What is strength? Strength, in its simplest term, is the ability to exert force. What is force? Force is mass time acceleration (F = ma). An easier to understand definition of force is anything that causes or tends to cause a change in motion. What is motion? (Are you confused yet? Don’t be – read on.) Motion is displacement of any object from one point to another; however, there are various types of motion that are important. Motion is straight line or linear, curvilinear, rotary (circular), and most importantly, general. General motion is a combination of all types of motion, which is what is considered to be normal human motion.
So what, you say. Well, this all has an ending. The first definition of strength we gave is too simplistic. In addition to this, strength was only considered important and associated with resistance training. Older textbooks state strength as the ability to exert force in a one-rep maximum lift. In recent years, however, the definition has drastically changed due to not only from the information previously stated (strength, force, and motion variables) but from substantial strength research from all around the world.
A more inclusive definition of strength from Knuttgen and Kraemer (1987) states “strength is the maximal force a muscle or muscle group can generate at a specified velocity.” Let’s put this into the example of throwing a baseball. A baseball has a certain mass. To launch the ball into the air to travel a certain distance we must impart a certain amount of muscular force from all the associated arm and shoulder muscles to get the ball traveling at a certain speed before we release it into the air. The muscles used must produce a certain amount of force to cause a change in motion of the ball (it original goes from a static position in your hand to dynamic flight). Once the ball leaves the thrower’s hand, it will travel in a curvilinear path for a certain distance, i.e. displaced from the hand to where it lands. The entire throwing motion is considered general motion since it involves all the variables listed above.
All this associated with strength? Absolutely! Every motion requires a certain amount of force or strength to complete that motion. This happens when we walk, run, step, bend/twist, squat, lift any object, or perform any type of human movement. An even better definition of strength could be “the ability to exert optimal or maximal force in any direction or at any velocity.” This applies not only to resistance training but to metabolic conditioning as well.
Now that we have a better understanding of the definition of strength, we need to break it down further. Since there are numerous sports, events, or tasks that individuals perform, strength, like energy systems, must be defined for each event. Every event has a task–specific or dominant type of strength that is specific to that event.
Initial training must focus on developing proper motor control as well as structural (connective tissue) integrity. This is known as the Foundational Level of training or General Physical Preparation (GPP). This GPP is strength development in multiple categories that physically “lays the foundation” for building specific strength later in the program. Once this foundation is built, every coach must determine what type of strength best defines the sport overall and each position for that sport. From anecdotal evidence, the general public tends to envision that strength is displayed slowly; however, from our updated definition, strength is the ability to exert force (either maximum or optimal) in any direction or at any velocity. Strength can be displayed over a variety of speeds depending on the amount of resistance encountered. An excellent model developed by Siff and Verkhoshansky (1993) shows the interconnection of strength and all the various fitness characteristics involved in sports and how they relate .
Any fitness quality, whether health-related or skill-related, is directly related to strength. Depending on whether strength is stated first or second in the hyphenation dictates the priority of that quality. Example: Strength-speed – this is indicative in weightlifting. Speed is crucial but strength must be displayed at its highest level (Note: strength and speed together are indicative of power output or F x V).
What about other sports? What sport requires speed? Almost all sports have an element of speed. What types of strength are involved in the 100 meter dash? Most sprinters require high levels of maximum or absolute strength (they must train their muscles for maximum force development) but how do they display this strength correctly and at a high velocity? We assess the event and conclude the resistance the sprinter must overcome is gravity (i.e. body weight in a linear motion as fast as possible). Muscles of the upper and lower body will contract to produce force to move the limbs as fast as possible back and forth to propel the body forward at the highest speed the sprinter can obtain. This is referred to as speed-strength, strength-skill (maintaining form), flexibility-strength, speed-flexibility, as well as core strength, which ties all forms together. It is not just simply speed, but a combination of various types of strength that optimize performance for maximum efficiency and effectiveness.
Assessing the type or types of strength involved in any activity is paramount in developing a training program for not only improving performance but, more importantly, decreasing any strength deficit of an athlete in any position that might increase risk of injury.
To learn more, see the NESTA Personal Fitness Trainer Certification.