This is a continuation of the previous post of Part 1, and picks up at the “Discussion” section:
This study demonstrates severely reduced quantitative muscle function and substantial impairment in physical function in patients with EDS‐HT compared to age‐ and sex‐matched controls.
muscle pain and muscle fatigue were omnipresent in the patient group, increased remarkably due to the muscle strength tests, and decreased very slowly after each test.
In addition, poorer physical function was determined in the patient group with the greatest dysfunction in walking and bending, indicating a clinically significant impact on the daily lives of the patients with EDS‐HT.
Our results regarding muscle strength are in line with the findings of previous reports on muscle weakness in other types of EDS.
Another study by Voermans et al demonstrated mild to moderate muscle weakness in various EDS types, in which patients with the hypermobility type caused by TN‐XB haploinsufficiency were least affected
This is peculiar, since by contrast, our results show considerable quadriceps and hamstrings muscle weakness in the EDS‐HT group with decreases of 33.3% to 42.9% in maximal muscle strength (PT/BW) compared to the healthy control group.
This is a huge difference in real life – we have only about half the strength of normal people at our activity level.
This discrepancy may be explained by the fact that EDS‐HT consists of a wide clinical spectrum ranging from very severe to milder phenotypes, in which EDS‐HT patients with TN‐XB haploinsufficiency represent only a minority.
Moreover, the findings of Voermans et al suggest that qualitative variation in muscular involvement among various types of EDS can be a reflection of the tissue‐specific distribution of involved molecules, such as TN‐X. Unfortunately, the molecular background is still unknown for the majority of patients with EDS‐HT (95%).
Coactivation of the quadriceps and hamstrings is considered to provide active stabilization of the knee when stabilization by the passive restraint system (ligaments and capsule) is lacking, which is typical in EDS.
However, muscle coactivation can only succeed in stabilizing the knee joint when there is sufficient muscle strength of both the quadriceps and hamstrings.
In this case, joint instability in EDS‐HT can be explained partially by the substantial muscle weakness in quadriceps and to a larger extent in the hamstrings, as observed in our patients.
Not only maximal strength, but also strength endurance, was remarkably affected in the patients with EDS‐HT compared to the healthy subjects.
The work capacity in the patients was significantly lower than in the control subjects, at the beginning as well as at the end of the isokinetic endurance test. Surprisingly, the decrease in work, or work fatigue, was similar in the patients and controls.
The fact that only data from patients who could complete the test (the “best” patients) were used in the statistical analyses is a plausible explanation for this observation.
However, from the static endurance test, it is clear that the patients are easily fatigued, as evidenced by a significantly shorter endurance time to maintain a specific posture. Unfortunately, there are currently no studies regarding muscle strength endurance in EDS with which to compare our results.
Several factors may be responsible for the muscle weakness observed in patients with EDS‐HT.
more likely hypothesis could be that the cause of muscle weakness in EDS is located in the ECM of the muscle itself.
Here they are referring to the extra-cellular matrix, the fluid in which our cells float.
- Abnormalities in muscle ECM composition,
- based on defective collagen function and
- a defective interaction with other ECM components,
may influence muscle function by altering force transmission.
A reduction of the force generated within the muscle fibers and transmitted via tendon onto the skeleton (myotendinous force transmission) can occur due to an increased compliance of the muscle–tendon complex…
With “increased compliance”, they mean it stretches easily.
…since more slack has to be taken up before the elastic component can transmit forces.
This is exactly what I’ve been thinking for years. As soon as I found out I have the slack connective tissue of EDS, I was able to understand why I had so much trouble gaining strength in just about any exercise I tried.
results show reduced passive muscle tension of the calf muscles, with no difference in muscle cross‐sectional area, and a reduced stiffness of the Achilles tendon in patients with EDS‐HT compared to healthy control subjects.
Structural modifications in the connective tissue of EDS‐HT patients are thought to be responsible for this increased muscle–tendon compliance
up to 40% of the muscle force generated within a muscle can be transmitted from muscle fibers onto the intra‐, inter‐, and extramuscular connective tissue to the skeleton (myofascial force transmission). Altered compliance of these myofascial pathways might decrease the force transmitted, resulting in muscle weakness.
Other problems may also contribute to the muscle weakness observed in patients with EDS‐HT, such as chronic pain and increased fatigability.
Our results show that both musculoskeletal pain and fatigue are emphatically present in the EDS‐HT group, which is in agreement with previous results in patients with EDS
Pain may cause inhibition of maximal voluntary contraction force, resulting in muscle weakness
As I’m sure many other people with EDS have noticed, it’s very hard to strain the muscles into severe pain. The body resists with all its might because it assumes pain equals injury, which should be rested, not stressed.
In addition, a positive and direct relationship between fatigue severity and muscle weakness in EDS has been suggested.
Moreover, it is striking that the exercise‐induced pain and fatigue in the patients with EDS‐HT increased disproportionately compared to the muscle performance, and remained extremely high and long‐lasting after the effort. The latter points to a delayed recuperation in EDS‐HT.
This explains why my muscles seem to get much more sore and stay sore much longer after intense exercise.
Mitochondrial dysfunction can account for a lower production rate of ATP in the muscle and nervous systems, which is associated with increased peripheral fatigue and pain
This study was not only focused on weakness in muscle strength and muscle strength endurance, but also on the impact of these factors on the patients’ functional capacities in daily life.
It’s OK to be weak when I’m lying on the couch, but not OK when my muscles are so weak that even climbing a single flight of stairs is too much and I have to rest.
Knee extensor muscle weakness has been associated with a reduction in
- walking capacity,
- stair climbing ability,
- getting up from a seated position,
- postural stability, and
- even the occurrence of falls
This explains why I find it so strenuous to maintain good posture. If I don’t constantly monitor myself and deliberately straighten, I crumple into a formless heap.
Indirectly, a slightly increased risk of falling was determined, which can be confirmed by a recent study that demonstrated increased falls and imbalance in patients with EDS‐HT.
Our poor proprioception certainly contributes to poor balance. If we don’t even know where our body parts are in space, how are we supposed to align them in balance while moving?
The fact that reduced muscle strength is a major contributor to physical impairment in EDS‐HT, which significantly affects the daily lives of EDS‐HT patients, may be a starting point for appropriate treatment.
EDS‐HT has no definitive treatment and therefore poses a management challenge.
In light of our findings, it may be appropriate for clinicians to consider interventions that improve muscle strength and muscle strength endurance, and…
But the problem is that such interventions/exercises don’t build muscle like they do in normal people.
…at the same time diminish pain and fatigue, which are known to compromise improvement of muscle strength.
Instead of getting stronger, I just hurt more when I push myself harder.
in adult patients with a heritable connective tissue disorder, whether muscle function can be improved by training and to what extent, and thereby improve physical function, requires evaluation in future studies.
I have the answer to that: muscle function can only be slightly increased no matter the amount of effort expended.
If I start doing a new exercise to build strength (like pushups to strengthen my arms), I can only improve about 10-20% in the first week and then I’m never able to do more.
In conclusion, this is the first extensive clinical study on lower extremity quantitative muscle function in patients with EDS‐HT.
The results demonstrate considerably reduced quadriceps and hamstrings muscle strength and muscle strength endurance in the EDS‐HT patients compared to the healthy subjects, which was also reflected in poorer functional performance and impaired physical function.
The muscle weakness may be due to muscle dysfunction rather than muscle atrophy, in which altered force transmission due to abnormalities in muscle extracellular matrix composition may play an important role.