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Trial registered on ANZCTR


Registration number
ACTRN12622000732785
Ethics application status
Approved
Date submitted
10/05/2022
Date registered
23/05/2022
Date last updated
23/05/2022
Date data sharing statement initially provided
23/05/2022
Date results information initially provided
23/05/2022
Type of registration
Retrospectively registered

Titles & IDs
Public title
Practical application of a mixed active and passive heat acclimation protocol in elite male Olympic team sport athletes
Scientific title
Practical application of a mixed active and passive heat acclimation protocol in elite male Olympic team sport athletes
Secondary ID [1] 307079 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Heat acclimation 326240 0
Athletic Performance 326241 0
Condition category
Condition code
Physical Medicine / Rehabilitation 323540 323540 0 0
Other physical medicine / rehabilitation

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Brief Name
The intervention examined the physiological, perceptual, and performance effects of 10-days of mixed active and passive heat acclimation incorporated into two weeks of normal rugby sevens training.

Why
Rugby sevens is often played in hot environmental conditions, and recent research has demonstrated the regular occurrence of high Tc (>39 °C) during international rugby sevens in hot/humid conditions; thus, the inclusion of heat acclimation (HA) when preparing for international rugby sevens tournaments in hot conditions is well-indicated. Consideration of the multiple factors influencing (HA) induction and retention, along with practical considerations for integration within an elite training schedule, creates complex questions regarding the optimal design of heat acclimation protocols.

What
Thermoregulatory, cardiovascular, and perceptual responses to heat stress were assessed using a specifically designed heat response test (HRT), intended to replicate the fixed and maximal intensity demands of a rugby sevens warm up and game. In total, four HRT were performed: Pre-HA (before the commencement of HA); Mid-HA (after five days of HA); Post-HA (after 10 days of HA); Decay (16 days after the end of HA). All HRTs and active HA sessions were performed in an environmental chamber maintained at 35 °C, 80% relative humidity (RH), replicating a possible scenario at the Tokyo 2020 Olympic Games. Participants refrained from strenuous exercise in the 24-hr before each HRT, and were instructed to arrive to the HRT in a euhydrated state (not thirsty). All HRT’s were performed at the same time of day (mornings) to account for circadian rhythms. During the HA protocol, all participants undertook a mixture of active (exercise) and passive (hot water immersion; HWI) heat exposures (see below for details). Participants were asked to undertake permissive dehydration (i.e. refrain from drinking if possible) during the HA sessions, as this has previously been shown to enhance responses to HA. During the entire 10-day acclimation process, the total heat exposure for each participant was 7 h 45 min.
Physiological and perceptual measures (as described below) were recorded during seated rest, after each warm-up stage, and after every third interval of the intermittent sprint section.
All participants undertook two active HA sessions per week (four active heat sessions in total), with these sessions being performed within 15 minutes of an on-field training session. The first session (HA1) consisted of ten 2-min intervals performed on a cycle ergometer separated by 2-min rest. During each cycling interval, participants were instructed to rapidly elevate and maintain their heart rate to 85% of their measured maximum. Mean 2-min power output was recorded by a researcher. The second session (HA2) consisted of 10-min fixed intensity cycling (5-min at 2.0 W·kg-1; 5-min at 3.0 W·kg-1); six 500 m rowing intervals (Concept 2 Inc., Morrinsville, VT), at a target pace of 1-min 50-s per 500 m, separated by 2-min rest; followed by a 10-min cycling interval where participants were instructed to keep their heart rate at 85% of their measured maximum, with mean power output being recorded.
All participants undertook four passive HWI sessions (two per week). HWI1 was performed without any prior exercise, as this coincided with a scheduled mid-week non-training day, while HWI2 was performed within 15 min of an on-field training session. All HWI were undertaken in an upright tub for 40 min in 40 °C water. Participants were instructed to stand, immersed to the top of the chest (including arms) for the first 25 min of each exposure, after which time they could elevate to the mammillary line, and bring their arms out of the water.
During all HRT’s, Tc was measured using a rectal thermistor (U thermistor, Grant Instruments Ltd., Cambridge, United Kingdom), self-inserted to a depth of 10 cm beyond the anal sphincter. Tc was recorded at 1-min intervals on a portable data logger (2020 series data logger, Grant Instruments Ltd., Cambridge, United Kingdom) and averaged over each measurement period. Heart rate (HR; Polar H10, Polar Electro Oy, Kempele, Finland) was monitored throughout each HRT as well as during the active HA sessions to prescribe exercise intensity. To estimate sweat loss, towel-dried, nude body mass (NBM) was recorded to 0.1 kg using digital scales (Tanita HD-351, Tanita Health Equipment H.K. Limited) before and immediately after each HRT and each HA session, this value was adjusted for a standardised amount of ingested liquid during the HRT (640 mL).
Rating of perceived exertion (RPE: 6-20 scale), thermal sensation (1-13 point scale), thermal comfort (1-10-point scale), and thirst sensation (Thirst: 1-9 point scale) were collected at the same time points described above. Additionally, RPE, thermal sensation and thermal comfort were collected at the end of each HA session (RPE during active sessions only).

Who Provided
All HRT and HA sessions were undertaken by trained physiologists and strength and conditioning practitioners

How
The intervention was face-to-face, and provided in groups

Where
The intervention was undertaken at the University of Waikato Adams Centre for High Performance, Mount Maunganui, New Zealand. The intervention utilized the environmental chamber and hot water immersion facilities at the centre.

When and How Much
In total, four HRT were performed: Pre-HA (before the commencement of HA); Mid-HA (after five days of HA); Post-HA (after 10 days of HA); Decay (16 days after the end of HA).
All participants undertook two active HA sessions per week and four passive HWI sessions (two per week). During the entire 10-day acclimation process, the total heat exposure for each participant was 7 h 45 min.

Tailoring
The intervention was not planned to be personalised or adapted.

Modifications
The intervention was not modified or adapted.

How Well
The intervention was 100% adhered to and delivered as planned. Attendance records
were used to monitor adherence to the intervention.
Intervention code [1] 323533 0
Treatment: Other
Comparator / control treatment
No control group
Control group
Uncontrolled

Outcomes
Primary outcome [1] 331295 0
Core temperature; measured using a rectal thermistor (U thermistor, Grant Instruments Ltd., Cambridge, United Kingdom), self-inserted to a depth of 10 cm beyond the anal sphincter. Tc was recorded at 1-min intervals on a portable data logger (2020 series data logger, Grant Instruments Ltd., Cambridge, United Kingdom) and averaged over each measurement period.
Timepoint [1] 331295 0
Resting, submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [1] 409457 0
Heart rate: monitored using a chest strap (Polar H10, Polar Electro Oy, Kempele, Finland)
Timepoint [1] 409457 0
Resting, submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [2] 409459 0
Thermal sensation: 1-13 point scale; (Gagge et al., 1967)
Timepoint [2] 409459 0
Resting, submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [3] 409764 0
Thermal comfort: 1-10-point scale; (Gagge et al., 1967)
Timepoint [3] 409764 0
Resting, submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [4] 409765 0
Thirst sensation: 1-9 point scale; (Riebe et al., 1997)
Timepoint [4] 409765 0
Resting, submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [5] 409766 0
Rating of Perceived Exertion: 6-20 scale, (Borg, 1970)
Timepoint [5] 409766 0
Submaximal exercise, maximal exercise during each of the four heat response tests
Secondary outcome [6] 409767 0
Peak and Mean Power output: As assessed using the output from a calibrated cycle ergometer (WattBike Ltd, Nottingham, UK)
Timepoint [6] 409767 0
Submaximal exercise, maximal exercise during each of the four heat response tests

Eligibility
Key inclusion criteria
Participants were eligible if they were current members of the New Zealand men's sevens team
Minimum age
18 Years
Maximum age
No limit
Sex
Males
Can healthy volunteers participate?
Yes
Key exclusion criteria
Declining to participate after reading the participant information sheet

Study design
Purpose of the study
Treatment
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Who is / are masked / blinded?



Intervention assignment
Other design features
Phase
Not Applicable
Type of endpoint/s
Statistical methods / analysis

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
4/09/2020
Date of last participant enrolment
Anticipated
Actual
7/09/2020
Date of last data collection
Anticipated
Actual
16/11/2020
Sample size
Target
12
Accrual to date
Final
12
Recruitment outside Australia
Country [1] 24755 0
New Zealand
State/province [1] 24755 0
Bay of Plenty

Funding & Sponsors
Funding source category [1] 311389 0
University
Name [1] 311389 0
University of Waikato
Country [1] 311389 0
New Zealand
Primary sponsor type
University
Name
University of Waikato
Address
Adams Centre for High Performance
52 Miro Street
Mount Maunganui 3116
NZ
Country
New Zealand
Secondary sponsor category [1] 312779 0
None
Name [1] 312779 0
Address [1] 312779 0
Country [1] 312779 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 310872 0
University of Waikato Human Research Ethics Committee
Ethics committee address [1] 310872 0
The University of Waikato
Private Bag 3105
Gate 1, Knighton Road
Hamilton, 3240
New Zealand
Ethics committee country [1] 310872 0
New Zealand
Date submitted for ethics approval [1] 310872 0
31/08/2018
Approval date [1] 310872 0
31/10/2018
Ethics approval number [1] 310872 0
UoW HREC(Health)2018#64

Summary
Brief summary
The purpose of the current study was to investigate the effectiveness of 10-days of mixed-methods HA, integrated within an elite rugby sevens teams training program. Furthermore, it was investigated whether any resulting physiological, perceptual and performance changes could be retained after 16 days of normal training, without any further heat stimulus.
It was hypothesised that 10-days of a mixed active and passive HA protocol would confer physiological, perceptual, and performance benefits that would be well-retained after 16 days of normal training, without any further heat stimulus.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 119174 0
Mr Stephen Fenemor
Address 119174 0
University of Waikato Adams Centre for High Performance
52 Miro Street,
Mount Maunganui, 3116
New Zealand
Country 119174 0
New Zealand
Phone 119174 0
+64 27 6970210
Fax 119174 0
Email 119174 0
sfenemor@waikato.ac.nz
Contact person for public queries
Name 119175 0
Mr Stephen Fenemor
Address 119175 0
University of Waikato Adams Centre for High Performance
52 Miro Street,
Mount Maunganui, 3116
New Zealand
Country 119175 0
New Zealand
Phone 119175 0
+64 27 6970210
Fax 119175 0
Email 119175 0
sfenemor@waikato.ac.nz
Contact person for scientific queries
Name 119176 0
Mr Stephen Fenemor
Address 119176 0
University of Waikato Adams Centre for High Performance
52 Miro Street,
Mount Maunganui, 3116
New Zealand
Country 119176 0
New Zealand
Phone 119176 0
+64 27 6970210
Fax 119176 0
Email 119176 0
sfenemor@waikato.ac.nz

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
The data sharing agreement with the national rugby union restricts access at this level


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.