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Strength and Conditioning and the Science of Specificity

By Loren Chiu - Super Training Digest Post - Date: Tue, 22 Nov 2005 00:11:05 -0800

Strength and Conditioning and the Science of Specificity by Loren Chiu — The current views of specificity, as applies to strength and conditioning are erroneous. There has been a trend in recent years towards training exercises that attempt to mimic or simulate actual sport skills. This is in line with the supposed belief that specificity refers to the exercise, which is not correct. Specificity refers to the adaptation. There are two broad categories of adaptation that need to be defined. There is skill learning (acquisition and retention) and there is transfer. The most specific training is skill learning. All aspects of the sport skill, such as the kinematics and kinetics are highly specific, because, well, it is the skill itself. We can include in skill learning all skills that have, in a very narrowly defined window, nearly identical kinematics and kinetics. However, as we change the kinematics and/or kinetics, the skill is not the same and becomes less specific.

This is the problem with simulating a sport skill in strength and conditioning, it actually makes it less specific. I'll give two examples. The first, many coaches will overload a movement pattern, such as throwing a baseball. However, as the mass of the ball increases, it alters the torque required at the shoulder and elbow (really at all joints, but the largest changes are in the upper extremity). This will alter the relative contribution of muscles, for example, to increase co-contraction of antagonists. DeRenne has studied in depth over- and under-loaded throwing and has found that it is only successful if a very narrow range of ball masses is utilized (+/- 1 ounce).

Another example, coaches will use drills to emphasize a portion of a sport skill. In weightlifting, for example, an empty broomstick may be utilized to focus on pulling under the bar. If we video the athlete performing the lift with an empty broomstick, we notice that the bar path is different than what we would want for a heavy lift (>90%). Additionally, the joint torques required are different. A similar example is running drills which are performed at a slower velocity than actual running. The joint angular velocities are slower, meaning that muscular rate of force development is lower, and possibly that different motor units are being recruited. We can not perform weightlifting correctly with excessively light loads, just as we cannot perform running correctly at slow velocity. Both of these, while commonly used, are different than the actual sport skill and therefore have low specificity.

So other than performing the sport skill (i.e. high movement specificity), how do we improve performance? Sport skills require specific metabolic and/or neuromuscular properties to be performed effectively. If we elicit adaptations that enhance these metabolic and/or neuromuscular properties, performance improves. This is the rationale for strength and conditioning training - specific adaptations. Now in discussing adaptations, another principle needs to be considered - the principle of loading (often referred to as overload, but this term is not truly correct - another issue for another time). In stimulating muscular adaptations, appropriate loading is required to 1) recruit the appropriate motor units and muscle fibers, 2) provide sufficient tension on these motor units and muscle fibers to stimulate adaptation, and 3) provide sufficient volume of tension to stimulate adaptation.

Is there a generality to muscular strength? Yes and no. A minimum level of muscular force is required for any given action. Of course, some actions require more force than others. In achieving this minimum level of force, there is a generality of strength. Amiridis et al. (2005) reported that electrostimulation training of the dorsiflexor muscles in elderly individuals improved standing balance (reducing postural sway). Of course this type of training would be considered non-specific - it is not even a voluntary action. It should be noted that electrostimulation activation of muscle recruits large (i.e. fast twitch) motor units first, and since balance correction requires rapid muscular contractions under reflex conditions, an appropriate voluntary strength training program having similar effects would require near-maximal loads.

At the same time sport skill can be enhanced by possessing strength qualities greater than the minimum required. As an athlete develops greater strength than the minimum, they are limited to that force that can be generated within the time constraints of the movement. So increasing maximal strength alone will not improve performance of rapid tasks, whereas increasing rate of force development will. Thus, the adaptations to training must be specific - i.e. in this example, adaptations that increase RFD and not maximal strength alone. Hakkinen et al. (1981 - two articles) have reported that explosive strength training, in conjunction with maximal strength training is required to improve explosive strength. It is important to note here that there is a relationship between maximum strength and the initial RFD, where initial RFD is important for high velocity tasks (Schmidtbleicher 1993; also unpublished data). Thus, optimal enhancement of explosive strength occurs in conjunction with maximal strength training (Harris et al. 2000).

Again the emphasis on appropriate loading, in particular magnitude of muscular tension, is raised. The classic study by Behm & Sale (1991) demonstrated that high force, high RFD isometric actions were as effective for improving movement velocity as high velocity movements. This is corroborated by Moss et al. (1997) where high force, high RFD training at 90% 1 RM improved power at all sub-maximal loads, whereas unloaded training and 30% 1 RM training improved power only at loads similar to the training load. While the training exercises were kinematically different (in these cases velocity) then the test measurements, they elicited an improvement in performance. We can conclude that an enhancement of explosive strength transfers to high velocity performance.

Additionally, see Newton and McEvoy (1994) where bench press and barbell pullover training improved baseball throwing velocity than explosive medicine ball throwing, and Smith et al. 1987, where resistance training on a Hydra-gym improved volleyball block jump performance more than volleyball training alone. Also, Tricoli et al. 2005 where training with weightlifting exercises improved jumping performance more than jump training alone (even though both training groups also performed traditional heavy resistance training such as squats). Although there are some visual similarities between WL and jumping, in reality, biomechanical analysis comparing WL to jumping indicates large kinematic differences (Canavan et al. 1996). There are, however, large kinetic similarities (Canavan et al. 1996, Garhammer and Gregor 1992).

From the available research, we can summarize that it is the kinetic parameters that are of primary importance when applying the principle of specificity. The kinematic parameters are of less importance. When we elicit the adaptations to the kinetic parameters that are appropriate (or specific) to the desired sport skill, these adaptations elicit a transfer effect that enhance performance of the sport skill.

Loren Chiu, Musculoskeletal Biomechanics Research Laboratory
Department of Biokinesiology and Physical Therapy, University of Southern California
pt.usc.edu/labs/mbrl/STUDENTS/Chiu.html - www.nsca-lift.org/SIGWeightlifting