Current Thoughts in Plyometrics

Plyometrics came into the forth front of training modalities in the 1970’s when athletes from the Eastern bloc began to dominate the medal tables, Verhoshansky training was known as shock or jumping training (Chu et al., 1989). Fred Witt the US track and field coach introduced the western world to plyometrics after watching Soviet athletes train; he then patented this training method as plyometrics in 1975.   Plyometrics utilises the stretch –shortening cycle by using a lengthening eccentric movement which is quickly followed by a shortening muscle movement (Chue et al., 1989).

Due to the high stress of Plyometrics training on the body, there are certain protocols to adhere to suggested by Wathen (1993). Lower extremities plyometrics suggest that you should be able to squat 1.5-2.5 of your body weight or squat 60 % of your bodyweight 5 times in 5 seconds. To commence upper body Plyometrics you should be able to bench your body weight or be able to complete 5 clap press ups.

Hoffman (2014) advises that a foot contact for each Plyometrics session depends on the athlete’s ability. The following suggestions are beginners would begin at 60-100 foot contacts, intermediate 100-150 foot contacts, and the advanced athletes at 120-200 foot contacts per session. Hoffman also suggests that you should have 48- 72 hours recovery from Plyometric activity. High intensity Plyometric exercises are meant to have a ratio of work to rest as 1:5 – 1:10 and for lower intensity plyometric exercises 1:1 (Voight et al., 1994).

Plyometric has been shown to increase sprinting speed or velocity (Markovic et al., 2007). Increase in speed and change of direction speed is required in all sports from squash to Rugby.  Markovic also suggests that sprinters who races over 40m, should improve their acceleration through plyometrics to improve their sprint times. Meylan and Malatesta (2009) conducted an 8 week training program consisting of low level plyometric drills for 14 children who were 13 years of age, in their training sessions for Football. The results were improvement of an average of 2.1% in their 10m time. Reasoning behind a 10 m test is that the average sprint in Football is 2.3 seconds, which relates to 10-12 metres sprint (Castanga et al . , 2003).

Rimmer and Sleivert (2000) also reported an improvement of 10 metre sprint time by 2.6 %, by doing 8 weeks of unilateral/horizontal plyometric exercises. According to Young (2006) sportsmen should do plyometrics as the average sprint distances in sport is between is 10m and 30m, ‘’ would appear that the ability to achieve maximum velocity within the shortest time frame is more important than the maximum velocity itself. That is, acceleration rather than maximum velocity would seem to be of greater importance’’.

Horizontal plyometric exercises are deemed to be more beneficial than vertical plyometric exercises for sprinting. Vertical exercises such as a jump squat can be deemed too slow with the average foot contact of > 0.7 seconds Young (1992).  Horizontal plyometric exercises research from Mero and Komin (1994). ‘’ Speed bounding, the nature of the foot contact, ground contact times, horizontal velocity, stride length, and rate and power production were more similar to maximum sprinting than the other training exercises’’.

Moreover, in highly trained middle and long distance runners can improve their running economy by using short term plyometric training (Saunders et al., 2006).  (Turnel et al., 2003) futher clarifies that running economy improves by 2-3% by completing a 6 week training program of plyometric training.

(Eben et al.,  2004) , claims that plyometric training is seen by the majority of researchers and coaches as their best training modality, when aiming to improve leg power and vertical jumping ability. (Blater and Noble 1979) research shows that increasing hip and thigh power increased explosiveness, which enables a higher vertical jump.  Bosco (1981) concludes that enhancing motor unit recruit enhances muscle ability to store kinetic energy within in the elastic components of the muscle. Further studies on the vertical jump was compiled by  Markovic in (2007), mean average vertical jump height increased from 4.7% to 8.7% depending if you were using a squat jump in comparison to a drop jump.

Plyometrics training in recent years can attribute to knee tendon injuries, due to the nature of high impact exercises. Majority of injuries occur in the landing phase of a jump in plyometric training according to Radcliffe (1988).  Plyometric has been associated with jumper’s knee. Curwin and Stanish (1984) concluded that “Strong eccentric contractions produce high levels of force, and repeated stretching of the extensor muscles results in damage to the tendon; loads of just 25 per cent max. Generated by the quadriceps can create microscopic splitting of the tendon”.  Repetitive high impact jumping can result in patellar tendinitis; this was reported by (Richards et al., 1996).  Further study from (Pezullo, et al., 1992) stated that the patella tendon is likely to produce micro traumas from the landing of a jump; the tendon is stressed further from an eccentric contraction rather than an eccentric contraction.

Plyometrics has been found to reduce neuromuscular imbalances preventing injuries.  Research from (Wilkinson et al., 2004) found that female’s athletes were seen to balance musculature between quadriceps and hamstring groups by increase knee flexion peak torque after plyometric training. Work by (Peterson et al., 2005) found that female athletes who use plyometrics in their training regime decrease lower extremity injuries.

From the literature review plyometrics produces more power, thus becoming a great component of athlete’s training tool.  Plyometrics allows for pure strength to become speed strength, which is a more akin to the sporting environment. Plyometrics are a high intensity exercise, therefore there should be care when a planning a session and a session within a macrocycle. Variables which need to be considered: are the athlete’s ability, number of contacts per session, exercise selection and rest. This will reduce the chance of runner’s knee.

References

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