Muscle strength and functional performance in EDS-HT
When EDS patients describe weakness, they are often told the solution is to build more muscle. Eat more protein, do more strengthening exercises, increase your muscle mass. The clinical logic is intuitive: weak muscles need more muscle. A 2012 study by Rombaut and colleagues published in Arthritis Care and Research shows this logic is wrong for EDS — and wrong in a way that has direct treatment implications. Women with hypermobility-type EDS showed substantially reduced muscle strength and functional performance compared to healthy controls. Their muscle mass was not dramatically reduced. The problem was not how much muscle they had. It was what the muscle could produce and sustain — a neuromuscular control failure embedded in a connective tissue environment that compromises every step between motor intention and force output. Building more of the same kind of muscle into the same broken system does not fix the system.
The Study: Measuring What Muscles Actually Do, Not Just How Much There Is
Rombaut and colleagues recruited women with hypermobility-type EDS (now classified as hEDS) and age-matched healthy controls and measured three different domains: maximal muscle strength using both isometric and isokinetic dynamometry, functional performance on standardized physical tests, and body composition using a method that quantifies lean tissue mass. The three-domain approach is what makes this study informative — it allows you to separate the amount of muscle from what that muscle produces and from how the whole system functions in integrated movement tasks.
Maximal isometric strength tests a muscle group's peak force output under static conditions. Isokinetic strength tests force production through a joint's range of motion at controlled velocity. These are different ways of stressing the neuromuscular system, and both showed significant deficits in EDS-HT patients. Functional tests — the timed up-and-go test, stair climbing performance, and six-minute walk distance — assess how the neuromuscular system performs in real movement tasks that involve coordination, balance, timing, and fatigue management across multiple muscle groups simultaneously. These also showed substantially worse performance in EDS-HT patients compared to controls.
The body composition analysis showed that lean tissue mass — the muscle mass component — was not dramatically reduced in EDS-HT patients relative to controls. The patients were not significantly sarcopenic. They were not simply deconditioned in the straightforward sense of having lost muscle mass. They had the muscle. They just could not produce or sustain the force output that their muscle mass should theoretically be capable of generating.
The Mechanism: Why Connective Tissue Controls Muscle Function
Muscle force generation involves multiple sequential steps, each of which depends on systems beyond the muscle tissue itself. A motor neuron fires, generating an action potential that travels to the neuromuscular junction. The signal is transmitted across the junction to the muscle fiber, producing a contraction. The contractile force of the muscle fiber is transmitted through tendon to bone, generating joint movement. The brain monitors all of this through proprioceptive feedback — sensory signals from mechanoreceptors in tendons, ligaments, and joint capsules that report the position, velocity, and loading state of the joint.
In EDS, multiple steps in this chain are compromised by connective tissue laxity. Force transmission is impaired because tendons that are overly compliant absorb energy that should be transmitted to the joint — the muscle contracts, but the tendon stretches rather than efficiently transmitting the force. Proprioceptive feedback is degraded because lax ligaments and tendons do not produce the same mechanoreceptor signals as tight ones — the information the nervous system receives about joint position and loading is delayed and imprecise. Motor control is impaired because the nervous system is receiving unreliable proprioceptive feedback, and its motor commands are calibrated based on that unreliable input.
The result is that a muscle group that has adequate contractile tissue cannot produce coordinated, powerful contractions because the system supporting those contractions is compromised. The motor control system compensates by generating lower-force, more tentative contractions — protective co-contraction strategies that prioritize joint safety over force output. The patient experiences this as weakness. It is not weakness in the sense of insufficient muscle fiber — it is weakness in the sense of a neuromuscular system that has learned, correctly, that full-force contractions in an unstable joint environment are dangerous.
What Proprioception Has to Do With Strength
The relationship between proprioception and strength in EDS is more direct than it might appear. The nervous system does not issue motor commands in a vacuum — it continuously updates its commands based on sensory feedback. When you reach for a glass, the motor cortex issues an initial command, but the movement is continuously updated based on real-time proprioceptive information about how the limb is moving relative to the intended trajectory. This feedback loop allows smooth, powerful, precisely calibrated movement.
When proprioceptive feedback is degraded — as it is in hypermobile joints where lax ligaments and tendons do not produce reliable mechanoreceptor signals — the feedback loop is compromised. The motor system is working with imprecise information and cannot calibrate its commands accurately. The result is that patients often cannot fully activate the muscles they have: the motor command is held back because the nervous system cannot confidently monitor what is happening in the joint during maximal contraction. The proprioceptive impairment research in EDS documents this deficit in detail and traces its autonomic consequences — degraded joint sensing cascades into impaired postural control and autonomic dysregulation.
The Treatment Implication: Motor Control Over Mass
The therapeutic implication of the Rombaut findings is specific. If the primary deficit in EDS-HT weakness is neuromuscular control rather than muscle mass, then the treatment target is neuromuscular control — and the exercise approach that most directly addresses neuromuscular control is not the same as the approach designed to maximize muscle mass.
Building muscle mass through high-volume, high-calorie protocols increases the amount of contractile tissue available but does not address the force transmission impairment caused by tendon compliance, the proprioceptive deficit caused by lax mechanoreceptors, or the motor control calibration problem that results from degraded sensory feedback. Patients who follow mass-building programs may gain lean tissue without meaningful improvement in strength output or functional performance — and report that standard strengthening "doesn't work" for them.
What does address the relevant deficit is exercise programming that focuses on joint stability, proprioceptive training, motor control precision, and progressive mechanical loading that drives tendon remodeling. Møller and colleagues demonstrated that progressive resistance training can increase tendon stiffness even in genetically confirmed classic EDS — directly addressing one of the key mechanical failure points in the Rombaut model. The approach is different from conventional strengthening in its emphasis: the goal is not more muscle, it is better integration between the muscle you have and the connective tissue and motor control system it operates within.
What This Means for Patients Who Have Tried and Failed at Standard Strengthening
If you have EDS and have worked at physical therapy or strengthening programs without seeing the improvements you expected, the Rombaut data provide a mechanistic framework for why. Your weakness is not primarily a muscle mass problem. It is a neuromuscular control problem in a connective tissue environment that degrades every step between your motor intention and your force output. An exercise program that adds muscle mass without improving joint stability, proprioceptive feedback quality, and motor control precision is not addressing the relevant mechanism.
The appropriate exercise target for EDS is not more mass. It is better function of the neuromuscular system you already have, within the connective tissue constraints you cannot eliminate. That means proprioceptive training, stability work, motor control drills, and progressive loading that drives tendon remodeling — with appropriate supervision to manage the increased injury risk that comes with impaired proprioception and lax joints. The goal is not to build your body to look stronger. It is to train your nervous system to use the body you have more effectively, with the connective tissue environment that condition has given you.