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Postexercise thermal and cardiovascular responses following fast and slow heating exercise protocols
Author(s) -
Kenny Glen P,
Wright Heather E,
Friesen Brian J
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1053.9
Subject(s) - hyperthermia , treadmill , medicine , rectal temperature , heart rate , thermoregulation , mean arterial pressure , cardiology , anesthesia , blood pressure , zoology , biology
Exercise‐induced hyperthermia can result in significant cardiovascular and thermoregulatory disturbances which can persist for a prolonged period. However, it is unclear if this response differs as a function of the time to reach hyperthermia. Therefore, we compared cardiovascular and thermoregulatory responses of subjects rendered hyperthermic by either a slow heating (SH) or fast heating (FH) exercise protocol performed in the heat (40°C). On separate days, 7 subjects either walked (4 mph, 2% grade, SH) or ran (7.5 mph, 2% grade, FH) on a treadmill until rectal temperature (T re ) increased to 39.5°C. Subjects then rested in the upright seated position in thermoneutral conditions (30°C) until T re returned to 38.0°C. Heart rate (HR) and mean arterial pressure (MAP) were assessed continuously. Change in plasma volume (ΔPV) from baseline rest was measured at end of recovery. The time to reach T re of 39.5°C was significantly longer during SH (76.5±6.5 min) compared to FH (35.5±3.3 min, p<0.05). However, the time to reach the T re recovery of 38.0°C was significantly greater during FH compared to SH (82.5±9.2 vs. 56.2±6.5 min, p<0.05). Despite a longer recovery during FH, a similar reduction in MAP (FH:−9.6±1.7 vs. SH: −10.1±3.4 mmHg) was observed at end‐recovery which was paralleled by similar elevations in HR (FH:83±2 vs. SH:87±5 bpm). Further, ΔPV was also similar between conditions (FH: −5.1±1.9 vs. SH: −5.8±2.8%) albeit reduced from end‐exercise values (FH:9.0±1.1% vs. SH:11.8±1.5%,p<0.05). Different exercise‐intensity ramping protocols performed to a similar level of thermal strain influence core temperature recovery time but not the level of cardiovascular strain. Support: Natural Sciences and Research Council of Canada.