Long-Term Effects of a 6-Week Power-Based Resistance Training and Fast Walking Interval Training Program on Physical Function, Muscle Power, Disability, and Frailty in Pre-Frail and Frail Older Adults

<b><i>Introduction:</i></b> Concurrent training has been shown to be a beneficial approach to improve overall health status in older adults. However, little is known about the adaptations of this type of training in the long term (i.e., after cessation of exercise), even less in older people affected by frailty syndrome. Therefore, this study aimed (i) to assess the effects of a 6-week concurrent training program composed of power-oriented resistance training and fast walking interval training on physical function, muscle power, disability in activities of daily living and frailty in pre-frail and frail older people, and (ii) to assess the effects of a 6-month detraining period on these outcomes. <b><i>Methods:</i></b> A total of 59 pre-frail and frail older adults (&gt;75 years old; Frailty Phenotype &gt;1) were allocated into intervention (INT; <i>n</i> = 32; 81.8 years; 21 women) or control (CON; <i>n</i> = 27; 82.5 years; 19 women) groups. Primary outcomes of this study were Short Physical Performance Battery (SPPB), relative sit-to-stand (STS) power, Barthel index, Lawton scale and Frailty Phenotype. Assessments were performed at baseline (PRE), after the concurrent training programme (POST) and after 6 months of follow-up (DET) in both groups. Mixed model repeated measures ANOVA with Bonferroni’s post hoc tests was used. <b><i>Results:</i></b> Immediately after the intervention (∆ = POST-PRE), INT improved SPPB (∆ = 3.0 points; <i>p</i> &lt; 0.001), relative STS power (∆ = 0.87 W·kg⁻¹; <i>p</i> &lt; 0.001) and reduced their frailty levels (∆ = −1.42 criteria; <i>p</i> &lt; 0.001), while no changes were observed in CON. After 6 months of detraining (∆ = DET-PRE), INT showed higher SPPB (∆ = 2.2 points; <i>p</i> &lt; 0.001), higher relative STS power (∆ = 0.73 W·kg⁻¹; <i>p</i> &lt; 0.001) and lower frailty (∆ = −1.24 criteria; <i>p</i> &lt; 0.001) values than those reported at baseline, which were significantly different than those reported by CON. Both, Barthel index and Lawton scale values were not modified during the study in either group. <b><i>Conclusions:</i></b> The 6-week concurrent training program improved physical function, muscle power and reduced frailty in pre-frail and frail older people and these improvements were maintained above baseline levels after 6 months of detraining. However, due to the individual variability found, future studies of long-term responders versus non-responders in frail populations are required.