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De Barros JA, Macartney MJ, Notley SR, Meade RD, Kenny GP. The utility of heart rate and heart rate variability to identify limits of tolerance to moderate-intensity work in the heat: a secondary analysis. Appl Physiol Nutr Metab 2024; 49:539-546. [PMID: 38170965 DOI: 10.1139/apnm-2023-0466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
We investigated the utility of heart rate (HR) and heart rate variability (HRV) for identifying individuals who may terminate work early due to excessive heat strain. Forty-eight men and women (median = 36 years; Q1 = 20 years; Q3 = 54 years) attempted 180 min of moderate-intensity work at a fixed metabolic rate (∼200 W/m2; ∼3.5 METs) in a hot environment (wet-bulb globe temperature: 32 °C). Receiver operating characteristics (ROC) curves were used to identify the ability of indices of HR (absolute HR, percentage of maximum HR, percentage of HR reserve) and HRV (root-mean-square of successive differences (RMSSD), high-frequency power, and detrended fluctuation analysis component alpha 1 (DFA α1)) to discriminate between participants who completed the 180 min work bout or terminated prematurely. Participants who terminated work prematurely (n = 26) exhibited higher HR and percentage of HR measures, as well as reduced RMSSD and DFA α1 after the first hour of work compared to participants who completed the bout. The discriminative utility of HR and HRV indices was strongest within the first hour of work, with percentage of HR reserve demonstrating excellent discriminative power (ROC area under curve (AUC) of 0.8). Stratifying participants by age and sex improved ROC AUC point estimates for most indices, particularly in female participants. The study provides preliminary evidence supporting the use of noninvasive cardiac monitoring for predicting work tolerance in healthy individuals exposed to occupational heat stress. HR and percentage of HR reserve were suggested to discriminate work termination most effectively. Further investigations are warranted to explore the influence of individual factors and refine the discriminative thresholds for early identification of excessive occupational heat strain.
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Affiliation(s)
- Jordan A De Barros
- School of Graduate Medicine, University of Wollongong, Wollongong, NSW, Australia
| | - Michael J Macartney
- School of Graduate Medicine, University of Wollongong, Wollongong, NSW, Australia
| | - Sean R Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
- Department of Defence, Defence Science and Technology Group, Melbourne, VIC 3207, Australia
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
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Kaltsatou A, Anifanti M, Flouris AD, Xiromerisiou G, Kouidi E. Validity of the CALERA Research Sensor to Assess Body Core Temperature during Maximum Exercise in Patients with Heart Failure. SENSORS (BASEL, SWITZERLAND) 2024; 24:807. [PMID: 38339524 PMCID: PMC10857250 DOI: 10.3390/s24030807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/20/2024] [Accepted: 01/23/2024] [Indexed: 02/12/2024]
Abstract
(1) Background: It is important to monitor the body core temperature (Tc) of individuals with chronic heart failure (CHF) during rest or exercise, as they are susceptible to complications. Gastrointestinal capsules are a robust indicator of the Tc at rest and during exercise. A practical and non-invasive sensor called CALERA Research was recently introduced, promising accuracy, sensitivity, continuous real-time analysis, repeatability, and reproducibility. This study aimed to assess the validity of the CALERA Research sensor when monitoring patients with CHF during periods of rest, throughout brief cardiopulmonary exercise testing, and during their subsequent recovery. (2) Methods: Twelve male CHF patients volunteered to participate in a 70-min protocol in a laboratory at 28 °C and 39% relative humidity. After remaining calm for 20 min, they underwent a symptom-limited stress test combined with ergospirometry on a treadmill, followed by 40 min of seated recovery. The Tc was continuously monitored by both Tc devices. (3) Results: The Tc values from the CALERA Research sensor and the gastrointestinal sensor showed no associations at rest (r = 0.056, p = 0.154) and during exercise (r = -0.015, p = 0.829) and a weak association during recovery (r = 0.292, p < 0.001). The Cohen's effect size of the differences between the two Tc assessment methods for rest, exercise, and recovery was 1.04 (large), 0.18 (none), and 0.45 (small), respectively. The 95% limit of agreement for the CALERA Research sensor was -0.057 ± 1.03 °C. (4) Conclusions: The CALERA sensor is a practical and, potentially, promising device, but it does not provide an accurate Tc estimation in CHF patients at rest, during brief exercise testing, and during recovery.
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Affiliation(s)
- Antonia Kaltsatou
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, 42100 Trikala, Greece; (A.K.); (A.D.F.)
| | - Maria Anifanti
- Sportsmedicine Laboratory, Department of Physical Education and Sport Science, Aristotle University of Thessaloniki, 57000 Thermi, Greece;
| | - Andreas D. Flouris
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, 42100 Trikala, Greece; (A.K.); (A.D.F.)
| | - Georgia Xiromerisiou
- Department of Neurology, University Hospital of Larissa, University of Thessaly, 41110 Larissa, Greece;
| | - Evangelia Kouidi
- Sportsmedicine Laboratory, Department of Physical Education and Sport Science, Aristotle University of Thessaloniki, 57000 Thermi, Greece;
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Bernard TE, Ashley CD, Wolf ST, Kenney WL. Core temperature and heart rate at the upper limit of the prescriptive zone. Physiol Rep 2023; 11:e15812. [PMID: 37688426 PMCID: PMC10492005 DOI: 10.14814/phy2.15812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 08/18/2023] [Accepted: 08/18/2023] [Indexed: 09/10/2023] Open
Abstract
The expressed goal of limiting workplace heat stress exposures to a core temperature (Tc ) of 38°C traces back to a 1969 World Health Organization Technical Report (WHO Series 412). The actual goal was to limit exposures to the upper limit of the prescriptive zone (ULPZ). To explore the physiological strain at the ULPZ, progressive heat stress protocol data from Penn State University (PSU) and University of South Florida (USF) below and at the ULPZ were used to articulate the relation of Tc and heart rate (HR) to metabolic rate (MR) with consideration of acclimatization state, clothing, exposure condition (PreULPZ vs. ULPZ), and sex. Regression models demonstrated the association of MR and sex with Tc and HR. At the ULPZ, women had systematically higher values of Tc and HR than men at the same MR likely due to higher relative demands. There was no effect for acclimatization state and clothing. As expected for individuals, Tc was practically constant below the ULPZ and HR exhibited increasing values approaching the ULPZ. At 490 W, the high MR cited in the WHO document, the mean Tc for men was near the 38°C limit with systematically lower Tc at lower MRs.
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Affiliation(s)
| | - Candi D. Ashley
- Exercise Science Program, College of EducationUniversity of South FloridaTampaFLUSA
| | - S. Tony Wolf
- Department of KinesiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
- Present address:
Department of KinesiologyUniversity of GeorgiaAthensGAUSA
| | - W. Larry Kenney
- Department of KinesiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
- Graduate Program in PhysiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
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Morrissey MC, Langan SP, Brewer GJ, Struder JF, Navarro JS, Nye MN, Casa DJ. Limitations associated with thermoregulation and cardiovascular research assessing laborers performing work in the heat. Am J Ind Med 2023; 66:267-280. [PMID: 36748881 DOI: 10.1002/ajim.23462] [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: 07/19/2022] [Revised: 12/13/2022] [Accepted: 01/10/2023] [Indexed: 02/08/2023]
Abstract
PURPOSE To quantify the current literature and limitations associated with research examining thermoregulatory and cardiovascular strain in laborers working in the heat. METHODS PubMed, SCOPUS, and SPORTDiscus were searched for terms related to the cardiovascular system, heat stress, and physical work. Qualifying studies included adult participants (18-65 years old), a labor-intensive environment or exercise protocol simulating a labor environment, a minimum duration of 120 min of physical work, and environmental heat stress (ambient temperature ≥26.0°C and ≥30% relative humidity). Studies included at least one of the following outcomes: pre- and peak physical work, core temperature, heart rate (HR), systolic blood pressure, diastolic blood pressure, HR variability, and rate pressure product. RESULTS Twenty-one out of 1559 potential studies qualified from our search. There was a total of 598 participants (mean = 28 ± 50 participants per study, range = 4-238 participants per study), which included 51 females (8.5%) and 547 males (91.5%). Of the participants, 3.8% had cardiovascular risk factors (diabetes: n = 10; hypertension: n = 13) and 96.2% were characterized as "healthy". Fifty-seven percent of the included studies were performed in a laboratory setting. CONCLUSIONS Studies were predominantly in men (91.5%), laboratory settings (57%), and "healthy" individuals (96.2%). To advance equity in protection against occupational heat stress and better inform future heat safety recommendations to protect all workers, future studies must focus on addressing these limitations. Employers, supervisors, and other safety stakeholders should consider these limitations while implementing current heat safety recommendations.
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Affiliation(s)
| | - Sean P Langan
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
| | - Gabrielle J Brewer
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
| | - Jeb F Struder
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
| | - John S Navarro
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
| | - Megan N Nye
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
| | - Douglas J Casa
- Korey Stringer Institute, University of Connecticut, Storrs, Connecticut, USA
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Bernard TE, Flach JW, Ashley CD. Group Outcomes for Time-Weighted Averaging in WBGT-Based Heat Stress Exposure Assessment. Ann Work Expo Health 2023; 67:345-353. [PMID: 36454581 DOI: 10.1093/annweh/wxac083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 10/17/2022] [Accepted: 11/02/2022] [Indexed: 12/02/2022] Open
Abstract
The wet bulb globe temperature (WBGT)-based occupational exposure limits (OELs) were developed from steady exposures to heat stress at constant WBGT and metabolic rate (M). The exposure limits were based on compensable heat stress exposures at the upper limit of the prescriptive zone for most healthy people. Professional practice allows for using time-weighted averages (TWAs) of WBGT and M to account for heterogeneous heat stress exposures. The purpose of the current paper was to report on the effectiveness of time-weighted averaging to assess occupational heat stress using published studies. Our hypothesis was using TWA-WBGT and TWA-M was as protective as the recommended OELs for steady exposures. The current paper reports on 62 observations of work that alternate between at least two heat stress conditions (usually work and recovery) reported in 16 papers. The TWA-WBGT and TWA-M were determined for all observations. ΔLimit was the observed TWA-WBGT minus the exposure limit at the TWA-M based on acclimatization state. The observations were then classified as above or below ΔLimit = 0. Each observation was also classified as uncompensable if the mean core temperature for the group was greater than 38°C or a less tolerant individual was above 38.5°C. When comparing exposure classifications to outcome classifications using 2 × 2 tables, the sensitivity and specificity for all observations were 0.72 and 0.73, respectively. The sensitivity was much less than the expected value near 1.0, and the large difference called into question the ability of TWAs to represent actual heat stress. There was some suspicion that there were differences between acclimatized and unacclimatized observations. Before any of these findings are embedded in policy or practice, a more careful evaluation of TWAs is required. In conclusion, we believe that the use of TWAs for heat stress analysis was not fully evaluated, and we proposed a framework for evaluation.
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Affiliation(s)
- Thomas E Bernard
- College of Public Health, University of South Florida, Tampa, FL 33612, USA
| | - John W Flach
- College of Public Health, University of South Florida, Tampa, FL 33612, USA
| | - Candi D Ashley
- Exercise Science Program, College of Education, University of South Florida, Tampa, FL 33620, USA
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Night-Time Heart Rate Variability during an Expedition to Mt Everest: A Case Report. Sports (Basel) 2023; 11:sports11020048. [PMID: 36828333 PMCID: PMC9959035 DOI: 10.3390/sports11020048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/12/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Mt Everest has been gaining popularity from casual hiking athletes, climbers, and ultra-endurance marathon runners. However, living and sleeping at altitude increases the risk of injury and illness. This is because travel to high altitudes adversely affects human physiology and performance, with unfavourable changes in body composition, exercise capacity, and mental function. This is a case report of a climber who reached the summit of Mt Everest from the north side. During his 40-day expedition, we collected sleep quality data and night-time heart rate variability. During the night inside the tent, the air temperature ranged from -12.9 to 1.8 °C (-5.8 ± 4.9 °C) and the relative humidity ranged from 26.1 to 78.9% (50.7 ± 16.9%). Awake time was 17.1 ± 6.0% of every sleep-time hour and increased with altitude (r = 0.42). Sleep time (r = -0.51) and subjective quality (r = 0.89) deteriorated with altitude. Resting heart rate increased (r = 0.70) and oxygen saturation decreased (r = -0.94) with altitude. The mean NN, RMSSD, total power, LF/HF, and SD1 and SD2 were computed using the NN time series. Altitude reduced the mean ΝΝ (r = -0.73), RMSSD (r = -0.31), total power (r = -0.60), LF/HF ratio (r = -0.40), SD1 (r = -0.31), and SD2 (r = -0.70). In conclusion, this case report shows that sleeping at high altitudes above 5500 m results in progressively reduced HRV, increased awakenings, as well as deteriorated sleep duration and subjective sleep quality. These findings provide further insight into the effects of high altitude on cardiac autonomic function and sleep quality and may have implications for individuals who frequently spend time at high altitudes, such as climbers.
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Mitsiou M, Dimitros E, Roumeliotis S, Liakopoulos V, Kouidi E, Deligiannis A. Effects of a Combined Intradialytic Exercise Training Program and Music on Cardiac Autonomic Nervous System Activity in Hemodialysis Patients. Life (Basel) 2022; 12:life12081276. [PMID: 36013455 PMCID: PMC9410492 DOI: 10.3390/life12081276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 08/17/2022] [Accepted: 08/18/2022] [Indexed: 11/16/2022] Open
Abstract
This study aimed to examine the effect of an intradialytic exercise program in combination with music on heart rate variability (HRV) indices and functional capacity in patients on maintenance hemodialysis (HD). Methods: Forty HD patients were randomized to four training groups for six months: the combined music and exercise group (Group A), the exercise group (Group B), the music group (Group C), and the control group (Group D). At baseline and after 6 months, all participants underwent both short- (for 30 min) and long- (for 24 h) term measurements of HRV and functional capacity assessment with a 6 min walking test (6MWT). Patients of groups A and C listened to preferred music. Results: Long-term HRV analysis showed that standard deviation of all normal-to-normal RR intervals (SDNN) and the square root of the mean squared differences of successive RR intervals (rMSSD) were significantly higher at the end of the study in groups A (by 13.2% and 47.3%), B (by 15.1% and 50%), and C (by 9.0% and 30.1%), compared to group D (p < 0.05). Values of rMSSD and percentage of RR intervals differing by more than 50 ms from the preceding RR interval (pNN50) were elevated in groups A (by 35.6% and 142.9%), B (by 36.1% and 75%), and C (by 15.2% and 28.6%), compared to baseline measurements (p < 0.05). Also, pNN50 was increased in group A compared to groups B (by 21.4%), C (by 88.9%), and D (by 142.9%) (p < 0.05). Similar results were noted by short-term HRV analysis. Functional capacity was improved at the end of the 6-month study in groups A (by 20.3% and 25.7%) and B (by 15.8% and 21.1%) compared to groups C and D (p < 0.05). Conclusions: Intradialytic exercise combined with music-listening can improve the functional capacity and cardiac autonomic nervous system activity in hemodialysis patients.
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Affiliation(s)
- Maria Mitsiou
- Laboratory of Sports Medicine, Aristotle University of Thessaloniki, 57001 Thessaloniki, Greece
| | - Eleftherios Dimitros
- Laboratory of Sports Medicine, Aristotle University of Thessaloniki, 57001 Thessaloniki, Greece
| | - Stefanos Roumeliotis
- Division of Nephrology and Hypertension, 1st Department of Medicine, AHEPA Hospital, Medical School, Aristotle University of Thessaloniki, 54636 Thessaloniki, Greece
- Correspondence: ; Tel.: +30-231-099-4694
| | - Vassilios Liakopoulos
- Division of Nephrology and Hypertension, 1st Department of Medicine, AHEPA Hospital, Medical School, Aristotle University of Thessaloniki, 54636 Thessaloniki, Greece
| | - Evangelia Kouidi
- Laboratory of Sports Medicine, Aristotle University of Thessaloniki, 57001 Thessaloniki, Greece
| | - Asterios Deligiannis
- Laboratory of Sports Medicine, Aristotle University of Thessaloniki, 57001 Thessaloniki, Greece
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