Specificity of Training

[Giorgio83]

"Transfer of training effect" deals with the degree of performance adaptation, which can result from a training exercise and is strongly related to the concept of training specificity. Mechanical specificity refers to the kinetic and kinematic associations between a training exercise and a physical performance. Thus mechanical specificity includes movement patterns, peak force, rate of force development, acceleration and velocity parameters. The more similar a training exercise is to the actual physical performance the greater the probabilities of transfer (Behm 1995, Sale 1992, Schmidt 1991).

There are various strength/power training methods which can be employed. However, the effects of these training methods on neuromuscular physiology and performance variables can be drastically different. Four types of training will be discussed; these training methods are: isometric, heavy weight training, high power or speed strength and intentionally slow training.

Table 1 compares the relative effects on the neuromuscular system resulting from 4 different types of training protocols (Hakkinen 1994, Jones et al 1999, Jones et al 2000, Stone et al 2001): isometric training, typical heavy weight training, dynamic explosive training and intentionally slow training.


Table 1: Specificity of Strength/Power Training: Relative Neuromuscular Adaptations




Isometric training, which reached peak popularity in the 1960's, has not been shown to produce extensive hypertrophy. Heavy weight training is characterised by loading that is typically 80% of 1 RM or higher and typically uses 5-8 repetitions. The load lifted may move slowly, even if performed explosively, because it is relative close to maximum values. Heavy weight training can produce marked hypertrophy, except during the initial stages of a beginning training programme. Speed-strength weight training with a high power output typically does not produce marked hypertrophy, except in sedentary individuals, but can result in profound alterations in the nervous system. Intentionally slow training has become popular among health clubs recently; basically a relatively light weight is moved in an intentionally slow movement pattern both eccentrically and concentrically. The intentionally slow movement can result in a high motor unit fatigue rate, which is believed to cause more motor units to be recruited. Proponents of intentionally slow movements believe that the time that a muscle is under tension enhances both hypertrophy and strength, Often this type of training is performed for only one set. Although, currently, there is little information concerning intentionally slow movement's effect on hypertrophy a few studies suggests that while some hypertrophy can occur it is not as extensive as that resulting form heavy weight training (Keeler et al 2001).

Differential effects have been noted for fibre type adaptations. Type II fibres typically display a faster rate of hypertrophy than type I fibres, although the reason for faster hypertrophy is not completely clear. Thus weight training can produce fibre hypertrophy such that the II/I cross-sectional area ratio increases; the degree of increase depends upon the type of training. There is evidence that high power training enhances the II/I ratio of cross-sectional area to a greater degree than other types of training. A high II/I ratio is likely advantageous in producing "explosiveness and high power outputs.

Table 2 compares training methods based on potential performance outcomes. Although angle specificity is often observed, isometric training can enhance measures of maximum strength, especially when maximum strength is measured isometrically. In relatively untrained subjects isometric training may enhance speed of movement, provided a conscious effort to move fast is made (Behm 1995). However, the effects on speed are relatively minor compared to speed strength training (Hakkinen 1994). Heavy weight training has its greatest effect on maximum strength as measured by a 1RM. Among beginners and novices, relatively large gains in power, rate of force development and speed can occur. Speed-strength training has its greatest effects on rate of force development and power output, with lesser effects on measures of maximum strength. Intentionally slow training has its greatest effect on measures of maximum strength, with much smaller and perhaps negative effects, on rate of force development, power and speed.


Table 2: Specificity of Strength/Power Training: Relative Performance Effects




The specificity effects of training are very apparent in a comparison between heavy weight training and speed strength training (Figure 9) carried out in a series of studies by Hakkinen and Komi (1985a 1985a). One group of physical education students were trained in the half squat using heavy weight training methods, another group used explosive jumping with weights of approximately 30% of their 1RM. Isomeric force-time curves measured pre-posts indicate different adaptations. The heavy weight-training group showed a 27% improvement in peak force but very little alteration in peak rate of force development. Simultaneous EMG tracings show alterations corresponding to changes in the force-time curve with only a 3% increased activation in the peak force region and no change in the peak force region. The gain in peak force shown by the heavy weight-training group was attributed to muscle hypertrophy. On the other hand the speed-strength group showed gains of 11% in the peak force region of the force-time curve and a 24% improvement in the peak rate of force development region. Simultaneous EMG tracings indicated that EMG enhancement generally corresponded to the gains in peak force and force development. Thus, the speed-strength group showed the greatest adaptations in the nervous system while the heavy weight-training group showed greater gains in hypertrophy.


Figure 9: Neural Adaptations to HRT




Another factor, which enhances the transfer of training to performance, deals with movement pattern. Movement pattern deals with applying forces in the most efficient manner and in the appropriate directions. Movement pattern specificity includes both intra and inter muscular specific aspects.

Movement pattern specificity (intra-muscular): Several studies have shown that there is a high degree of intra-muscular task specificity. These studies indicate that for a given movement, there are groups of motor neurones, which are activated in a specific manner for a specific task. If the task is changed, through alterations in movement pattern or perhaps velocity, then the neuronal task group will be changed. This type of data lends support for the practice among bodybuilders of using many different exercises to more fully develop a muscle (Antonio 2000).

Movement pattern specificity (inter-muscular): The pattern of activation of whole muscles, as well as the efficient use of reflexes and stretch shortening cycles is also task specific. In this respect the functional role of muscles as agonist, antagonist or stabilisers must be classified with care. These functional roles can change from single joint to multiple joint movements and with changes movement velocity (Zajac and Gordon 1989). Thus in sports or daily living settings in which multiple joint movements occur, especially those requiring high power or high velocity, transfer of training effect is more likely accomplished using complex multi-joint movements which have similar kinetic and kinematic characteristics.

Because of the high degree of task specificity, gains in strength may be effected by a number of factors including the number of joints involved, velocity of movement and position (Rach and Morehouse 1957, Zajac and Gordon 1989, Stone et al 2001). For example, Thorstensson (1977) trained university physical education students in the half squat for 8 weeks. Pre-post measurements indicated approximately a 75% improvement in the 1 RM half squat (Figure 10). However, the improvement in the isometric leg press was only about 40% and essentially no improvement occurred in the seated leg extension. Although the half squat training effected muscles used in all three tests it is clear that movement pattern differences altered the apparent strength gains. These data also indicate that the greater the similarities between training exercises and performance the greater the transfer.


Figure 10: Movement Pattern Specificity





(Tratto da http://www.education.ed.ac.uk/cis/st...ls.html#table1)