Physiological responses to incremental exercise in the heat following internal and external precooling

C. A. James*, A. J. Richardson, P. W. Watt, O. R. Gibson, N. S. Maxwell

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

34 Citations (Scopus)


Twelve males completed three incremental, discontinuous treadmill tests in the heat [31.9(1.0)°C, 61.9(8.9)%] to determine speed at two fixed blood lactate concentrations (2 and 3.5mmol/L), running economy (RE), and maximum oxygen uptake ( V ˙ O 2 m a x ). Trials involved 20min of either internal cooling (ICE, 7.5g/kg ice slurry ingestion) or mixed-methods external cooling (EXT, cold towels, forearm immersion, ice vest, and cooling shorts), alongside no intervention (CON). Following precooling, participants ran 0.3km/h faster at 2mmol/L and 0.2km/h faster at 3.5mmol/L (P=0.04, partial η2=0.27). Statistical differences were observed vs CON for ICE (P=0.03, d=0.15), but not EXT (P=0.12, d=0.15). There was no effect of cooling on RE (P=0.81, partial η2=0.02), nor on V ˙ O 2 m a x (P=0.69, partial η2=0.04). An effect for cooling on physiological strain index was observed (P<0.01, partial η2=0.41), with differences vs CON for EXT (P=0.02, d=0.36), but not ICE (P=0.06, d=0.36). Precooling reduced thermal sensation (P<0.01, partial η2=0.66) in both cooling groups (P<0.01). Results indicate ICE and EXT provide similar physiological responses for exercise up to 30min duration in the heat. Differing thermoregulatory responses are suggestive of specific event characteristics determining the choice of cooling. Precooling appears to reduce blood lactate accumulation and reduce thermoregulatory and perceptual strain during incremental exercise.

Original languageEnglish
Pages (from-to)190-199
Number of pages10
JournalScandinavian Journal of Medicine and Science in Sports
Issue numberS1
Early online date6 May 2015
Publication statusPublished - Jun 2015

Scopus Subject Areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

User-Defined Keywords

  • Endurance
  • External cooling
  • Ice slurry
  • Lactate threshold
  • Precooling
  • Thermoregulation


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