In Tension Part 1: The Good & The Bad, we discussed that tension may not always be what we think. Understanding the origin of tension and the purpose it has on human movement is critical to developing, treating, or training the athlete.
As a review, the definition of tension – an internal state of tissue that is maintained continuously, also known as a partial contraction. This exists at rest in a relaxed state and increases with stretch.
Physiologically, tension is monitored by the muscle spindles (stimulated with a stretch) and golgi tendon organs (stimulated with external load). To truly understand tension, the body has to be challenged to create a response – MOVEMENT! Muscle spindles have three types of gamma fibers that detect tension.
Type 1 – detects unfamiliar and or new movement. You will experience or perceive tension in the tissues involved with movement!
Type 2 – detects familiar and accustomed movement. Not a lot of tension will be experienced or perceived necessarily.
Type 3 – detects unlearned, unfamiliar, and or new movements. Very similar to type 1 fibers and tension will be experienced.
Therefore, if the movement is new or novel to the athlete, tension is likely and because it is not a learned movement, the observation of a flaw or dysfunction could be interpreted. But this may not be the case. The solution? Give the athlete an opportunity to practice (fast learning) to permit the gamma fibers (type 1/3) to accommodate or adapt to the movement. This also means you don’t stretch or treat this form of tension unless clinical reason would suggest so.
Furthermore, the concept of tensegrity, a concept that has been around in the fascia world for some time now, epitomizes the notion that tension is maintained continuously. Tensegrity is a degree of tension throughout the elaborate and comprehensive fascial network that provides continuous feedback about where the entire body or limb is in space (kinesthetic awareness). Moreover, kinesthetic awareness is a function of adequate proprioception (limb position, limb movement, and muscle contraction). Therefore if proprioception is inadequate with movement, tension can be elevated in the body. With this all said, excessive tension can be a by-product of inadequate proprioception. Said another way, excessive tension can be perceived due to altered joint control and multiple body segments lacking coordination through a movement pattern. Remember, fascia plays a role with communicating between remote body segments and supplying sufficient tension to regulate movement, which ultimately provides kinesthetic awareness. This form of tension is good!
One has to understand that phasic and tonic muscles respond differently when it comes to producing a contraction. Tonic muscles are responsible for controlling joints during movement, whereas phasic muscles are responsible for generating force to create movement. Tonic muscles when deconditioned or dysfunctional will present as hypertonic or hypotonic (low tension). Whereas phasic muscles will present as being hypertonic if deconditioned or dysfunctional. Tonic muscles respond to joint (dys) function which is consistent with the role of such muscles. However, phasic muscles respond to tonic muscle function during movement. The interplay between the two types of muscles needs to be accounted for during the movement assessment. For example, is the movement strategy a control or coordination issue, or a capacity issue (phasic muscles)?
Furthermore, tension can also be interpreted by receptors called nociceptors. These receptors are designed to monitor for threats to the body (thermal, chemical, and mechanical forms). In the health and fitness world we tend to interpret mechanical forms of threat. This is in the form of aberrant, unlearned, unstable, and dysfunctional movement patterns. Depending on the duration of the altered state of movement, this can lend itself to ingrained habits. As a result, even if the movement is corrected, but tension is still perceived in a threatening way, the nociceptors may not have adapted to the change and require time for a new perception to be created!
So on to the test I had asked you to go through with hamstring tension:
“The next time you experience or come across hamstring tension during a hamstring stretch I want you to consider the following: What happens if…”
- You provide resistance in either adduction (groin) or abduction (glute) during the stretch of the hamstring?
EXPLANATION: If providing resistance to either or both muscle groups resulted in reduced hamstring tension, then one possibility for reduced sensation of hamstring tension was due to an improvement in hip centration (joint articulation control through movement) which could reduce threat (nociception). So from a rehab/treatment standpoint, stimulate the muscle(s) that offset the tension with motor recruitment strategies (isometrics, electrical stimulation, etc.). Now, if applying resistance increases tension to the hamstring, this would suggest that excessive tension was created during resistance and resting tension of the abductors and or the adductors was high to begin with and needs to be addressed (stretch, self-mobilization, clinically evaluated).
- You perform isometric contraction of the hamstring (minimum of 10 seconds at 80% maximal effort for 5 repetitions) and reassess?
EXPLANATION: The contraction induced a stretch reflex and modulates the threshold of sensitivity of the muscle spindle to perceiving a stretch. So what?? Isometric contraction at, just below, or graduated through increasing range will allow the body to accommodate the stretch perception so that it is more tolerable to a stretch. The key here is the intention of effort which needs to be >80% effort to provide sufficient neurological input to stimulate the muscle fibers and enhance the irradiation principle (the spread of neurological stimuli to the working muscle or muscle groups).
- You change your posture. For example if you assess the hamstring standing (i.e. toe touch), perform instead supine or lying your back?
EXPLANATION: The postural demand places different load demands on the system that the body must accommodate. This will provide insight into the athletes preferred methods of training and stretching. Moreover, this also provides critical information about what positions the athlete does not tolerate and insight into the lack of variability of motion he or she has. Movement variability is a concept that defines the available options an athlete possesses to move efficiently. The less variation in training (movement direction, load, contraction types, volume, labile vs. non labile conditions) will expose the athlete’s inability to accommodate certain positions and tasks because they have created a contraction history (thixotropic effects) based on how they move. This contraction history is the body’s way of adapting to repeated exposure to stimulus (exercise, work tasks, posture, etc…). The body will move well in directions it is used to (tissue will be compliant with appropriate tension to permit motion) vs. other unaccustomed positions (tissue will be less compliant – thickened and excessive tension that does not permit appropriate motion).
- You perform a core exercise of your choice and then reassess the hamstring?
EXPLANATION: This is similar in principle as the first scenario with the abductors and adductors. The important note to take from the core exercise is that the stimulation of the core to facilitate control of lower extremity movement (in this case SLR) reduces the nociceptive input (threat due to an uncontrolled pelvis and core musculature) that alleviates a reflexic response of hamstring tension.
- You perform a stretch or mobility exercise to the ankle?
EXPLANATION: This scenario provides insight into the interconnectedness of tissues within the body especially at or near attachment sites. In this case the distal femur and proximal tibia, which we also call the back of the knee! The interface between the distal hamstring and proximal gastrocnemius is a common site for excessive tension to be identified. Whether this is the skin itself, crural-tensor fascia or the actual interface, it can be challenging to know which exactly the culprit is. Nonetheless, understanding the anatomical relationship can provide insight. In this case the hamstring tension can be influenced by the calf tension because of the anatomical relationship. Therefore, inducing a stretch reflex response via the calf (dorsi flexing the ankle) may in some cases alleviate hamstring tension.
So, now that we have some explanations as to what may be going on, do you remember what happened? If nothing changed that is also an acceptable outcome of any of these scenarios. The lack of change can represent a couple of things:
- The stimulus applied (resistance, stretch, activation of a particular region) was insufficient to produce a change. This may imply that more bouts of resistance or longer stretch duration or multiple sites of activation are necessary to create a change.
- The stimulus applied was appropriate and sufficient but the issue maybe the hamstring itself! Yes, that’s right. Now you have concluded that the issue at hand is actually the hamstring and not something else, and so the athlete needs to be clinically evaluated (fibrosis, significant neurological injury or other form of soft tissue pathology).
The intention here is to have you evaluate and understand that tension may be a by-product of poor kinesthetic awareness as a function of altered function in surrounding structures. The goal was to have you appreciate that there can be a multitude of reasons why the hamstring was tight and that a subtle change can be a big difference in alleviating the tension. Remember, NOT all tension is bad. Tension may be good as the body is attempting to protect itself from further harm. If the body did not regulate itself this way there would be more injuries!
In the AMA seminars we explore the various sources of tension that compromise movement and narrow down what can be managed with simple strategies and when a referral for clinical consultation is most appropriate.