title: Does Short-Duration Heat Exposure at a Matched Cardiovascular Intensity Improve Intermittent-Running Performance in a Cool Environment?
abstract: OBJECTIVE
  To investigate whether a 5-d cycling training block in the heat (35°C) in Australian Rules footballers was superior to exercising at the same relative intensity in cool conditions (15°C) for improving intermittent-running performance in a cool environment (<18°C).
  
  
  METHODS
  Using a parallel-group design, 12 semiprofessional football players performed 5 d of cycling exercise (70% heart-rate reserve [HRR] for 45 min [5 × 50-min sessions in total]) in a hot (HEAT, 35°C ± 1°C, 56% ± 9% RH) or cool environment (COOL, 15°C ± 3°C, 81% ± 10% RH). A 30-15 Intermittent Fitness Test to assess intermittent running performance (VIFT) was conducted in a cool environment (17°C ± 2°C, 58 ± 5% RH) before and twice after (1 and 3 d) the intervention.
  
  
  RESULTS
  There was a likely small increase in VIFTin each group (HEAT, 0.5 ± 0.3 km/h, 1.5 ± 0.8 × smallest worthwhile change [SWC]; COOL, 0.4 ± 0.4 km/h, 1.6 ± 1.2 × SWC) 3 d postintervention, with no difference in change between the groups (0.5% ± 1.9%, 0.4 ± 1.4 × SWC). Cycle power output during the intervention was almost certainly lower in the HEAT group (HEAT 1.8 ± 0.2 W/kg vs COOL 2.5 ± 0.3 W/kg, -21.7 ± 3.2 × SWC, 100/0/0).
  
  
  CONCLUSIONS
  When cardiovascularexercise intensity is matched (ie, 70% HRR) between environmental conditions, there is no additional performance benefit from short-duration moderate-intensity heat exposure (5 × 50 min) for semiprofessional footballers exercising in cool conditions. However, the similar positive adaptations may occur in HEAT with 30% lower mechanical load, which may be of interest for load management during intense training or rehabilitation phases.
authors.forename: Calvin P
authors.initials: CP
authors.lastname: Philp
authors.forename: Martin
authors.initials: M
authors.lastname: Buchheit
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Kitic
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Minson
authors.forename: James W
authors.initials: JW
authors.lastname: Fell
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D056352:Athletes; D054874:Athletic Performance; D003080:Cold Temperature; D005538:Football; D006358:Hot Temperature; D006801:Humans; D008297:Male; D012420:Running / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
keywords: VIFT; football; heat acclimation; plasma volume; relative-intensity exercise