There are a number of physiological concepts that must be incorporated into an effective resistance training program, the most important being the Principle of Specificity or Specific Adaptation To Imposed Demands (the SAID Principle). Essentially, this principle implies that the body will adapt to the specific stress placed upon it. In other words, you get what you train for. When applying this principle it is important to understand that the body must progress through different stages of adaptation to reach the desired goal. Different tissues of the body develop at different rates and respond to different stimulus. For instance connective tissues recover slower to training than muscle, but must also be strong to allow efficient muscle force production. Training for muscular strength and/or size, before training for connective tissue strength and endurance will ultimately lead to injuries. It is like trying to build a building without first laying down a solid foundation. To prepare the body for high levels of training postural stabilization is required.
Strength is the ability of the neuromuscular system to produce internal tension on muscles and connective tissue (tendons) that pull on a bone to overcome an external load. The adaptations that can result from resistance training are categorized as stabilization, strength and power. Regardless of the individual goal resistance training begins at the stabilization level. The aim of stabilization training is to maintain correct posture during movements and to do so for extended periods of time. For example, it would be ridiculous for an individual to attempt a heavy bench press, if he/she can't perform a single push up with correct form.
Once sufficient levels of muscular endurance and stability are achieved during the stabilization phase, the next progression is strength. At this point the process can be broken into 3 main adaptations strength endurance, hypertrophy (muscular size) and maximal strength.
Strength endurance is being able to produce high levels of force over extended periods of time with minimal rest. This is similar to intensely boxing (specialized strength endurance) for 2-3 minutes, before resting for 1 minute prior to the next round. Whereas muscular endurance involves low levels of force over prolonged periods of time with minimal rest, which is indicative of long distance running. In regards to resistance training, the adaptation of strength endurance occurs by using high levels of force performed for 6-12 repetitions per 3-5 sets, and minimal rest between sets. This is a progression from the muscular endurance phase which involves low levels of force executed for 12-25 repetitions per 1-3 sets, with minimal rest between efforts.
Hypertrophy is the enlargement of skeletal muscle fibers in response to increased volumes of resistance training. New trainees will not achieve visible hypertrophy for 4-8 weeks, but the process begins at the early stages of training regardless of intensity. To induce hypertrophy muscle fibers need to be recruited through effective communication between the nervous system and each individual muscle fiber. This qualifies the importance of the initial stabilization phase of training which emphasises the development of the nervous system and its influence on muscle recruitment via motor units, which link muscle fibers to the nervous system. By performing high repetitions at low velocities during stabilization training a beginner can establish a proper connection between the brain and muscles, before entering into other realms of the resistance training continuum.
Maximal Strength is the maximum force a muscle can exert in a single effort, regardless of the speed of movement. For a muscle to produce maximum force all of the muscle's motor units must be recruited, so that all possible muscle fibers are involved in the contraction. Stabilization training improves maximum efforts by improving the neuromuscular system's ability to recruit motor units within a muscle, as well as coordinate synergies with other muscles that stabilize unwanted movement, and also muscles that decelerate movement.
Power is the ability to generate the greatest amount of force in the shortest period of time. Power combines the adaptations of stability and strength and applies them at realistic speeds and force encountered in sporting activities and life situations. Power (Power = force x velocity) is improved by increasing either variable. Power training increases the rate of force production by increasing the number of motor units activated in conjunction with the speed that they are activated. Training for this adaptation involves moving both heavy and light loads as fast as possible in a controlled manner.
Resistance training results in various strength adaptations. The question is what phase(s) or adaptation(s) are most beneficial for a competitive boxer? The answer is dependant on the fighter's specific goals, physical structure and even style of boxing. Generally, boxers spend a significant amount of time developing their stamina, and with good reason. Constantly moving around the ring and punching over a two or three-minute round for 4-12 rounds requires a sustainable effort of both high intensity aerobic and anaerobic output. A resistance training program which uses challenging loads that can only be moved for 6-12 repetitions, performed repeatedly for multiple sets (3-5) and with minimal rest between sets will produce strength endurance adaptation. This is a very desired outcome for boxers. However, stabilization training should be the beginning point for all first time trainees, before training for strength endurance adaptation. Even after graduating from the stabilization phase, it is wise to incorporate a functional amount of stabilization exercises into your resistance program to maintain the efficiency of the neuromuscular system while focusing on the progressive phases of strength or power.