Changes in Lung Function During Exercise Are Independently Mediated by Increases in Deep Body Temperature
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BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2016-000210 on 2 June 2017. Downloaded from Open Access Original article Changes in lung function during exercise are independently mediated by increases in deep body temperature Michael J Tipton,1 Pippa Kadinopoulos,2 Dan Roiz de Sa,1,3 Martin J Barwood4 To cite: Tipton MJ, ABSTRACT What are the new findings? Kadinopoulos P, Sa DR, Background This study examined whether an et al. Changes in lung increase in deep body temperature contributes to " function during exercise are This study demonstrates, for the first time, that increases in ventilatory flow indicative of independently mediated by body temperature, independently of exercise, increases in deep body bronchodilatation. changes lung function in a very similar way to temperature. BMJ Open Method The study employed a within-participant that seen with exercise. Sport Exerc Med 2017;3: repeated measures design. Nine participants (mean " These original lung function data address a e000210. doi:10.1136/ (SD): age 22 (3) years; height 177.7 (8.3) cm; mass largely ignored factor that has significant implica- bmjsem-2016-000210 80.2 (19.1) kg) completed three conditions: exercise tions for the experimental design and interpreta- (EXERC; 30 min); 40 C water immersion (IMM40; tion of studies investigating the impact of Accepted 28 February 2017 30 min) to passively raise rectal temperature (Tre) and exercise, as well as other interventions that raise 35 C immersion (IMM35; 30 min) asa thermoneutral body temperature. control for IMM40. A forced vital capacity (FVC) manoeuvre was performed at the start of the test and every 10 min thereafter. Forced expiratory volume in 1 s (FEV1), FEV1/FVC, 25%, 50% and 75% maximal and mechanical stretching of the airway walls expiratory flow during FVC (forced expiratory flow and a reflex inhibition of bronchomotor tone (FEF)25, FEF50, FEF75) were also measured. Data were via slowly adapting pulmonary stretch recep- copyright. compared using a repeated measures two-way analysis tors; mechanical and length–tension effects of variance, with a 0.05 a level. on airway smooth muscle.10–13 Results Rectal temperature (Tre) peaked after 30 min One factor that has been largely overlooked in the EXERC (mean (SD) 38.0 (0.3)C) and IMM40 is body temperature. While it has been estab- (38.2 (0.2) C) conditions and both were higher lished that cooling and heating skeletal (p<0.05) than at the corresponding time in the thermoneutral condition (37.2 (0.2)C). At this time, muscle and connective tissue change their physical and physiological properties and FEV was 4.5 (0.6), 4.6 (0.3) and 4.4 (0.6) L, http://bmjopensem.bmj.com/ 1 14 15 respectively. Tre, FEV1 and FEV1/FVC were greater in function, little is known about the effect the IMM40 and EXERC conditions compared with the of the increase in body temperature associ- IMM35 condition. Interaction effects were evident for ated with exercise on the respiratory tissues FEF50 and FEF75 (p<0.05), being higher in IMM40 and and lung function. Suman et al16 suggested EXERC conditions. that within a population with asthma the Conclusion Increasing deep body temperature, increase in deep body temperature (Tdb) that independently, contributes to the increased airflow occurs as a result of exercising for over 1 ascribed to bronchodilatation when exercising. Department of Sport and 20 min has a negative effect on airway Exercise Science, Extreme Environments Laboratory patency. The study showed a bronchodilatory on September 27, 2021 by guest. Protected (EEL), University of INTRODUCTION response up to 15 min of exercise, thereafter Portsmouth, Portsmouth, UK a significant bronchoconstriction. They 2 In healthy individuals, exercise produces HMS Nelson, HM Naval hypothesised that the increase in tempera- Base Portsmouth, either a mild bronchodilatation, facilitating Portsmouth, UK an increase in airflow without a significant ture caused bronchial vasodilatation 3Environmental Medicine & increase in airway resistance and the work of resulting in engorged blood vessels and/or an Science Unit, Institute of breathing,1 or has no effect.2 In healthy indi- increase in the permeability of the endothe- Naval Medicine, Gosport, UK 4 viduals and patients with asthma, drug- lium, resulting in airway obstruction. Tdb was Department of Sport, Health not measured in the study. Suman et al12 and Nutrition, Leeds Trinity induced bronchoconstriction is reversed by 3 University, Leeds, UK exercise. The suggested mechanisms for this examined isocapnic ventilation and exercise include: parasympathetic/sympathetic in a population with asthma. They suggested 4 5–8 Correspondence to balance ; endogenous catecholamines ; that an increase in oesophageal temperature Michael J Tipton; michael. prostaglandin E2 release from mast cells and may aggravate the already hyperactive [email protected] airway epithelial cells4 9; deep inspirations airways by increasing airway mucosal blood Tipton MJ, et al. BMJ Open Sport Exerc Med 2017;3:e000210. doi:10.1136/bmjsem-2016-000210 1 BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2016-000210 on 2 June 2017. Downloaded from Open Access Figure 1 Mean rectal temperature (C) data for each condition over the experimental period. Conditions and significant differences as marked () = p<0.1 in this comparison (n=9). Tre EXERCISE, rectal temperature during clothed exercise for 30 minutes; Tre IMM35, rectal temperature during 35 C water immersion; Tre IMM40, rectal temperature during 40 C water immersion. flow. The increase in warm blood may also cause vascular induced hyperventilation has also been reported by oedema and congestion, resulting in airway obstruction. Hayashi et al,18 who reported an increase in minute Choukroun et al17 reported that immersion in ventilation when immersed in 35 C and 45 C water 19 cold water compared with thermoneutral water compared with 10 C water. In contrast, Martin et al copyright. produced a significant reduction (À3%, p<0.05) in reported that warm water heating failed to change vital capacity (VC). Between thermoneutral water and ventilation levels. hot water there was a significant increase (+3%, The measurement of airway resistance is technically p<0.05) in VC. It was suggested that the increase in difficult during exercise,20 and neither airway diameter ventilation was due to modifications in respiratory nor smooth muscle activation can be measured in muscle functioning (possibly hyperventilation) due to exercising humans; spirometry is therefore used to the increased deep body temperature. Hyperthermia- indicate changes in these values. The most widely used http://bmjopensem.bmj.com/ on September 27, 2021 by guest. Protected Figure 2 Mean (SD) FEV1 (L) data for each condition over the experimental period. Conditions and significant differences as marked (n=9). FEV1, forced expiratory volume in 1s. ; IMM35, 35 C water immersion; IMM40, 40 C water immersion; EXERCISE, clothed exercise for 30 minutes 2 Tipton MJ, et al. BMJ Open Sport Exerc Med 2017;3:e000210. doi:10.1136/bmjsem-2016-000210 BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2016-000210 on 2 June 2017. Downloaded from Open Access Figure 3 Mean (SD) FEV1/FVC (%) data for each condition over the experimental period. Conditions and significant differences as marked (n=9). FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; IMM35, 35 C water immersion; IMM40, 40C water immersion; EXERCISE, clothed exercise for 30 minutes. pulmonary function test for the diagnosis and indica- into components helps identify the areas of dysfunction tion of severity of lung disease is spirometry. This within the respiratory tract. FEF can be measured at provides a measurement of VC, forced vital capacity various percentages of expired gas flow and is repre- (FVC), forced expiratory volume (FEV), FEV in 1 s sented as FEF25 (FEF where 25% of FVC has been (FEV1) or as a forced expiratory flow (FEF). The meas- expired), FEF50 and FEF75. The FEF25–75 per cent copyright. ures of flow indirectly depend on the resistance to air represents the forced mid-expiratory flow over the being expired.21 When healthy, most airway resistance middle 50% of the FVC curve; it reflects airflow in the occurs in fourth-generation to eighth-generation distal airways and is considered to be effort indepen- 23 airways, and therefore FEV1 largely reflects large dent. However it is dependent on the FVC, and airway obstruction22 but gives little information on changes to FVC will necessarily affect the portion of airflow in the smaller airways unless there is significant the flow volume curve examined.22 In clinical measure- obstructive lung disease. Partitioning the FVC curve ments of airway obstruction, especially in the smaller http://bmjopensem.bmj.com/ on September 27, 2021 by guest. Protected Figure 4 Mean (SD) FEF50 (L/s) data for each condition over the experimental period. Conditions and significant differences as marked (n=9). FEF50, forced expiratory flow 50% FVC; IMM35, 35C water immersion; IMM40, 40C water immersion; EXERCISE, clothed exercise for 30 minutes. Tipton MJ, et al. BMJ Open Sport Exerc Med 2017;3:e000210. doi:10.1136/bmjsem-2016-000210 3 BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2016-000210 on 2 June 2017. Downloaded from Open Access Figure 5 Mean (SD) FEF75 (L/s) data for each condition over the experimental period. Conditions and significant differences as marked (n=9). FEF75, forced expiratory flow 75% FVC; IMM35, 35C water immersion; IMM40, 40C water immersion, EXERCISE, clothed exercise for 30 minutes. airways, it would be expected that FEF25–75, FEF25, deformities (kyphosis, scoliosis, pectus excavatum). FEF50 and FEF75 would be reduced, whereas in Participants were also excluded if they were unable to restrictive airway disorders these values may be normal achieve a reliable baseline measure during the respira- or reduced. When investigating decrements in airway tory manoeuvre familiarisation session, or if their function occurring with exercise-induced broncho- baseline spirometry showed values representative of a copyright.