Research and evidence have repeatedly shown that the amount of resistance (load) used for a specific exercise is probably the most important variable in resistance training (McDonagh & Davies 1984, Spassov 1988). The amount of tension imposed upon the muscle is critical to obtain a strength response. The degree of loading is usually described in terms of repetitions maximum (RM); for example, the maximal weight that can be lifted correctly four consecutive times without significant rest would be known as the 4RM. The relationship between repetitions and the maximum is known as the 1RM continuum. Strength can be classified into many different types, each defined by different capabilities of the neuromuscular system and different time frames of strength expression. Some types of strength can be defined more specifically by the type of muscular contraction. This section will classify and describe the different contraction types that APX adopts into its cirriculum of program design. Poliquin’s Classification of Strength Qualities. APX endorsed.

LIMIT STRENGTH (Maximal Involuntary Strength): The peak force or torque the neuromuscular system is capable of exerting in a single maximal contraction. Limit strength is characterized by an instinctive survival response to a life-threatening situation that involves little or no prior thought or preparation.

MAXIMAL STRENGTH: The peak force or torque the neuromuscular system is capable of exerting in a single maximal voluntary contraction, without respect to time. There are three types of voluntary maximal strength, one for each type of muscular contraction: isometric, concentric and eccentric.

• Isometric (Static) Contraction: A muscle develops tension while its length remains unchanged, thus producing no external movement. In other words, a muscle develops tension without a change in joint angle. However, the muscle belly and accompanying fascia do shorten internally during the process of developing tension, but the shortening in the agonist is countered equally by a shortening in the antagonist. In certain athletic movements, such as moving out of starting blocks in sprinting, an isometric contraction in the set position precedes a concentric contraction, but there is no external movement.

• Concentric Contraction: The muscle develops tension and shortens, causing movement to occur.

  • During a chin-up, the joint angle at the elbow is decreased from 180 degrees to 15 degrees as the biceps work concentrically, resulting in an elevation of the body.

• Eccentric Contraction: The muscle lengthens while producing tension, thus braking or controlling the speed of movement. This contraction is exemplified by the action of the quadriceps during the lowering phase of the squat.

  • An eccentric contraction of the biceps occurs by lowering the body from the completed chin-up position, with the elbow joint angle increasing from the 15 degrees to 180 degrees.

  • During the positive phase in the bench press, the triceps contract concentrically as the joint angle at the elbow increases, but contract eccentrically as the joint angle decreases during the return phase (the weight moves up, then down, respectively).The highest forces that the human body is voluntarily capable of occur during an eccentric contraction; i.e. forces of 40-50% above values produced by concentric contractions. Maximal eccentric strength exercises provide the maximal stimulus to the neuromuscular system, but at a cost to the athlete of greater levels of muscle soreness.

• Isokinetic Contraction: “Same speed,” meaning that the muscle performs a maximal contraction in moving the joint at a constant speed throughout the full range of motion. With an isokinetic action, the contraction is maximal throughout the range of motion; thus, the amount of resistance the muscle is working against varies depending on the length of lever arm offered by the changing joint angle.

  • An accommodating resistance apparatus allows a constant and predetermined speed of movement. The force exerted by the contracting muscle must be maximal during an isokinetic contraction. Some isokinetic devices also allow the maximum speed of contraction to be preset and thereby enable the simulation of contraction speeds required by a specific sport.

  • Isokinetic strength training is most specific to the so-called isokinetic sports, such as swimming, synchronized swimming, canoeing and kayaking, where acceleration occurs against the resistance provided against the resistance provided by water (i.e., water is an isokinetic medium). It has a low specificity in sports such as sprinting, jumping and throwing, where acceleration against gravity plays a major role.

  • Isokinetic strength does provide the option in any sport of exposing the nervous system to a different stimulus for all athletes, thus adhering to the principle of variety.

Maximal strength plays a major role in sports where great external resistance must be overcome, such as hammer throwing, shot-putting and weightlifting. Its importance as a determinant of athletic performance diminishes as the duration of the event increases. For example, swimming for 50 meters requires more maximal strength than swimming for 1500 meters. Strength requirements vary greatly from one sport to another. Sports of an intermittent nature (such as racquetball, which require intense bursts of power spaced between lower-intensity recovery periods, are also dependent on high levels of maximal strength.

SPEED STRENGTH (Power or Fast Strength, Elastic Strength): The ability of the neuromuscular system to produce the greatest possible force in the shortest possible time frame. The capacity of the neuromuscular system to overcome resistance with the greatest contraction speed possible. Speed strength encompasses three other strength qualities: starting strength, explosive strength and reactive strength. Speed Strength Applications: Speed strength is a high priority in most cyclical sports, such as in the field events: in the sprinting, kicking, jumping and throwing activities of team sports, and in the starts and acceleration phases of sprinting, cycling, rowing, cross-country skiing, ice skating and kayaking.

• Starting Strength: The capacity to generate maximal force at the beginning of a muscular contraction; also the capacity to overcome resistance and initiate movement.

  • Starting strength is of importance in movements that require great initial speed, such as boxing blows and racquetball thrusts. Starting strength is a key determinant of performance in sports where the resistance to overcome is relatively light. It is dependent on the number of motor units accessed at the beginning of the contraction.

• Explosive Strength: 1. The capacity to develop a vertical rise in force once movement has been initiated, measured in terms of the increase in force per unit of time. 2. The ability of the neuromuscular system to continue developing the already initiated force as quickly as possible. 3. The rate at which one can develop maximal or peak force.

  • Explosive strength is a key determinant of performance in sports where the resistance to overcome is relatively great, such as wrestling, hammer-throwing and shot-putting.

• Reactive Strength (the Stretch-Shortening Cycle): The ability to quickly switch from an eccentric contraction to a concentric contraction.

  • Also known active strength, regulates performance in sports where stretch-shortening activity of the musculature is great — such as volleyball, basketball and weightlifting.

PLYOMETRICS: A form of training that utilizes fast eccentric contractions followed by explosive concentric contractions. Activities such as bounding, depth jumping and certain forms of medicine ball work satisfy this requirement. The term “plyometric” refers to the enhancement of force development of a concentric contraction that occurs when it is immediately preceded by a rapid eccentric contraction.

• In training, plyometrics bridge the gap between pure strength training and speed-strength training. This training method aims to produce the explosive-reactive movements inherent in jumping, throwing and sprinting, as well as takedowns in wrestling.

STRENGTH ENDURANCE (MUSCULAR ENDURANCE): 1. The athlete’s tolerance level to fatigue in strength performances of longer duration. 2. The capacity of a muscle to maintain consistent force output with repeated contractions over time at a percentage of maximal strength superior to 30 percent. 3. The capacity of muscles to resist fatigue, while generating force over a period of time.

• Strength endurance is characterized by high strength levels coupled with high levels of endurance.

• Strength endurance is of particular importance in cyclical endurance events such as rowing, cross-country skiing, swimming and canoeing/kayaking, where the ability to overcome exceptional resistance must be maintained over long periods. It also plays a key role in sports or events of a cyclical nature such as gymnastics, wrestling, boxing, judo, downhill skiing and most team sports.

ABSOLUTE STRENGTH: The maximum force an athlete can generate, irrespective of body weight and time of force development.

• Body weight and performance are closely correlated in athletes where absolute strength is an important physical quality, such as throwers and football linemen. Athletes can use maximal strength gains through hypertrophy methods.

RELATIVE STRENGTH: The maximum force an athlete can generate per unit of bodyweight irrespective of time of force development.

• High relative strength is of critical importance to performance in sports in which athletes have to move their entire body weight such as jumps, gymnastics and sports that involve weight classes, such as judo wrestling, and boxing. Strength training for these athletes should aim at improving the neural drive (maximal weights/nervous system methods).

OPTIMAL STRENGTH: The optimal level of maximal strength needed for a particular sport (any further increase in maximal strength needed for a particular sport (any further increase in maximal strength would not improve performance).

In sports such as powerlifting, where strength is expressed at slow speeds, the level of optimal strength is open-ended; that is, the more strength the athlete has, the higher the sports performance. In sports where motor skill predominates, such as table tennis, the levels of optimal strength are quite low, since maximal strength and performance are not highly correlated in these sports.

• Accumulation Phase: A training phase where the main stressor is volume. Increased muscle cross-section or increased strength endurance levels are sought in this phase.

• Intensification Phase: A training phase where the main stressor is intensity. Increases in relative strength or speed-strength are sought in this phase.

In strength training, the total volume of work varies considerably from one sport to another. What represents intensification for one sport is accumulation for another. For example, when synchronized swimmers are working in the 6-8RM range, they are doing intensification work; for weightlifters this range represents accumulation.