Exercise in the Heat Flashcards
Endurance performance in the heat - Galloway and Maughan, (1997)
- 8 males cycled at 70% Vo2max in; 11°C, 21°C and 31°C
- TTE was reduced by 45% at 31°C compared to 11°C
Endurance performance in the heat - Ely et al, (1997)
- Marathon performance decrease with rise in temperature, dependant on ability
Elite: A rise in temperature from 10°C to 25°C resulted in a 3% decline in marathon performance
Recreational: The same temperature increase resulted in an 11% decrease in Marathon performance
Paula Radcliffe - Performance in the heat
- Radcliffe ran 2003 Marathon WR in 10°C
- Performance 1 year later in Syndey Olympics at >24°C was impaired by 8%
Heat leading to catastrophe
- 8 years of Olympics marathon data
- When temperature is <25°C - 79% of Olympic runners complete the marathon
- When temperature in <25°C - just 54% of runners complete the marathon
Strategies to resist against the heat - Kay et al (1999)
Pre-cooling
- Self-paced 30min TT in 31°C with 60% humidity, with/without pre-cooling
- Significantly reduced Tcore at start time in pre-cooling group
- Significantly increased distance covered in TT in pre-cooling group
Strategies to resist against the heat - Arngrimmson et al (2004)
Ice-vest
- 17 runners performed 38 minute warm-up with/without ice-vest, before running 5km in 31°C and 50% humidity
- Lower Tcore with ice vest
- Reduced 5km TT by 13 seconds
Strategies to resist against the heat - Lee et al (2008)
Fluid Ingestion
- Cycled at 66% Vo2max until exhaustion at 35°C and 60% humidity
- 2 groups, 1 had cold group (4°C), other had hot drink (37°C) before and during the trail
- Increased TTE with cold drink
- Reduced RPE and Tcore with cold drink
Strategies against the heat - Siegal et al (2016)
Ice-fluid
- Running at VT until exhaustion in 34°C, 55% humidity
- Cold water (4°C) vs ice-slurry (-1°C)
- Increase TTE in ice-slurry condition
Performance decrement in the heat - CV drift/strain - Galloway and Maughan (1997)
- 31°C group had a significantly higher HR at the same work rate as other groups
- Suggests CV drift = Increase in HR during exercise with little or no increase in intensity
Performance decrement in the heat - CV drift/strain - Wingo et al (1995)
- 9 males cycled at 60% Vo2max in 35°C for 30 mins vs CON
- Increase HR by 12%
- Decrease SV by 16%
- Decrease Vo2max by 19%
- Due to the decrease in SV, HR had to increase but did not do so to the same rate, therefore decreasing Vo2max
CV strain hypothesis - Ely et al (2010)
- Body has to thermoregulate o protect Tcore
- Essential shunting of blood to the peripheries reduces venous return, and therefore decreasing the SV and Q
Perfomance decrement in the heat - preservation of Tcore - Gonzalez-Alonso (1999)
- 7 males cycling at 60% Vo2max until exhaustion
- Started at 3 different core temps; pre-cooling (>36°C), normal (37°C) and hyperthermic (>38°C)
- The increase in Tcore was directly related to the decrease in Q and SV
- Higher HR and shorter TTE in hot trial
- Exhaustion occurred at the same core temp (40.2°C) in all trials
Performance decrement in the heat - preservation of Tcore - Nielson et al (1993)
- Cycled at 60% Vo2max until exhaustion on 10 consecutive days at 40°C
- TTE doubled after 10 days - showing adaptation
- Tcore never went above 40.2°C
- Suggests a ‘critical temperature hypothesis’ - decreasing Tcore will prolonged TTE
Tucker et al (2004) - central fatigue and exercise in the heat
- 10 males performed 20km TT at either 35°C or 15°C
- No difference in Tcore until last 20% of TT
- TT significantly longer in hot conditions
- Despite little increase in Tcore, there was reduced TT, reduced power output and reduced Vastus Lateralis iEMG
- Potentially anticipatory protection against heat (central governor)
Nybo and Nielson, (2001)
- Cycled at 60% Vo2max at either; 18°C for 1 hour or 40°C for 50 mins (had to be stopped due to overheating)
- Followed by 2-min max knee extensor exercise
- VA = 82% in cool conditions
- VA = 54% in hot conditions
