Science of Sport: Plyometrics - A grown-up approach to youth training

How To Win: Free regular world-class triathlon training tips. Enter email here:

Plyometrics is a popular and effective training technique used by coaches whose athletes need to be proficient in speed, power or agility. It is also a tool whose underpinning principles are often poorly understood, and in the wrong hands it can increase an athlete’s injury risk. The potential consequences are particularly serious for one group: adolescent athletes.

There is arguably a broader responsibility to be shared among health and sports therapy professionals to help educate coaches (often part-time and less experienced) who are working with talented youngsters, so that they do not unwittingly increase their trainees’ injury risk. This may involve some tricky interventions, but that is no reason for avoiding the issue.

The basics of plyometrics

In the useful definition of Wilson et al: ‘Plyometric training uses the acceleration and deceleration of bodyweight as the overload in dynamic activities such as depth jumping and bounding’⁽¹⁾. The technique first became popular in the 1960s and 1970s when east European coaches achieved impressive results in jumping events. Since then, research has conclusively demonstrated the efficacy of plyometric training in sports requiring dynamic movements.

Plyometrics provides the link that can turn strength from traditional weight training into on-court or onfield explosive power. For optimal results, plyometrics should be combined with strength training as part of a periodised programme.

The exercises are performed at high velocity over short time frames and ‘promote the ability to utilise the stretch-shorten cycle by enhancing the use of elastic energy and the stretch reflex’⁽²⁾.

Plyometric exercises for the lower limbs consist of bounding, hopping, jumping from a height and rebounding etc; for the upper limb they usually involve throwing medicine balls in different ways, such as rotating or overhead double or single arm throws.

Upper and lower limb exercises can be combined for sport specificity and to enhance neuromuscular coordination of multiple body segments.

Adolescent risk

Adolescents are at an increased risk of injury during plyometric training for three main reasons:

• Active growth plates are a particularly weak site within the musculoskeletal chain and can be overloaded acutely or chronically with this type of exercise.
• The musculoskeletal system has had a much shorter period overall in which to adapt to strength and power training.
• Adolescents normally have poorer body awareness and core stability than adults. Poor control of technique during plyometrics can increase the load on susceptible structures.

If plyometric training is poorly incorporated into an overall training programme it will contribute to the overuse injuries listed in the table above. Acute injures will present as avulsion fractures (ligament/ tendonbone tears, rather then muscle tears, depending on the adolescent’s level of development) or joint sprains.

Apophysitis problems, where bone degeneration and inflammation occur (such as Sever’s condition and Osgood-Schlatters), are too often considered as ‘self-limiting’ conditions. Young athletes are told just to manage the pain until the affected growth plate becomes inactive. I will consider a less passive approach to such conditions in a future issue of SIB.

The inclusion of plyometrics with high training loads into the programmes of serious young athletes, must progress in three phases.

1. Pre-16s should not do plyometrics: as a general rule athletes under the age of 16 should not undertake plyometric training. But this guidance needs to be related to the individual’s own level of base training and physical maturity.

This base training includes core stability and the fundamentals of strength training in the gym. If a 16- year-old has had no base training, they need to achieve an appropriate level before starting a plyometric programme.

2. Introduce plyometrics within a periodised scheme: When the athlete is ready to begin plyometrics, this element must be incorporated as part of the comprehensive periodised programme. Table 2 below shows the stages at which plyometrics fits into a programme, bearing in mind that this will vary depending on the specific sport and the cycle of competitive phases throughout the year. This integration ensures that the athlete’s body is given the best chance to adapt to training and be ready for the demands of the plyometric component, thereby minimising injury risk and optimising performance benefits.

3. The plyometrics component must be progressive: the plyometrics programme needs to be graded in terms of the stress placed on the body. It should begin with low- to medium-level exercises such as ankle bounces or a single standing long jump, and progress to highlevel exercises, such as depth jumps or continuous hurdle hops.

The timing of plyometric sessions should be planned carefully. For example, doing plyometrics after a hard skills or team session would be counterproductive.

Plyometrics should only be done when the athlete is recovered and fresh. A plyometric session should always begin with a good dynamic warm-up, to prevent injury and ensure quality. Warm-up should consist of some ballistic stretches and some low-level plyometric exercises performed at a reduced intensity. Beginners should start at 85-90% of maximum so that they can pay more attention to technique and be progressed to 100% as they develop.

Make the programme measurable

The general training principles of overload and specificity apply. A good measure of training volume is the number of ground contacts during a single session, which should always be monitored closely. This allows the coach to overload the athlete in a controlled progression.

Allowing the athlete to recover between sets is essential to ensure they can maintain technique and still exert maximal effort. Rough benchmarks for ground contacts are shown in Table 3.

Education, education, education

When dealing with youngsters in a typically fragmented training context, it is the responsibility of all relevant health professionals to equip themselves with a basic understanding and then to ensure this knowledge is sharedproperly.

For example, a 16-year-old elite basketball player might be playing at school, club and representative level. He may therefore be training and playing five to six times a week under three different coaches, each with their own coaching agenda and programme. Very likely, they will not be communicating with one another.

The part-time school coach decides to start including some disorganised plyometric drills for extra fitness, and slots them in at the end of team training, when the athletes are already fatigued. Within a week, the young player has started getting anterior knee pain.

He continues to play and train, and within a month the injury has progressed to a very irritated patella tendinopathy. If no one addresses his training regime, educates the part-time school coach on how to incorporate plyometrics correctly into a training programme and advises on the need for inter-coach communication, the player will struggle to overcome his injury. Moreover, the injury is potentially a long-term problem that could hamper his progress to becoming an elite adult player.

The role of sports support professionals in managing and educating their amateur and less knowledgeable colleagues goes beyond the issue of a single training technique. It may also require comment and review of the volume, level and intensity of exercises during full training, and on return from injury, and even advice on the need to ensure correct technique.

The coach should also be made aware of the need to assess each young player individually, adapting their training regime to meet their specific level of physical and training maturity, their overall training load and injury status.

Without a good understanding of elite training regimes, the sports health professional cannot confidently provide this essential advice and support to others.

Sean Fyfe

References

1. Wilson, Greg; 1993, Plyometric training, Strength and Conditioning Coach, P(1), p 3-5
2. Bosco et al; 1982, Consideration of the training of the elastic potential of the human skeletal muscle, Volleyball technical journal, 6, 75-80

How To Win: free regular running training tips. Enter email here: