National Physical Therapy Examination (NPTE) Practice Exam

What is the most likely cause of decreased muscle endurance in the L4 myotome after a 4-second contraction?

1. A single nerve root lesion

2. A central nervous system lesion

3. Femoral nerve compression

4. Central spinal stenosis

The correct answer is: A single nerve root lesion

Decreased muscle endurance in the L4 myotome after a 4-second contraction is most likely caused by a single nerve root lesion. The L4 myotome primarily governs the strength and function of muscles in the lower limb, particularly the quadriceps and some aspects of the hip adductor muscles. When there is an isolated lesion affecting the L4 nerve root, it can lead to weakness and endurance issues in the associated muscles. In the case of a nerve root lesion, the integrity of the motor neuron and its capacity to generate sustained contractions would be compromised. This could result in rapid fatigue or diminished endurance when the muscle is required to perform even a short duration of contraction, such as in this scenario. While other conditions, such as central nervous system lesions or peripheral nerve compressions like femoral nerve compression, could affect muscle function and endurance, they generally present with broader symptoms affecting multiple myotomes or other neurological signs. Central spinal stenosis could also impact nerve function, but the symptoms would typically be more widespread and not localized solely to the L4 myotome, and often include radicular pain or sensory deficits as well. This context solidifies the understanding that a single nerve root lesion is the most direct and likely factor leading to