Power Up Your Performance: The Benefits of Plyometric Training
Plyometric training (PT) has emerged as a crucial component of athletic training programs, offering numerous benefits for athletes. By incorporating PT into a comprehensive regimen that includes strength, mobility and balance training, athletes can optimize their performance while reducing the risk of injuries.¹ This blog explores the importance of PT for developing power, improving deceleration abilities, reducing muscle strain risks, and preventing common injuries such as anterior cruciate ligament (ACL) tears.²
WHAT IS PLYOMETRIC TRAINING?
PT is an effective way to improve both force absorption and production in short periods of time. It also has the benefit of training the athlete in functional movements where injuries most commonly occur, such as jumping, decelerating and changing direction. By training these movement strategies through plyometric exercises, combined with strength training, the athlete is able to absorb these forces through their musculature avoiding the development of sub-optimal force absorption strategies. ³⁻⁴
Plyometric exercises are classified as movements that contain an eccentric muscle contraction immediately followed by a rapid concentric muscle contraction. This muscle action is referred to as the stretch shortening cycle (SSC) due to the lengthening (eccentric) of the muscle being followed by a rapid shortening (concentric). ⁵⁻⁶ Common examples of plyometric activities include jumping, hopping, running and bounding, where there is a focus on high force outputs with a short ground contact time. Jumping, pivoting and cutting all have plyometric demands and occur in most sports, therefore the concept of power development through plyometric exercises is critical. By practicing these actions, the athlete will be better equipped to manage the forces their body is exposed to during sport, thus reducing the risk of injury.⁷
IMPORTANCE FOR DECELERATION:
The ability to decelerate effectively is crucial for athletic performance and injury prevention which is often overlooked. Speed is an important component of many sport and can be divided into raw speed and effective speed. Raw speed can be measured with tests such as the 40-yard dash, and is useful for sports such as track sprinting which only requires linear straight-ahead speed. In sports that require quick stops and starts and rapid changes of direction, effective speed has a greater relationship to athletic performance.⁷ Deceleration and change of direction are important components of many sports such as basketball, tennis and rugby, where the athlete requires effective speed. Optimising an athlete’s effective speed is critical for reducing their risk of injury, as tasks requiring deceleration such as changing direction are common movements where athletes sustain injuries.⁸
Deceleration allows athletes to control their movement, change direction, and perform various sport-specific actions. During deceleration, muscles work eccentrically in order to dissipate forces created during acceleration and store energy that can be used if a concentric contraction is required.⁶ Weak eccentric strength will result in a weakened SSC and potential injury as the body is exposed to a larger eccentric force than what it is capable of absorbing. PT is instrumental in developing the eccentric strength required for deceleration, enabling athletes to absorb and dissipate forces efficiently. By training deceleration strategies through plyometric exercises, athletes can improve their neuromuscular control and reduce the risk of injury during deceleration tasks.⁶⁻⁷
The ability to eccentrically dissipate forces during deceleration and then quickly reaccelerate through concentric muscle action is known as reactive strength.⁹ Reactive strength is often measured by jump height divided by ground contact time on tasks such as a depth jump. Reactive strength involves the ability of the muscle to quickly transition from an eccentric to a concentric contraction.⁹ PT is essential to developing reactive strength and effectively enhancing an athlete’s effective speed. Reactive strength is improved most effectively when PT is combined with eccentric strengthening. Eccentric strengthening will increase the ability to effectively absorb and dissipate forces, which the athlete can then learn to effectively utilise to enhance the succeeding concentric phase by using PT.⁵
IMPORTANCE FOR REDUCING MUSCLE STRAIN RISK:
Muscle strains commonly occur during the eccentric phase of movements, such as landing, twisting, and kicking. PT plays a crucial role in increasing eccentric strength and rate of force acceptance, enabling athletes to better tolerate high forces during ground contact. By improving eccentric force acceptance, athletes can dissipate forces more effectively and reduce the risk of muscle strains. The ability to match and control the forces from initial ground contact in the first 250ms occurs via eccentric muscle contraction. 10 The inability to tolerate these high forces rapidly is a common mechanism of injury. In order to enhance eccentric force acceptance within the first 250ms of ground contact, the athlete must train eccentric strength as well as plyometric capacity.¹⁰
PT also aids in strengthening tendons, such as the Achilles tendon, potentially reducing the likelihood of tendon pathologies. Small variations with drop jump training can adjust Achilles tendon loads and performance outcomes. 11 When the knees are kept relatively extended at landing and push off, there were greater improvements in drop-jump height and Achilles tendon stiffness. When knee bend was up to 80-90 degrees at landing and push-off, greater improvements were seen in the counter-movement jump.¹¹ Practically this means that knee angle can be adjusted during the drop-jumps to alter the amount of load on the Achilles tendon, where greater injury reduction adaptations to the Achilles tendon will be seen with drop jumps in a relatively extended position.
Additionally, plyometric exercises can enhance hamstring strength and balance the hamstring-to-quadriceps ratio, reducing the risk of hamstring injuries. It has been suggested that eccentric strengthening may reduce the risk of hamstring injury, with exercises such as the Nordic hamstring curls being widely used.¹² Studies investigating the use of the Nordic hamstring curl found that teams using this exercise had reduced hamstring injury rates of up to 51% when compared with teams who did not use any injury prevention measures.¹² This suggests that there is significant benefit in improving eccentric strength with strengthening exercises in addition to PT. If eccentric strength is improved, this may improve the amount of force that the body is capable of absorbing during the eccentric phase of the SSC, thus improving plyometric capacity.
REDUCING THE RISK OF ACL INJURIES:
ACL injuries are a significant concern for athletes, particularly in sports that involve deceleration, change of direction and landing. PT has been extensively studied for its effectiveness in reducing ACL injury risk. ACL injuries most commonly occur during non-contact movements such as decelerating, changing direction and landing.⁸⁻¹³ When athletes lack the ability to absorb ground reaction forces through their musculature, they have a condition known as ligament dominance.⁸ This results in more ground reaction forces being absorbed through the joints and ligaments, leaving them more vulnerable to injury. As per Newton’s third law of motion, for every action there is an equal and opposite reaction.⁸ When an athlete is landing from a jump or changing direction, there is an equal and opposite force in the direction of the athlete’s centre of mass. If the athlete’s centre of mass is shifted away from the ground contact by trunk instability, the ground reaction force will continue in the direction of the centre of mass, causing a valgus force to be placed on the knee.¹³⁻¹⁴
Not only does this improve performance, but it also reduces the risk of injury. PT can decrease stress on the ACL (via reduced ligament dominance) and appropriately transfer it across the muscles, bones and tendons, allowing for improved force dispersal and less force applied directly to the knee.¹³ Important to this is sufficient eccentric strength, providing the underlying framework for the SSC to effectively operate.
Through repetition of plyometric movement strategies with adequate underlying strength to ensure good technique, the athlete will have sufficient neuromuscular control to ensure they move effectively during their sport, thereby reducing their injury risk. By enhancing the neuromuscular control and movement patterns plyometric exercises reduce the reliance on suboptimal movement patterns that can increase the risk of ACL injuries.¹⁴ By combining PT with strengthening exercises, athletes can further enhance their eccentric strength, supporting the effective operation of the stretch shortening cycle and reducing ACL injury risk.
FOUNDATIONAL STRENGTH REQUIREMENTS AND SAFE PRESCRIPTION:
While baseline strength is important, PT can be performed by athletes of all strength levels when appropriately prescribed. It is crucial to begin with low-intensity plyometric exercises and progress gradually to more complex variations.³ PT should be integrated into a holistic training program that addresses individual needs, ensuring a combination of strength, mobility and balance training. Athletes should consider their strength levels, experience with PT and gradually increase the number of ground contacts in each session, following principles of progressive overload.²⁻³ A gradual progression from low to high intensity plyometric exercises are recommended, with examples shown below in Figure 1.
Figure 1 - Progression of plyometric exercises from least complex to most complex³
CONCLUSION:
Plyometric training is an indispensable component of athletic training, providing significant benefits for performance enhancement and injury prevention. By incorporating PT into training programs, athletes can develop power, improve deceleration abilities, reduce muscle strain risks, and prevent common injuries such as ACL tears. With appropriate prescription and a comprehensive training approach, athletes can optimize their performance and minimize the risk of injuries, setting the stage for success in their respective sports.
REFERENCES:
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