to use one method for both goals.

Personal trainers have many factors to consider when writing an effective exercise prescription and therefore must evaluate each variable to create the optimal training stress. Keeping in mind client-specific goals, a premeditated plan should be developed that reflects the desired adaptations. Differentiating between training for absolute strength or force production improvements and maximal power outputs is vital to appropriate exercise prescription and the success of your clientele. Utilizing the right equipment for each job, at the optimal resistance and movement speed will ultimately determine the extent of a client’s results and the attainment of their training goals.