The aims of this study were (1) to analyse the effects of a 6-month multicomponent training (MCT) on the physical fitness of older adults with or at risk of frailty; (2) to study the consequences of a 4-month detraining period; (3) to analyse the influence of frailty status on the training and detraining adaptations. A total of 102 robust, frail and prefrail older adults (80.1 ± 6.1 y) were divided into an intervention (TRAIN) and control group (CON). The TRAIN performed a 6-month MCT, while the CON continued with their usual lifestyle. Fitness assessment was mainly based on the Senior Fitness Test. Four evaluations were carried out; at baseline, and at 3, 6 and 10 months from baseline. Linear mixed models were performed to analyse group by time interactions and to compare differences in changes within groups between different time points. After 6-month MCT, TRAIN showed greater improvements for all fitness variables (group effects p < 0.05, except for flexibility) when compared to the CON. During the 4-month detraining period, TRAIN significantly decreased their balance, upper-limb flexibility and upper and lower-limb strength (all p < 0.05). CON only decreased upper-limb flexibility. When accounting for frailty status in the TRAIN, the frail-prefrail showed lower adaptations to the training and were more affected by detraining than the robust. The presented MCT is a good strategy to improve fitness in this population, but its positive effects are limited in time. It is, therefore, critical to avoid detraining periods.Trial registration: ClinicalTrials.gov identifier: NCT03831841.HighlightsOur 6-month MCT-program improves the physical fitness of robust, frail and prefrail older adultsA detraining period of four months partially deteriorates the physical fitness of robust, frail and prefrail older adults, so it is recommended to promote ongoing exercise programs or smaller break periodsIt seems that those older adults with a more advanced frailty status may not benefit from exercise to the same degree and will be more affected by detraining. Therefore, trainers may need to individualize training protocols to obtain the greatest exercise benefits.
Keywords: Aging; endurance; exercise; health; strength.