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Plyometrics and throwing

Plyometrics and throwing

Part II of Sean Fyfe’s look at the use of explosive power training in sports therapy

In last month’s SIB(July-Aug 2007) we looked at the role that plyometric training can play in rehabilitating athletes with lower-limb injuries. Arguably the same approach could be used for upper-limb training and rehab, so we now take a look at what research evidence there is for plyometric-type training related to the upper limb, and whether it holds any useful pointers for rehab work.

One of the most important upper-limb sporting movements is the throw; indeed, in many sports the balance of a game can hang on the speed and accuracy of a single throw.

According to the definition of Chmielewski and colleagues, to which we referred in part 1 of this article, throwing is an obvious example of a plyometric movement:

‘Plyometric exercise is an activity that involves and capitalises on the mechanisms of the stretchshortening cycle to increase the efficiency of force production at a joint or increase performance(1).’

Baseball pitchers throw at speeds of up to 160 km/hr and professional tennis players serve balls that cross the court at up to 250km/hr. This equates to a rotation speed at the shoulder joint (‘shoulder angular velocity’) of more than 7,000 degrees per second, made possible by the arm moving through a series of stretchshortening cycles to produce a rapid development of force (see SIB60, June 2006 for more on this action).

If the sports therapist is going to fully rehabilitate clients with upper-limb injuries who are involved in throwing sports, they need to understand the type of upper-limb plyometric or explosive type training that these athletes undertake. Keeping in mind that the medical and therapeutic staff share the job of returning the athlete to pre-injury performance levels, the research we report on here should help determine what, if any, upperlimb plyometric exercises might usefully be included in late stage rehabilitation.

The research

In a 2001 literature review of studies examining the effectiveness of various training methods for improving throwing performance, DeRenne et al(2)looked at 26 articles across the three training categories widely used in periodised training programmes (see box overleaf). Of these studies, 22 reported increases in throwing velocity, one found a decrease and three found no change after the training period.

But the lack of consistency across the studies in terms of their training periods, weekly volumes, exercises used or percentage changes achieved in throwing velocity meant that the reviewers’ conclusions are rather limited.

Overall, the three categories of exercises (general, special and specific) target different training effects and all three types are successful in improving throwing velocity. It is safe to assume that a training programme should include elements of all three categories. Traditionally, this would have been done sequentially, the athlete moving from general to specific exercises over time. These days the prevailing thinking is towards a more integrated approach, ensuring that some sportand movementspecific training takes place all year round.

Despite the limited conclusions of the review, there are still some useful findings worth noting from some of the research studies that it examined.

Strength training

Within the category of general strength training, many of the earlier studies such as Toyoshima et al(3)concentrated purely on upper-body work. These studies show that even such basic training methods can produce gains in throwing velocity. More recent studies included lower body and trunk exercises to make better use of ground reaction forces for the throwing action. While this makes good sense in theory, there is little in the literature to confirm its added value.

Another recent trend favours a preferential use of certain upper-body exercises such as bench press, lat pulldown and barbell pullover, all of which strengthen the powerful adductors and internal rotators of the shoulder. This approach seems to correlate with greater improvements than just using free weight shoulder exercises. My own tendency would be to include both types of exercise, to avoid muscular imbalances and hence injury.

Special training

‘Special’ exercises need to be performed explosively. So in this phase of training straightforward strength exercises are performed explosively (at speed) alongside more complicated movements that target power and the linking of lower and upper body, such as the clean and jerk. The only study in the literature (Lachowetz et al(4)) to use traditional strength training explosively does not help much, because the training is combined with cable pulley work and other specific throwing action exercises.

Newton and McEvoy(5)compared traditional isotonic resistance exercises with medicine ball upper-limb plyometric drills in baseball players with no previous experience of weight training. Both groups benefited from strength gains, but only the isotonic training group showed enhanced throwing velocity. This suggests that in untrainedpopulations it is probably necessary to train for basic strength before training for throwing velocity.

The same team (McEvoy and Newton 1998(6)) used squat jumps and bench throws (Smith machine bench press, using light weights, in which you throw the bar up and catch it) of weights at 30-50% 1RM and achieved a ‘significant increase’ in throwing velocity in the treatment group.

Specific training

The third training category – throwing-speed specific – concentrates on the athlete generating excess force (by using weighted throwing implements or resistance tubing) or excess speed (by minimising weight and/or drag). The literature review suggests that ‘overspeed’ training works better than ‘over-force’ training, but that either modality will improve on results obtained from just practising throwing (DeRenne et al, 1990(7)).

In 1994 DeRenne looked at the effect of a combined programme of over-speed and overforce training in baseball pitchers(8). The researchers tested two five-week programmes with different combinations of force and speed, and found that both groups showed a significant increase in throwing velocity.

Another interesting study, only recently published (Carter et al 2007(9)), compared an eight-week baseball training programme of high volume upper-limb plyometrics with a regular strength and conditioning regime (no upper-limb plyometrics). This study found no difference in isokinetic strength between the two groups, but the plyometrics group demonstrated a 2mph increase in throwing velocity. The exercises for this study included rotation against tubing resistance, medicine ball overhead football throws and weighted baseball throws.

[072-TABL6]

What it all means

Overall, the research is deficient in two main respects. First, we need more work done on an integrated training approach that mixes up the different components, to tell us whether this is a more effective regime for increasing throwing velocity than the traditional separation of elements. And second, we need to know whether the results obtained using baseball hold good for other throwing sports, as the research literature is heavily dominated by this one sport.

So what can we learn from the studies we do have? We know that plyometric training has a positive impact on the function of the neuromuscular system, resulting in improved postural control and joint position sense. Swanik et al in 2002(10)found that upper-limb plyometrics improved upperlimb joint position sense. It seems clear to me, therefore, that the sports therapist charged with returning a throwing athlete to pre-injury levels of performance will want to use plyometric training as part of the latestage rehabilitation work.

References

1. Chmielewski, L, Gregory, M et al (2006). ‘Plyometric Exercise in the Rehabilitation of Athletes: Physiological Responses and Clinical Application’ J Orthop Sports Phys Ther, Vol 36(5), May.

2. DeRenne, C, Kwok, HW,et al C (2001) ‘Effects of General, Special, and Specific Resistance training on Throwing Velocity in Baseball: A Brief Review’. Journal of Strength and Conditioning Research, 15(1), 148-156

3. Toyoshima, S, Hoshikawa et al (1973) ‘ForceVelocity Relation in Throwing’. Res. Q. 44:86-95.

4. Lachowetz ,TJ, Evon J, et al (1998)’The Effects of an Upper Body Strength Program on Intercollegiate Baseball Throwing Velocity’. Journal of Strength and Conditioning Research.12:116-119.

5. Newton ,RU, McEvoy, KP (1994) ‘Baseball Throwing Velocity: A comparison of Medicine Ball Training and weight Training’. Journal of Strength and Conditioning Research.8:198-203.

6. McEvoy, KP, Newton, RU (1998) ‘Baseball Throwing Speed and Base Running: The Effects of Ballistic Resistance Training’. Journal of Strength and Conditioning Research.12(4):216-221.

7. DeRenne, C, Ho K, et al (1990) ’Effects of Weighted Implement Training on Throwing Velocity’. J. Appl. Sports Sci Res.4:16-19.

8. DeRenne, C, Buxton, BP et al (1994). ’Effects of Under and Over weighted Implement training on Pitching Velocity’. Journal of Strength and Conditioning Research.8:247-250.

9. Carter, AB, Kaminski ,TW et al (2007) ‘Effects of High Volume Upper Extremity Plyometric Training on Throwing Velocity and Functional Strength Ratios of the Shoulder Rotators in Collegiate Baseball Players’. Journal of Strength and Conditioning Research, 21(1), 208-15

10. Swanik, CB, Swanik, KA (1999) ‘Plyometrics in Rehabilitating the Lower Extremity’. Athl Ther Today. 4:16-22, 32-13,63.

Further reading:

Van Den Tillar, R (2004) 'Effect of Different Training Programs on the Velocity of Overarm Throwing: A Brief Review'. Journal of Strength and Conditioning Research, 18(2) 388-396

Wilk KE, Voight ML et al (1993) 'Stretch-Shortening Drills for the Upper Extremities: Theory and Clinical Application’. JOSPT, 17(5), 225-239.

 

Plyometrics and throwing