Effects of internal cooling on physical performance, physiological and perceptional parameters when exercising in the heat: A systematic review with meta-analyses

Juliane Heydenreich; Karsten Koehler; Hans Braun; Mareike Grosshauser; Helmut Heseker; Daniel Koenig; Alfonso Lampen; Stephanie Mosler; Andreas Niess; Alexandra Schek; Anja Carlsohn

doi:10.3389/fphys.2023.1125969

Effects of internal cooling on physical performance, physiological and perceptional parameters when exercising in the heat: A systematic review with meta-analyses

Front Physiol. 2023 Apr 11:14:1125969. doi: 10.3389/fphys.2023.1125969. eCollection 2023.

Authors

Juliane Heydenreich^{1

2}, Karsten Koehler^{1

3}, Hans Braun^{1

4}, Mareike Grosshauser^{1

5}, Helmut Heseker^{1

6}, Daniel Koenig^{1

7}, Alfonso Lampen^{1

8}, Stephanie Mosler^{1

9}, Andreas Niess^{1

10}, Alexandra Schek^{1

11}, Anja Carlsohn^{1

12}

Affiliations

¹ Working Group Sports Nutrition of German Nutrition Society, Bonn, Germany.
² Institute of Sports Sciences, Johannes Gutenberg-University of Mainz, Mainz, Germany.
³ Department of Sport and Health Sciences, Technical University of Munich, Munich, Germany.
⁴ Manfred Donike Institute for Doping Analysis, Institute of Biochemistry, German Sport University Cologne, Cologne, Germany.
⁵ Olympic Center Rhineland-Palatinate/Saarland, Saarbrücken, Germany.
⁶ Institute of Nutrition, Consumption and Health, University of Paderborn, Paderborn, Germany.
⁷ Division of Sports Medicine, Exercise Physiology and Prevention, Center for Sport Science and University Sports, University of Vienna, Vienna, Austria.
⁸ Risk Assessment Strategies, German Federal Institute for Risk Assessment, Berlin, Germany.
⁹ Olympic Center Stuttgart, Stuttgart, Germany.
¹⁰ Department of Sports Medicine, University Hospital Tübingen, Tübingen, Germany.
¹¹ Editorial Team of the Journal Leistungssport, German Olympic Sports Confederation, Frankfurt, Germany.
¹² Department of Nutrition and Home Economics, University of Applied Science Hamburg, Hamburg, Germany.

Abstract

Background: An elevated core temperature (Tcore) increases the risk of performance impairments and heat-related illness. Internal cooling (IC) has the potential to lower Tcore when exercising in the heat. The aim of the review was to systematically analyze the effects of IC on performance, physiological, and perceptional parameters. Methods: A systematic literature search was performed in the PubMed database on 17 December 2021. Intervention studies were included assessing the effects of IC on performance, physiological, or perceptional outcomes. Data extraction and quality assessment were conducted for the included literature. The standardized mean differences (SMD) and 95% Confidence Intervals (CI) were calculated using the inverse-variance method and a random-effects model. Results: 47 intervention studies involving 486 active subjects (13.7% female; mean age 20-42 years) were included in the meta-analysis. IC resulted in significant positive effects on time to exhaustion [SMD (95% CI) 0.40 (0.13; 0.67), p < 0.01]. IC significantly reduced Tcore [-0.19 (22120.34; -0.05), p < 0.05], sweat rate [-0.20 (-0.34; -0.06), p < 0.01], thermal sensation [-0.17 (-0.33; -0.01), p < 0.05], whereas no effects were found on skin temperature, blood lactate, and thermal comfort (p > 0.05). IC resulted in a borderline significant reduction in time trial performance [0.31 (-0.60; -0.02), p = 0.06], heart rate [-0.13 (-0.27; 0.01), p = 0.06], rate of perceived exertion [-0.16 (-0.31; -0.00), p = 0.05] and borderline increased mean power output [0.22 (0.00; 0.44), p = 0.05]. Discussion: IC has the potential to affect endurance performance and selected physiological and perceptional parameters positively. However, its effectiveness depends on the method used and the time point of administration. Future research should confirm the laboratory-based results in the field setting and involve non-endurance activities and female athletes. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022336623.

Keywords: athlete; core temperature; ice; menthol; perceptional cooling; physical cooling; sweat rate; time trial.

Publication types

Systematic Review