Interview Questions for Plyometrics Training

Plyometric exercises, often called jump training, leverage the stretch-shortening cycle (SSC) to generate explosive power. The SSC involves three phases: eccentric (muscle lengthening), amortization (brief transition phase), and concentric (muscle shortening). During the eccentric phase, elastic energy is stored in the muscles and tendons. The amortization phase is crucial – a shorter amortization phase leads to more powerful concentric contraction. The stored energy is then released during the concentric phase, resulting in a powerful, forceful movement. This process is akin to a spring being compressed (eccentric) and then released (concentric) – the quicker the release, the more forceful the rebound.

Physiologically, plyometrics stimulates the neuromuscular system, improving neural adaptations and increasing the rate of force development. This means your muscles can fire more quickly and powerfully, leading to enhanced athletic performance. It also increases muscle strength and power, improves speed and agility, and increases bone density.

Plyometric exercises are categorized based on the type of movement and intensity. Some common examples include:

• Lower Body: Box jumps (various heights), depth jumps (jumping from a box), jump squats, single-leg hops, lateral bounds, and stair jumps. These are excellent for improving lower body power, crucial for sports like basketball, volleyball, and sprinting.
• Upper Body: Medicine ball throws (chest pass, overhead throw), clap push-ups, and plyometric push-ups. These exercises enhance upper body power, benefiting sports like boxing, swimming, and weightlifting.
• Combination Exercises: These combine upper and lower body movements, such as medicine ball slams or jump lunges. They are great for full-body power development.

The application of plyometrics varies depending on the athlete’s sport and training goals. A basketball player might focus on box jumps and lateral bounds to enhance vertical leap and agility. A volleyball player might prioritize medicine ball throws and jump serves to improve power and precision. A sprinter might concentrate on depth jumps to increase acceleration speed.

Assessing an athlete’s readiness for plyometrics involves a thorough evaluation of their physical capabilities and injury history. I typically use a multi-faceted approach:

• Strength Assessment: The athlete should demonstrate adequate strength in fundamental movements like squats, lunges, and push-ups. A weakness in these areas significantly increases injury risk during plyometrics.
• Balance and Coordination Tests: Single-leg stance tests and other balance drills assess neuromuscular control. Good balance is crucial for executing plyometrics safely and effectively. Poor balance indicates a need for pre-habilitation work before starting plyometrics.
• Jumping and Landing Mechanics: Observing the athlete’s jumping and landing technique can reveal potential weaknesses that might lead to injuries. Poor technique needs correction before initiating plyometric training.
• Medical History: Any history of ankle sprains, knee injuries, or lower back problems requires careful consideration. Previous injuries could be exacerbated by plyometric training.

If an athlete doesn’t meet these criteria, a progressive strength and conditioning program will address their deficiencies before they begin plyometric exercises.

Several contraindications exist for plyometric training, primarily those related to joint health and overall fitness level:

• Recent injuries: Athletes recovering from ankle, knee, or lower back injuries should avoid plyometrics until fully healed. Premature return to plyometrics can result in re-injury.
• Joint instability: Individuals with joint laxity or instability are at higher risk of injury. Their proprioception and joint stability should be improved before attempting plyometrics.
• Obesity: Excessive weight increases stress on joints and can elevate the injury risk during plyometrics.
• Cardiovascular issues: Individuals with cardiac conditions should consult their physician before starting any plyometric training program.
• Poor balance and coordination: As mentioned previously, inadequate balance and coordination can lead to injury.

Careful consideration of these factors is essential to ensure the athlete’s safety and prevent potential injuries. If any of these contraindications are present, alternative training methods should be considered until the issues are resolved.

Proper warm-up and cool-down are crucial for optimizing the effectiveness and safety of plyometric training. A thorough warm-up prepares the body for the demands of plyometrics by:

• Increasing muscle temperature: This improves elasticity and reduces the risk of muscle tears.
• Enhancing blood flow: This delivers oxygen and nutrients to the muscles.
• Activating the neuromuscular system: This prepares the nervous system for quick, powerful movements.

A typical warm-up might include 5-10 minutes of light cardio, followed by dynamic stretching exercises such as leg swings, arm circles, and torso twists. A cool-down, consisting of static stretches held for 20-30 seconds per muscle group, promotes muscle recovery and reduces post-exercise soreness. It’s vital to stretch the muscles actively used during the plyometric session. The cool-down should never be skipped.

A beginner’s plyometric program should prioritize proper technique and gradual progression to avoid injuries. The program should start with low-intensity exercises and gradually increase the intensity and volume as the athlete progresses.

• Phase 1 (Weeks 1-4): Focus on bodyweight exercises with low impact, like jump squats (low reps), and bounding (short distances). Emphasize perfect technique over volume. Include plenty of rest between sets.
• Phase 2 (Weeks 5-8): Gradually increase the intensity by introducing exercises such as box jumps (low box height), single-leg hops, and medicine ball throws (lighter weight). Gradually increase sets and reps, always keeping proper form paramount.
• Phase 3 (Weeks 9-12): Continue to increase the intensity and volume of the exercises. Introduce more challenging variations, such as higher box jumps, more challenging plyometric drills, and heavier medicine balls. The emphasis remains on maintaining proper form and gradually increasing the training load.

Throughout the program, monitor the athlete for any signs of fatigue or pain, and adjust the program accordingly. Regular assessment of progress and technique is essential.

An advanced athlete’s plyometric program can be significantly more intense and varied compared to a beginner’s program. It focuses on increasing power and explosiveness while managing fatigue and injury risk. This might involve:

• High-intensity exercises: Depth jumps, single-leg hops with increased height and distance, complex plyometric drills, and plyometric exercises with heavier weights.
• Increased volume: Higher reps, sets, and training frequency.
• Advanced variations: Incorporating advanced variations of exercises, such as plyometric exercises on uneven surfaces or with additional challenges such as incorporating reactive elements.
• Periodization: Implementing periodization to strategically vary the training load and intensity throughout the year, allowing for periods of high-intensity training followed by recovery and maintenance phases. This ensures the athlete avoids overtraining and maximizes performance.

The program should be tailored to the athlete’s specific sport and training goals, with careful monitoring of their progress. Regular feedback and adjustment of the program based on performance and recovery are essential.

Progressing plyometric exercises to increase intensity is a gradual process crucial for injury prevention and performance enhancement. We systematically increase the intensity by manipulating several variables. Think of it like climbing a ladder – you wouldn’t jump to the top rung immediately!

• Increase the Height: Start with low-impact exercises like box jumps from a low box (6-12 inches), gradually increasing the height as the athlete improves (e.g., 18 inches, 24 inches, etc.).
• Increase the Weight: Add resistance by wearing a weighted vest, holding dumbbells, or using resistance bands. This must be carefully controlled and introduced gradually.
• Increase the Number of Repetitions or Sets: Begin with lower repetitions and sets, progressively increasing volume as the athlete demonstrates appropriate technique and strength. Remember, quality over quantity.
• Increase the Speed of Movement: Once the athlete is proficient, increase the speed and power of the movement. This requires precise control and excellent landing mechanics.
• Increase the Complexity of the Exercise: Move from simpler exercises like squat jumps to more complex variations such as depth jumps or lateral bounds. This improves coordination and adaptability.

Example: An athlete might start with 1 set of 10 box jumps from a 12-inch box, progress to 2 sets of 12 reps on a 18-inch box, and then to 3 sets of 15 reps on a 24-inch box, all while maintaining proper form and ensuring sufficient rest between sets and sessions.

Monitoring an athlete’s progress in plyometrics is essential to ensure safe and effective training. We use a multifaceted approach to gauge improvement.

• Performance Measures: Track the athlete’s jump height (using a Vertec or similar device), jump distance, and the number of repetitions they can perform with proper technique.
• Qualitative Assessment: Observe the athlete’s form throughout the exercises, looking for consistency, power, and proper landing mechanics. Video analysis is extremely useful here.
• Subjective Feedback: Gather feedback from the athlete regarding their perceived exertion, muscle soreness, and any pain or discomfort experienced. This helps identify potential problems early on.
• Strength Testing: Regular strength testing, particularly of the lower body, is vital. This provides a baseline of the athlete’s capacity to support the plyometric workload.
• Rate of Perceived Exertion (RPE): Use RPE scales to help athletes self-monitor their effort level. This subjective measure helps avoid overtraining and promotes individualization.

By combining these methods, we get a holistic view of the athlete’s progress and can adjust the training program accordingly. Any significant decrease in performance or increase in pain necessitates a review and possible modification of the training plan.

Modifying plyometrics for diverse populations requires careful consideration of age, injury history, and fitness levels. The key is to adapt the exercises, not necessarily eliminate them entirely.

• Age: Younger athletes might start with simpler exercises, reduced repetitions, and a greater emphasis on proper technique. Older athletes may benefit from modifications focusing on balance and stability, using lower heights and lighter weights.
• Injury History: Athletes with previous injuries, such as ankle sprains or knee issues, need modified exercises to reduce stress on the injured area. This might involve avoiding high-impact movements or incorporating exercises that focus on strengthening the surrounding musculature.
• Fitness Level: Beginners should start with lower intensity exercises and gradually progress. Experienced athletes can handle greater intensity and complexity.

Examples: Instead of depth jumps from a high box, an athlete with a knee injury might perform step-ups or box jumps from a lower height. An older adult could perform seated plyometrics to minimize stress on the joints. A beginner might start with low-impact exercises like A-skips or bounding drills.

A thorough assessment of the individual’s capabilities is crucial before implementing any plyometric program. A well-structured progression plan is essential for all populations.

Plyometrics plays a significant role in injury prevention by improving neuromuscular control, strength, and power. A strong, coordinated neuromuscular system is better equipped to absorb forces and reduce the risk of injury.

• Enhanced Neuromuscular Control: Plyometrics trains the body to efficiently react to sudden changes in force, helping to prevent injuries from unexpected movements or impacts.
• Improved Muscle Strength and Power: Stronger muscles can better withstand stresses, decreasing the risk of muscle strains and tears.
• Increased Joint Stability: Plyometrics strengthens the muscles that stabilize joints, thus protecting them from injury.
• Improved Balance and Proprioception: Many plyometric exercises challenge balance and coordination, thus enhancing proprioception (awareness of body position in space). This is crucial for injury prevention.

Example: A basketball player who regularly performs plyometrics, such as box jumps and lateral bounds, will develop stronger leg muscles and enhanced ankle stability, reducing their risk of ankle sprains during gameplay.

Several common mistakes can undermine the effectiveness and safety of plyometric training. Avoiding these mistakes is key to successful outcomes.

• Ignoring Proper Warm-up: Failing to adequately prepare the muscles and joints before plyometrics significantly increases the risk of injury.
• Poor Technique: Incorrect form reduces effectiveness and increases injury risk. A qualified coach’s guidance is essential.
• Overtraining: Overdoing it leads to fatigue, muscle soreness, and potential injuries. Adequate rest and recovery are crucial.
• Ignoring Pain: Continuing training despite pain is a recipe for disaster. Stop immediately and seek professional assessment.
• Improper Progression: Rushing the progression too quickly, without proper adaptation, is a common cause of injuries.
• Insufficient Strength Base: Plyometrics should not be initiated before establishing sufficient strength in the targeted muscle groups. A strong foundation prevents injuries.

Example: Performing box jumps with a rounded back increases the risk of back injury, whereas a proper warm-up reduces the chance of muscle strains. Consistent monitoring of form and adhering to the progression plan is essential to avoid injuries.

Ensuring proper landing mechanics during plyometric exercises is paramount for safety and effectiveness. The focus is on absorbing impact and minimizing stress on joints.

• Soft Landing: Athletes should land softly, absorbing the impact through flexion of the ankles, knees, and hips. This cushions the joints.
• Foot Placement: Landing with feet shoulder-width apart and slightly flexed, rather than rigid, distributes forces effectively.
• Controlled Descent: The descent should be controlled, preventing jarring impacts on the joints.
• Posture: Maintain a straight back and engaged core throughout the landing phase to provide stability and minimize stress on the spine.
• Immediate Recovery: After landing, the athlete should immediately recover by initiating the next jump or movement.

Example: Landing with straight legs during a depth jump can lead to severe knee injuries, whereas a soft landing, with the knees bent, effectively absorbs the impact.

Regular practice and coaching feedback are essential for perfecting these mechanics. Video analysis is also valuable to identify areas needing improvement.

Eccentric strength, the ability of a muscle to control lengthening under tension, is fundamental to plyometrics. It’s the braking phase of the movement – the critical moment when you absorb impact.

• Impact Absorption: Strong eccentric strength in the lower body muscles (quadriceps, hamstrings, glutes, and calves) helps absorb the shock of landing, reducing stress on the joints and minimizing injury risk.
• Power Generation: The eccentric phase prepares the muscles for the subsequent concentric (power) phase. A powerful eccentric action provides a greater spring-like effect.
• Injury Prevention: Insufficient eccentric strength increases the risk of muscle strains and tears. It’s the foundation of safe plyometrics.

Example: During a depth jump, the eccentric phase is the controlled lowering of the body after jumping from the box. Strong eccentric strength in the quadriceps and hamstrings is crucial to absorb the impact when landing, and this then enables a more powerful subsequent jump.

Eccentric strength training should be incorporated into any plyometric program to optimize performance and minimize injury risk. Exercises focusing on controlled lowering, like slow squats and step-downs, are particularly beneficial.

The amortization phase in plyometrics is the crucial period between the eccentric (loading) and concentric (explosive) phases of a jump or movement. Think of it as the brief pause where your muscles are absorbing force before you powerfully unleash it. It’s the ‘transition’ phase, and its efficiency is key to maximizing power output. A longer amortization phase means a less powerful jump because the muscles lose some of the stored elastic energy. Ideally, it should be short and controlled, minimizing energy loss and maximizing the transfer of elastic energy into the concentric phase.

For example, in a depth jump, the amortization phase is the time between your landing and the subsequent jump. A long, uncontrolled amortization (soft knees, slow upward movement) wastes energy, resulting in a lower jump. A short, controlled amortization (stiffening of the legs followed by a rapid upward drive) conserves energy and translates to a more powerful jump. This is why proper landing technique is paramount in plyometrics.

Plyometrics shouldn’t be implemented in isolation. It’s best incorporated into a broader strength and conditioning program as a specialized component designed to enhance power. Think of it as the ‘icing on the cake,’ building on a solid foundation of strength and conditioning.

• Phase 1: Foundation Phase – Before introducing plyometrics, athletes should possess adequate strength and conditioning levels. This includes a good base of strength training (squats, deadlifts, lunges) for developing muscle strength and hypertrophy. Also crucial is sufficient flexibility and mobility work to ensure proper joint health.
• Phase 2: Plyometric Integration – Start with low-impact plyometrics (e.g., box jumps from low heights, ankle hops). Gradually progress to more advanced exercises (e.g., depth jumps, jump squats) as strength, power, and technique improve. The volume and intensity should be adjusted based on individual needs and progression.
• Phase 3: Periodization – Plyometric training should be periodized. This means cycling through different intensities and volumes. During pre-season, you might focus on building the foundation, using higher volumes. As competition approaches, you might decrease volume and focus on higher intensity plyometrics to improve power output. Recovery is also crucial for avoiding overuse injuries.

For instance, a basketball player’s program might include strength training on Mondays and Wednesdays, plyometrics on Tuesdays and Thursdays, and flexibility work on Fridays. This balanced approach helps to avoid overtraining.

Measuring the effectiveness of a plyometric program involves both subjective and objective measures.

• Objective Measures: These quantify performance. Examples include jump height (using a Vertec or similar device), countermovement jump height, sprint times, and power output measured via force plates. Tracking these metrics over time provides valuable insights into progress.
• Subjective Measures: These evaluate the athlete’s perception. This could involve rating of perceived exertion (RPE) scales after each session to gauge fatigue levels and assessing qualitative aspects of technique. Video analysis can also help identify areas of improvement in jump technique and landing mechanics.

A combination of objective and subjective data provides a complete picture of progress and helps identify any areas where adjustments need to be made. For example, if an athlete’s jump height isn’t increasing despite consistent training, it might indicate a need for technique adjustments or a modification to the program.

Plyometrics offers significant benefits but also carries potential risks. A well-designed and properly implemented program minimizes the risks while maximizing the benefits.

• Benefits: Improved power, speed, agility, vertical jump height, and overall athletic performance. It also enhances neuromuscular coordination and improves bone density.
• Risks: Overuse injuries (tendinitis, stress fractures), muscle strains, joint injuries (sprains, dislocations), and even potentially serious injuries if proper technique isn’t followed. These risks can be significantly mitigated with proper progression, adequate recovery, and careful attention to technique.

For example, athletes should be properly warmed up before plyometric training to prepare the muscles and joints. The training program should be gradually progressed, starting with low-impact exercises and increasing the intensity and volume over time. Sufficient rest and recovery are crucial to allow the body to adapt and repair itself.

Both depth jumps and box jumps are plyometric exercises focusing on lower-body power, but they differ significantly in execution and the emphasis on specific muscle groups.

• Depth Jumps: These involve stepping off a platform (typically 16-30 inches) and landing with bent knees, immediately jumping as high as possible. Depth jumps emphasize eccentric strength (force absorption during landing) and quick amortization phase (transition between landing and jumping) more than box jumps. They are more technically challenging and require better landing mechanics.
• Box Jumps: These involve jumping onto a box from a standing position. Box jumps are generally considered less technically demanding and focus more on concentric power (the explosive jump itself). They provide a more controlled environment than depth jumps for the concentric phase.

Imagine a basketball player who needs to improve the power of both their quick jumps (defense and rebounds) and their explosive jumps (shooting, dunking). They would likely benefit from both depth jumps (for quicker reactions and force absorption) and box jumps (for increasing the height of their explosive jumps). The choice depends on the specific training goals.

Overtraining in plyometrics is a serious concern that can lead to injuries and hinder performance. Recognizing the signs is crucial.

• Monitor Fatigue: Track athlete’s RPE (rate of perceived exertion), sleep patterns, and overall mood. Increased fatigue, irritability, and decreased performance are red flags.
• Reduce Volume/Intensity: If signs of overtraining appear, reduce the volume (number of sets and reps) and intensity of plyometric exercises. This gives the body a chance to recover.
• Incorporate Active Recovery: Replace high-intensity plyometric sessions with lower-intensity activities like light cardio or mobility exercises. Prioritize sufficient sleep and nutrition.
• Listen to your body: Pay close attention to pain or discomfort. Persistent pain requires medical attention.

For example, if an athlete experiences persistent knee pain after plyometric sessions, it’s crucial to address this immediately by reducing training volume, assessing technique, and possibly seeking professional evaluation. Ignoring these signs can lead to more serious injuries.

The optimal volume and frequency for plyometric training depend heavily on individual factors such as training experience, athletic goals, and overall conditioning levels. There’s no one-size-fits-all answer. However, a few general guidelines are provided:

• Frequency: Ideally, plyometrics are performed 1-3 times per week, with adequate rest days in between to allow for recovery. Overtraining is a risk. Beginners might start with once a week, experienced athletes might do up to 3 times.
• Volume: Volume is determined by the number of sets, reps, and the type of plyometric exercise performed. Beginners should start with lower volumes (e.g., 2-3 sets of 8-10 reps), while experienced athletes can gradually increase volume as strength and technique improve. Total jumps per week should remain below 100-150 for most individuals.

It’s important to consider the specificity of the training. An athlete training for a sport requiring high power output might require higher volume and frequency compared to an athlete with more general fitness goals. Remember, progression should be gradual and carefully monitored. A properly designed plyometric plan always places a high emphasis on progressive overload while maintaining proper technique.

Plyometrics, often called “jump training,” is crucial for enhancing power and speed because it leverages the stretch-shortening cycle (SSC). The SSC is a physiological mechanism where a pre-stretch of a muscle immediately precedes a concentric contraction, resulting in a more powerful and explosive movement. Think of a coiled spring: the stretch stores energy, and the subsequent release unleashes that stored energy as force.

In practical terms, plyometrics trains the body to efficiently transfer energy from the eccentric (lengthening) phase of a movement to the concentric (shortening) phase. This leads to significant improvements in both the rate of force development (how quickly you can generate force) and the overall power output (force x velocity). For instance, a basketball player performing box jumps improves their ability to jump higher and faster for rebounds and shots, while a sprinter using depth jumps enhances their explosive start and acceleration.

• Increased Rate of Force Development: Plyometrics strengthens the neuromuscular connection, enabling quicker muscle activation.
• Enhanced Power Output: The SSC maximizes force production, leading to more powerful movements.
• Improved Speed: Greater power translates to increased speed during locomotion and sport-specific actions.

While both reactive and ballistic training involve explosive movements, they differ in the level of external stimulus and the emphasis on stretch-shortening cycle (SSC) utilization.

Reactive training emphasizes the body’s reaction to an external stimulus. Exercises like depth jumps (jumping down from a box and immediately jumping back up) fall into this category. The external stimulus (the landing) triggers the stretch reflex and subsequent powerful concentric contraction. The focus is on rapid adaptation and efficient SSC utilization under unpredictable conditions.

Ballistic training, on the other hand, focuses on performing explosive movements with less external stimulus, often relying on momentum and pre-stretch of muscles. Examples include medicine ball throws or jump throws. While the SSC is utilized, the emphasis is on generating high velocity through maximal concentric effort; the reactive component is less pronounced.

In essence, reactive training is more about reacting to external forces and utilizing the SSC efficiently for maximum power, while ballistic training is about generating maximal velocity through ballistic movements.

Adapting plyometric training to different sports requires a thorough understanding of the specific demands of each sport. The exercises, intensity, volume, and frequency must align with the required movement patterns and energy systems.

• Basketball: Focus on vertical jump height, agility drills, and quick changes of direction using exercises like box jumps, lateral bounds, and jump squats.
• Sprints: Emphasize horizontal power and acceleration with depth jumps, single-leg hops, and bounds. Incorporating plyometrics into sprint training must be carefully managed to prevent excessive fatigue.
• Volleyball: Combine vertical and horizontal plyometrics, incorporating exercises that mimic spiking and blocking motions. Plyometrics are particularly important for powerful jumps and efficient arm movements.
• Tennis: Focus on power and agility for quick movements and powerful shots. Exercises might include lateral bounds, jumps over hurdles, and medicine ball throws. The training is highly specific to the player’s needs.

The key is to ensure the chosen plyometric exercises directly translate to the demands of the sport. For example, a long jumper would benefit from plyometrics focused on horizontal distance, while a high jumper needs exercises that emphasize vertical height.

Imagine your muscles are like supercharged rubber bands. Plyometrics is a type of exercise that teaches your muscles to store and release energy quickly, making you stronger and faster. It’s like practicing jumping and landing repeatedly, but in a controlled and progressively challenging way.

We use jumps, hops, and bounds to train your muscles to become more efficient and powerful. These movements help you develop explosive strength, which will help you with everyday activities like lifting objects or quickly changing direction. Think of it as building your inner spring!

It’s important to note that we’ll start slowly and gradually increase the intensity to avoid injuries. Safety and proper technique are paramount.

I once worked with a volleyball player recovering from a knee injury. Her initial program included box jumps, but due to her limited range of motion and lingering pain, we had to modify it significantly. We started with very low box heights, focusing on proper landing mechanics and controlling her knee throughout the movement. We progressed very gradually, incorporating exercises like single-leg hops on a flat surface to improve balance and strengthen the injured leg before slowly increasing the box height. We also substituted certain exercises with less impact-heavy alternatives such as medicine ball throws and resistance band work to build strength in a controlled manner. Through careful monitoring and progressive overload, we successfully reintroduced box jumps to her program after several weeks, ensuring her knee remained pain-free and stable.

Addressing client concerns about the safety of plyometrics is crucial. I typically explain that while plyometrics are intense, they are safe when performed correctly under proper guidance. I emphasize the importance of a comprehensive warm-up, proper technique, and a gradual progression in intensity and complexity. I also explain that we’ll start with low-impact variations and gradually increase the difficulty only after proper mastery of the basic exercises.

I will often show them videos and demonstrations of correct form and explain the risk factors associated with incorrect technique. This includes discussions on proper landing mechanics (soft landings to absorb impact, minimizing stress on joints) and the importance of listening to their body and stopping if they experience pain.

Furthermore, I might initially prescribe a program that incorporates a low volume of plyometrics alongside other training modalities to build a foundation of strength and conditioning before gradually increasing the plyometric load.

I have found great success incorporating variations of plyometric exercises to meet the specific needs of my clients. One example is using depth jumps onto a slightly unstable surface, such as a wobble board, to improve balance and proprioception (body awareness). This challenges the neuromuscular system and enhances the overall effectiveness of the training.

Another innovation is incorporating plyometric movements into functional training circuits. For example, combining a depth jump with a medicine ball slam and a kettlebell swing. This type of circuit training enhances coordination, power, and overall conditioning.

Furthermore, I have explored using resistance bands to modify plyometrics, increasing the resistance during the eccentric (lowering) phase of a jump. This enhances muscle activation and improves strength.