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Introduction to Bernstein's Theory on Movement Construction

Physiological Aspects Affecting Strength and Power

Today’s discussion will focus on the physiological aspects affecting strength and power, specifically in the development of Rate of Force Development (RFD). To grasp this concept, it’s essential to understand force transmission through tissues as it affects our ability to produce force and develop the rate of force.

What is Rate of Force Development?

Rate of Force Development is defined as explosive force. It’s not the same as speed or power, although it’s closely related to both and significantly influences them. Every sport has critical time periods where the ability to develop force rapidly is crucial, often in 250 milliseconds or less.

Mechanisms and Measurement of RFD

RFD is essentially the change in force per change in time. It’s measured both isometrically and dynamically, using multi-joint activities. Depending on factors like positional specificity, isometric parameters can correlate well with dynamic measurements of maximal force and sports performance.

Relationship between Maximal Strength and RFD

RFD is closely related to maximal strength. Stronger athletes tend to display higher peaks and average rates of force development. However, while there’s overlap in the mechanisms increasing maximal strength and RFD, they’re not exactly the same.

Primary Mechanisms of RFD

There are three main mechanisms we’ll discuss:

  1. Motor Unit Recruitment: Rate coding and motor unit recruitment order are consistent, whether in fast or slow contractions. In isometric and low-speed movements, motor unit recruitment is maintained up to 80-90% of maximal force, then rate coding takes over.
  2. Muscle Fiber Type: Type II, or fast-twitch fibers, handle calcium better than Type I fibers, allowing for faster activation and greater rate of force development. The ratio and size of Type II fibers compared to Type I provide an advantage in explosive force production.
  3. Tissue Stiffness: Muscle stiffness has a strong relationship with RFD. The stiffer the tissue, the better it will transmit force. Strength training can positively increase tissue stiffness, improving both maximal force production and RFD.
Influence of Training

The type of training can influence both the magnitude of force production and RFD and movement speed. Evidence suggests that training to failure is not the most effective method for improving force production and RFD.

Based on Mike Stone’s video content, here are some examples of exercises that can be especially effective for improving rate of force development (RFD):

Isometric Exercises
  1. Isometric Squat: Maintain a squat position at a specific angle (e.g., 90 degrees) for a determined period. This helps increase strength and tissue stiffness, crucial for improving RFD.
  2. Isometric Deadlift: Perform the deadlift with the bar fixed at a specific height using a rack. This allows training strength at a specific point in the range of motion.
Dynamic Exercises
  1. Plyometric Jumps: Exercises like box jumps, depth jumps, and counter-movement jumps are excellent for enhancing explosiveness and RFD.
  2. Medicine Ball Throws: Throwing a medicine ball against the wall or floor can help improve upper body explosiveness and force transfer.
Olympic Lifts
  1. Snatch: This Olympic lifting movement is excellent for developing explosive strength and speed.
  2. Clean and Jerk: Another Olympic lift that trains total body power and improves both maximal strength and RFD.
High-Speed Resistance Exercises
  1. Jump Squats: Performing a squat and finishing with an explosive jump enhances leg force development rate.
  2. Accelerated Deadlift: Lifting the deadlift with a focus on maximal acceleration from the ground to the final position.
Variable Resistance Training
  1. Bands and Chains: Using resistance bands or chains during exercises like bench press or squats can increase resistance as the movement is completed, thus improving both strength and RFD.
Core and Stability Exercises
  1. Explosive Planks: Incorporating explosive movements, such as quick hand pushes while maintaining a plank position.
  2. Explosive Medicine Ball Rotations: Quickly rotating while holding a medicine ball improves the ability to produce force rapidly in the trunk.
Additional Considerations
  • Positional Specificity: Ensure exercises are performed in specific positions resembling sports or competition movements.
  • Load Progression: Gradually increase the load and speed of exercises to continue challenging the neuromuscular system and improve RFD.
  • Frequency and Volume: Train with the appropriate frequency and volume to avoid overtraining and maximize positive adaptations.

Incorporating these exercises and principles into your training routine can significantly improve rate of force development, translating into better sports performance and greater ability to produce force quickly and efficiently.

Conclusions

To achieve peak performance, it’s crucial to enhance both maximal strength and force transmission, including RFD. Key mechanisms include neuromuscular adaptations and increases in tissue stiffness. The relationship between muscle cross-sectional area and the proportion of Type II fibers is also a key factor. Proper training can lead to significant improvements in these areas, optimizing sports performance. Link to Wheeler Academy Sports Science.

 

Author

Carlos Wheeler

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