Visser AE, et al. - Using a validated questionnaire, experts assessed the link between physical activity (PA) and amyotrophic lateral sclerosis (ALS) in population-based case–control studies in three European countries. Data regarding educational level, smoking, alcohol habits and lifetime PA levels in both leisure and work time were obtained by questionnaire and quantified using metabolic equivalent of task scores. A positive link was discovered between PA and risk of ALS using harmonized methodology to objectively quantify PA levels, with some recommendations for population differences.