Loeffler L1, Landis E1, Kissel K1, Denis J1, Harris B1, Christiansen L2, Formiga M1, Cohen M1, Perez M1, Cahalin L1
1University of Miami Miller School of Medicine, Physical Therapy, Coral Gables, United States, 2University of Miami, Miami Project to Cure Paralysis, Miami, United States
Background: Acute intermittent hypoxia (AIH) has been used as a therapeutic modality to improve neurologic and cardiorespiratory function in individuals with spinal cord injuries, but there is limited research on its effects in the neurologically intact population. Heart rate recovery (HRR) is an important prognostic measure that is easily obtained after exercise or functional tasks with a faster HRR implying better fitness, health, and survival. The relationship of physical activity (PA) on HRR after AIH has not been investigated.
Purpose: The purpose of this study was to examine the relationship between PA and HRR after AIH in healthy young adults.
Methods: 16 healthy participants (8 men, 8 women) with mean±SD age, height, and weight of 24±2years, 170.5±9cm, and 69.8±16kg, respectively, randomly underwent a session of AIH which involved 1-minute of inspired oxygen (FiO2) of 10% followed by 1-minute of FiO2 of 21% repeated for 30 minutes. Heart rate (HR) was digitally recorded from a finger pulse oximeter every 4 seconds at baseline, during intervention, and for 60 minutes post-AIH. Level of PA was measured with the International Physical Activity Questionnaire.
Results: No adverse reactions occurred during AIH. The mean±SD HR at baseline during the AIH trial was 73.1±7.8 bpm. During AIH, the HR increased significantly (p 0.05) at minute 1:20 and remained significantly increased throughout the 30-minute session, followed by a post-AIH HR that was significantly lower than baseline throughout the 60-minute recovery. A near significant relationship was observed between % change in HR at baseline to minute-2 post-AIH and vigorous PA metabolic equivalents (METs) as well as days of vigorous exercise/week (r= -.46 and -.48; p=.07 and .05, respectively). Also, participants who vigorously exercised > 3 days/week or achieved > 1,440 METs had a significantly greater reduction in HR from baseline to minute-2 post-AIH (14.5% versus 1.5% and 13.8% versus 3.3%, respectively; p 0.05). Chi-square analyses demonstrated that the number of participants who achieved at least a 10% reduction in HR from baseline to minute 2 post-AIH was significantly greater for those who vigorously exercised > 3 days/week (p=.03) and nearly significant for subjects who achieved > 1,440 METs (p=0.09).
Conclusion(s): AIH alone can significantly affect HRR which is related to PA. Greater PA was associated with a faster HRR with > 3 days of vigorous exercise or > 1,440 METs eliciting the fastest HRR. These results are supported by previous literature demonstrating better health, fitness, and survival in subjects with a more rapid HRR after PA.
Implications: The HRR after AIH may be useful to better understand fitness level in subjects unable to perform PA due to disease or disability. A HRR of at least 10% after AIH may identify individuals with greater health and fitness. However, further investigation is warranted.
Keywords: physical activity, heart rate recovery, cardiorespiratory response
Funding acknowledgements: Miami Project to Cure Paralysis
Purpose: The purpose of this study was to examine the relationship between PA and HRR after AIH in healthy young adults.
Methods: 16 healthy participants (8 men, 8 women) with mean±SD age, height, and weight of 24±2years, 170.5±9cm, and 69.8±16kg, respectively, randomly underwent a session of AIH which involved 1-minute of inspired oxygen (FiO2) of 10% followed by 1-minute of FiO2 of 21% repeated for 30 minutes. Heart rate (HR) was digitally recorded from a finger pulse oximeter every 4 seconds at baseline, during intervention, and for 60 minutes post-AIH. Level of PA was measured with the International Physical Activity Questionnaire.
Results: No adverse reactions occurred during AIH. The mean±SD HR at baseline during the AIH trial was 73.1±7.8 bpm. During AIH, the HR increased significantly (p 0.05) at minute 1:20 and remained significantly increased throughout the 30-minute session, followed by a post-AIH HR that was significantly lower than baseline throughout the 60-minute recovery. A near significant relationship was observed between % change in HR at baseline to minute-2 post-AIH and vigorous PA metabolic equivalents (METs) as well as days of vigorous exercise/week (r= -.46 and -.48; p=.07 and .05, respectively). Also, participants who vigorously exercised > 3 days/week or achieved > 1,440 METs had a significantly greater reduction in HR from baseline to minute-2 post-AIH (14.5% versus 1.5% and 13.8% versus 3.3%, respectively; p 0.05). Chi-square analyses demonstrated that the number of participants who achieved at least a 10% reduction in HR from baseline to minute 2 post-AIH was significantly greater for those who vigorously exercised > 3 days/week (p=.03) and nearly significant for subjects who achieved > 1,440 METs (p=0.09).
Conclusion(s): AIH alone can significantly affect HRR which is related to PA. Greater PA was associated with a faster HRR with > 3 days of vigorous exercise or > 1,440 METs eliciting the fastest HRR. These results are supported by previous literature demonstrating better health, fitness, and survival in subjects with a more rapid HRR after PA.
Implications: The HRR after AIH may be useful to better understand fitness level in subjects unable to perform PA due to disease or disability. A HRR of at least 10% after AIH may identify individuals with greater health and fitness. However, further investigation is warranted.
Keywords: physical activity, heart rate recovery, cardiorespiratory response
Funding acknowledgements: Miami Project to Cure Paralysis
Topic: Cardiorespiratory; Health promotion & wellbeing/healthy ageing; Disability & rehabilitation
Ethics approval required: Yes
Institution: University of Miami
Ethics committee: Institutional Review Board
Ethics number: 997
All authors, affiliations and abstracts have been published as submitted.
