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Updated: Oct 17, 2025
Methods to Quantify Pharmacologically Induced Alterations in Motor Function in Human Incomplete SCI
Published on: April 18, 2011
Early movement restriction deteriorates motor function and soleus muscle physiology
Marie-Hélène Canu1, Valérie Montel1, Julie Dereumetz1
1Univ. Lille, Univ Artois, Univ Littoral Côte d'Opale, ULR 7369, URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, F-59000 Lille, France.
Insights
Early movement restriction in rats caused lasting muscle atrophy and motor deficits, highlighting the critical role of proprioceptive feedback in sensorimotor development. These findings offer insights for treating neurodevelopmental disorders.
Area of Science:
- Neuroscience
- Developmental Biology
- Muscle Physiology
Background:
- Sensorimotor development is crucial for typical motor function.
- Movement restriction can lead to sensorimotor deficits without apparent brain damage.
- The interplay between nervous system and muscle in altered sensorimotor behavior is complex.
Purpose of the Study:
- To evaluate the impact of early sensorimotor restriction (SMR) on soleus muscle and sensorimotor performance in rats.
- To determine if SMR-induced changes could be reversed upon resuming typical activity.
Main Methods:
- Rats underwent hind limb immobilization (SMR) from birth to postnatal day 28 (PND28).
- Soleus muscle properties (contractile, CSA, MHC) and motor function were assessed at PND28 and PND60.
- Hoffmann reflex was used to evaluate spinal excitability.
Main Results:
- SMR rats showed soleus muscle atrophy, reduced CSA, force loss, and delayed maturation at PND28.
- Spinal hyperreflexia and spasticity were observed.
- While most changes reversed by PND60, muscle atrophy persisted.
- Motor tests requiring limb coordination (rotarod, locomotion) showed enduring deficits, despite increased spontaneous activity.
Conclusions:
- Proprioceptive feedback is as vital as motor activity for typical motor function development.
- Persistent motor alterations suggest long-term impacts of early SMR.
- Understanding hypoactivity, muscle properties, and motor commands may inform therapies for neurodevelopmental disorders.
Abstract:
Children with low physical activity and interactions with environment experience atypical sensorimotor development and maturation leading to anatomical and functional disorganization of the sensorimotor circuitry and also to enduring altered motor function. Previous data have shown that postnatal movement restriction in rats results in locomotor disturbances, functional disorganization and hyperexcitability of the hind limb representations in the somatosensory and motor cortices, without apparent brain damage. Due to the reciprocal interplay between the nervous system and muscle, it is difficult to determine whether muscle alteration is the cause or the result of the altered sensorimotor behavior (Canu et al., 2019). In the present paper, our objectives were to evaluate the impact of early movement restriction leading to sensorimotor restriction (SMR) during development on the postural soleus muscle and on sensorimotor performance in rats, and to determine whether changes were reversed when typical activity was resumed. Rats were submitted to SMR by hind limb immobilization for 16 h / day from birth to postnatal day 28 (PND28). In situ isometric contractile properties of soleus muscle, fiber cross sectional area (CSA) and myosin heavy chain content (MHC) were studied at PND28 and PND60. In addition, the motor function was evaluated weekly from PND28 to PND60. At PND28, SMR rats presented a severe atrophy of soleus muscle, a decrease in CSA and a force loss. The muscle maturation appeared delayed, with persistence of neonatal forms of MHC. Changes in kinetic properties were moderate or absent. The Hoffmann reflex provided evidence for spinal hyperreflexia and signs of spasticity. Most changes were reversed at PND60, except muscle atrophy. Functional motor tests that require a good limb coordination, i.e. rotarod and locomotion, showed an enduring alteration related to SMR, even after one month of 'typical' activity. On the other hand, paw withdrawal test and grip test were poorly affected by SMR whereas spontaneous locomotor activity increased over time. Our results support the idea that proprioceptive feedback is at least as important as the amount of motor activity to promote a typical development of motor function. A better knowledge of the interplay between hypoactivity, muscle properties and central motor commands may offer therapeutic perspectives for children suffering from neurodevelopmental disorders.
