Performance and Physiological Response to the Buffalo Concussion Treadmill Test Can Identify Autonomic Dysfunction in the General Adult Population With Mild Traumatic Brain Injury: A Prospective Observational Study

Objective: To explore the underlying mechanisms impacting on the Buffalo Concussion Treadmill Test (BCTT) performance in a general adult population with mild traumatic brain injury (TBI). Setting: Outpatient TBI rehabilitation service. Participants: Twenty-one adults with mild TBI, 17 healthy active adults, and 14 healthy sedentary adults. Design: Prospective observational study comparing BCTT performance and associated physiological responses between 3 participant groups. Main Measures: During a single BCTT session, test duration, reason for test termination, age-predicted maximum heart rate (HR), and HR recovery (HRR) were recorded. Results: Fifty-two adults (60.8% male, mean ± SD age: 37.8 ± 14.6 years) were recruited. The group with mild TBI demonstrated a significantly shorter test duration (10.8 ± 5.7 min) compared to the healthy active (14.1 ± 2.9 min) and sedentary (11.6 ± 3.0 min) groups (P <.05). Eight participants (38.1%) stopped due to symptom exacerbation. The group with mild TBI had a significantly (P <.05) lower age-predicted maximum HR (84.3 ± 9.8%), compared to both healthy active (90.0 ± 0.2%) and sedentary adults (89.3 ± 2.8%) at test termination. Fast and slow phase HRR were significantly better in the healthy active group (fast: 69.6 ± 18.2 beats per minute [bpm], slow: 79.0 ± 13.8 bpm) compared to both the mild TBI (fast: 44.5 ± 18.7 bpm, slow: 61.1 ± 20.4 bpm) and healthy sedentary groups (fast 49.6 ± 20.1 bpm, slow 63.0 ± 11.7 bpm) (P <.05), with no significant difference between adults with mild TBI and healthy sedentary groups. When controlling for levels of physical activity there was no longer a detectable significant difference between the healthy active and sedentary groups in HRR. Conclusion: This study demonstrates that the inability to exercise to a threshold HR of 90% of an individual's age-predicted maximum HR is a better indicator of autonomic dysfunction. HRR may be prolonged in those with a mild TBI, but caution should be taken if attributing this to physiological dysfunction as the predominant factor appears to be physical activity levels.