The classical strength and conditioning approach that is used by many strength coaches and other professionals in the sports performance realm tends to be very muscle focused. This is important, but tends to overlook certain important components relevant to elite sport performance. Connective tissue plays a critical role in the kinetic chain and maximizing output in terms of throwing velocity and should receive more training consideration than it does.
Proximal to Distal Movement and the Kinetic Chain
All athletic movements that effectively use the kinetic chain, use a proximal to distal sequence of activation. This means muscles located proximally (closer to the center of the body) produce a large amount of force relatively slowly (slower rate of force development or “RFD”). Then, if the movement is properly sequenced, the smaller muscles, with lower force producing capabilities, but faster RFD, that are located more distally (farther from the center of the body) transfer/amplify that energy.
This can be easily seen in movements like sprinting and throwing. In sprinting, the hips are producing a ton of force and the elastic tissues of the ankle are amplifying and transferring that energy with every step.
The same can be seen in the arm during throwing. The pec and the lat aggressively accelerate the arm and the more distal segments of the arm transfer/amplify that energy to the baseball. This is one of the reasons that maintaining a loose grip on the baseball and a relaxed arm for as long as possible is a must. If the distal muscles fire too early, energy will not be effectively transferred and amplified.
For too long this was viewed as solely muscle driven, but recently we’ve discovered the important role that connective tissue plays in transferring and amplifying this energy as part of the proximal to distal sequence.
Connective tissue helps maintain the shape and form of various structures in the body, and within this category is where we find fascia, tendons, and ligaments (both of which can be categorized as fascia). Previously fascia and other connective tissue was seen more as a support structure, rather than playing a significant role in energy transfer, force amplification, and proprioception like we now know it does.
So, what role does connective tissue play in throwing velocity and pitching performance? Well, connective tissue such as fascia and tendons are the links between the body segments that allow the “kinetic chain” to produce such high output movements. The reflexive return that can be achieved when elastic energy is optimally stored and released happens at higher velocities than what can be achieved through volitional, “muscle-driven” movement.
Robert Schleip, one of the world’s experts on fascia defines it as, “The fibrous collagenous tissues that are part of a body wide tensional force transmission system.” Fascia is connective tissue composed primarily of collagen that forms the internal architecture of the human body. It’s a tensional system that surrounds whole muscles like plastic wrap, surrounds groups of muscle fibers, wraps organs, connects muscle to bone (tendons are fascia), and connects bone to bone (ligaments are fascia as well). A popular analogy for fascia is that of opening up an orange-if you looked inside of our bodies we would look similar to that.
Fascia has three main properties: viscosity, elasticity, and plasticity.
- Viscosity: Fascia is primarily composed of collagen and water so hydration is extremely important for how well fascia glides. Well-hydrated fascia should glide over itself, poorly hydrated fascia does not glide well and can have important movement implications.
- Elasticity: Fascia can store and release a lot of elastic energy. As discussed above, this is extremely important for power and speed-based movements as elastic recoils/reflexive recoils happen faster and more powerfully than volitional movement.
- Plasticity: Fascia is extremely adaptable. Davis’ Law governs this quality, stating that soft tissue will remodel based on the stresses placed upon it. This is extremely encouraging as it means that even less elastically-inclined athletes can improve in this regard if training is properly planned.
Other important qualities related to fascia are proprioception and force transmission. When it comes to proprioception, there are ten times the sensory receptors in your fascia as your muscle (Stillwell, 1957). This means that fascia is important for understanding where your body is in space and how to move smoothly and connect movements. If fascia is not trained properly, proprioception can be compromised.
On the force transmission side of things, fascia helps transmit force throughout the body based on its connections to nearby muscles. This is the concept behind “Anatomy Trains” by Thomas Myers.
Impact on Throwing Velocity
In order to throw at high velocities athletes must not only have high maximal force production capabilities, they also must be able to produce large amounts of force very quickly, through extreme ranges of motion, and transfer and amplify energy, which means storing and utilizing elastic energy efficiently.
During the pitching delivery, the lower body produces large amounts of force which must then be transferred through the body via a series of contractions, relaxations, accelerations, and decelerations. Without connective tissue that is well-hydrated and able to glide, very elastic, and specifically trained for the movements required, energy will be lost as heat.
In order to maximize the transfer of energy a few qualities must be appreciated: timing, range of motion, stiffness, and reflexes.
In order to effectively throw and take advantage of the SSC, athletes must be able to effectively store and utilize elastic energy. Elastic energy is stored during the deformation of tissues such as muscles and fascia (remember this is a broad category) and is utilized when that tissue returns to its original length. With regards to the human body, this elastic energy cannot be stored indefinitely. In order for elastic energy utilization to be maximized timing is important as cross bridges have a half-life of about 120-150ms (Cavagna, 1977). This is why the series of accelerations and decelerations that occur as energy moves through the kinetic chain must be timed properly-if they are not energy will be lost.
Range of Motion
An optimized pitching delivery involves moving through some pretty extreme positions and ranges of motion (ROM). This is where length-tension relationships and reflexes play a role. Every muscle has an optimal length range to create tension or force, and tension is maximized when the number of cross bridges is maximized. If a muscle is too short or too long, the number of cross bridges that can form is not maximized. Meaning, there’s a Goldilocks effect here with the length of a muscle fiber. Additionally, the passive piece of this equation is the elastic elements; the tendons, the fascia, and the aponeuroses. These components can create more passive force the more they are stretched. Therefore, altering the length tension relationship in favor of greater force production at longer muscle lengths can have a positive impact on both health and performance. Shorter optimum muscle lengths may be more likely to lead to injury as more of the muscle’s operating range is in the descending force range (Brockett et al., 2004). Meaning that, even though a muscle may be put through a specific range of motion during movement, it may only be able to apply significant force through a portion of it and may be weak through the end range. For example, if a pitcher’s throwing side pec has a short optimum length, it may not be able to apply maximal force through the entire range of horizontal abduction it goes through during throwing. Or, if the pec stays in its optimal range for the entire throwing motion, it will not maximize the benefit of passive force from the elastic components.
Connective tissue stiffness and compliance are both needed in athletic movement. Stiffness is defined as the resistance to change length when force is applied. Stiffer connective tissue will require more applied force to have a given change in length. More compliant connective tissue will require less applied force to have the same change in length.
Compliance is required when producing force, and stiffness is required to transfer energy. Producing force is characterized by longer time periods. In the case of pitching this would apply to the longer force development period from the beginning of the delivery until foot strike. Stiffness is characterized by shorter time periods in order to take advantage of the stretch reflex and the stretch-shortening cycle. In the case of pitching this would apply to the lead leg block to maximize energy transfer into the torso.
The fact that connective tissue is viscoelastic can help guide our decision making in terms of improving stiffness. Fast movements tend to increase connective tissue stiffness, while slow movements tend to increase compliance. This is because when an athlete moves fast the collagen molecules will move as a sheet, but during slow movements the collagen molecules slide past each other and break a large number of cross links, leading to decreased stiffness. Think about slowly entering a pool vs belly flopping. During high velocity movements few cross links are broken, but more are created leading to an increase in cross links, increasing stiffness. When stiffness increases, force transfer improves and rate of force development (RFD) improves as stiffness can be thought of as:
RFD=Signal from brain to muscle–>stiffness of tendon–>force transmitted to bone.
Reflexes go hand-in-hand with the proprioceptors discussed previously. In terms of reflexes, plyometrics (such as throwing) rely on the myotatic (stretch) reflex in order to enhance the power of the concentric action. This reflex relies on the sensitivity of sensors within the muscle tendon unit (muscle spindles and golgi tendon organs) to determine how powerful the subsequent contraction will be.
Muscle spindles sense the magnitude and speed of a stretch and when they sense a stretch that is too great or fast, they send a signal to contract the muscle and resist any further stretch.
Golgi tendon organs (GTO) have a similar job, but involving tension or force rather than stretch. When GTOs sense too much force is being produced, they send a signal to relax the muscle and stop the contraction, they are like the governor on a motor. The governor keeps the driver from driving at “unsafe” speeds, but eliminates the possibility of high speeds.
Both of these elements are present to keep athletes from injuring themselves, but in less-trained athletes the ceiling is often set far too low.
In order to maximize the output an athlete is capable of, the level of “cut off” for both muscle spindles and GTO must be raised. This can be done through strength training through a full range of motion and properly sequencing and progressing your plyometrics.
By training the muscle to move heavy weights through deep ranges of motion the muscle spindles raise the point at which they sense danger and allow for a greater range of motion prior to signaling a contraction.
Training heavy also helps raise the cut-off for the GTO. This helps enhance the output during throwing because when the tissues (muscles, tendons, fascia, aponeuroses) are stretched and the muscle spindle activates, a now larger force will be produced than before and with the enhanced stretch and force output the power of the movement will be greater.
Now that we know why paying attention to connective tissue is important, let’s discuss why it was ignored for so long and some training principles that can help maximize its performance.
Fascia and its adaptations to training have long been ignored because unlike other qualities and variables in training it is hard to measure objectively. Additionally, while muscles adapt to training relatively quickly, fascia may take 6-24 months to improve elasticity (Myers, 2011).
Connective tissue changes are maximized through short duration sessions spaced out by roughly 6 hours (Baar, 2017). So, the movements that are aimed at connective tissue changes should be performed first in a session. Additionally, variety in terms of movement selection and direction help train the elasticity, viscosity, plasticity, of fascia. Specificity is extremely important in terms of driving adaptation, however, if too little variety is present, the tissue will be unprepared for the movement variability present from throw to throw. Potentially increasing injury risk.
Now let’s discuss how we can specifically attack each of the elements discussed previously.
In order to maximize the stretch on the elastic elements, ROM should be improved if it is currently a limiting factor. Eccentric movements, such as those present at the beginning of plyometrics, may lead to a more compliant muscle tendon unit at shorter ranges of motion, with increasing stiffness as length increases. This means that it may be possible to store more elastic energy due to a greater stretch (more compliance) while releasing this energy at a higher speed due to the increased stiffness at the end of the stretch (Brughelli and Cronin, 2007).
Athletes who lack adequate stiffness, which can be seen in measures such as the reactive strength index (RSI), or just by watching athletes who plod along or don’t bounce off the ground, should train to improve this quality. As we know from the information above, stiffness is improved through high velocity movements as well as overcoming isometrics.
Improving performance related to proprioceptors involves raising the tolerance at which these receptors sense danger. By training the muscle to move heavy weights through deep ranges of motion the muscle spindles raise the point at which they sense danger and allow for a greater range of motion prior to signaling a contraction.
Training heavy also helps raise the cut-off for the GTO, like the governor on a motor. The governor keeps the driver from driving at “unsafe” speeds, but eliminates the possibility of high speeds. This helps enhance the output during plyometrics because when the tissues (muscles, tendons, fascia, aponeuroses) are stretched and the muscle spindle activates, a now larger force will be produced than before and with the enhanced stretch and force output the power of the movement will be greater.
When undertaking these training methods, it is important to respect the process of preparation and train in an extensive to intensive manner, as well as general to specific. Extensive training involves higher volume, lower intensity movements in order to prepare the neuromuscular system and tissues for the intensity that will be undertaken later. Intensive training utilizes more intense movements involving high eccentric force and maximal effort. This may mean using oscillatory variations as they can bridge the gap between the weight room and plyometrics and can help an athlete learn to contract and relax more quickly and rhythmically. As training progresses the movements also become more specific to throwing in terms of direction, velocity, order of muscle firing, etc.
Connective tissue helps to connect movements throughout the kinetic chain, transferring energy and amplifying force. While the adaptation time for connective tissue is longer than muscle, the ability to leverage stiffness, range of motion, and reflexes can pay huge dividends. In order for throwers to maximize their velocity and injury-resistance, more attention should be paid to the connective tissue. Through the use of specific training principles the ability of connective tissue to store and release elastic energy can be vastly improved-ultimately providing the opportunity for improved throwing velocity.