Plyometrics
Figure 1 (Pire, 2006).
Background of Plyometrics
What are plyometics?
Plyometrics are defined by Chu (1983, p.20) as, ‘ specific exercises which encompass rapid stretching of a muscle(s) that is undergoing eccentric stress and followed by a concentric rapid contraction of that muscle(s) for the purpose of developing a forceful movement over a short period of time’ .
Plyometric exercises are drills that link absolute strength and speed to produce explosive reactions in movements (Chu and Plummer, 1984, p.30) for both upper and lower extremities (Andrews et al, 1993, p.225).
How can plyometrics benefit?
Plyometrics are beneficial as they are one of the most time-efficient training methods which can also be used with or without equipment for various exercises and for different muscle groups in the body (Andrews et al, 1993, p.225; Barnes 2003, p.13).
This type of strength and conditioning exercise is popular for both adults and children. (Faigenbaum 2006, p.13; Bloomfield et al, 1985 p.1985)
Plyometrics are used over a range of sports such as:
- Volleyball
- Basketball
- Track and field
- Football
- Cross country skiers
(Franks and Howley 2007; Sharkey 2002)
Throughout these sporting activities plyometrics improves the capacity for explosive power and the ability to reduce their amortization phase time; which should be as short as possible (Radcliff and Farentinos 1985; Franks and Howley 2007). This is achieved by completing exercises involving jumps, skips, throws and hops (Franks and Howley 2007).
Figure 1, track and field. (Pire, 2006).
In health plyometrics is mainly focused on preparing children for when they are older. According to Faigenbaum (2006, p.14) plyometric exercises are used to improve fundamentals of fitness skills and performance with the addition of preventing injury in sports participation. Further studies by Bloomfield et al (1985, p.1985) showed through weight bearing exercises such as plyometrics; gains in bone health are seen in children, this however is not the case for adults but completing plyometrics as a child can have potential gains for future bone health.
Figure 3, an example of children’s plyometrics.(Faigenbaum, 2006, p.14).
Specifics
Plyometrics can be done on various surfaces which can cause different training outcomes, for example in a study by Fiorini et al (2007, p.42) a comparison of grass and sand surfaces found that power improvement was significantly better from grass, however the sand tested participants experienced less muscle soreness. Plyometric exercises can be completed in children and adults (Faigenbaum, 2006 p.13; Bloomfield et al, 1985, p.1985; Read and Cisar, 2001, p.279). Plyometrics improves power and tributes to reducing amortization phase time (Radcliff and Farentinos 1985; Franks and Howley 2007). It is also suitable to be used within training programs, this also a way of involving this type of training into research (Adams et al, 1992, p.36).
Physiological Rationale
Children vs. adults.
For children, plyometrics proves to be more health and experience beneficial compared to adults, this is linked with bone health, however it has been argued that plyometrics is unsafe for children (Bloomfield et al, 1985, p1985.; Faigenbaum, 2006 p.14; Sharkey 2002). This is an understandable point as when an adult risks are still present and increased by low experience levels, being overweight, poor technique and over use of plyometrics exercises (Sewell, Watkins and Griffin, 2005). Stated by Howley and Franks (2007); and Sharkey (2002) risks are potential knee problems or muscular skeletal injuries in adults.
Adult Plyometrics
Over research conducted it has been shown that plyometrics can be used alongside other areas of strength and conditioning; such as resistance training (Haff, 2006 p.5). Studies done on plyometric depth jumps have tested with ground reaction forces, counter movement jumps, vertical jumps (Read and Cisar, 2001, p279), squatting and training programs (Adams et al, 1992, p.36) to view outcomes on training influence.
Training for plyometrics has been reported for early training reps are recommended by Howley and Franks (2007) to be 6-10 reps for 1-3 sets, but from Cissi (2006, p.23-24) recommend plyometrics are done at maximal strength for 3 sets of 5 repetitions or 5 sets of 5 repetitions with no set training stage. The underlying principles of plyometrics for improvement of strength and power are the trans-pre-load and elastic recoil of the muscles used (Sewell, Watkins and Griffin, 2005), i.e. lower limbs in jumps.
To produce positive outcomes from plyometrics skills required are:
- Co-ordination
- Timing
- Muscle control
However these are also improved through training, for new athletes with no experience form childhood may suffer the risk of injuries due to poor technique as not all populations have the availability to train as a child (Sewell, Watkins and Griffin, 2005).
Overall plyometics are suitable to develop experience (Faiigenbaum, 2006, p.14) and bone health when a child to follow through to adulthood (Bloomfield et al, 1985, p.1985), but views of it being unsafe for children still are present (Faigenbaum, 2006, p.16), however Marginson et al (2005) states in children after intense plyometric training soreness and tissue damage is less in children than adults. Plyometircs for adults is time-effective training techniques to improve power, strength and ability (Andrews et al, 1993, p.225; Barnes 2003, p.13; Radcliff and Farentinos 1985; Franks and Howley 2007), but with poor technique, being overweight or an overload of training can cause detrimental effects with knee problems and musculoskeletal injuries with risk outweighing benefits of this training method in some circumstances (Sharkey, 2002; Howley and Franks, 2007).
Exercise Techniques
Plyometrics consist of various different types exercises of jumps, leaps and bounds for the lower limbs; however exercises can be completed for the upper limbs. Pire (2006) states in accordance to NSCA guidelines that before lower limb plyometrics can be completed, a squat one rep max test with one and a half times body weight as a minimum should be completed perfectly and parallel. This can be augmented by Pire (2006) also stating that other resources recommend perfect parallel squats with 75% and 60% of body weight added for either 5 repetitions or seconds. Recommendations to state if ready to perform plyometrics are that a resistance training program has to have been completed for minimum of three months; this is because the higher the strength level is, the more force can be produced from the ground; then more powerful moves can be completed (Pire 2006).
Warm up is essential for plyometrics, this prevents injuries and prepares the body for the exercises to be completed, furthermore the plyometrics to be completed being sports specific will also reduce injury risk (Pire, 2006).
Athletic ready position is used for the stages before a plyometric jump is completed; this is a vital to enhance jumping ability. The correct way to complete this is as follows:
- Stand on balls of the feet, little more than shoulder width apart.
- Back strait.
- Hips, knees and ankle slightly flexed (this prepares for eccentric loading before the jump).
- Hands in-front of the trunk with flexed but relaxed elbows.
- Head up, looking forward.
- Ready to jump.
(Pire, 2006)
Figure 4, correct and incorrect athletic positions. (Pire, 2006).
Within plyometrics different levels are associated with different intensities of the exercises. These are as follows:
Level 1 – This is the athlete that has been following a strength training program with no plyometric experience.
Level 2 – Alike level 1 taking part in a strength training program, but having experience of plyometrics for three months.
Level 3 – This is the athlete that on a regular basis trains in plyometrics and strength training for longer than three months. (Pire, 2006).
Lower limb plyometric examples are as follows:
- Pogo jump
- Squat jump
- Box jump (single response)
- Rocket jump
- Star jumps
- Double-leg but kick
- Knee-tuck jump
- Split jump
- Double/single scissor jump
- Single-leg stride jump
- Stride jump crossover
- Quick leap
(Farentinos and Radcliffe, 1999)
Pogo Jump
Figure 5, pogo jump sequence. (Farentinos and Radcliffe, 1999).
The Pogo jump is the basic beginning drill in teaching plyometric jumps, the process of this drill starts off with taking an upright stance, with slightly bent knees, chest out and shoulder back in conjunction with the correct athletic positioning (1).moving onto using arms and shoulders in an upward direction when blocking, emphasising the take-off projecting hips forward like in an accentuated vertical jump take off (2). The slight flexion of the hips, knees and hips should be extended and emphasizes also (2/3). Throughout the jump from take-off to landing the feet should be dorsiflexed, this allows for a quicker and more explosive take off with secure contact time (3/4). On landing hips, knees and ankles should be again slightly flexed with the correct athletic positioning (4). (Pire, 2006; Farentinos and Radcliffe, 1999).
Squat jump
Figure 6, squat jump sequence. (Farentinos and Radcliffe, 1999).
The squat jump is another basic drill used for developing power in the lower limbs, suitable for many sport specific athletes with the primary goal in this drill to jump as high as possible every time with maximal effort. The squat jump should be started by a relaxed upright stance, feet shoulder width apart interlocking fingers and palms behind and resting on the back of the head. The interlocking is used to ensure a good posture at take-off and landing. For this drill to start firstly flex downwards into a half squat position (1); extending the hips, knees and ankles immediately at half squat position as quick as possible but this should only follow reaching half squat position acceptably (1/2). On landing the half squat position should be done with flexed hips knees and ankles, pausing for a check of quality then proceeding first position, rest, repeat (3/4).
(Farentinos and Radcliffe, 1999).
Box jump
Figure 7, box jump sequence. (Farentinos and Radcliffe, 1999).
The box jump is a more advanced plyometric drill after pogo and squat jump drills, with the main use of the box to reduce forces produced during landing impact, used to provide a target to reach in vertical hip projections. To start, initial athletic positioning should be conducted at arms-length away from the platform. When in the athletic position; this should be completed quite aggressively ready to rapidly extend the hips, knees and ankles in an explosive fashion with blocking arms (1/2/3). Feet should remain in a dorsiflexed manor. On landing on the platform, hips, knees and ankles should be flexed and pausing to asses’ quality (4). (Pire, 2006; Farentinos and Radcliffe, 1999).
Programme Guidelines and Exercise Prescription for Track and Field Jump Events
For track and field jump events, plyometric exercises are useful in training. Exercises to improve jump ability are standing broad jump, split jumps, target hops, vertical scoop toss, wood chops and high pulls (Pire, 2006). More advanced plyometric jump exercises are sets of tuck jumps, multiple hops over cones, standing lateral jump, one-legged jumps, box jumps, depth jumps and hanging cleans (Pire, 2006). Through a study done by Adams et al (1992, p.39) it is shown that training consisting of both plyometrics and weightlifting can increase vertical jump ability. This is further supported by Bosco (1982, p.27) who states this process of training improves motor unit recruitment allowing for more kinetic energy to be stored in the muscle which improves explosive power ability, hence vertical jump height improves. Sets and repetitions for plyometric jump exercise consist of 1-2 sets of 10 repetitions, although sets with weight the repetitions drop to 5 (Pire, 2006). To progress plyometric training depends on the athletes conditioning, experience and training level/history, from this assessment frequency, volume and intensity of the training can be progress, for example for tuck jumps, from one session a week of 1 set of 5 repetitions can be progressed to three sessions a week of 2 sets of 10 repetitions for that particular exercise (Pire, 2006). Even though plyometrics can improve jump ability, training with poor technique, being overweight or overloading in training can cause negative effects of knee problems and musculoskeletal injuries with risk outweighing benefits with risks (Sharkey, 2002; Howley and Franks, 2007).
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