Advantages of Force in Stretch exercises
- Combines strength, stretching, endurance, balance, and stabilization exercise in a functional demanding position with regards to the myofascial lines
- Pattern specific to functional movement patterns
- Problematic and reduced movement patterns are identified and addressed
- Beneficial effect on chronic and acute pain
- Improves range of motion through stabilization of movement patterns
- Adds sarcomeres in series at end range of motion, giving more force in weak positions
- Results in improved joint positional sense
- Optimizes movement patterns based on proprioceptive feedback, leading to a potential change of cortical reorganization (if the pattern has been previously compensated)
- Leads to improved dynamic balance
- Improves collagen synthesis
The aim of KiD exercises is multi-functional, it incorporates many different elements which when put together form a functional exercise. The aim is to create a goal-directed activity which improves the brain and body’s ability to maintain optimal activity level of the muscles and connective tissue to balance the body during regular daily activity as well as physically demanding body position’s (such as those experienced in sports). It is also aimed towards maintaining a good level of stability in sudden unpredicted situations where high level of muscle action is needed to avoid injury (slipping when walking, avoiding falls etc). This constantly evolving and changing demand of muscle activity needs good reference points to give indication for how to properly set the right muscle tone and direction for the needed action, and this demands (among other) proper proprioceptive signaling (1, 2). This type of signaling is negatively affected by damage to muscle tissue as well as fascial tissue, improving the relevant signaling of this tissue is needed in order for the brain to receive necessary information to base it’s decision on how to regulate the correct activity levels for the actions needed to be performed (2, 3). Part of this rehabilitation is creating goal-directed activity towards improvement of positional awareness, the better the understanding of position the better the resulting activity level will be. (2, 4)
Pain is also positively affected by these exercises, but the exercises should be used in a context where attention is given not exclusively towards improving ROM of the individual muscle. Rather, an understanding of why the ROM is limited, and what co-factors which are imposing this ROM to be limited as well as understanding why pain is present is important in understanding how to use the exercises effectively.
Advantages to adding Force in Stretch to standard exercise therapy
- These exercise types complement each other well
- During regular exercise types, the problem is often that the patient may make small adjustments which are difficult to spot in which they compensate away from a certain structure. This structure needs attention and to be re-coordinated into a normal movement pattern
- KiD exercises addresses these compensated movement behaviors and makes it specific in such a way that the tissue is being directly addressed through it’s complete ROM for the entire movement line so that it can not compensate away, getting a specific effect towards the problematic area.
Neuro training – challenging the status quo
In order for the organism to regulate the fascia and muscle system the body and brain needs to be challenged by using specific overall movements which demands the system to adapt and thereby induce change which affects both the fascial and muscle system based on goal-directed behavior and demand for further stability. Lasting effect and health are more likely to succeed when the behavior leads to a support of the system (and thereby plastic adaptation), rather than just improving ROM without a goal-directed behavior.
The body only receives information and sensorimotor information when it is actively “moving” and transmits feedback from the muscles and fascia. The perception of movement requires signals from tendons, fasciae, muscles, joints and more. The movements and activities of the exercises become very specific and, so to speak, overly clear and actively executed, the resulting information from the sensors leads to prevention or correction of biomechanical imbalances.
It is important to note that muscles never work in isolation, but always function with connective tissue, tendons and fascia which are activated and synchronized together.
One of the concepts which is important in understanding the Force in Stretch exercises, is the myofascial lines. The concept is that muscles are connected through chains via the fascia. This connection is functional as it helps maintain a structural integrity through stabilization by having more structures give support to the same function. If there is a weakening of the chain at a certain aspect, then other muscles may help improve the overall function of the chain by giving more support by way of compensation. Systematic reviews suggests in fact that most skeletal muscles of the human body are directly linked by connective tissue in this regards (5, 6, 7).
There is also moderate evidence for proving intermuscular tension transfer between the involved muscles and structures connected in the same chain (7). These force transfers are again speculated in having an impact in overuse conditions as well as on sports performance.
There has also been done recent studies towards the upper limb chains, where the author’s conclude that there is good evidence for direct serial tissue continuity extending from the neck and shoulder region to the forearms (6)
Another study shows that improving ROM of the lower part of one chain (gastrocnemius and hamstrings), can improve ROM of upper part of the same chain line by demonstrating improvement of the cervical ROM as a result (8). Following this, another study with regards to the same myofascial chain (back chain/line) asked whether this improvement was better than affecting the local tissue, meaning could cervical ROM be improved just as much or more with local therapeutic intervention? The results were that there were no statistical difference between local or remote effect on the same line, they both showed acute improvement of cervical ROM compared to the control group (9). Yet a third and fourth study which also focused on the back chain/line. The first of these showed that affecting the plantar fascia under the foot improved flexibility of the hamstrings and lumbar spine (10). While a follow-up study showed that there was no difference in effect of intervention. Whether it was addressing the hamstrings muscle or the fascia under the plantar surface of the foot, both groups showed improvement of functional sit and reach by 2,5cm (11). For this reason, when we apply this logic to these exercises, we try to activate several muscles which are along the same chain to get as much effect as possible. We are not as interested in individual muscle activity, but rather in a goal-directed functional activity instead.
So the first concept of Force in Stretch is to understand that we don’t address individual muscles, but rather focus on functional myofascial chains.
Force in Stretch – giving resistance
Another aspect of the Force in stretch exercises is the application of resistance in a stretched position which is relevant to the myofascial chains. There are many variants of therapeutic interventions that uses similar concepts. Examples are:
- Muscle-energy techniques
- PNF contract-relax and hold-relax
- Eccentric exercises
For management of pain
Studies have shown benefit for reducing chronic and acute pain by putting a muscle into a stretched position and having the patient apply force to the muscle being stretched, and stretching further again after the contraction (12, 13, 14, 15)
There is also an agreement that muscle activation in stretched position and then stretching is more effective than static stretching alone in improving pain and functional disability (14)
Improving range of motion – power in instability
Muscle activation in stretch has also been found to result in better hamstrings flexibility compared to the control groups (other stretching techniques and no intervention) (16), as well as improved cervical range of motion (15)
When comparing regular stretching to strengthening in a lengthened position for a period of 8 weeks, the results show that there is an increase in muscle length from strengthening in a lengthened position, while stretching did not result in any lasting effect (17). This form of muscle lengthening is considered to be affected by adding sarcomere in series at the ends of existing myofibrils (18, 19, 20, 21, 22, 23. Conversely, exercise which consists of only shortening contractions, which is typical for endurance exercises, leads to a decrease in the number of sarcomere in series (24), and thus loss of muscle length and a more compromised stability in the end-range of motion.
Immobilization has also been shown to create a decrease in sarcomere along the fibres compared to control groups (19). Where in healthy cats who were immobilized in shortened and lengthened position, the study showed that there was an 20% increase of sarcomeres in series in the group which was immobilized in a lengthened position compared to normal muscles. The shortened group had a 40% decrease of sarcomeres in series compared to normal (20) (none of these seem to have any limitations which hindered them from performing isometric contractions in this state.
Proprioception and joint positional sense
Studies have shown that optimal movement patterns can gradually be adapted over time if there is relevant proprioceptive feedback available, but that it is dependent on both the mechanical state of the body and the availability of the sensory feedback during a goal directed behavior (1). For this reason, using the full range of motion and being able to sense one’s position during an exercise is important, and should be challenged. Pain, such as lower back pain can alter normal proprioceptive signaling , leading to a change of cortical reorganization related to movement – altering motor control strategies and force direction (25). These changes may lead to increased spinal loading, degeneration of intervertebral discs and other tissues (3) due to compensation of normal movement patterns. Interestingly, studies have also shown that motor patterns adapt not only to current pain, but also to anticipation of pain if there has been pain related to a movement at an earlier time, so an earlier injury might cause a long-term change in movement (26). This highlights the importance of re-activating and sensing ‘lost’ movement patterns which are related to structures which may have been previously damaged.
It is also important that the exercises are functional in regard to improving joint position sense, as this will facilitate a higher level of motor control and joint stability during daily activities as well as sporting activity. A study highlights that using the same intensity improves joint position sense compared to alternating intensity levels (27). With the force in stretch, both the intensity and the time under tension (which is more precise than an individual repetition) remains the same throughout the exercise.
Activating muscles in stretched position for both agonistic and antagonistic patterns of the hip has also been shown to give improved dynamic balance (28), possibly due to increased positional body awareness in time and space.
Function of force in stretch
Based on this, we see that strengthening from a lengthened position has a positive effect on improving muscle length. Understanding that the muscle length is elongated when the contractile activity is more active and finely tuned (increases with improved joint positioning sense) and more stable due to newly formed sarcomere in series which again allows the muscle length to elongate due to increased stability. Whereas a decrease in sarcomere number appears to be the mechanism which prevents the muscle from being overstretched – leading to less flexibility and increased stiffness (20) It is shown that the contractile elements can dynamically stabilize joints in their end-range of motion if there is e.g. lax capsule and ligaments (29). Creating an exercise program which then mimics this demand by working on these muscles in a functional myofascial line and in their end range of motion improves the ability of the muscles to stabilize from such a position. Which is one of the concepts of force in stretch exercises.
Applying resistance towards chronically injured tendons by way of eccentric training (muscle contraction while lengthening), has been shown to give favorable outcome in form of improved collagen synthesis (30). And the same form of exercise has also been shown to have positive effect on avoiding re-injury of the hamstrings (31)