Remote Limb Ischemic Conditioning and Motor Learning: Evaluation of Factors Influencing Response in Older Adults

Abstract

Remote limb ischemic conditioning (RLIC) is a clinically feasible method of promoting tissue protection against subsequent ischemic insult. Recent findings from our lab demonstrated that RLIC robustly enhances motor learning in young, healthy humans. The next step is to determine which individuals would receive maximum benefit from RLIC before applying these findings to clinical rehabilitation populations such as stroke. Numerous factors, such as age, sex, body mass index (BMI), and cardiovascular comorbidities may influence the response. Sixty-nine participants aged 40-80 were randomized to receive either RLIC (n = 33) or sham (n = 36) conditioning. Participants underwent seven consecutive sessions consisting of RLIC or sham conditioning with a blood pressure cuff on the upper extremity and motor training on a stability platform balance task, with two follow-up sessions. Balance change (post-test-pre-test) was compared across participants, groups, and the factors of age, sex, BMI, and comorbidities. Participants in both groups improved their performance on the balance task from pre- to post-test. Overall balance change was independently associated with age and BMI. There was no difference in balance change between RLIC and Sham groups. However, RLIC significantly enhanced balance performance in participants with no comorbidities. Compared with our previous study in young adults, middle-aged and older adults demonstrated smaller improvements on the balance task. RLIC enhanced learning in middle-aged and older adults only in the absence of pre-defined comorbidities. RLIC may be a promising tool for enhancing motor recovery, but the accumulation of comorbidity with age may decrease its effectiveness.

Keywords: Cardiovascular disease; Comorbidity; Ischemic preconditioning; Psychomotor performance.

Conflict of interest statement

Conflict of Interest: The authors declare that they have no conflict of interest.

Figures

Figure 1.

CONSORT diagram showing flow of participants through the study.

Figure 2.

Balance changes for RLIC and Sham groups. A. Average number of seconds in balance out of 30 seconds, averaged across 5 trials at each time point. There was no significant difference between groups (RLIC and Sham) at any time point. Black solid line represents RLIC, gray dashed line represents Sham group. Error bars represent standard deviations. FU = Follow Up. B. Average balance change (Post-test – Pre-test) in seconds for all participants in each group. Error bars represent standard deviations.

Figure 3.

Age and BMI are independent predictors of learning on the balance task. Scatter plots illustrate the independent effects of age (A) and BMI (B) on balance change, regardless of group. Black squares indicate RLIC and gray circles indicate Sham participants. Linear regression analysis revealed independent effects of age (R2=0.118, p=0.004) and BMI (R2=0.137, p=0.002).

Figure 4.

Effect of 1+ comorbidities on balance change. Effect of 1+ comorbidities on balance change (post-test – pre-test) averaged for RLIC and Sham groups. Only in the absence of any pre-defined comorbidities did RLIC significantly enhance motor learning in our sample. Gray bars indicate Sham participant average balance change; black bars indicate RLIC participant average balance change. Error bars represent standard deviation. Small numbers inside bar graph indicate number of participants in each subgroup. * indicates significance at p