Novel Approach to Characterize Heterogeneity in an Aerobic Exercise Intervention.

PURPOSE: Exercise intervention studies for brain health can be difficult to interpret due to heterogeneity in exercise intensity, exercise duration, and in adherence to the exercise intervention. This study aimed to characterize heterogeneity in these components in a cohort of healthy middle-aged and older adults who participated in a prescribed six-month supervised aerobic exercise intervention as part of the Brain in Motion (BIM) study.

METHODS AND RESULTS: Group-based multi-trajectory analysis (GBMTA) was used to characterize variation in the trajectory of exercise intensity and duration for male and female participants in the first three-months of the exercise program. The GBMTA for males and females revealed two distinct trajectory subgroups, namely, "High-Increasing" (HI) and "Low-Increasing" (LI). Logistic regression was used to assess the association between the identified latent subgroups and i) demographic characteristics, ii) physiological characteristics including cardiovascular and cerebrovascular function, iii) genetic characteristics, and IV) adherence with American College of Sports Medicine (ACSM) guidelines on exercise for older adults. Of the 196 participants, 54.1% met the ACSM aerobic exercise targets for intensity and duration during the intervention. Aerobic fitness (V[Combining Dot Above]O2max; OR=1.27, p<0.01), was significantly different between these trajectory subgroups in males, and cerebrovascular function (CVR; OR=0.14, p<0.01) was significantly different between these trajectory subgroups in females.

CONCLUSION: This novel approach to tracking a pre-specified exercise program highlights that there are individual and group-specific variations within a prescribed exercise intervention. Characterizing exercise adherence in this way holds promise in developing optimized exercise prescriptions tailored to individual baseline characteristics, and additionally highlighting those participants at greatest risk of not meeting minimum dosage requirements for physiological and/or cognitive health.