Charlie’s input is recognised…
An Argument Against Specificity in Strength Training
In recent years there appears to have been an over specification in strength training. This often appears to be an attempt by an individual to appear more skilled, knowledgeable or innovative. For those who understand strength science however the effect is very much the opposite.
Neural adaptations that increase strength and rate of force development (RFD) can be both general and specific to the exercise being performed (see below). The most significant adaptations, increased rate coding and recruitment, are general adaptations in the central nervous system. Strength exercises that recruit large numbers of motor units raise ‘organism’ strength, i.e. potential strength in all movements. Additionally, large compound movements cause both acute and chronic increases in circulating anabolic hormones that increase the ability to adapt to a training stimulus.
A threshold in intensity (>75% for an experienced lifter) must be breached in order to stimulate increases in strength. Most specific exercises however do not (safely) permit the expression of maximum force. For example, maximum force is inhibited in asymmetric exercises (e.g. lunges) because of decreased stability.
Conversion phases attempt to move the velocity and kinematics of strength exercises closer to that of the sport. Unfortunately, specific exercises do not generally provide sufficient stimulus to maintain maximum force capabilities. In any case, the actual sport frequently provides sufficient ‘specific’ stimuli. Finally, any significant change in stimulus will have an associated conditioning risk that necessitates a preparatory period of lower intensity and volume.
Stimulus for rate of force development should be present through all training cycles not simply introduced close to competition. The skill is optimising performance by changing the focus of training, e.g. emphasising RFD whilst retaining sufficient stimulus to maintain maximum force.
To illustrate, let us consider the example of a golf player. Some coaches may advocate an array of wonderful exercises that mimic the rotational aspects of the drive. I however contend time would be better spent raising organism strength and RFD with general movements, i.e. squat and overhead medicine ball throws. If a strength stimulus is omitted entirely, the potential to increase RFD and hence performance, is limited and optimal performance will never be achieved.
- Increased Recruitment
a. The strength deficit is defined as the difference between the force produced in a muscle by maximal voluntary contraction and the force produced by electro-stimulation of a muscle’s nerve cells. Training decreases the strength deficit by increasing the ability of an individual to recruit fast twitch motor units. Fast twitch motor units have high threshold neurones, axons with high conduction velocities and fibres with large cross sectional areas. The shortening velocity of a fast twitch fibre can be up to four times faster than a slow twitch fibre and hence, if recruited, will significantly increase RFD.
b. Typically, motor units are recruited in order of size; hence the largest and fastest units are recruited last. Recent research (Scmidtbleicher, 1996) however, suggests training may permit preferential recruitment of high threshold fast twitch motor units earlier in the recruitment order. This adaptation contributes to improvements in RFD.
c. The Golgi tendon organs, arranged in series with the muscle, respond to increased tension by inhibiting maximum force development. Exposure to high forces decreases the sensitivity of the Golgi tendon and hence also decreases inhibition.
- Rate Coding
- Rate coding is the number of nerve impulses per second that the motor neurone can transmit to the muscle fibres. Rate coding controls the gradation of force, in large proximal muscles in the range, 80% to maximum. Training can increase maximum force by increasing frequency of stimulation, and RFD by reducing time to tetanus. (Tetanus is the prolonged (maximal) contraction of a motor unit resulting from the fusion of many successive ‘twitches’)
- Intermuscular coordination
a. Strength, in a specific movement, is increased by a more efficient interaction of the muscles involved in the movement. Intermuscular coordination becomes more significant with movement complexity. The Olympic lifts, for example, require greater coordination than a single joint ‘isolation’ exercise.
b. An unskilled athlete has higher net resistance at any given load since the agonists must overcome both the load and the force produced by the antagonists.
c. Training reduces ‘reciprocal’ inhibition, i.e. activation of antagonists in response to high forces.
d. Increasing the strength of stabilising muscles improves the efficiency of force transmission. For example in the clean, the spinal erectors, abdominal and obliques co-contract to increase the stiffness of the spine such that force generated in the knee and hip extensors can be transmitted to the upper body.
- Intramuscular Coordination
- Whilst research is currently inconclusive, synchronising the activation of motor units within a muscle may increase force and RFD.