Aerobic exercise is a nonpharmacological intervention that has been shown to improve not only cardiovascular fitness, but also depressive symptoms, and cognition following traumatic brain injury.
National surveillance data indicates there are approximately 3 million new cases of traumatic brain injury (TBI) each year in the United States and the incidence of TBI has been increasing since 1995, particularly for adults over the age of 65.1 TBI is a serious public health problem in the United States and a leading cause of death and long-term disability in adults.2
In the general population, regular exercise is associated with better overall health, reduced risk for disease, and increased longevity.3 Following a brain injury, aerobic exercise promotes cardiovascular fitness, cognitive recovery, and reductions in mood disorders.4
Physical inactivity, increased sedentary behavior, and greater perceived fatigue are commonly reported following TBI.5 People with TBI may benefit from aerobic exercise as it has been associated with improved cardiovascular fitness and diminished fatigue. Lisa Chin and colleagues6 enrolled a small sample of adults with nonpenetrating TBI in a 12-week aerobic training program to assess the impact of vigorous exercise on cardiorespiratory fitness. Participants (N=10) completed a cardiopulmonary exercise test measuring gas exchange during exercise (ie, oxygen consumption and carbon dioxide output), and completed the Fatigue Severity Scale (FSS) at baseline and following the 12-week exercise training. Participants engaged in supervised exercise training on a treadmill for 30 minutes, 3 times per week. Participants exercised at a vigorous intensity, maintaining 70% to 80% of heart rate reserve during exercise. At the completion of the 12-week training, statistically significant changes were noted in peak oxygen consumption, time to fatigue, and peak work rate. Participants also reported significantly lower fatigue as evidenced by statistically significant decreases in FSS composite scores.
In a systematic review of controlled clinical trials and randomized controlled trails with adults with neurologic disorders, McDowell and colleagues reported that aerobic exercise improved cognition, particularly attention and cognitive flexibility in adults with TBI, and improvements in motor learning for adults with stroke.7
Chin and colleagues enrolled a small volunteer sample of ambulatory adults with chronic, nonpenetrating TBI into a 12-week aerobic exercise training program to determine the effect of exercise on cognitive performance.8 Participants (N=7) received 30 minutes of supervised vigorous aerobic exercise training on a treadmill, 3 times per week. Cognitive function was assessed at baseline prior to the beginning of aerobic exercise training, and at the completion of the 12-week intervention. Cognitive function was assessed using the Trail Making Test, parts A & B (TMT-A and TMT-B), and the Repeatable Battery of the Assessment of Neuropsychological Status (RBANS).
Additionally, sleep quality and depressive symptoms were assessed at baseline and the completion of the intervention using the Pittsburg Sleep Quality Index (PSQI) and the Beck Depression Inventory (BDI-II), respectively. At the completion of the study, statistically significant improvement was observed in cognitive performance as evidenced by improved TMT-A and TMT-B scores, and RBANS total score.No change, however, was noted in sleep quality or depressive symptoms.
Exercise may promote cognitive recovery via a variety of mechanisms, such as increasing neural repair and neuroplasticity, modulating neurotransmitter systems (particularly dopamine), and decreasing neuroinflammation.4
Mood disorders are commonly reported following TBI.9 About 50% of individuals with TBI report clinically significant levels of anxiety and depression within the first year of injury and mood disorders are often a chronic consequence of TBI.10
Ali Weinstein and colleagues11 enrolled 12 ambulatory adults with nonpenetrating TBI into a 12-week aerobic exercise training program to determine the effect of exercise on mood. Changes in mood before and after exercise were measured using the Profile of Mood Status – Short Form (POMS-SF). Measurements of mood were obtained at baseline (week 1), week 4, week 8, and week 12 (conclusion of the intervention). The POMS-SF scoring generates a total mood disturbance (TMD) score, with higher scores indicating a more negative mood state. Participants were engaged in 30 minutes of intensive aerobic exercise, 3 times per week. Apart from the 30-minute exercise sessions, participants engaged in a 5 to 10 minute warm-up and cool-down period. The 30-minute exercise sessions were maintained at 70% to 80% of the participants’ heart rate reserve. Heart rate was continuously monitored during exercise and the target range (ie, 70% to 80%) was maintained by adjusting the speed and/or grade of the treadmill. Analyses showed improvement in mood as evidenced by significantly lower TMD scores between week 1 and week 12. Improvements in mood were detectable after a single exercise bout in week 1. The greatest changes in POMS-SF scores were noted in the Fatigue-Inertia and the Anger-Hostility subscales.
In a pilot study to determine the feasibility of aerobic exercise for lowering depressive symptoms, Marika Schwandt and colleagues enrolled a small sample (N=4) of community dwelling adults with TBI and residual physical impairments in to a 12-week supervised aerobic exercise program.12 The primary outcome measure was the Hamilton Rating Scale for Depression (HAMD). Scores on the HAMD range from 0 to 63, with higher scores indicating more severe depression. The HAMD was administered at baseline, at the midpoint of the intervention, and at 12 weeks following the conclusion of the intervention. Additional measures obtained at baseline and at 12 weeks included assessment of functional aerobic capacity (heart rate above 70% of age-predicted maximum), perceived exertion as assessed by the Borg Perceived Exertion Scale, the Rosenberg Self Esteem Scale, and frequency of attendance and completion of a survey to examine participant perceptions of the program. The intervention consisted of a warm-up (stretching or below target heart rate aerobic activity), 30 minutes of intensive aerobic exercise (intensity determined by a score of 5 to 6 on the Borg Scale and a heart rate of 60% to 75% of age-predicted maximum), and a 10-minute cool down. The intervention was delivered 3 times per week for 12 weeks. Depending upon physical limitations, participants worked with a research physical therapist to chose among a cycle, treadmill or recumbent step machine to safely set and reach aerobic thresholds. After the 12-week intervention, HAMD scores decreased from the moderate-to-severe and severe levels of depression at baseline, to mild-to-moderate and no symptoms at the completion of the program. Additionally, heart rate was lower at post-intervention, Borg scores were lower indicating less perceived effort, and self-esteem improved as evidenced by higher Rosenberg Self-Esteem Scale scores.
Aerobic exercise is associated with improved outcomes following TBI, not only in cardiovascular fitness, but also in cognitive performance and mood disorders. However, many studies appearing in the literature are proof-of-concept, pilot studies, or pre-post observational studies with small sample sizes, and as such, have numerous methodological limitations. Well-designed randomized controlled trials are needed to test the efficacy of aerobic exercise and rehabilitation outcomes.
Dr Seale is the regional director of clinical services at the Centre for Neuro Skills, which operates post-acute brain injury rehabilitation programs in California and Texas. He is licensed in Texas as a chemical dependency counselor and psychological associate with independent practice. He also holds a clinical appointment at the University of Texas Medical Branch (UTMB) in Galveston in the Department of Rehabilitation Sciences.
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