The Effects of Exercise on Cognitive Recovery after Acquired Brain Injury in Animal Models: A Systematic Review

Abstract

The objective of the present paper is to review the current status of exercise as a tool to promote cognitive rehabilitation after acquired brain injury (ABI) in animal model-based research. Searches were conducted on the PubMed, Scopus, and psycINFO databases in February 2014. Search strings used were: exercise (and) animal model (or) rodent (or) rat (and) traumatic brain injury (or) cerebral ischemia (or) brain irradiation. Studies were selected if they were (1) in English, (2) used adult animals subjected to acquired brain injury, (3) used exercise as an intervention tool after inflicted injury, (4) used exercise paradigms demanding movement of all extremities, (5) had exercise intervention effects that could be distinguished from other potential intervention effects, and (6) contained at least one measure of cognitive and/or emotional function. Out of 2308 hits, 22 publications fulfilled the criteria. The studies were examined relative to cognitive effects associated with three themes: exercise type (forced or voluntary), timing of exercise (early or late), and dose-related factors (intensity, duration, etc.). The studies indicate that exercise in many cases can promote cognitive recovery after brain injury. However, the optimal parameters to ensure cognitive rehabilitation efficacy still elude us, due to considerable methodological variations between studies.

Delayed voluntary exercise does not enhance cognitive performance after hippocampal injury: an investigation of differentially distributed exercise protocols

“…Secondly, animal studies on effects of voluntary exercise starting in the early stages after ABI (i.e., during the first three postinjury weeks) show a somewhat mixed picture. Some studies find positive effects on cognitive recovery, some report no changes and some find detrimental effects (Wogensen et al, 2015). Research on the effects of forced exercise paradigms after ABI generally find positive effects of early initiated exercise (Itoh et al, 2011, Kim et al, 2010, Sim et al, 2004).…”

“…Given this picture, one may be tempted to conclude that exercise most effectively promotes cognitive recovery when administered in the early postinjury stages. However, the available data regarding effects of late exercise on cognitive recovery after brain injury is limited to only a few studies (Wogensen et al, 2015). A delayed administration of exercise most closely resembles the clinical practice, where exercise is sometimes used as a supportive intervention in comprehensive rehabilitation programs in the postacute phase after ABI.…”

“…These distances are comparable to distances found in other studies showing recovery enhancing effects after late voluntary exercise (Gram et al, 2016; Piao et al, 2013; Wong-Goodrich et al, 2010). Positive effects of post-ABI voluntary exercise on cognitive recovery have been found in animals running between approximately 100 m and (more than) 8 km a day (Wogensen et al, 2015), showing that both short and long distances can promote recovery. In our study we see no such recovery promoting effects.…”

“…Most data stems from preclinical models of brain injury (El-Tamawy et al, 2014; Grealy et al, 1999). Animal model-based research shows that exercise can promote cognitive recovery under certain circumstances, but findings are not consistent (Wogensen et al, 2015). Many animal model based studies have focused on the cognitive effects of exercise initiated early after injury (0–4 days postinjury).…”

“…A scarcely investigated, but potentially important, factor is the temporal distribution of exercise – that is, whether one should exercise daily or whether there should be resting day(s) between exercise sessions. In most animal model studies, animals exercise every day (Wogensen et al, 2015). However, in a study by Cechetti et al (2012) animals exposed to bilateral common carotid artery occlusion, were exercised three times a week for 12 weeks.…”