Acute pain impairs locomotor learning and retention in older adults.

Pain and its negative health consequences disproportionately affect older adults. Physical therapists play a critical role in pain management and many active interventions rely on motor learning principles. Recent evidence shows that motor learning under painful conditions impairs its subsequent retention. However, research to date has focused on young adults even though age-related cognitive decline and reduced endogenous pain inhibition could leave older adults more vulnerable to pain-related motor learning and retention impairments. Therefore, we examined whether pain differentially affects motor learning and retention in younger versus older adults. Thirty younger and thirty older healthy adults were randomized to learn a novel asymmetric walking pattern under either a pain-free control condition or an acute capsaicin-heat pain condition. All participants completed baseline, learning, and retention testing, with learning driven by distorted visual step-length feedback to induce a gait asymmetry of 9%. Experiencing acute pain during learning was associated with reduced learning (Pain: 6.6% ± 0.4, Control: 8.1% ± 0.5, F(1,59)=6.04, p=0.02, η²ₚ=0.10) and reduced 24-hour retention (Pain: 2.6% ± 0.7, Control: 5.9% ± 0.7, F(1,59)=10.22, p<0.01, η²ₚ=0.16) in younger and older adults. Notably, retention deficits were absent in short-term (within-session) retention and emerged only at the 24-hour test (F(1,56)=11.7, p<0.001). Additionally, older adults showed reduced learning compared to their younger counterparts (F(1,59)=4.71, p=0.03, η²ₚ=0.08). These findings demonstrate that acute pain similarly impairs retention of a newly learned gait pattern in younger and older adults, which may reduce the effectiveness of motor learning-based interventions used in rehabilitation. PERSPECTIVE: This article examines the effects of pain on motor learning and retention in younger and older adults. Pain impairs retention across age groups, with deficits emerging after 24 h. Clinicians should recognize that active interventions performed in patients experiencing pain may result in reduced retention of newly learned movement patterns.