This study was carried out over a period of 26 weeks divided in two phases. The first phase of the study was an eight-week period (weeks 3-10), during which subjects were familiarized to RT. This RT period was conducted to standardize training status, and to overcome strong neural adaptations known to occur within the first few weeks of RT. Phase 2, supplementation phase, the participants was randomized in three groups and started 12 weeks dedicated to supplementation plus RT (weeks 13-24). At the beginning and the end of each phase of the experiment, two weeks were allocated for evaluations (weeks 1-2, 11-12 and 25-26) consisting of anthropometric, body composition, one repetition maximum tests (1RM), phase angle, body water, blood samples and dietary intake measurements.

Recruitment was carried out through newspaper and radio advertising, and home delivery of leaflets in the central area and residential neighborhoods. All participants completed health history and physical activity questionnaires and met the following inclusion criteria: 60 years old or more, physically independent, free from cardiac or orthopedic dysfunction, not receiving hormonal replacement and/or thyroid therapy, not using equipment that would prevent the accomplishment of protocols and tests, and not performing any regular physical exercise for 6 months preceding the beginning of the study. Participants have passed a diagnostic graded exercise stress test with 12-lead electrocardiogram reviewed by a cardiologist and were released with no restrictions for participation in this investigation. Eighty-three Brazilian older women (≥ 60 years old), volunteered to participate in this investigation. After individual interviews, thirteen volunteers were excluded because they did not meet the inclusion criteria. Seventy participants were submitted to a standardized resistance training (RT) program, for eight weeks. After the assessments, the participants were randomly divided into three groups according relative strength (ratio of total strength obtained on 1-RM tests by body mass): (1) whey protein pre- and placebo post- RT (whey protein-placebo, (2) placebo pre- and whey protein post- RT, and (3) placebo pre- and post- RT. A blinded researcher was responsible for generating random numbers for participant allocation. All groups were submitted to the same RT program and 66 participants completed the experiment. The reasons for withdrawal from the study was reported as personal reasons and transportation issues.

Written informed consent was obtained from all participants after a detailed description of investigation procedures was provided. This investigation was conducted according to the Declaration of Helsinki and was approved by the local University Ethics Committee (nº 1.700.756).

The paired t-test was used to analyze the effects (pre- vs post-) of the first phase. Two-way analysis of variance for repeated measures was applied for intra- and inter-group comparisons. When the baseline was different (ANOVA one-way), two-way analysis of covariance (ANCOVA) for repeated measures was applied for comparisons, with baseline scores used as covariates. When an F-ratio was significant, Fisher's post hoc test was employed to identify mean differences. The statistical power was determined to verify the statistical power of the analysis. For all statistical analyses, significance was accepted at P\<0.05.