An interventional study of High-Intensity Interval Training and Sprint Interval Training in Exercise Training Adaptation, sponsored by National and Kapodistrian University of Athens. Completed at 1 site in Greece. Open to participants aged 16 Years to 28 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-07.
Sponsored by National and Kapodistrian University of Athens · Not applicable, Interventional, and Basic science
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 (COMB), or a control condition (CON). The study protocol included a six-week detraining period before baseline (PRE) assessments, followed by a six-week training intervention and a subsequent six-week detraining period. Physiological assessments and blood sampling were performed at PRE and immediately after the training intervention (POST) to evaluate training-related changes. Sprint kayak performance over 500 m was assessed at PRE and POST, with additional assessments conducted 15 and 30 days after completion of the subsequent six-week detraining period. The study aimed to examine the effects of different training modalities on physiological responses, circulating molecular markers, and 500-m kayak performance, as well as changes in performance following detraining.
This study used a matched randomized, four-parallel-group interventional design to investigate physiological, molecular, and performance adaptations to different training modalities in national-level kayak athletes. Thirty-two athletes (24 males and 8 females), each with at least four years of kayaking experience, participated in the study.
Before baseline (PRE) assessments, participants completed a six-week detraining period. Participants were subsequently matched according to sex and baseline 500-m performance and allocated by randomization to one of four parallel groups: high-intensity interval training (HIIT), sprint interval training (SIT), combined training (COMB), or control (CON). Each group consisted of eight athletes (six males and two females).
The training intervention lasted six weeks, with three scheduled sessions per week. The HIIT group performed 6 x 30-s intervals at 110% of VO2max with 60-s recovery periods. The SIT group performed 6 x 15-s intervals at approximately 140% of VO2max with 150-s recovery periods. The COMB group performed one HIIT session, one SIT session, and one 45-min continuous training session at 80% of VO2max per week. The CON group performed three 1-h walking sessions per week.
Physiological assessments were performed before (PRE) and immediately after (POST) the training intervention and included maximal oxygen uptake (VO2max), power output associated with maximal oxygen uptake (POVO2max), power output at the second ventilatory threshold (POVT2), power output corresponding to 75% of VO2max, blood lactate concentration, and maximal heart rate.
Blood samples were collected at PRE and POST to assess circulating markers 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).
A 500-m kayak performance test was conducted at PRE and POST. Following completion of the POST assessments, participants completed a subsequent six-week detraining period. Additional 500-m performance assessments were conducted 15 and 30 days after completion of the six-week detraining period to assess changes in 500-m performance following detraining.
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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 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 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 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 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.
Also known as: HIIT
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.
Also known as: SIT
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.
Also known as: COMB
Participants performed three 1-hour walking sessions per week for six weeks and did not participate in the experimental high-intensity training protocols.
Also known as: CON
Change in maximal oxygen uptake (VO₂max)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
500-m kayak performance
Time required to complete a 500-m maximal-effort kayak ergometer performance test, recorded in seconds. Lower values indicate faster performance.
Time frame: Baseline (PRE), immediately after the 6-week intervention (POST), and 15 and 30 days after completion of the 6-week detraining period
Change in power output at VO₂max (POVO₂max)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in power output at the second ventilatory threshold (POVT₂)
Power output at the second ventilatory threshold (POVT₂) was determined 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 submaximal aerobic performance.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in power output at 75% of VO₂max (PO75%VO₂max)
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).
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in blood lactate concentration
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in maximal heart rate (HRmax)
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).
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in circulating interleukin-6 (IL-6)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in circulating vascular endothelial growth factor A (VEGF-A)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in circulating hypoxia-inducible factor-1 alpha (HIF-1α)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Change in total antioxidant capacity (TAC)
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.
Time frame: Baseline (PRE) and immediately after the 6-week intervention (POST)
Plan to share: No — Individual participant data (IPD) will not be shared because participant consent did not include provisions for public or unrestricted sharing of individual-level data.
Ran from Nov 2024 to primary completion in Apr 2025, 5 months.
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