The aim of this study is to investigate the effects of a lower-body strength training regime combined with protein supplementation in pre-frail elderly individuals. Participants are randomized to a group performing three weekly sessions of heavy-load strength training for 10 weeks and receiving daily protein supplementation, or a non-training, non-supplemented control group. The endpoints are changes in body composition, the relative changes in different compartments of the quadriceps femoris muscles, and the relationships between changes in muscle mass, muscle thickness, strength, and functional capacity. The investigators hypothesize that 10 weeks of heavy load strength training and protein supplementation will elicit improvements in muscle mass, strength, and functional performance. Moreover, it is hypothesized that improvements in strength will correlate with the improvements in functional performance.

Aging is accompanied by a loss of muscle mass and strength. Because muscle strength is associated with functional performance in elderly individuals, various tasks of daily living is hampered by the overall decline. The consequence is a vicious circle, where inactivity caused by reduced functional capacity accelerates the loss of muscle mass, strength and physical function. The Short Physical Performance Battery (SPPB) is commonly used to assess functional capacity, where individuals with a score of 10 or less out of maximum 12 may be categorized as pre-frail. Because small-to-moderate limitations in functional status assessed by SPPB is associated with higher odds of losing future mobility, these individuals represent a group of great interest. Strategies to improve functional capacity in this population are therefore important. It is established that heavy-load strength training, alone or in combination with protein supplementation, can improve muscle mass, strength, and function in elderly individuals. However, most studies have focused on healthy older adults, and less is known about the effects of heavy-load strength training in pre-frail elderly individuals. Moreover, the extent to which training-induced gains in muscle mass and size are related to improvements in strength and functional capacity is still poorly understood, because few intervention studies in this population have quantified hypertrophy precisely. Hence, the aim of this study is to investigate the effects of 10 weeks of heavy load strength training, performed three times per week, on muscle mass (DXA scan), muscle thickness (ultrasound), muscle strength (dynamic and isometric), rate of force development, chair rise ability, and gait velocity. Participants are randomized to a group performing three weekly sessions of heavy-load strength training or a control group. In addition, to optimize gains in muscle mass and strength, the strength training group will receive daily protein supplementation throughout the intervention period. The investigators hypothesize that the intervention will improve muscle mass, muscle thickness and strength, and that improvements in muscle strength and rate of force development will be correlated with improvements in functional capacity.

Inclusion Criteria:

• Age > 75
• Short Physical Performance Battery (SPPB) score ≤ 10

Exclusion Criteria:

• Lactose intolerance
• Milk allergy
• Diseases or musculoskeletal disorders contraindicating training/testing