Children With DMD Have Excessive Activation of Leg Muscles, Study Finds

Children with Duchenne muscular dystrophy (DMD) show signs of excessive activity in certain leg muscles, an apparent reaction by the body to compensate for the instability caused by muscle weakness associated with this disease. This compensation mechanism may have a negative impact on the muscles and increase the effort necessary to move, according to new research by a group of French investigators.

The study “Muscle Activation during Gait in Children with Duchenne Muscular Dystrophy,” was published in the journal PLOS ONE.

In patients with DMD, gait loss starts around the age 3 to 6, and is considered a milestone in the progression of this disease. Although certain anomalies in the pelvis, knee and ankle have been found among DMD patients, resulting from muscle weakness, muscle shortening and changes in the bones and articulations, the patterns of muscle activity in these patients are poorly understood. This limits  knowledge about the contribution of each leg in abnormal gait patterns.

The objective of this study was to compare muscle activation and changes in muscular activity in the legs of children with DMD to healthy children of the same age and gender. To do so, researchers followed 16 DMD children and 15 control subjects, analyzing the activity of several leg muscles, namely the rectus femoris (RF), vastus lateralis (VL), medial hamstrings (HS), tibialis anterior (TA) and gastrocnemius soleus (GAS).

The results indicated that muscle activity of the RF, HS and TA muscles were increased, and that GAS activity was prolonged throughout the gait cycle compared to control children. This observation confirmed that the principal muscles of both legs are hyperactive during movement in children with DMD. The team also observed that muscle hyperactivity during gait increased with the progression of the disease. Simply put, children with DMD needed greater muscle activity to produce the same levels of force.

The increase in the activity of these muscles is thought to result from a mechanism meant to compensate muscle weakness in the whole leg, lack of muscle strength, postural abnormalities and loss of balance, that results from the previous three factors.

“However, the predominance of this compensatory mechanism in (these) muscles could have negative consequences, such as reducing the efficiency of joint motion and increasing the energy cost of gait,” the study authors wrote.

“Simple therapeutic solutions such as targeted physiotherapy or ankle-foot orthoses could improve stability and reduce abnormal muscle activity. However, more evidence is necessary for the formal recommendation of these interventions,” they concluded.