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Trial registered on ANZCTR


Registration number
ACTRN12624001349538
Ethics application status
Approved
Date submitted
22/10/2024
Date registered
8/11/2024
Date last updated
8/11/2024
Date data sharing statement initially provided
8/11/2024
Type of registration
Retrospectively registered

Titles & IDs
Public title
The effects of hot-water immersion on force steadiness and motor unit discharge rate variability
Scientific title
The effects of passively increased muscle and core temperature on force steadiness and motor unit discharge rate variability in young healthy adults
Secondary ID [1] 313266 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Impact of temperature on healthy muscle function 335536 0
Condition category
Condition code
Musculoskeletal 332107 332107 0 0
Normal musculoskeletal and cartilage development and function

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Participants attended two water immersion sessions, each lasting 90 minutes, with temperatures set at 36°C and 42°C in a counterbalanced order. A washout period of 7 days was maintained between sessions. Core temperature and thermal sensation were monitored throughout each session. If a participant felt uncomfortable with the heat or their core temperature reached 39.5°C, the session would be ended.

Each immersion session was conducted in a laboratory setting at an ambient temperature of 23°C. Participants wore swimsuits and sat steadily in an inflatable bath during the 90 minutes. They were permitted to drink water ad libitum throughout the session and had an electric fan directed at their upper body to aid with thermal comfort.
Intervention code [1] 329808 0
Lifestyle
Comparator / control treatment
A single session of water immersion at 36ºC up to the waist level for 90 minutes.
Control group
Active

Outcomes
Primary outcome [1] 339695 0
Force steadiness.
Timepoint [1] 339695 0
Force steadiness was measured at three time points: before water immersion at 36°C or 42°C (Pre), immediately after immersion (Post-1), and 15 minutes following the water immersion (Post-2).
Primary outcome [2] 339752 0
Motor unit discharge rate variability.
Timepoint [2] 339752 0
Motor unit discharge rate variability was measured at three time points: before water immersion at 36°C or 42°C (Pre), immediately after immersion (Post-1), and 15 minutes following the water immersion (Post-2).
Secondary outcome [1] 440918 0
Muscle temperature.
Timepoint [1] 440918 0
Immediately before each force steadiness assessment, at Pre, Post-1 and Post-2.
Secondary outcome [2] 441133 0
Core temperature.
Timepoint [2] 441133 0
Immediately before each force steadiness assessment, at Pre, Post-1 and Post-2.

Eligibility
Key inclusion criteria
Healthy adults.
Minimum age
18 Years
Maximum age
39 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Medical conditions contraindicating heat stress, musculoskeletal injury, or pregnancy.

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation is not concealed
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table created by computer software (i.e. computerised sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Statistical methods / analysis
The sample size was based on our earlier studies (PMID: 33487572; PMID: 36610040), which demonstrated that 15 participants were sufficient to detect neuromuscular changes following 90 minutes of hot-water immersion at 42°C. Levene’s and Shapiro-Wilk’s tests were initially used to verify equality of error variances and normality, while Mauchly’s test assessed sphericity, with Greenhouse-Geisser correction applied as needed.

Linear mixed-effects models were fitted using the lmer Test package in R (version 4.0.5, RStudio: 1.4.1717) to analyze the coefficient of variation of torque and motor unit discharge rate (MUDR). The force steadiness model included the coefficient of variation of torque as the dependent variable, with water temperature condition, time points, and contraction intensity as fixed effects. The MUDR variability model additionally included muscle (vastus lateralis vs. vastus medialis) as a fixed effect. For pairwise comparisons, Holm-Bonferroni correction was used when an interaction or main effect was observed.

Core and muscle temperature data were analyzed with a two-way repeated-measures ANOVA (water-immersion condition x time point), followed by Bonferroni post-hoc tests. The significance level was set at a = 0.05.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
10/06/2019
Date of last participant enrolment
Anticipated
Actual
20/11/2019
Date of last data collection
Anticipated
Actual
28/11/2019
Sample size
Target
20
Accrual to date
Final
15
Recruitment in Australia
Recruitment state(s)
QLD

Funding & Sponsors
Funding source category [1] 317764 0
University
Name [1] 317764 0
Queensland University of Technology
Country [1] 317764 0
Australia
Primary sponsor type
University
Name
Queensland University of Technology
Address
Country
Australia
Secondary sponsor category [1] 320085 0
None
Name [1] 320085 0
None
Address [1] 320085 0
Country [1] 320085 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 316376 0
Queensland University of Technology University Human Research Ethics Committee
Ethics committee address [1] 316376 0
https://www.qut.edu.au/research/why-qut/ethics-and-integrity
Ethics committee country [1] 316376 0
Australia
Date submitted for ethics approval [1] 316376 0
08/10/2018
Approval date [1] 316376 0
04/01/2019
Ethics approval number [1] 316376 0
1800000977

Summary
Brief summary
This study aimed to test whether passive increases in muscle and core temperature following a single session of hot-water immersion affect force steadiness and motor unit discharge rate variability. It was hypothesized that increased muscle temperature would impair force steadiness and increase the coefficient of variation in motor discharge rates. Additionally, it was expected that elevated core temperature would exacerbate these changes due to central activation fatigue. To test these hypotheses, the study evaluated force steadiness and motor unit discharge rate variability immediately after a 90-minute hot-water immersion at 42ºC, with elevated muscle and core temperatures, and again 15 minutes later, when muscle temperature remained elevated but core temperature had returned to baseline.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 137698 0
Dr Patrick Rodrigues
Address 137698 0
The University of Waikato. C/-The Mailroom Gate 3A 209 Silverdale Road. Hamilton 3216 - Waikato,
Country 137698 0
New Zealand
Phone 137698 0
+64 210716854
Fax 137698 0
Email 137698 0
[email protected]
Contact person for public queries
Name 137699 0
Patrick Rodrigues
Address 137699 0
The University of Waikato. C/-The Mailroom Gate 3A 209 Silverdale Road. Hamilton 3216 - Waikato,
Country 137699 0
New Zealand
Phone 137699 0
+64 210716854
Fax 137699 0
Email 137699 0
[email protected]
Contact person for scientific queries
Name 137700 0
Patrick Rodrigues
Address 137700 0
The University of Waikato. C/-The Mailroom Gate 3A 209 Silverdale Road. Hamilton 3216 - Waikato,
Country 137700 0
New Zealand
Phone 137700 0
+64 210716854
Fax 137700 0
Email 137700 0
[email protected]

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment


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.