Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies was asked to provide a scientific opinion on a list of health claims pursuant to Article 13 of Regulation (EC) No 1924/2006. This opinion addresses the scientific substantiation of health claims in relation to β-hydroxy β-methylbutyrate monohydrate (HMB) alone or in combination with α-ketoisocaproic acid (KIC) and reduction of muscle tissue damage during exercise, increase in lean body mass, increase in muscle strength, increase in endurance performance, skeletal muscle tissue repair and faster recovery from muscle fatigue after exercise. The scientific substantiation is based on the information provided by the Member States in the consolidated list of Article 13 health claims and references that EFSA has received from Member States or directly from stakeholders. The food constituent that is the subject of the health claims is HMB, either alone or in combination with KIC. The Panel considers that HMB either alone or in combination with KIC is sufficiently characterised.