Practical Management: A Standardized Aerobic Exercise Program for Adolescents With Concussion in the Absence of Graded Exercise Testing

Abstract

Aerobic exercise is safe and beneficial for adolescent athletes recovering from sport-related concussion (SRC). The results of systematic graded exercise testing are used to create individualized, subsymptom heart rate threshold (HRt) aerobic exercise treatment programs for adolescents after SRC. Many clinicians, however, do not have access to graded exercise tests. This article presents a safe, systematic, evidence-based exercise program that clinicians can prescribe, progress, and modify to help manage acute pediatric SRC without the need for formal exercise testing. The exercise prescription accounts for sex and days since injury but not age because our analysis indicates age does not significantly affect the HRt on graded exercise testing. This article provides clinicians without access to graded exercise testing a viable option for prescribing exercise treatment to adolescents in the early phase after SRC.

INTRODUCTION

Approximately 3.8 million sport- and recreation-related brain injuries occur in the United States each year, the majority of which are concussion.¹ Spontaneous recovery from sport-related concussion (SRC) typically occurs within 14 days (adults) to 28 days (children/adolescents) of injury. A significant minority (15%-30%) of patients suffer persisting postconcussive symptoms (PPCS), which is defined as symptoms persisting for more than 28 days.² In 2 randomized controlled trials (RCTs), individualized aerobic exercise treatment instituted within 10 days of injury, based on the heart rate threshold (HRt) at the more than mild concussion-related symptom exacerbation point on the Buffalo Concussion Treadmill Test (BCTT), was shown to safely facilitate recovery from SRC and to reduce the incidence of PPCS.^3,4 Thus, a personalized exercise prescription for SRC treatment is derived ideally from the results of systematic graded exercise testing.^3–6 The target HR for the subsymptom threshold exercise training/treatment program is set at 90% of the HRt and is modified regularly (every few days to once a week) by retesting to establish a new HRt or by using clinical acumen to increase the target HR systematically according to the individual's level of exercise tolerance.

Although systematic evaluation of the individual HRt on graded exercise testing seems to be the most effective way to establish the target HR for exercise treatment of SRC, it is not always possible because of financial, proficiency, equipment, or time barriers.⁷ In addition, clinics that use telemedicine may be unable to do graded exercise tests remotely. Lack of access to systematic exercise testing should not prevent clinicians from prescribing an individualized exercise prescription for concussion management. In a previous study, we outlined a subthreshold exercise program for concussed adolescents who do not require graded exercise testing.⁷ In that study, however, we did not account for the effect of days since injury or sex on the HR prescription.⁷ The purpose of this article is to provide clinicians with a data-driven, standardized aerobic exercise treatment program to help adolescents safely recover from SRC during the early phase after injury that does not require systematic exercise testing.

Creating the Heart Rate Threshold Prescription

Data were combined from 2 studies,^3,8 the details of which are presented in Supplemental Digital Content 1, Supplement File 1, https://links.lww.com/JSM/A359. Both studies included adolescent (13- to 18-year-old) athletes with SRC who presented to sports medicine clinics within 10 days of injury. Our data confirmed that sex and days since injury, but not age, affected the HRt of adolescent athletes (Table 1). Exercise recommendations are limited to the first 4 weeks because a concussion that lasts 28 days or longer is considered to be prolonged² and typically requires a multimodal treatment approach (eg, vestibular, vision, and psychological treatments) in addition to aerobic exercise.² Previous studies have used 80% of the HRt on graded exercise testing as the target HR prescription,⁴ but more recently, we have used 90% of the HRt and have found it to be safe.³ The increase in the target HR goal is supported by the principle that greater exercise intensity is more likely to affect positive physiological change in the general population.⁹

TABLE 1. - HR Prescription Parameters for Exercise Treatment of SRC Without Graded Exertion Testing

Weeks from Injury	Estimated Max HR on BCTT (bpm)	HR Prescription (90%HRt, bpm)
Males
Week 1	129-132	116-119
Week 2	138-141	124-127
Week 3	147-150	132-135
Week 4	157-160	141-144
Females
Week 1	137-140	123-126
Week 2	146-148	131-134
Week 3	155-157	140-143
Week 4	163-166	147-150

INTENSITY OF THE EXERCISE PRESCRIPTION

Before instituting this early and proactive approach to concussion treatment, the patient must not have any cardiovascular, vestibular, or musculoskeletal contraindications to engaging in a progressive aerobic exercise training program.¹⁰ The exercise prescription should ideally follow the FITT principle:⁹frequency, intensity, type, and time.Table 1 provides a suggested intensity (target HR) for concussed adolescents from initial injury through week 4 of recovery. The patient is instructed to reach and sustain the target HR for the duration of the exercise session. This is not always possible because of natural variation in HR, so an HR a few (2-5) beats above or below the target HR is reasonable. To help ensure that the target HR is met and maintained, the patient should wear an HR sensor such as an Apple watch, Polar HR monitor, Garmin HR monitor, or Fitbit device. Notably, some research has found that the HR output from Fitbit devices is approximately 5 bpm lower than actual HRs.¹¹ If an HR monitor is unavailable, patients can be taught to take their carotid or radial pulse intermittently during the exercise bout.

Exercise intolerance, defined as the inability to exercise to near age-appropriate maximum HR because of exacerbation of concussion-related symptoms (including profound fatigue), is commonly observed after concussion.¹² Previously, it has been defined as an increase of 3 or more points in any symptom (including the emergence of a new symptom) on a 10-point visual analog scale (VAS) during systematic exercise testing when compared with the pretest resting value.^3,4 For safety reasons during unsupervised home or gym-based exercise sessions, we had generally recommend that patients stop exercise once they experience a change of 2 or more points when compared with the pre-exercise resting value.^3,4 To conform to emerging international recommendations on SRC management from the Concussion in Sport Group (Amsterdam 2022), the more than mild exacerbation point of concussion-related symptoms is now defined as a > 2-point increase in either a single symptom, a combination of symptoms, and/or by the addition of a new symptom(s) during exercise testing as well as during exercise treatment. This helps to prevent significant symptom exacerbation that may delay recovery. If a patient exceeds the symptom exacerbation threshold, it is recommended to stop exercise and to resume at the same exercise intensity (HR) when the symptom severity has returned to pre-exercise resting levels.^3,4 Symptom exacerbation is typically brief, and patients can resume exercise as soon as the following day.¹³

Type and Volume of the Exercise Prescription

The bulk of the evidence supports the use of controlled aerobic exercise to safely treat concussion,^2–6 but there is little evidence to indicate which mode of aerobic exercise is the most effective. Patients are allowed to use the form of aerobic exercise they prefer as long they adhere to the target HR prescription intensity. There is limited data on the use of resistance training for improving concussion recovery. Unregulated resistance training may be deleterious to concussion recovery during the acute phase of injury because of the rapid fluctuations in blood pressure experienced during this type of exercise. There is some evidence that stretching exercise may be beneficial for some patients, but it is less effective than aerobic exercise.^3,4 Other studies have shown efficacy with multimodal treatment approaches that include coordination exercises, visualization, and imagery exercises.¹⁴ Although other active treatments can be added to concussion management programs, it is recommended that aerobic exercise (eg, swimming, running, and walking) form the foundation for the exercise prescription to treat acutely concussed adolescents. Some forms of aerobic exercise require sufficient vestibular function, eg, outdoor cycling. Aerobic exercise that requires good balance is not recommended in the early phase after injury because concussed patients often experience vestibular dysfunction.² Activities that require increased cervical motion such as outdoor biking may also exacerbate concussion-associated cervical pain.¹⁵ Studies have confirmed that concussed patients have a significantly increased risk (approximately 2- to 3-fold) of lower extremity orthopedic injury during sport participation after concussion, predominantly within the first 3 to 4 months.^16,17 Therefore, patients should choose a form of aerobic exercise that does not put them at greater risk of further injury.

The volume of exercise is determined by multiplying session time by the number of days performed and is typically reported in minutes per week.⁹ Previous studies have used exercise volumes that range from 10- to 30-minute sessions, 3 to 7 days per week.¹⁸ Two RCTs of early prescribed exercise treatment confirmed that a subthreshold aerobic exercise prescription for 20 minutes a day, 5 to 6 days per week, had good participant adherence and was more effective than a stretching exercise program for safely facilitating recovery from SRC and for significantly reducing the incidence of PPCS.^3,4 A secondary analysis from one of these RCTs,³ which determined adherence objectively using HR monitor data, found that adherent participants (defined as completing ≥ 2/3 of their prescription) were more symptomatic and were more exercise intolerant at their initial visit (ie, they had more severe concussion), yet they recovered faster than those who were not as well adherent.¹⁹ Therefore, the current data suggest that adolescents after SRC, regardless of symptom burden, benefit greatly from subthreshold aerobic exercise treatment performed 5 days a week for at least 20 min/d at their individual target HR.

Patients choose to adhere to exercise prescriptions for varying reasons, including motivation, level of competition, and the requirement of medical clearance. It is possible for patients to achieve an exercise volume of 100 min/wk (5 days* 20 minutes) using different frequencies or times. Although it is not recommended to complete 100 minutes of exercise in a single bout, others have shown that adolescents after SRC benefit from an exercise volume well above 100 minutes per week.²⁰ Provided that patients stay below their symptom-exacerbation HR threshold (ie, intensity), they can exercise well beyond their prescribed duration (volume) with no ill effects.¹⁹ Regular modification of the exercise prescription will improve effectiveness and adherence.^3,4,7 To assist clinicians who do not have access to exercise testing, we have developed a handout that outlines the exercise prescription methodology (see Supplemental File 2, Supplemental Digital Content 2, https://links.lww.com/JSM/A360).

Other Considerations

It is recommended that a gradual warm-up to the target HR and a gradual cool-down period be a part of each exercise bout. The warm-up should typically last about 5 min, gradually raising the HR until the target HR is reached. The cool-down should typically last about 5 min and should bring the HR down as close to the pre-exercise HR as possible.⁹ The 20 minutes or so of exercise at the target HR does not include warm-up and cool-down times.

The exercise prescription is adaptable. For example, if a patient finds the program is too easy and is not becoming symptomatic at the target HR, the intensity or volume of the prescription can be increased to help ensure the treatment has the best chance to be effective.⁹ Conversely, the exercise prescription is adjusted if the patient at the target HR consistently experiences concussion-related symptom exacerbation of >2 points from the pre-exercise value.^3,4,7 Patients are advised to stop their exercise session once they reach the more than mild symptom exacerbation point (>2 points) and resume exercise the next day, provided the symptom exacerbation has subsided. Patients experiencing a prolonged (>24 hours) or severe (≥8/10) increase in concussion-related symptoms during exercise should stop and notify their health care provider. Ideally, patients receiving exercise treatment should be evaluated weekly (in-person or virtually) for the first 4 weeks after injury because this frequency provides the best opportunity to determine cardiovascular physiological recovery.^2–4 This frequency also allows for reassessment, modification of the exercise prescription, and consideration of timely prescription of other treatments such as vestibular rehabilitation²¹ and cervical therapy,²² which can improve outcome if instituted earlier in recovery. Clinicians should consider each patient's needs when prescribing and progressing exercise to ensure the program is safe but challenging enough to evoke positive adaptation throughout recovery.

LIMITATIONS AND FUTURE RESEARCH

We included studies that used BCTT examinations only and did not include data from other modes of graded exercise tests such as the Buffalo Concussion Bike Test. Our recommendations are based on data from acutely concussed adolescent athletes; thus, the results are not generalizable to other populations. Future studies should examine exercise prescriptions for patients of different ages, various fitness levels, and for those who experience PPCS. In addition, future studies should compare the effectiveness of exercise interventions derived from a graded exercise test versus exercise interventions guided by subjective symptom responses only.

CONCLUSIONS

Although it is ideal to base an aerobic exercise prescription for the treatment of SRC on the HRt established during systematic exercise testing, it is not always possible. This review presents a practical way for clinicians to prescribe subsymptom threshold aerobic exercise treatment for SRC that does not require an exercise test and that accounts for the effects of sex and days since injury. We hope this approach allows more practitioners to prescribe early aerobic exercise treatment to help their patients recover faster from SRC.