Change in VO_2max and time trial performance in response to high-intensity interval training prescribed using...

Area of Science:

• Exercise Physiology
• Sports Science
• Cardiovascular Health

Background:

• High-intensity interval training (HIIT) is known to enhance maximal oxygen uptake (VO2max) and oxidative capacity.
• However, a significant portion of individuals (20-40%) exhibit minimal or no improvement in VO2max in response to standardized HIIT protocols.
• This variability suggests that a homogeneous approach to HIIT prescription may not be optimal for all individuals.

Purpose of the Study:

• To investigate the effects of prescribing HIIT based on ventilatory threshold (VT) on VO2max and cycling performance.
• To assess individual variability in response to VT-prescribed HIIT.

Main Methods:

• Fourteen active adults completed nine HIIT sessions on a cycle ergometer, with training intensity set at 130% of their VT.
• Each session involved 8-10 intervals of 1-minute duration, separated by 75-second recovery periods.
• VO2max and 5-mile cycling time trial performance were assessed at baseline and post-intervention. A control group of 14 participants did not undergo training.

Main Results:

• HIIT significantly increased VO2max by 6%, cycling performance by 2.5%, and absolute VT by 9 W compared to the control group.
• Despite these group-level improvements, only 57% of participants showed meaningful gains in VO2max and cycling performance.
• Two participants demonstrated no improvement in either VO2max or cycling performance.

Conclusions:

• Prescribing HIIT using VT can lead to significant physiological and performance adaptations.
• A substantial inter-individual variability in response to VT-prescribed HIIT persists.
• Increasing the volume of HIIT may be necessary to elicit optimal training responses in all individuals.