Plyometrics training is training that utilises the stretch shortening cycle of the muscle.
This typically involves ground contact times of less than 200 milliseconds. For example, this can be exercises such as hops, skips and bounce.
Sprinting would also classify as plyometric training due to the short ground contact times experienced by athletes. Plyometrics is a really impactful means of training because it enables a series of adaptations that are specific to sprint and change of direction performance, both of which are vital to hockey performance on the field.
Mechanical Energy Flow
Mechanical energy flow describes how the forces acting on one part of the body contribute to forces acting on all segments of the body this is due to the transfer of forces between joints during running plyometrics provides adaptations that improve mechanical energy flow by improving the efficiency of the transfer of forces between different joints. In part this is due to improvements in tendon stiffness and elasticity of the athlete.
Some of the key adaptations from plyometric training include improved tendon stiffness as measured by Young's modulus, as well as improved tendon cross sectional area.
A tissue with very little stiffness can withstand only a very low load can absorb only a small amount of energy and is therefore more prone to injury. A stiffer joint can withstand greater loading, and can absorb high amounts of energy, which can also be useful for improving performance and reducing injury risk.
The double threaded nut and bolt system as explained by Fonseca et al (2007) represents joints acting in unison and helps us to understand joint stiffness in more detail. In summary, a joint which is less stiff, is more compliant and therefore will be the area that is affected most during contact with the ground.
By improving stiffness of joints, we can reduce deformation and improve performance in sprinting based tasks.
Benefit to Athletes
One of the key benefits to athletes is improved sprint performance by reducing ground contact time.
- Rimmer and Sleivert (2000) found that at approximately 37 metres, ground contact times were significantly reduced in the sprint performance via a plyometric intervention.
- Equally, leg stiffness and reactive strength index in young athletes can also be improved, as was found by Lloyd and Oliver (2012). However, this was found to be age specific and not all ages responded in the same manner.
Benefits to Hockey Players
- Singh et al (2018) found slight improvements in 10 metre time in elite hockey players using drop jump variations with an emphasis on drop height, but no statistically significant impact on change of direction. There were challenges with impacting speed using low volume plyometric interventions. And this was even more the case where the emphasis was placed on drop height.
- Moran et al. (2017) found that low dose plyometric training has a positive impact on 10 metre time in more mature youth hockey players than less mature players. This is in line with research from Lloyd and Oliver (2012) which found similar age specific adaptations. Based on this research, they advised 60 foot contacts performed twice per week as an appropriate intervention for youth athletes. Seeking to improve acceleration performance via plyometric interventions.
- Sener et al. (2021) also found that high intensity and low intensity plyometrics in the warm up significantly improved 10 metre and 30 metre sprint times and agility performance both five and 10 minutes after completion of this intervention.
This means that in the short term plyometrics can also be of benefit because it impacts performance in hockey specific tasks such as short distance sprints, and agility performance. However, the authors advised individualization of the training, because athletes did not all respond in exactly the same manner at different time points.
Types of Plyometrics
There are a range of different types of plyometrics ranging from short ground contact to long ground contact and from high intensity to low intensity forms.
High intensity plyometrics on one end of the spectrum would be exercises such as drop jumps, where an athlete drops from a box which increases landing velocity and forces experienced during landing.
Less intensive plyometrics can be exercises such as double foot pogo jumps, where the emphasis is on a very short ground contact time but less force is experienced.
Some examples of exercises that are beneficial to hockey players include:
- Pogo jumps
- Drop jumps
- Single leg hops
- Box to box jumps
- Single leg pogo variations
- Repeated hops
- Lateral hop variations
- Depth jumps
These should be completed in a progressive manner, and interventions should always be individualised wherever possible. For example, youth athletes will potentially complete less intensive higher volume plyometric training that seeks to develop capacity of the tissue and tendon tolerate fast stretch shortening cycle activities.
However, more advanced athletes may be completing high intensity plyometric exercises such as drop jumps, where the emphasis is on very fast ground contact time with the overload provided by the drop height from a box
Typical guidance would be to measure plyometrics for ground contact times. So for example, 40, 60 or 80 ground contacts per session. These ground contacts can be made up of eight sets of 10 or four sets of 20, depending on the type of exercise.
The intensity of the exercise is super important, as this will dictate the forces that the tissues will experience and thus the type of adaptation that will occur as well. As the risk of injury to the athlete.
In summary, some key details for plyometric training include:
- Ensure that progressions and exercises are age appropriate
- They are a very powerful training stimulus but should be completed with plenty of rest between exercises to ensure high quality
- They can be used in a warm up/movement prep as an impactful means of improving short term performance
- Plyometrics can improve 10m sprint performance, which is highly relevant to hockey
- Ground contacts should be gradually increased over time to provide progressive overload
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Lloyd, R. S., Oliver, J. L., Hughes, M. G., & Williams, C. A. (2012). The effects of 4-weeks of plyometric training on reactive strength index and leg stiffness in male youths. The Journal of Strength & Conditioning Research, 26(10), 2812-2819.
Moran, J., Sandercock, G. R., Ramírez-Campillo, R., Todd, O., Collison, J., & Parry, D. A. (2017). Maturation-related effect of low-dose plyometric training on performance in youth hockey players. Pediatric Exercise Science, 29(2), 194-202.
Rimmer, E., & Sleivert, G. (2000). Effects of a plyometrics intervention program on sprint performance. The Journal of Strength & Conditioning Research, 14(3), 295-301.
Sener, T., Sozbir, K., & Karli, U. (2021). Acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes. Isokinetics and Exercise Science, 29(1), 1-9.Singh, J., Appleby, B. B., & Lavender, A. P. (2018). Effect of plyometric training on speed and change of direction ability in elite field hockey players. Sports, 6(4), 144.