Strength but not power training increases soluble alpha klotho levels in pre-frail older adults

Loss of physical function is a growing health concern in aging populations. Resistance training, including strength training (ST) and power training (PT), is the main therapeutic approach, yet evidence regarding the most effective modality remains inconsistent. Soluble alpha klotho (sαKL) is a protein increasingly recognized for its role in muscle function and may serve as a biomarker of training responsiveness due to its association with aging, muscle integrity, and exercise-induced adaptions. Therefore, we aimed to investigate whether ST and PT differentially influence sαKL levels in older adults.

69 prefrail, community-dwelling older adults (65-94 years) were randomly assigned to 12 weeks of ST, PT, or a control group (ClinicalTrials.gov: NCT00783159). In a post hoc analysis serum sαKL levels and physical performance measures before and after the intervention were analyzed.

23 participants were allocated to ST, 24 to PT and 22 to the control group. The participants had a mean age of 77 years, 70 % were female. There were no baseline differences between groups. Both ST and PT led to significant improvements in the Short Physical Performance Battery (SPPB) but only ST increased sαKL levels.

Twelve weeks of ST, but not PT, significantly increased circulating sαKL levels in pre-frail older adults. Given the beneficial health effects of increased sαKL, these findings suggest that ST may offer additional biological advantages relevant to healthy aging. sαKL may serve as a promising biomarker for training-induced adaptions, but prospective trials are needed to confirm long-term effects and further clarify underlying mechanisms.