Although resistance exercise interventions have been shown to be beneficial in prefrail or frail older adults it remains unclear whether there are residual effects when the training is followed by a period of detraining. The aim of this study was to establish the sustainability of a muscle power or muscle strength training effect in prefrail older adults following training and detraining.

Background: Among current operational definitions of frailty, the criteria proposed by Fried and colleagues have attracted great scientific interest. However, these criteria have usually been applied in epidemiological and only rarely in interventional studies. Objective: The present paper aims at testing the applicability of the Fried frailty criteria in the context of the recruitment process of a randomized controlled trial in prefrail older persons, and it discusses the respective scientific literature. Methods: Recruitment was promoted by newspaper articles as well as by targeted mail to customers of a local health insurance company and to recently treated patients of a geriatric day clinic. Furthermore, presentations were given in assisted living facilities. Potential candidates were screened for prefrailty, i.e. to see whether they met 1 or 2 of the Fried criteria (weight loss, handgrip strength, gait speed, exhaustion, physical activity). Results: A total of 298 people were screened. Among them 181 were not frail, 116 were prefrail and 1 was diagnosed as frail. The most prevalent criterion was exhaustion (24% of those screened). The second most prevalent criterion was low handgrip strength (20%). Low gait speed (8%), low physical activity (2%) and weight loss (2%) had a lower prevalence. According to the Geriatric Depression Scale, 14% of those who met the criterion ‘exhaustion’ were depressed. With regard to the Minnesota Leisure Time Physical Activity Questionnaire, used for the evaluation of ‘physical activity’, only 3 activities among the 18 selected by Fried were applicable to our cohort. Conclusions: Under the study conditions, good applicability of the Fried criteria was observed. Nevertheless, further refinement may be expedient in several criteria, especially exhaustion and physical activity, to enhance clinical usefulness. It may be helpful to adapt the cutoffs when applying the criteria to a European population.