Physiological and Molecular Adaptations to Different Training Modalities in National-level Kayak Athletes

November 6, 2026 updated by: APOSTOLOS PAPANDREOU, National and Kapodistrian University of Athens

Physiological and Molecular Responses to Different Intensities of High-Intensity Interval Training and Continuous Training in National-Level Kayak Athletes

This interventional study evaluated physiological, molecular, and performance adaptations to different high-intensity training modalities in national-level kayak athletes. Thirty-two athletes were allocated to four parallel groups: high-intensity interval training (HIIT), sprint interval training (SIT), combined training This interventional study investigated physiological, systemic biomarker, and performance responses to different training modalities in national-level flatwater kayak athletes. Thirty-two athletes (24 males and 8 females) were randomly allocated within sex strata to four parallel groups: high-intensity interval training (HIIT), sprint interval training (SIT), combined training (COMB), and control (CON), with eight participants per group (six males and two females).

The study included an initial six-week detraining period, baseline (PRE) assessments, a six-week training intervention, and post-intervention (POST) assessments. POST venous blood samples were collected 48-72 hours after the final training session, following a recovery period. Physiological and performance assessments were conducted during the POST testing period.

Following the intervention, participants underwent a further six-week detraining period. Kayak performance over 500 m was assessed at PRE and POST and reassessed 15 and 30 days after the beginning of the post-intervention detraining period.

The study aimed to compare the effects of different training modalities on physiological responses, circulating systemic biomarkers, and 500-m kayak performance, as well as performance changes during detraining.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This study employed a sex-stratified randomized, four-parallel-group interventional design to investigate physiological, systemic biomarker, and performance responses to different training modalities in national-level flatwater kayak athletes.

Thirty-two athletes (24 males and 8 females), each with at least four years of kayaking experience, participated in the study. Participants were initially stratified according to sex and subsequently randomly allocated by drawing lots to four parallel groups: high-intensity interval training (HIIT), sprint interval training (SIT), combined training (COMB), and control (CON). Each group comprised eight athletes (six males and two females). Baseline 500-m performance, maximal oxygen uptake (VO2max), body mass, and training experience were not used as matching or allocation criteria. Participants were not reassigned after randomization to achieve baseline equivalence.

Before baseline (PRE) assessments, participants completed a six-week detraining period. PRE assessments were conducted between December 20 and 23, 2024. The six-week training intervention commenced on December 26, 2024, with three scheduled sessions per week.

The HIIT group performed six 30-second intervals at a power output corresponding to 110% of the power output associated with VO2max, separated by 60-second recovery periods. The SIT group performed six 15-second intervals at approximately 140% of the power output associated with VO2max, separated by 150-second recovery periods. The COMB group completed one HIIT session, one SIT session, and one 45-minute continuous training session at 80% of the power output associated with VO2max per week. The CON group performed three 60-minute walking sessions per week.

Physiological assessments were performed before (PRE) and after (POST) the intervention and included maximal oxygen uptake (VO2max), power output associated with maximal oxygen uptake (POVO2max), power output at the second ventilatory threshold (POVT2), blood lactate concentration, and maximal heart rate (HRmax). Additional physiological outcomes, including power output corresponding to 75% of VO2max, were assessed as specified in the original study protocol.

Venous blood samples were collected at PRE and POST to assess circulating biomarkers related to inflammatory, angiogenic, hypoxia-related, and antioxidant responses, including interleukin-6 (IL-6), vascular endothelial growth factor A (VEGF-A), hypoxia-inducible factor-1 alpha (HIF-1 alpha), and total antioxidant capacity (TAC).

Importantly, POST venous blood sampling was performed 48-72 hours after the final training session of the six-week intervention, following a recovery period without additional training sessions. The POST physiological assessments were conducted subsequently, during the post-intervention testing period. Therefore, the POST blood samples were not collected immediately after the final exercise session.

A maximal-effort 500-m kayak ergometer performance test was conducted at PRE and POST. Following completion of the intervention and POST assessments, participants underwent a further six-week detraining period. Additional 500-m performance assessments were conducted 15 and 30 days after the beginning of this subsequent detraining period to evaluate the retention of training-induced performance adaptations.

The original intervention involved all 32 athletes. A subsequent secondary analysis restricted to the 24 male athletes (six per group) examined circulating systemic biomarker responses and their associations with physiological adaptations to the different training modalities.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
32

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Greece
    • Attica
      • Athens, Attica, Greece, 17237
        • National and Kapodistrian University of Athens

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

16 years to 28 years (Child, Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • National-level flatwater kayak athlete.
  • At least 4 years of systematic kayak training experience.
  • Active participation in kayak training and competition.
  • Able to complete the prescribed training interventions and physiological and performance testing procedures.

Exclusion Criteria:

  • Injury or illness that prevented participation in the training intervention or testing procedures.
  • Inability to complete the prescribed intervention or required study assessments.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: High-Intensity Interval Training (HIIT)

Participants performed high-intensity interval training three times per week for six weeks. Each session included 6 × 30-s intervals at 110% of VO₂max with 60-s passive recovery periods.
Behavioral: High-Intensity Interval Training

Participants performed high-intensity interval training three times per week for six weeks. Each training session consisted of 6 × 30-second intervals at 110% of VO₂max, with 60-second recovery periods between intervals.

Other Names:
  • HIIT
Experimental: Sprint Interval Training (SIT)

Participants performed sprint interval training three times per week for six weeks. Each session included 6 × 15-s intervals at approximately 140% of VO₂max with 150-s passive recovery periods.
Behavioral: Sprint Interval Training

Participants performed sprint interval training three times per week for six weeks. Each training session consisted of 6 × 15-second intervals at approximately 140% of VO₂max, with 150-second recovery periods between intervals.

Other Names:
  • SIT
Experimental: Combined Training (COMB)

Participants performed combined training for six weeks, consisting of one HIIT session, one SIT session, and one 45-min continuous training session at 80% of VO₂max per week.
Behavioral: Combined High-Intensity and Continuous Training

Participants performed combined training for six weeks, with three training sessions per week. The weekly program consisted of one high-intensity interval training session (6 × 30-second intervals at 110% of VO₂max with 60-second recovery periods), one sprint interval training session (6 × 15-second intervals at approximately 140% of VO₂max with 150-second recovery periods), and one 45-minute continuous training session at 80% of VO₂max.

Other Names:
  • COMB
Active Comparator: Control (CON)

Participants performed three 1-h walking sessions per week for six weeks and did not participate in the experimental high-intensity training protocols.
Behavioral: Control

Participants performed three 1-hour walking sessions per week for six weeks and did not participate in the experimental high-intensity training protocols.

Other Names:
  • CON

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in maximal oxygen uptake (VO₂max)
Time Frame: Baseline (PRE) and during the post-intervention (POST) assessment period following the 6-week training intervention.

Maximal oxygen uptake (VO₂max) was assessed using an incremental kayak ergometer test before (PRE) and after (POST) the 6-week intervention. VO₂max was used to evaluate changes in aerobic physiological capacity following the different training interventions.
Baseline (PRE) and during the post-intervention (POST) assessment period following the 6-week training intervention.
500-m kayak performance
Time Frame: Baseline (PRE), post-intervention (POST), and 15 and 30 days after the start of the subsequent 6-week detraining period.

Time required to complete a 500-m maximal-effort kayak ergometer performance test, recorded in seconds. Lower values indicate faster performance.
Baseline (PRE), post-intervention (POST), and 15 and 30 days after the start of the subsequent 6-week detraining period.
Change in power output at VO₂max (POVO₂max)
Time Frame: Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.

Power output at VO₂max (POVO₂max) was assessed during the incremental kayak ergometer test before (PRE) and after (POST) the 6-week intervention. The outcome was expressed in watts (W) and used to evaluate changes in maximal aerobic power.
Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.
Change in power output at the second ventilatory threshold (POVT₂)
Time Frame: Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.

Power output at the second ventilatory threshold (POVT₂) was determined during an incremental kayak ergometer test conducted before (PRE) and after (POST) the 6-week training intervention. VT₂ was identified from ventilatory and gas-exchange responses, and the corresponding power output was expressed in watts (W). Changes in POVT₂ were used to evaluate submaximal aerobic adaptations to the different training interventions.
Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.
Change in power output at 75% of VO₂max (PO75%VO₂max)
Time Frame: Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.

Power output corresponding to 75% of VO₂max was determined from the oxygen uptake-power relationship obtained during the incremental kayak ergometer test before (PRE) and after (POST) the 6-week intervention. The outcome was expressed in watts (W).
Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.
Change in blood lactate concentration
Time Frame: Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.

Blood lactate concentration was measured 3 minutes after completion of the incremental kayak ergometer test before (PRE) and after (POST) the 6-week intervention. The outcome was expressed in mmol/L.
Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.
Change in maximal heart rate (HRmax)
Time Frame: Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.

Maximal heart rate (HRmax) was recorded during the incremental kayak ergometer test before (PRE) and after (POST) the 6-week intervention. The outcome was expressed in beats per minute (bpm).
Baseline (PRE) and during the POST testing period, following venous blood sampling performed 48-72 hours after the final training session.
Change in circulating interleukin-6 (IL-6)
Time Frame: Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.

Serum interleukin-6 (IL-6) concentration was assessed from venous blood samples collected before (PRE) and after (POST) the 6-week intervention to evaluate changes in the circulating inflammatory response.
Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.
Change in circulating vascular endothelial growth factor A (VEGF-A)
Time Frame: Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.

Serum vascular endothelial growth factor A (VEGF-A) concentration was assessed from venous blood samples collected before (PRE) and after (POST) the 6-week intervention to evaluate changes in the circulating angiogenic response.
Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.
Change in circulating hypoxia-inducible factor-1 alpha (HIF-1α)
Time Frame: Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.

Serum hypoxia-inducible factor-1 alpha (HIF-1α) concentration was assessed from venous blood samples collected before (PRE) and after (POST) the 6-week intervention to evaluate changes in the circulating hypoxia-related response.
Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.
Change in total antioxidant capacity (TAC)
Time Frame: Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.

Serum total antioxidant capacity (TAC) was assessed from venous blood samples collected before (PRE) and after (POST) the 6-week intervention to evaluate changes in systemic antioxidant capacity.
Baseline (PRE) and 48-72 hours after the final training session (POST), following the 6-week intervention.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
National and Kapodistrian University of Athens

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
November 8, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 23, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
April 23, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 30, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 6, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 7, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 12, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 6, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 3422/Δ5

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared because participant consent did not include provisions for public or unrestricted sharing of individual-level data.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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