ALS is a fatal, progressive degenerative motor neuron disease that affects the upper and lower motor neurons, which results in muscle weakness. Though ALS is idiopathic, there are a number of risk factors associated with an increased onset and progression of the disease, which include: oxidative stress, smoking in women, and exposure to hazardous chemicals and metals. A positive mood, combined with safe physical activity and a balanced diet, may prolong the lifespan of people with ALS. When designing an exercise program, it is important to assess the current stage of ALS and the physical status of the individual. Some researchers have suggested that physical activity is detrimental for disease progression. However, evidence appears to support the prescription of moderate-intensity exercise towards people in the early-stages of ALS. More research is needed to establish appropriate exercise guidelines and assess the impact that exercise has on the quality of life in people with various stages of ALS.