• exercise;
  • functional activity;
  • outcome expectations;
  • self-efficacy

The purpose of this study was to translate the original English version of the Self-Efficacy and Outcome Expectations Scales for Exercise and Functional Activity and to establish their reliability in older Thai adults in geriatric rehabilitation. This study used a correlational design with repeated measures. Reliability of the Self-Efficacy for Exercise Scale (SEES), the Self-Efficacy for Functional Activity Scale (SEFAS), the Outcome Expectations for Exercise Scale (OEES), and the Outcome Expectations for Functional Activity Scale (OEFAS) developed by Resnick was measured in 20 older adults aged 60 years or older after hip or knee replacement or another orthopedic surgery of their lower extremity. All scales were translated into Thai and back translated into English according to the process described by Marin and Marin. The instruments were administered twice—the 1st and 2nd day in the participants' geriatric rehabilitation program (i.e., the 4th and 5th postoperative day). Results indicated that there was sufficient evidence for internal consistency of the SEES, SEFAS, OEES, and OEFAS with alpha coefficients of 0.84, 0.86, 0.70, and 0.86 respectively. Test-retest reliability of the tools was also demonstrated with Spearman correlation coefficients of 0.84 for the SEES, 0.87 for the SEFAS, 0.61 for the OEES, and 0.54 for the OEFAS. The findings from this study provide important information for instrument adaptation and the applicability of these scales for further studies of older Thai adults.