Exercise Methodology

Question 1

In your study, you found that the SRC group had a greater body weight and GLETQ score compared to the HC group. How might these factors have influenced the results of your study?

Answer 1

• The differences in body weight and GLETQ scores between the SRC and HC groups could have potentially influenced the results of our study. A higher body weight in the SRC group may have contributed to the more intense workload and higher steady-state heart rate observed during the exercise intervention. This is because the BCBT protocol used to determine the appropriate exercise intensity was based on a body weight to power/watt conversion. Consequently, individuals with a higher body weight would have exercised at a higher workload to maintain the target heart rate.

Furthermore, the higher GLETQ scores in the SRC group suggest that these individuals were more physically active prior to their concussion compared to the HC group. This difference in baseline physical fitness could have affected their response to the exercise intervention and their ability to tolerate higher workloads. However, it is important to note that despite these differences, the exercise intervention was tailored to each participant’s individual heart rate threshold (HRt) determined during the BCBT, ensuring that the intensity was appropriate for their current fitness level and post-concussion status.

Question 2

How did you control for potential confounding variables, such as age, sex, and BMI, when comparing the SRC and HC groups?

Answer 2

• To control for potential confounding variables, we employed a matched-pairs design. Each participant in the SRC group was matched with a participant in the HC group based on age and sex. This approach helps to minimize the influence of these factors on the study results. Additionally, while there was a difference in body weight between the groups, we did not find a statistically significant difference in BMI. This suggests that the groups were relatively comparable in terms of body composition.

Furthermore, our statistical analyses using independent samples t-tests allowed us to compare the means of various demographic and health characteristics between the SRC and HC groups while considering the variability within each group. This approach helps to account for potential confounding variables and provides a more robust assessment of between-group differences.

Question 3

The SRC group completed two separate visits, while the HC group completed a single visit. How did you ensure that the exercise intervention was consistent between the two groups?

Answer 3

• To ensure consistency in the exercise intervention between the SRC and HC groups, we used the heart rate threshold (HRt) determined during the BCBT as a benchmark. For the SRC group, the BCBT was conducted during Visit 1 to establish the appropriate exercise intensity for each individual. The exercise intervention was then administered during Visit 2 at 80% of the participant-specific HRt.
• For the HC group, who completed the study in a single visit, we used the HRt value determined by their age- and sex-matched SRC counterpart’s BCBT performance. This means that each HC participant exercised at the same relative intensity (80% of HRt) as their matched SRC participant. This approach ensures that the exercise intervention was consistent between the two groups, allowing for a valid comparison of their responses to the intervention.

Moreover, during the exercise intervention, the workload was manually adjusted to maintain the target heart rate range (85-100% of the 80% HRt) for both groups. This further ensures that the exercise intensity was consistent and appropriate for each participant, regardless of their group assignment.

Question 4

What is the rationale behind including a 2.5-minute warm-up and cool-down period in your exercise intervention protocol, and how did you determine the appropriate duration for these periods?

Answer 4

• The inclusion of a 2.5-minute warm-up and cool-down period in the exercise intervention protocol is based on established guidelines for safe and effective exercise. Warm-up periods prepare the body for physical activity by gradually increasing heart rate, blood flow, and muscle temperature, reducing the risk of injury and enhancing performance (Woods et al., 2007). Cool-down periods allow for a gradual return to resting state, preventing potential dizziness or fainting caused by abrupt cessation of exercise (Van Hooren & Peake, 2018). The 2.5-minute duration was chosen as it aligns with the minimum recommended warm-up and cool-down durations for moderate-intensity aerobic exercise (ACSM, 2018).

Question 5

What factors influenced your decision to use the BCBT as the exercise test in your study?

Answer 5

The Buffalo Concussion Bike Test (BCBT) was chosen as the exercise test in this study due to its specific design for assessing physiological recovery and guiding return-to-sport decisions following a sports-related concussion (SRC) (Haider et al., 2019). The BCBT offers several advantages over other graded aerobic exercise tests, such as improved accessibility, safety, versatility, and precision in symptom management (Haider et al., 2019; Janssen et al., 2022).

Question 6

Your study employed a 15-minute active exercise intervention. What is the scientific basis for choosing this duration, and how does it align with current research on the optimal exercise duration for inducing post-exercise cognitive benefits in concussed populations?

Answer 6

The 15-minute active exercise intervention duration was chosen based on previous research demonstrating that acute bouts of moderate-intensity aerobic exercise lasting 10-20 minutes can induce post-exercise cognitive benefits in healthy populations (Chang et al., 2012; Ludyga et al., 2016). While there is limited research on the optimal exercise duration for concussed populations, a study by Maerlender et al. (2015) found that moderate physical activity for 15-20 minutes did not negatively affect recovery time or symptoms in collegiate athletes with SRC. As such, the 15-minute duration was selected to balance the potential cognitive benefits with the need to avoid exacerbating concussion symptoms.

Question 7

You mentioned using a weight-to-power output conversion sheet in your study. Could you provide more information on the source of this sheet and its specific contents?

Answer 7

• The weight-to-power output conversion sheet used in this study was derived from the original BCBT protocol developed by Haider et al. (2019). The sheet provides a standardized method for determining the appropriate power output (in watts) based on the participant’s body weight, ensuring a consistent and individualized exercise intensity across participants. The specific contents of the sheet include weight ranges (in kg) progressing arithmetically with a common difference of 2.5 and corresponding power outputs for each stage of the BCBT protocol that increasing by increments of 5, from minute 0 to 30 minutes. The weight range was from 35kg-120kg.

Question 8

In your study, a recumbent bike was chosen over a stationary bike. Please justify this choice and discuss whether the differences in posture between an upright and recumbent bike could potentially influence cerebral blood flow.

Answer 8

A recumbent bike was chosen over a stationary bike in this study to prioritize participant comfort and safety. Recumbent bikes provide better back support and stability, reducing the risk of falls or balance issues that may be more prevalent in individuals with SRC (Haider et al., 2019). While differences in posture between upright and recumbent bikes could potentially influence cerebral blood flow, research suggests that the cardiovascular responses and oxygen uptake are similar between the two bike types during submaximal exercise (Egaña et al., 2010). Therefore, the choice of a recumbent bike is unlikely to significantly impact the study’s outcomes related to cerebral blood flow and cognitive performance.

Question 9

What was the rationale behind using a score of 17 on the Borg Rating of Perceived Exertion as the cut-off point for terminating the BCBT?

Answer 9

The rationale behind using a score of 17 on the Borg Rating of Perceived Exertion (RPE) as the cut-off point for terminating the BCBT is based on the original protocol developed by Haider et al. (2019). An RPE of 17 corresponds to a “very hard” level of exertion, indicating that the participant is exercising at a high intensity but not at maximal effort. This cut-off point ensures that participants are challenged sufficiently to assess their exercise tolerance while minimizing the risk of overexertion and potential symptom exacerbation.

Question 10

Considering that the Borg Rating of Perceived Exertion is a subjective tool, what measures did you take to ensure that SRC participants did not overexert themselves or underreport their exertion ratings?

Answer 10

• To ensure that SRC participants did not overexert themselves or underreport their exertion ratings, several measures were taken. First, participants were familiarized with the Borg RPE scale and provided with clear instructions on how to rate their perceived exertion. Second, the research team closely monitored participants’ heart rate, symptoms, and overall well-being throughout the BCBT and exercise intervention. If any concerning signs or symptoms were observed, the test or intervention was terminated immediately. Finally, participants were encouraged to communicate openly about their exertion levels and any symptoms experienced during the study.

Question 11

Why was there a minimum 24-hour gap between conducting the BCBT and the aerobic exercise intervention in your study?

Answer 11

The minimum 24-hour gap between conducting the BCBT and the aerobic exercise intervention was implemented to allow sufficient recovery time for participants and to minimize the potential influence of fatigue on the exercise intervention outcomes. This gap ensures that the effects observed during the exercise intervention can be attributed to the acute bout of exercise rather than residual fatigue from the BCBT. Additionally, this time gap aligns with the recommended rest period between concussion assessments (McCrory et al., 2017).

Question 12

What factors influenced your decision to set the warm-up and cool-down periods at 40 RPM and the active exercise phase at 60 RPM? Please explain the rationale behind these specific cadence choices.

Answer 12

The decision to set the warm-up and cool-down periods at 40 RPM and the active exercise phase at 60 RPM was based on the original BCBT protocol (Haider et al., 2019) and general recommendations for aerobic exercise on a recumbent bike. The lower cadence of 40 RPM during the warm-up and cool-down allows for a gradual increase and decrease in intensity, respectively, minimizing the risk of sudden changes in heart rate and blood pressure. The higher cadence of 60 RPM during the active exercise phase ensures that participants are exercising at a moderate intensity, which has been shown to elicit cognitive benefits (Chang et al., 2012). These specific cadence choices strike a balance between exercise effectiveness and participant comfort, considering the unique needs of individuals with SRC.

Question 13

In your study, the SRC and HC groups were matched based on age and sex, but the exercise intensity for the HC group was determined by their matched SRC counterpart’s weight and HRt during the BCBT. This suggests that the exercise intensity for the HC group was not personalized. How do you address this limitation, and what strategies would you employ to ensure better matching between SRC and HC groups in future research?

Answer 13

• I acknowledge that determining the exercise intensity for the HC group based on their matched SRC counterpart’s weight and HRt during the BCBT may not have been the most optimal approach, as it did not account for individual differences in fitness levels and exercise tolerance within the HC group. This descision was driven by time constraints surrounding recruitment should the inclusion criteria become more stringent, and the screening process more rigorous and involved. If I could do a follow-up study, I would address these limitations.

Instead of relying on the SRC counterpart’s weight and HRt, future studies could determine the exercise intensity for each HC participant based on their individual fitness level and exercise tolerance. This can be achieved by having the HC participants undergo a similar graded exercise test, such as the BCBT or a standard submaximal exercise test, to determine their personalized HRt or a target heart rate range for the exercise intervention. In addition to age and sex, future studies should consider matching SRC and HC groups based on other relevant factors that may influence exercise tolerance and fitness levels, such as body mass index (BMI), physical activity levels, and sports participation. This can be achieved by using more comprehensive questionnaires to assess physical activity levels and fitness. Increasing the sample size in future studies would help to minimize the impact of individual differences in fitness levels and exercise tolerance within the HC group. A larger sample size would also increase the statistical power to detect meaningful differences between the SRC and HC groups while accounting for potential confounding factors.

Question 14

To account for individual differences in fitness levels and exercise tolerance within the HC group, you could have made them do the BCBT as well, and have two visits similar to the protocol for the SRC group. Justify your choice to have the HC group exercise at their matched counterpart’s HRt in the SRC group.

Answer 14

• My choice to have the HC group exercise at their matched counterpart’s HRt in the SRC group can be justified for the following reasons:
• 1. Comparability and efficiency: By having the HC group exercise at the same relative intensity (i.e., 80% of HRt) as their matched SRC counterpart, I ensure that both groups are engaging in a comparable level of exercise while streamlining the study protocol. This allows for a more direct comparison of the effects of exercise on cognitive function between the two groups, as the relative exercise intensity is controlled. Had I individualized HRts for both the SRC and HC groups, I would have needed to go through an additional matching process and significantly increased my sample size to ensure proper matching between groups, which would have required more time and resources.
• 2. Safety: The BCBT is designed to determine a safe and appropriate exercise intensity for individuals with a recent SRC. By using the HRt derived from the SRC group’s BCBT performance, I can be confident that the exercise intensity prescribed for the HC group is also safe and unlikely to cause any adverse events.
     While having the HC group complete the BCBT and attend two visits similar to the SRC group could have provided additional data on their individual fitness levels and exercise tolerance, the approach I chose allows for a valid comparison between the two groups while prioritizing safety, efficiency, and comparability.

Question 15

If the SRC and HC groups were matched based on HRt (120 bpm average, 18.2 SD), How come the SRC group has a significantly higher steady-state heartrate (i.e., last 2 minutes of exercise before cool-down) [127.2 (17.9) versus 114.6 (14.6)]?

Answer 15

• The SRC and HC groups were matched based on HRt, but this does not ensure identical cardiovascular responses to exercise. HRt represents the heart rate at symptom exacerbation or voluntary exhaustion during the BCBT, whereas steady-state heart rate reflects the cardiovascular response to submaximal exercise. The significantly higher average body weight in the SRC group (84.1 kg vs. 68.9 kg) resulted in a more intense workload during the intervention (93.3 W vs. 69.5 W) due to the BCBT protocol’s body weight to power/watt conversion. This higher workload likely contributed to the higher steady-state heart rate observed in the SRC group.
• Moreover, the workload was manually adjusted to maintain the target HR within 85-100% of the 80% HRt value. This wide maintenance range allowed for considerable variations in steady-state HR between participants without necessitating manual workload adjustments. For instance, an individual with an 80% HRt of 130 bpm could have maintained a steady-state HR anywhere between 110 (85%) and 130 bpm (100%).
• Additionally, the concussion sustained by the SRC group may have temporarily altered their normal cardiovascular response to exercise, resulting in a higher steady-state heart rate compared to the HC group. This disruption could be due to the autonomic dysfunction that has been observed in some individuals following a concussion (Leddy et al., 2007; Gall et al., 2004).The autonomic nervous system plays a crucial role in regulating heart rate and other cardiovascular functions during exercise. It consists of two main branches: the sympathetic nervous system, which increases heart rate and cardiac output, and the parasympathetic nervous system, which decreases heart rate and promotes recovery (Aubert et al., 2003).In some cases, concussions have been shown to disrupt the balance between the sympathetic and parasympathetic nervous systems, leading to autonomic dysfunction (Leddy et al., 2007; Gall et al., 2004). This imbalance may cause an exaggerated sympathetic response or a diminished parasympathetic response, resulting in a higher steady-state heart rate during exercise (Abaji et al., 2016). Furthermore, concussions have been associated with reduced heart rate variability (HRV), which is a measure of the variation in time intervals between heartbeats (Gall et al., 2004). Lower HRV has been linked to impaired autonomic function and may contribute to the altered cardiovascular response to exercise observed in the SRC group (Senthinathan et al., 2017).

In summary, the higher steady-state heart rate in the SRC group can be primarily attributed to their higher body weight, resulting in a more intense workload, and the potential concussion-related physiological changes that may have temporarily altered their cardiovascular response to exercise.

Question 16

What alternative graded aerobic exercise tests designed for concussion rehabilitation could have been considered instead of the BCBT?

Answer 16

• Aside from the BCBT, only the BCTT was specifically designed for concussion rehabilitation. The remaining tests that were considered were meant general cardiovascular fitness and endurance.
• 1. Buffalo Concussion Treadmill Test (BCTT)
• Description:
  ○ The BCTT is a widely used protocol to evaluate exercise tolerance in individuals with concussion.
  ○ It involves walking on a treadmill at a speed of 3.6 mph with a 0% incline.
  ○ Every minute, the incline is increased by 1% until the patient reaches exhaustion or experiences symptoms.
• Purpose:
  ○ To determine the exercise threshold and identify any exacerbation of symptoms.
  ○ To help create a tailored rehabilitation plan based on individual tolerance.
• 2. McMaster All-Out Progressive Continuous Cycling Test
• Description:
  ○ This test uses a stationary bike, starting at a low resistance.
  ○ The resistance is gradually increased every minute until the patient reaches exhaustion or experiences a significant increase in symptoms.
• Purpose:
  ○ To evaluate exercise tolerance in a non-weight-bearing manner, which can be beneficial for patients with lower extremity injuries or balance issues.
  ○ To determine the safe level of exertion and guide exercise progression.
• Reference:
  ○ Leiper, J. B., & Staunton, C. A. (1995). Exercise physiology laboratory manual. McMaster University, Hamilton, Ontario.
• 3. Modified Balke Protocol
• Description:
  ○ This test is a variation of the original Balke protocol and is used to assess aerobic capacity in concussed patients.
  ○ The patient starts at a walking pace of 3.3 mph on a treadmill.
  ○ The incline is increased by 2.5% every two minutes until the patient reaches volitional fatigue or significant symptom exacerbation.
• Purpose:
  ○ To safely determine the aerobic capacity and threshold for symptom exacerbation.
  ○ To assist in guiding the progression of exercise intensity during rehabilitation.
• Reference:
  ○ Balke, B., & Ware, R. W. (1959). An experimental study of physical fitness of Air Force personnel. US Armed Forces Medical Journal, 10, 675-688.
• 4. Bruce Protocol
• Description:
  ○ The Bruce protocol is a standardized treadmill test that increases both speed and incline every three minutes.
  ○ The test starts at a speed of 1.7 mph with a 10% incline, and the difficulty is progressively increased until the patient cannot continue.
• Purpose:
  ○ To assess cardiovascular fitness and endurance.
  ○ While not specific to concussion, it can be adapted for patients with concussions to determine safe exercise limits.
• Reference:
  Bruce, R. A. (1971). Exercise testing of patients with coronary artery disease. Annals of Clinical Research, 3(6), 323-332.

Question 17

What are some similarities and differences between the BCBT and the All-Out Cycling Test and why did you choose the BCBT?

Answer 17

• Commonalities:
  ○ Both tests are designed to assess exercise tolerance and are useful in concussion rehabilitation.
  ○ Both involve incremental increases in workload/resistance and monitor heart rate, RPE, and symptoms.
  ○ Both require a warm-up and cool-down phase to ensure patient safety.
• Differences:
  ○ Focus: The McMaster test is more general for aerobic capacity assessment, whereas the BCBT is specifically designed for concussion patients, focusing on autonomic function and symptom exacerbation.
  ○ Incremental Protocol: The McMaster test uses minute-by-minute resistance increases, while the BCBT typically increases resistance every 2 minutes.
  ○ Termination Criteria: The McMaster test stops primarily based on volitional exhaustion and symptom exacerbation, whereas the BCBT has an additional criterion of reaching 85% of age-predicted maximum heart rate.
  ○ Clinical Validation: The BCBT has specific validation for concussion patients, making it more specialized for this population.
• Clinical Applications:
  ○ McMaster Test: Useful for a broader range of patients, including those with musculoskeletal limitations or balance issues. It provides a detailed assessment of aerobic capacity in a non-weight-bearing manner.
  ○ BCBT: More suitable for concussion patients to understand their specific exercise tolerance and autonomic response, helping to tailor concussion-specific rehabilitation programs.

Question 18

How can dehydration impact CBF and executive function, and is i.e., ~500 mL of water consumed 1 h before exercise enough?

Answer 18

• Impact on Cerebral Blood Flow (CBF):
  ○ Dehydration causes a reduction in blood volume, which in turn leads to a decrease in cardiac output.
  ○ The decrease in cardiac output results in lower cerebral perfusion pressure, as there is less blood flow reaching the brain.
  ○ To maintain adequate oxygen and nutrient delivery to the brain, the cerebral vasculature will dilate in response to dehydration. This helps to offset the reduction in blood flow.
  ○ However, the cerebrovascular dilatory capacity has limits, and prolonged dehydration can eventually lead to a decrease in overall CBF.
• Impact on Executive Function:
  ○ Reduced CBF due to dehydration can impair the delivery of oxygen and glucose to the brain regions responsible for executive function, such as the prefrontal cortex.
  ○ This can lead to decreased neuronal activity and efficiency within the executive function networks, resulting in poorer performance on tasks that require cognitive control, working memory, and decision-making.
  ○ Studies have shown that even mild dehydration (e.g., 1-2% body weight loss) can negatively impact various aspects of executive function, including attention, processing speed, and problem-solving.
• Regarding the impact of water consumption:
  ○ Consuming approximately 500 mL (about 16 oz) of water 1 hour before exercise may help to partially offset the effects of dehydration on CBF and executive function.
  ○ Hydrating prior to exercise can help maintain blood volume and cerebral perfusion, which can support better cognitive performance during and after the exercise session.

Question 19

How did you know what workload to set the bike on at Visit 2 to reach HRt? How fast did they reach this threshold?

Answer 19

• We made note of the workload at which the SRC grouped reached voluntary exhaustion based on the RPE, and after the 2.5 minute warmup at 40 RPM 50 Watts, we increased the intensity to the noted workload and monitored their HR continiously.
• If the exceeded their HRt or were outside of the 85-100% range, we would adjust the workload accordingly.
• All participants reached their HRt within 6 mins (i.e., 3 stages) of the start of the active exercise.
• For the HC group, we increased the workload every 2 minutes by 10 watts and observed changes in HR.
  We added 10 more increments to our increases per stage if HR was not accelerating appropriately, we stopped manipulating the workload once they were within the 85-100% range.