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Renaghan E, Wittels HL, Feigenbaum LA, Wishon MJ, Chong S, Wittels ED, Hendricks S, Hecocks D, Bellamy K, Girardi J, Lee S, Vo T, McDonald SM, Wittels SH. Exposures to Elevated Core Temperatures during Football Training: The Impact on Autonomic Nervous System Recovery and Function. Sports (Basel) 2023; 12:8. [PMID: 38251282 PMCID: PMC10819443 DOI: 10.3390/sports12010008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 12/14/2023] [Accepted: 12/20/2023] [Indexed: 01/23/2024] Open
Abstract
Exercising with elevated core temperatures may negatively affect autonomic nervous system (ANS) function. Additionally, longer training duration under higher core temperatures may augment these negative effects. This study evaluated the relationship between exercise training duration and 24 h ANS recovery and function at ≥37 °C, ≥38 °C and ≥39 °C core temperature thresholds in a sample of male Division I (D1) collegiate American football athletes. Fifty athletes were followed over their 25-week season. Using armband monitors (Warfighter MonitorTM, Tiger Tech Solutions, Inc., Miami, FL, USA), core temperature (°C) and 24 h post-exercise baseline heart rate (HR), HR recovery and heart rate variability (HRV) were measured. For HRV, two time-domain indices were measured: the root mean square of the standard deviation of the NN interval (rMSSD) and the standard deviation of the NN interval (SDNN). Linear regression models were performed to evaluate the associations between exercise training duration and ANS recovery (baseline HR and HRV) and function (HR recovery) at ≥37 °C, ≥38 °C and ≥39 °C core temperature thresholds. On average, the athletes were 21.3 (± 1.4) years old, weighed 103.0 (±20.2) kg and had a body fat percentage of 15.4% (±7.8%, 3.0% to 36.0%). The duration of training sessions was, on average, 161.1 (±40.6) min and they ranged from 90.1 to 339.6 min. Statistically significant associations between training duration and 24 h ANS recovery and function were observed at both the ≥38.0 °C (baseline HR: β = 0.10 ± 0.02, R2 = 0.26, p < 0.0000; HR recovery: β = -0.06 ± 0.02, R2 = 0.21, p = 0.0002; rMSSD: β = -0.11 ± 0.02, R2 = 0.24, p < 0.0000; and SDNN: β = -0.16 ± 0.04, R2 = 0.22, p < 0.0000) and ≥39.0 °C thresholds (β = 0.39 ± 0.05, R2 = 0.62, p < 0.0000; HR recovery: β = -0.26 ± 0.04, R2 = 0.52, p < 0.0000; rMSSD: β = -0.37 ± 0.05, R2 = 0.58, p < 0.0000; and SDNN: β = -0.67 ± 0.09, R2 = 0.59, p < 0.0000). With increasing core temperatures, increases in slope steepness and strengths of the associations were observed, indicating accelerated ANS deterioration. These findings demonstrate that exercise training under elevated core temperatures (≥38 °C) may negatively influence ANS recovery and function 24 h post exercise and progressively worsen.
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Affiliation(s)
- Eric Renaghan
- Department of Athletics, Sports Science, University of Miami, Miami, FL 33146, USA; (E.R.); (L.A.F.)
| | - Harrison L. Wittels
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Luis A. Feigenbaum
- Department of Athletics, Sports Science, University of Miami, Miami, FL 33146, USA; (E.R.); (L.A.F.)
- Department of Physical Therapy, Miller School of Medicine, University of Miami, Miami, FL 33146, USA;
| | - Michael J. Wishon
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Stephanie Chong
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Eva D. Wittels
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Stephanie Hendricks
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Dustin Hecocks
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
| | - Kyle Bellamy
- Department of Athletics, Nutrition, University of Miami, Miami, FL 33146, USA;
| | - Joe Girardi
- Department of Physical Therapy, Miller School of Medicine, University of Miami, Miami, FL 33146, USA;
| | - Stephen Lee
- United States Army Research Laboratory, Adelphi, MD 20783, USA;
| | - Tri Vo
- Navy Medical Center—San Diego, San Diego, CA 92134, USA;
| | - Samantha M. McDonald
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
- School of Kinesiology and Recreation, Illinois State University, Normal, IL 61761, USA
| | - S. Howard Wittels
- Tiger Tech Solutions, Inc., Miami, FL 33156, USA; (H.L.W.); (M.J.W.); (S.C.); (E.D.W.); (S.H.); (D.H.); (S.H.W.)
- Department of Anesthesiology, Mount Sinai Medical Center, Miami, FL 33140, USA
- Department of Anesthesiology, Wertheim School of Medicine, Florida International University, Miami, FL 33199, USA
- Miami Beach Anesthesiology Associates, Miami, FL 33140, USA
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