european college of sport science

PP-PH02 Physiology 2
Hot conditions increased significantly HR (+9 ±5 bpm) and Tskin (+5 ±1°C) independently of the simulated altitude (both P < 0.001),
whereas altitude exposure reduced SpO2 independently of the environmental temperature (96 ±1 vs. 88 ±4% in sea level and hypoxic
conditions, P < 0.001). [La] values failed to be significantly different within conditions (5.6 ±3.4, 8.7 ±2.6, 7.9 ±6.2 and 10.0 ±5.4 mmol.L-1
in CON, HYP, HOT and H+H, respectively). There was no significant interaction effect between temperature and altitude on HR, Tskin,
SpO2 and [La].
However, our data displayed a significant (P = 0.011) interaction effect on time to exhaustion. This interaction was due to a slightly reduced
effect of either a hot (-34.6 ±14.8% from CON to HOT vs. -25.6 ±19.9% from HYP to H+H) or an altitude (-35.7 ±14.5% from CON to
HYP vs. -26.0 ±19.7% from HOT to H+H) exposure when the other stressor is already present. That suggests that some limiting factors for
performance are common to both a hot and hypoxic environment. In line with this, subjects stopped exercising at equivalent Tcore (38.5
±0.6, 38.2 ±0.6, 38.4 ±0.7 and 38.4 ±0.5°C) and RPE (18.7 ±1.7, 19.3 ±1.0, 19.2 ±1.3 and 19.3 ±0.9) in CON, HYP, HOT and H+H.
Conclusion
There is no cumulative effect of combining hot and hypoxic environment on cardiovascular, metabolic or perceived strains despite exercise
performance being reduced.
HYPERTHERMIA INDUCES OXIDATIVE STRESS IN RESTING BUT NOT IN EXERCISING HUMANS
LAITANO, O., KALSI, K.K., POOK, M., TRANGMAR, S., OLIVEIRA, A.R., GONZÁLEZ-ALONSO, J.
BRUNEL UNIVERSITY, UK. UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL, BRAZIL.
Hyperthermia imposes a severe stress to multiple regulatory systems including the redox system which is important for maintaining
cellular homeostasis in resting and exercising humans. Glutathione (GSH) protects cells against oxidation by providing a substrate for
glutathione peroxidase. GSH removes hydrogen ions and organic peroxides resulting in the formation of oxidized glutathione (GSSG).
Therefore, the GSH/GSSG ratio is a sensitive marker of oxidative stress. The aim of this study was to determine the effects of isolated
hyperthermia on oxidative stress in resting and exercising humans. We hypothesized that isolated hyperthermia would increase oxidative
stress as indicated by alterations in GSH metabolism reflecting a decrease in GSH/GSSG ratio ([GSH-GSSG]/[GSSG]). Eight healthy
males took part in this study. Participants wore a water-perfused suit and performed a 6 min one-legged knee extensor exercise at 50%
of their predetermined maximal peak power output both under control and hyperthermic conditions while maintaining euhydration by
ingesting1.3 ± 0.3 L of water. Following the control trial and a 15 min resting period, hot water (~ 48°C) was perfused through the suit for
~75 min in order to increase rectal temperature from 37.0 ± 0.3 to 38.3 ± 0.4 ºC and skin temperature from 33.1 ± 1.6 to 38.7 ± 0.9ºC.
Blood samples were withdrawn before and at the fifth minute during both exercise bouts for determination of GSH and GSSG concentration
by spectrophotometry assay. At rest, hyperthermia did not alter GSH (620 ± 289 vs 693 ± 379 µM, p= 0.093), but increased GSSG (6 ±
4 vs 12 ± 8 µM, p = 0.012), thereby leading to a significant reduction in the GSH/GSSG ratio (127 ± 84 vs 64 ± 51 µM, p= 0.017). This indicates
an independent hyperthermia-induced oxidative stress. Conversely, during exercise hyperthermia increased both GSH (569 ± 313
vs 821 ± 440 µM, p = 0.036) and GSSG (6 ± 3 vs 16 ± 17 µM, p = 0.012). Consequently, GSH/GSSG ratio did not change (108 ± 71 vs 88 ±
67, p = 0.208). In conclusion, these results in humans demonstrate that hyperthermia induces oxidative stress at rest but not during
exercise because a parallel increase in antioxidant defense offsets hyperthermia-induced oxidative stress.
Supported by the Gatorade Sports Science Institute & Brazil’s Ministry of Education
EFFECT OF WORKING IN HOT ENVIRONMENT ON HEALTH AND PHYSICAL ABILITIES: AN OIL AND GAS INDUSTRY
STUDY
RACINAIS, S., GIRARD, O., WALSH, A., KNEZ, W., GAOUA, N., GRANTHAM, J.
ASPETAR
Purpose: To investigate the alterations in physical work capacity occurring in the summer of a Middle Eastern country (Qatar – outside
temperature between 40 and 50ºC).
Methods: A group of 40 workers (oil and gas industry) with no previous experience of working in a Qatari summer volunteered to participate
in a one-year follow-up project.
- Blood pressure and arterial oxygen saturation were obtained during the pre-experimental screening (April, before their first summer) as
well as before (6 a.m.) and after (4 p.m.) work in the summer (August) and the following winter (January). Handgrip force was measured
at the same time.
- Normalised physical activity (tri-axial accelerometer) and core temperature (ingestible pill) were recorded during the same working day.
Results: Blood pressure recorded before work decreased (P < 0.001) from April to August (from 136 ±13 and 84 ±11 to 125 ±11 and 77 ±9
mmHg for systolic and diastolic, respectively) but returned (P < 0.05) close to baseline values in January (130 ±16 and 80 ±11). Oxygen
saturation decreased also (P < 0.01) from pre-screening (98.5 ±1%) to the summer (98.0 ±1%) and increased (P < 0.01) the following winter
(98.5 ±1%). Both blood pressure and oxygen saturation were reduced (P &#8804; 0.05) following the day of work but without interaction
with the period of the year. Maximal handgrip force was significantly lower (P < 0.005) in August (38 ±7 kg) than in January (40 ±8 kg)
independently of time-of-day.
Data at work. The normalised physical activity (acceleration) during the working hours was significantly (P < 0.02) lower in the summer
(0.10 ±0.04 g) as compared to the winter (0.11 ±0.03 g). Average core temperature during work was significantly (P < 0.005) higher in
August (37.4 ±0.2ºC) than in January (37.2 ±0.2ºC). However, no workers became hyperthermic as the highest observed value during the
continuous recording was 38.3ºC.
Discussion: The Company in which this survey was performed applies safety rules based on heat index (HI). The work/rest period (minutes)
were reduced to 30/10 for a HI of 39-49, 20/10 for a HI of 50-53, and work stopped for a HI > 54. The summer data presented here
were obtained on days with the highest HI (up to 53). Our data showed a reduced activity during the summer as a consequence of both
these safety rules and the self-pacing of the worker. However, despite this reduced activity, central temperatures were higher in the
summer month and workers presented with symptoms consistent with chronic fatigue (reduced blood pressure and saturation) associated
with reduced maximal voluntary strength capacity.
Conclusion: None of these alterations were dependent of being tested before or after work suggesting that there were not linked to acute
fatigue due to the day of work but rather to the presence of chronic alterations persisting during the summer months.
254 14 TH
ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE