This is a great tool for finding primary biomedical journal articles with links to some full-text. CINAHL
This is a great tool for finding education, health promotion, and psychosocial health articles along with research articles.
Here are a few different search strategies to try:
1. ALS or "Amyotrophic Lateral Sclerosis" or lou gehrig's disease
2. Rehab* or Physical Therap* or Exercise Therap*