The purpose of this study is to determine the muscle strength of a muscle in the thigh after 12 weeks of home exercise.

Study participation lasts a total of three months and includes two study visits. Subjects are asked to undergo strength testing, physical exams, lab draws, and muscle biopsies at each study visit. Muscle biopsies are done in the quadriceps muscle. In between study visits, subjects are asked to maintain a weekly exercise regimen given to them by the study physical therapist.

Inclusion Criteria:

• Diagnosis of possible, probable or definite amyotrophic lateral sclerosis (ALS) based on the revised El-Escorial criteria
• Presence in ipsilateral leg of either weakness in any muscle group or of active denervation by needle electromyography (EMG) which is a surrogate marker of early denervation
• Ipsilateral quadriceps femoris strength: >=4
• Ambulatory with or without assistance
• Revised ALS Functional Rating Scale (ALSFRS-R) Score > 30
• Forced expiratory vital capacity (FVC) >50% of predicted

Exclusion Criteria:

• ALSFRS-R ≤ 30
• Quadriceps femoris strength <4
• Unable to walk or uses wheelchair as primary means of mobility
• More than mild atrophy of quadriceps
• Bleeding disorder or uptake of anticoagulants
• Unwilling to comply with exercise and needle muscle biopsy
• Not a good research candidate according to the medical opinion of investigator