Physical Activity and Perceived Barriers in Individuals with Moderate-to-Severe Traumatic Brain Injury

Abstract

Introduction:

Regular physical activity (PA), especially aerobic exercise, may benefit cognitive function in middle-aged and older adults, but promoting regular PA in individuals with traumatic brain injury (TBI) remains a challenge.

Objective:

To characterize PA and perceived barriers to PA in younger (<45 years) and middle age and older (≥45 years) individuals ≥1 year after moderate-to-severe TBI.

Design:

Multi-center survey study

Setting:

Community

Participants:

Persons who met the following criteria were included in the study: 1) 18 years and older; 2) English speaking; 3) History of moderate-to-severe TBI; 4) Followed in a TBI Model Systems Center for at least 1 year; and 5) Able to complete the survey independently.

Intervention:

Not applicable

Main Outcome Measure(s):

Physical activity level measured by Rapid Assessment of Physical Activity questionnaire (RAPA) and self-reported barriers to PA.

Results:

472 participants completed the survey (response rate of 21%). More individuals in the younger group (<45 years old) met CDC recommended aerobic PA guidelines compared to the middle-aged and older group (≥ 45 years old) (62% vs 36%, p < 0.001). Lack of motivation, lack of time, and fatigue were the most reported barriers. Perceived barriers to PA varied by age and PA level: the middle-aged and older individuals (≥ 45 years old) were more likely to report no barriers and inactive individuals (RAPA ≤ 5) more likely to report lack of motivation and money, pain, and lack of resources.

Conclusion:

Participants of age ≥45 years were less likely to meet the CDC PA guidelines than younger individuals after moderate-to-severe TBI. As perceived barriers to PA varied between age groups and PA levels, individualized approaches may be needed to promote physical activity in this population.

INTRODUCTION

Around 69 million individuals worldwide and 2.5 million in the United States sustain a traumatic brain injury (TBI) each year,^1,2 representing a major public health concern and source of disability globally.² Moderate-to-severe TBIs result in approximately 235,000 hospitalizations annually, a number increasing over time,^3,4 and may lead to long-term functional and cognitive impairment.^5,6 While cognition can be affected globally, specific deficits can be most notably observed with verbal fluency and delayed recall with substantial individual variability.⁷ Many survivors of moderate-to-severe TBIs experienced functional improvement through 1 and 2 years, followed by a decline by 5 years.^7–9 Increasing evidence suggested that age was associated with worse functional outcome and higher risk of developing dementia after TBI.^8,10–12

While there is a dearth of rigorous evidence for preventing this neurodegeneration after TBI, regular physical activity (PA), especially aerobic exercise, may benefit cognitive function in middle-aged and older adults by reducing risks of cardiovascular disease and improving brain perfusion.^13–15 However, only 21% middle-aged (45–64 years old) and 13% older-age (≥ 65 years old) met the Center for Disease Control and Prevention (CDC) physical activity guidelines, which were lower compared to younger age groups (28% for age 35–44, 31% for age 25–34, and 34% for age 18–24).¹⁶ Little is known about how often or how intensively people with TBI engage in PA after injury.¹⁷ Prior research suggests that people with TBI generally have decreased participation in leisure and social activities after injury compared to pre-injury baseline and exhibit inadequate levels of PA.^17–19 However, these studies have been based on small sample sizes with geographic bias and didn’t address the age difference in PA levels.

Several small studies have also found that regular aerobic PA may attenuate the neurodegenerative process and improve mood symptoms in individuals with TBI.^20–24 Yet, despite these promising benefits, promoting regular aerobic PA in individuals with TBI remains a challenge.²¹ Pilot studies assessing the feasibility of exercise programs in the population with TBI have reported challenges to recruitment as well as poor adherence to the prescribed programs.^25,26 Therefore, identifying perceived barriers to PA, is crucial to the success of future clinical trials studying the efficacy of programs for promoting PA in people with TBI.

Prior smaller studies have reported that general barriers to PA in individuals with TBI include self-consciousness and lack of gym accessibility, time, knowledge, energy, and motivation^27,28, and suggested that these barriers vary by age.²⁹ However, no large studies have examined barriers to PA in individuals with moderate-to-severe TBI, especially in middle-aged and older individuals with moderate-to-severe TBI who may benefit from regular physical activity the most.

To address these limitations, this study aimed to characterize PA levels and perceived barriers to PA in middle-aged and older (≥ 45 years) and younger (18–44 years) individuals after moderate-to-severe TBI in a multi-center cohort.

METHODS

Participants

This prospective study surveyed participants enrolled in the TBI Model Systems (TBIMS) program³⁰ who met the following criteria: 1) 18 years old and older at injury; 2) English speaking; 3) prospectively followed at a TBIMS Center for at least 1 year post-injury; and 4) consented to be reached via email or text message. Participants were excluded from the study if they: 1) could not complete a survey online or via telephone independently, or 2) were not fluent in English. All TBIMS participants met the criteria for moderate-to-severe TBI which was defined as history of moderate to severe TBI defined as posttraumatic amnesia (PTA) >24 hours, loss of consciousness (LOC) >30 minutes, Glasgow coma scale (GCS) <13, or intracranial neuroimaging abnormalities within 72 hours prior to hospital admission.³¹ Eight TBIMS sites recruited for this study. A total of 2665 eligible participants were identified at these sites.

Survey Design

The study was approved by the Institutional Review Board at the primary site. Local approvals from other TBIMS sites were obtained if required. A customized survey and data entry form were created in the REDCap database at the primary study site.³² The survey assessed the following:

Physical Activity Level

The Rapid Assessment of Physical Activity (RAPA) questionnaire, captured via REDCap, measured current PA level. RAPA is consistent with Center for Disease Control and Prevention (CDC) physical activity guidelines recommending 30 minutes or more of moderate activity on most days or every day.³³ It demonstrated strong criterion validity for assessing PA among adults including those older than 50 years.³⁴ RAPA has been used with multiple populations across the lifespan, including individuals with TBI and depression.^26,35–37 Participants are first shown a visual prompt describing types of light (i.e. leisure walking, stretching, light house/yard work), moderate (i.e. fast/brisk walking, aerobics class, strength training), and vigorous activities (i.e. jogging, running, tennis), then respond to questions measuring level and frequency of aerobic activities. Only the items relating to aerobic exercise were included in scoring, although participants were asked about strength and flexibility exercises. RAPA score was determined based on the highest level and frequency of reported aerobic activities. RAPA scores range from 1 to 7, with scores ≤5 denoting sedentary to underactive (inactive) lifestyles and scores ≥ 6 denoting active lifestyles³⁴. RAPA questionnaires were scored by two researchers independently and three cases with discordant RAPA scores were discussed to obtain an agreement.

Perceived Barriers to Physical Activity

Potential barriers to PA for participants were identified using a checklist of 14 perceived barriers generated from a prior study in patients with acquired brain injury.²⁷ Subjects were asked to mark all potential barriers that applied to them. The perceived barriers were categorized into: a) knowledge barriers (lack of knowledge of how or where to exercise); b) personal barriers (lack of motivation, fatigue, and fear of injury); c) environmental barriers (lack of time and lack of money); and d) miscellaneous (no barriers and other) (Table 2)

Table 2.

Characterization of physical activities and perceived barriers to physical activity reported (N=472)

Variable	Level		Total at Level
			n (%)
*PA type	No Physical Activity		27 (6%)
	Light Activity	House and yard work	317 (67%)
		Leisure walking	315 (67%)
		Flexibility exercises	169 (36%)
	Moderate Activity	Muscular strength and muscular endurance exercises	187 (40%)
		Aerobic and fitness classes	39 (8%)
	Vigorous Activity	Aerobic Activities (i.e., fast walking, jogging, running, biking)	178 (38%)
		Active sports	70 (15%)
	Other		49 (10%)
*Where do you exercise?	Home		348 (74%)
	Gym		131 (28%)
	Outdoors		272 (58%)
	PT/OT Sessions		14 (3%)
	Other		32 (7%)
Frequency of PA	Never		10 (2%)
	≤1/week		37 (8%)
	2–3/week		142 (31%)
	4–5/week		119 (26%)
	>5/week		144 (32%)
How long have you been doing PA regularly?	<1 month		52 (12%)
	1–6 months		59 (13%)
	12–14 months		53 (12%)
	>2 years		288 (64%)
Perceived barriers to physical activity
Knowledge barriers*	Seeing no need for exercise		10 (2%)
	Lack of knowledge of how or where to exercise		14 (3%)
Personal barriers*	Lack of motivation		119 (25%)
	Fatigue		95 (20%)
	Pain		59 (13%)
	Fear of injury		32 (7%)
	Fear of worsening condition		18 (4%)
	Discomfort at gym		12 (3%)
	Lack of time		99 (21%)
Environmental barriers*	Limited access to gym		40 (8%)
	Lack of money		22 (5%)
	Lack of necessary resources		21 (4%)
Miscellaneous*	No Barriers		158 (33%)
	Other		52 (11%)

^*Participants were allowed to select multiple responses for this category. PA: physical activity

Demographic Data

Age, sex, education level, state of residence, employment, living situation, income, driving ability, and use of assistive devices were collected. As generally accepted in lifespan and aging literature, participants were further grouped by age: the younger group representing early adulthood and early middle age between 18–44 years old, and the middle-aged and older group (≥ 45 years old) representing late middle age (45–64 years) and late adulthood (65 years and older).^16,38

The survey was reviewed by two consumer advisory groups – the North Texas TBIMS Consumer Advisory Board and the Parkland Hospital Community Advisory Panel – representing the TBI and general patient populations respectively. The purpose of these reviews was to ensure that the language was easily understandable by consumers. A public link to the REDCap survey was sent to eligible participants via email or text message. The full survey is available as supplemental material.

Statistical Analyses

Data were analyzed using descriptive and summary statistics. Chi-squared analyses were used to compare PA levels and perceived barriers between younger and middle-aged and older groups, and perceived barriers between inactive (RAPA ≤ 5) and active groups (RAPA ≥6). A multivariable logistic regression was conducted with all potential demographic and barrier variables included into the model to identify associations with active PA level (RAPA scores ≥6). Because some categories had small frequencies, certain categories were combined as follows: Age 18–34, Age 65+, and <High School/High School or GED. A stepwise model was initially fit to the data that included variables significant at p<0.15, then a final model was fit to the data retaining only those variables significant at p<0.05. The overall significance level was set at p < 0.05. All analyses were performed using IBM SPSS Statistics, Version 26.0 (IBM Corporation, Armonk, NY).

RESULTS

Demographic Data

A total of 2665 surveys were sent out during February 2020 and September 2020, and 472 participants completed the survey (21% response rate). Participant demographic data are listed in Table 1. Fifty percent of participants were 18–44 years old, while the remaining 50% were ≥45 years old. Most participants were male (66.7%) and had at least partial college or vocational training (80.5%). Thirty-seven percent had an annual household income <$50,000. Nearly half were employed part-time or full-time, while 18% and 20% were unemployed or retired, respectively. Most participants lived with other individuals (78%) and were able to drive independently with no distance restrictions (75%). Most participants (80%) did not use an assistive device to walk.

Table 1.

Demographics of survey participants (N=472)

Variable	Level	Total at Level
		n (%)
Age Group	18–34	129 (27%)
	35–44	106 (22%)
	45–54	81 (17%)
	55–64	83 (18%)
	≥ 65	72 (15%)
Sex	Male	315 (67%)
	Female	154 (33%)
	Other	3 (1%)
Education	≤ High School or GED	92 (19%)
	Some college, vocational training, or Associate’s degree	165 (35%)
	Bachelor	118 (25%)
	Masters or Doctorate	97 (20%)
*Work Situation	Student	28 (6%)
	Unemployed	87 (18%)
	Part-time	45 (10%)
	Full-time	176 (37%)
	Self-employed	36 (8%)
	Retired	96 (20%)
	Other	53 (11%)
Houshold Income	< $49,999	171 (37%)
	$50,000 − $100,000	119 (25%)
	>$100,000	99 (21%)
	Prefer not to say	83 (18%)
Living Situation	Lives Alone	98 (21%)
	Lives with others	368 (78%)
	Living in an Assisted Living facility	6 (1%)
*Driving Situation	Drives everywhere	354 (75%)
	Driven by family and friends	87 (18%)
	Takes bus or DART	36 (8%)
	Drives short distances (<5 miles)	31 (7%)
	Takes Uber or Lyft	29 (6%)
	Takes disability-specific transportation	9 (2%)
Assistive Device	No device	379 (80%)
	Walker	2 (0%)
	Braces	10 (2%)
	Cane	24 (5%)
	Wheelchair	9 (2%)
	Orthotic	9 (2%)
	Other	5 (1%)
	More than one	39 (8%)

^*Participants were allowed to select multiple responses for this category

Physical Activity Level

Characterization of physical activity is listed in Table 2. The most commonly reported activities were light PA, including house and yard work and leisure walking (each reported by >65%), followed by flexibility and strength training exercises (each reported by > 35%). Thirty-six percent of participants reported engaging in aerobic activities, like running or biking. The majority (90%) reported that they engaged in PA at least twice a week, and 64% reported that they had been regularly participating in PA for over 2 years.

Most (55%) participants did not meet the CDC recommendations for weekly aerobic physical activity, with a RAPA score ≤ 5. Over 40% reported complete inactivity, sporadic light-moderate activity, or weekly light activity. Younger adults (< 45 years) more often met the CDC PA guidelines, (n=138, 58%) than did the middle-aged and older individuals (≥45 years) (n=76, 32%) (p <0.001) (Table 3).

Table 3.

Physical activity level and perceived barriers to physical activity by age group

Age Groups		18 – 44	45+	p
Physical Activity Level
RAPA (n, %)	≤ 5	98 (42 %)	160 (68 %)	< 0.001
	≥ 6	138 (58%)	76 (32%)
Barriers to exercise *
No barriers (n, %)		62 (26 %)	96 (41%)	0.001
Lack of time (n, %)		73 (31 %)	26 (11%)	<0.001
Discomfort at gym (n, %)		24 (10 %)	16 (7%)	0.04
Fatigue (n, %)		65 (28 %)	30 (13 %)	< 0.001

^*Participants were allowed to select multiple responses. Chi-squared analysis was used to compare the group difference. Only barriers with statistical significance (p < 0.05) were presented in the table.

Perceived Barriers to Physical Activity

Perceived barriers to PA are presented in Table 2. Personal barriers were most frequently reported, as 25% reported lack of motivation, lack of time (21%), or fatigue (20%). Thirty-three percent of participants reported “no barrier, I exercise regularly”.

Several age-related differences were identified. For example, the younger group cited fatigue, lack of time, and discomfort in the gym as perceived barriers more frequently than the middle-aged and older group (all p <0.05) (Table 3). Middle-aged and older adults were significantly more likely to report no barriers to PA than younger adults (p <0.01) (Table 3).

PA level-related differences were also identified. The inactive individuals (RAPA≤5) were more likely to report lack of motivation, lack of money, lack of necessary resources, and pain as perceived barriers compared to the active individuals (RAPA ≥6) (p<0.01). Active individuals were more likely to report no barriers (all p <0.01).

Multivariable Logistic Regression

The following potentially relevant demographic and barrier variables were included in a multivariable logistic regression model: age, sex, education, work situation, household income, living situation, driving situation, the use of an assistive device, and all perceived barriers listed in the survey. Among these variables, only age and education level distribution were significantly different between physically active (RAPA ≥ 6) and inactive groups (RAPA ≤5) (p < 0.001 for age and p= 0.004 for education respectively). The final model showed a significant association between PA and age and education (Table 4). Together these variables resulted in an excellent fit of the model to the data (Hosmer-Lemeshow p=0.689). As expected, younger age was associated with higher levels of PA; individuals 18–34 years of age were 8.09 (OR 95% CI: 3.65–17.94) and individuals 35–44 of age were 8.87 (OR 95% CI: 3.90–20.15) times more likely to be active than those who were 65+ years old. Higher levels of education were associated with higher levels of PA; individuals with Master’s degrees were 3.98 times more likely (OR 95% CI: 1.87–8.47) to be physically active (RAPA ≥ 6) than those with less than or equal to high school/GED education. Those reporting no barriers were 9.15 (OR 95% CI: 5.40–15.51) times more likely to be physically active ( RAPA ≥6) compared to those reporting one or more barriers, while those reporting lack of time were 2.13 (OR 95% CI: 1.23–3.70) times more likely to be physically active than those reporting having enough time.

Table 4.

Multivariable logistic regression model to evaluate the relationship between physical activity level and age, education, and perceived barriers to physical activity

Variables	Odds ratio	95% CI
Age [ref:65+]
18–34	8.09	3.65–17.94
35–44	8.87	3.90–20.15
45–54	1.76	0.78–3.99
55–64	1.56	0.69–3.51
Education [ref: ≤ High School/GED]
Some college, vocational training, or associate degree	1.17	0.63–2.2
Bachelor’s degree	3.06	1.58–5.96
Master’s degree	3.98	1.87–8.47
Doctoral degree	2.95	0.93–9.40
Barriers
Lack of time (vs having enough time)	2.13	1.23–3.70
No barrier (vs any barrier)	9.15	5.40–15.51

DISCUSSION

We characterized PA levels in people after moderate-to-severe TBI in a large multicenter sample, identifying important differences in perceived barriers to PA by age and between those able to meet versus not meet recommended CDC guidelines for aerobic activity. Our data suggest that: 1) middle-aged and older individuals with TBI (≥45) were more likely not to meet the CDC PA guidelines but perceive less barriers to PA; 2) perceived barriers to PA vary by PA level.

Physical Activity Level in TBI

In our cohort, only 45% of participants met the CDC-recommended minimum aerobic PA level, while, in the general population, 54% of individuals meet these guidelines.^39,40 However, a higher proportion of young adults (18–44 years) in this cohort met PA recommendations compared to the general population of the same age range, as reported by CDC in 2011 (65% vs 50–57%).⁴¹ This difference may represent the nationwide trend of 0.9%/year increase in meeting the PA guideline in the past decade.⁴⁰ On the other hand, the guideline adherence in our middle-aged and older group (35%) was much lower when compared to the same age group in the general population (51–53% in age group 45 and older) reported in 2011.⁴¹ As in the general population,⁴² we also observed that PA guideline adherence is inversely correlated with age. Our results suggest there is a need to promote regular PA in individuals with TBI older than 45.

Perceived barriers to physical activity by age

The most common barriers to PA in our cohort were motivation, time, and fatigue, similar to what other studies have reported in TBI populations.^27,43 However, these barriers were not the same across age groups. In our cohort, younger individuals reported lack of time more frequently than the older group. Younger participants were also more likely to report discomfort in the gym, which may be due to self-conscious emotions of embarrassment becoming less problematic with older age.^{44, 45} Finally, the younger group also cited fatigue more frequently than the middle-aged and older group, which is the opposite from what might be expected. This may be related to the idea that middle-aged and older adults are significantly more likely to perceive their health in a positive manner than are younger adults.^46,47

Interestingly, adults older than 45 years more frequently reported no barriers despite being less likely to meet PA recommendations than younger individuals. This may be due to older adults’ perception of their PA participation to be satisfactory for their age, which is consistent with the aforementioned idea of more positive perception of health with increasing age. Another contributing explanation may relate to knowledge of PA recommendations. Most individuals, especially older adults, are unable to accurately identify guidelines for aerobic PA,^48–51 with a large number underestimating the minimum recommendations⁴⁹ – thus, many may incorrectly assume their current activity to be sufficient. Additionally, as we did not explore beliefs surrounding the efficacy of exercise in this survey, participants who reported no barriers also may have been unaware of the benefits of regular PA.²⁷ This potential lack of knowledge in both PA benefits and guidelines reinforces the importance of increased education in encouraging PA participation. While knowledge alone may not be sufficient to promote behavior change, it allows individuals to make more health-informed decisions,⁵² and may be a critical step to promote regular PA at the recommended level for TBI survivors.

The relationship between perceived barriers to physical activity and age can be complex, and age-related barrier differences may also inform the individualization of health interventions to target demographics. Individualized exercise interventions with a self-management component may be considered to address the unique barriers faced by each participant.

Perceived barriers to physical activity by PA level

In this survey, we also observed that the perceived barriers varied by physical activity level. For instance, less active participants cited motivation, pain, cost, and resources as barriers more so than more active participants, suggesting that targeting those concerns may boost PA. However, the potential multifactorial origins of these concerns may create challenges. Lack of motivation can arise from frontal dysexecutive syndrome, mood disorders, pain symptoms, and general fatigue after TBI, while pain can stem from prior injuries or health conditions. While not captured in this survey, chronic medical conditions and their associated pharmacological interventions may also contribute to these barriers, especially as many conditions and drugs can cause fatigue and amotivation. Issues with cost and resources may be linked to factors influencing socioeconomic status, such as employment and education. Unfortunately, individuals with TBI often experience high rates of chronic pain, mood disorders, psychiatric illnesses, unemployment, and reliance on financial assistance.^53,54 Therefore, effective strategies to promote PA may require consideration of the increased burden of physical, mental, and socioeconomic issues in TBI survivors with inactive lifestyles, and identification of the unique contributing etiologies to address these barriers appropriately.

Surprisingly, participants who reported being active were also more likely to report lack of PA knowledge. Therefore, it may be useful to assess baseline PA knowledge prior to exercise program initiation.

Limitations and Future Directions

Our study has several limitations. First, our sample may not be representative of the overall population with TBI due to our recruitment method. The survey was primarily disseminated through electronic means, which may be biased towards self-selected higher-functioning individuals or those with more resources as demonstrated by the demographic data (i.e. 21% above $100,000 for household annual income, 45% with either a bachelor or master’s degree, and 21% living alone). As a result, individuals with severe disabilities (and thus lower activity level) may be less likely to have been captured in the data. Additionally, only 20% of eligible participants responded to our survey, and the other 80% of may have unique characteristics. RAPA has not been modified to reflect the changes in the CDC physical activity guidelines for older adults (65 years and older) with comorbidities (i.e. TBI), which encourage this population to be physically active as their abilities and conditions allow if they cannot do 150 minutes of moderate-intensity aerobic activity a week.¹³ Therefore, some of the older adults in our cohort may be meeting the modified activity guidelines. The survey was written in English and non-English speaking individuals with TBI were not included in this study. Some information regarding potential contributing variables such as race/ethnicity and the time of the initial injury were not collected in the survey. Therefore, the generalizability of the results of this study may be limited. Second, despite efforts to ensure clarity, our survey may have presented challenges to individuals with TBI, who may exhibit greater cognitive impairment than the general population. Design differences also limited direct comparisons to prior studies. For instance, our survey had an option to denote “No barrier, I am exercising regularly” while the survey used in other studies, such as Pinto et al.,²⁸ did not. Because one-third of our participants chose that response exclusively, the prevalence of barriers in our study was much lower than found in other studies. It is unclear if these differences arose from population or survey differences. The self-reporting nature of the survey did not allow researchers to determine if the barriers were objectively present. The survey also limited the breadth of barriers reported to the ones listed, and therefore, may not have captured other salient obstacles. Third, because of the subjective nature of survey responses, future research should focus on more objective measures of PA, such as the use of activity or heart rate monitors to better assess PA level in individuals with TBI.^55,56 Fourth, only a small portion of participants between 18–34 and > 65 years of age were included in this survey. This can be partially explained by the typical age distribution of TBI survivors but may also relate to willingness to participate (especially in younger individuals) or lack of technology literacy (especially in older adults). Further studies will be needed to address the barriers to physical activity in these age groups. Finally, this survey was conducted during the COVID pandemic, therefore COVID-related restriction and social distancing might affect the reported physical activity habits (i.e. “where do you exercise”) and perceived barriers.

Despite these limitations, our study provides valuable insight for the design of future exercise programs/trials and for clinical practice to promote PA in individuals with TBI. Our study suggests that an effort may need to be made to educate and mobilize the middle-aged and older individuals with TBI. Knowledge of potential barriers may help clinicians tailor problem-solving therapy (PST) to patients. PST is a self-management intervention that has been shown to be an effective adjunctive treatment for improving self-efficacy for PA in many populations,^57–61 helping participants to develop strategies to address specific obstacles and promoting motivation. Technology-based strategies may also be effective not only in increasing PA but also promoting adherence.⁶² While not yet studied in individuals with TBI, elements of existing web- and app-based approaches have been shown to effectively address the common needs that were detailed in our study. For instance, gamified technological experiences have been shown to increase motivation, self-efficacy, PA enjoyment, and energy in both younger and older age groups.^63–65 A centralized electronic platform for organized information may also bridge the knowledge gap that many individuals with TBI may face.

Conclusions

This large multicenter survey study in individuals with moderate-to-severe TBI demonstrated that middle-aged and older persons with TBI are more likely not to meet the CDC PA guideline than younger adults. Perceived barriers to PA vary by age and PA level, with fatigue, lack of motivation, and time being the most often reported barriers. Our findings provide valuable information for future clinical trials and clinical practice to promote regular PA in this population.

Abbreviations:

CDC

Center for Disease Control and Prevention

IRB

Institutional Review Board

PA

physical activity

PST

problem-solving training

RAPA

Rapid Assessment of Physical Activity

TBI

traumatic brain injury

TBIMS

TBI Model Systems