Impact of Pre-cooling in Adolescent Tennis Athletes
Condition: Risk of Heat Stress
MeSH terms: Heat Stress Disorders
Study type: Interventional

Summary: 
      Many tennis tournaments are played outdoors in hot and humid conditions, which poses a
      significant challenge particularly for children athletes. The purpose of this investigation
      is to examine if a precooling method can reduce thermal strain and consequently improve the
      performance of adolescent tennis athletes while exercising in hot conditions.
    

Detailed description: 
      Matches were conducted on hard-court surfaces separated by 24h (n=4 pairs) or 144h (n=1pair)
      between 9am and 6pm and were played in winning two sets. Participants were paired according
      to their level of play and competed against the same component at the same time of the day in
      both matches.

      Three hours before the start of their scheduled match, each player ingested a telemetric pill
      in order to estimate the visceral temperature. Upon arrival, all participants provided a
      urine sample for assessment of urine specific gravity as an indicator of their hydration
      status and they emptied their bladders before were weighed. They were weighed twice, at
      baseline and at the end of the match with a precision weight scale (Kern DE 150K2D, KERN &
      SOHN GmbH, Balingen, Germany). During the match the participants consumed water and any other
      sport drink and food ad libitum. The total weight of the players' food and fluids that was
      consumed was measured using a precision weight scale. If participants wished to urinate
      during the match, they were asked to use a urine cup and their urine was weighed.

      One hour before the match, the precooling group was wearing a Cooling Cap (WElkins Sideline
      Cooling System, SCS) for 45 minutes. On removal from a -20oC freezer, the cap surface was
      10.7±2.5oC. After 45 minutes, participants removed the cap and they performed a 5 minutes
      standardized warm-up (running around the court and running exercises from baseline to net and
      back to baseline) and 10 min tennis specific warm up (rallies and serves) on court. Each
      participant, before the warm-up, was outfitted with a heart rate chest strap and iBUTTON
      sensors at four sites of the body (chest, upper arm, thigh and calf).

      The scoring and timing characteristics of the matches complied with 2016 ITF rules. Three new
      balls were used for each match with the players retrieving balls between points. Matches were
      filmed from one end of the court, using a digital video camera (Sony DCR-VX2000E PAL, Japan).
      Participants were performed on perceptual measurements at baseline, after each set, and at
      the end of the match.

      Thermoregulatory, cardiovascular and perceptual responses were recorded with standardized
      techniques: 1) visceral temperature using telemetric pill (BodyCap, Caen, France) was
      continuously recorded throughout the match; 2) skin temperature using iBUTTON sensors (type
      DS1921 H, Maxim/Dallas Semiconductor Corp., USA) on chest, upper arm, thigh and calf was
      recorded continuously; 3) heart rate (HR) variability data were sampled through short-range
      telemetry at 1,000 Hz with a Polar RS800CX (Polar Electro , Kempele, Finland). The heart rate
      monitor signal will be transferred to the Polar Precision Performance Software (release 3.00;
      Polar Electro Oy); 4) thermal comfort (scale 1-5), thermal sensation (scale 1-10) and rating
      of perceived exertion using standardized questionnaires were recorded at baseline, after each
      set, and at the end of the match.

      Hydration status was recorded with urine specific gravity. All the collected urine samples
      will be analyzed using a refractrometer (Atago, Tokyo, Japan) for the determination of urine
      specific gravity. Euhydration will be defined as urine specific gravity <1.02 according to
      internationally accepted standards.

      A digital video camera (Sony DCR-VX2000E PAL, Japan) was used to record the match - play
      characteristics. The footage was used to conduct the retrospective notational analysis. The
      quantitative performance indices that assessed had been: games and points won in each set and
      normalized to the number of games and points that record in each set respectively. Also
      unforced errors, first and second serve accuracy, aces, shots per rally and direction changes
      in each point calculated. Point's duration, between point-duration as well the effective
      point time calculated. The effective point time starting with the ball toss of the serve and
      ending when the ball passed the player or bounced twice on court. In case of double fault,
      starting time recorded from the beginning of the second serve.

      Environmental data including air temperature, relative humidity, and wind speed were measured
      continuously using a portable weather station (Kestrel 5500FW Fire Weather Meter Pro, USA).
      The weather station was placed 1 meter above the ground according to the manufacturer's
      guidelines.
    

Intervention name(s): Thermal stress and performance using a pre-cooling protocol; Thermal stress and performance without a pre-cooling protocol
Intervention type(s): Behavioral; Biological
Intervention description(s): One hour before a tennis match, participants were wearing a Cooling Cap (WElkins Sideline Cooling System, SCS) for 45 minutes. During the tennis match the following variables were monitored: heart rate, core temperature, skin temperature, thermal sensation and comfort, rating of perceived exertion and hydration status.; During a tennis match the following variables were monitored: heart rate, core temperature, skin temperature, thermal sensation and comfort, rating of perceived exertion and hydration status.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Participant)
Primary purpose: Prevention
Keywords: heat stress; heat strain; performance; children; exercise; thermal