Document Type

Peer-Reviewed Article

Publication Date



Athletic Training


Heat exposure and hypohydration induce physiological and psychological strain during exercise; however, it is unknown if the separate effects of heat exposure and hypohydration are synergistic when co-occurring during loaded exercise. This study compared separate and combined effects of heat exposure and hypohydration on physiological strain, mood state, and visual vigilance during loaded exercise. Twelve males (mean±SD; age, 20±2 years; body mass, 74.0±8.2 kg; maximal oxygen uptake, 57.0±6.0 mLkg-1min-1) completed 4 trials under the following conditions: euhydrated temperate (EUT), hypohydrated temperate (HYT), euhydrated hot (EUH), and hypohydrated hot (HYH). Exercise was 90 min of treadmill walking (∼50% VO2 max, 5% grade) while carrying a 45 lb rucksack. Profile of Mood States and the Scanning Visual Vigilance Test were completed pre and post exercise. The separate effects of heat exposure (EUH) and hypohydration (HYT) on post-exercise Tre were similar (38.25±0.63°C vs. 38.22±0.29°C, respectively, p>0.05), while in combination (HYH), post-exercise Tre was far greater (39.32±0.43°C). Increase in Tre per 1% body mass loss (BML) for HYH (vs. EUH) was greater than HYT (vs. EUT) (0.32°C vs. 0.04°C, respectively, p=0.02); HR increase per 1% BML for HYH (vs. EUH) was 7 bpm compared to HYT (vs. EUT) at 3 bpm (p=0.30). HYH induced greater mood disturbance (post-pre exercise) (35±21 units) compared to other conditions (EUT=3±9 units; HYT=3±16 units; EUH=16±26 units; p0.05). Independently, heat exposure and hypohydration induced similar physiological strain during loaded exercise; when combined, heat exposure with hypohydration, synergistically exacerbated physiological strain and mood disturbance.


This research was conducted in the Human Performance Laboratory, Department of Kinesiology at the University of Connecticut, Storrs, CT.

Version posted is the authors' accepted manuscript.






Journal of Strength and Conditioning Research