Resistance training combined with protein or amino acids supplementation has been shown to be promising for mitigating age-related disabilities and comorbidities. Randomized controlled trials supporting this possibility are still scarce. These series of clinical trials aim to investigate the chronic effects of different strategies of protein and derivatives supplementation in association with resistance training on selected health-related parameters in pre-frail and frail elderly.This is a 16-month, double-blind, randomized, placebo-controlled, parallel-group clinical trial involving a series of investigations. Participants will be divided into nine groups, allowing the assessement of the effects of (1) isolated leucine supplementation; (2) protein source (whey vs. soy); (3) combination of whey protein and creatine; and (4) sexual dimorphism to the response of protein intake plus resistance training (men vs. women). All participants will undergo a supervised, resistance training program.

Inclusion Criteria:

• elderly people
• frailty or pre-frailty, according to Fried et al., (2001) criteria.

Exclusion Criteria:

• on exogenous insulin and steroid-based drugs
• chronic obstructive pulmonary disease or respiratory failure
• use of protein and /or amine-based dietary supplements
• on restrictive diets (e.g. calorie or food group restrictions)
• on resistance training
• untreated cardiovascular, metabolic, or other chronic disease
• any musculoskeletal condition precluding resistance training