Shorter High-Intensity Cycling Intervals Reduce Performance and Perceived Fatigability at Work-Matched but Not Task...

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Work-to-rest ratios in high-intensity interval training (HIIT) significantly impact physiological responses and exercise tolerance.
• Understanding how different work and rest durations affect neuromuscular, perceptual, and cardiorespiratory systems is crucial for optimizing training protocols.

Purpose of the Study:

• To compare neuromuscular, perceptual, and cardiorespiratory responses to work-to-rest ratio-matched HIIT protocols with varying work and rest interval durations.
• To determine the influence of different HIIT interval structures on exercise tolerance and performance fatigability.

Main Methods:

• Twelve healthy participants completed three randomized cycling protocols to task failure at 90% peak power output: 3-min work/3-min rest HIIT (HIIT 3min), 1-min work/1-min rest HIIT (HIIT 1min), and constant load (CL).
• Neuromuscular function was assessed using the interpolated twitch technique during maximal voluntary contractions and femoral nerve stimulation.
• Perceptual responses (effort, pain, dyspnea) and cardiorespiratory measures were recorded throughout the protocols.

Main Results:

• HIIT 1min protocol allowed for significantly greater total work completed compared to HIIT 3min and CL.
• Neuromuscular fatigue, indicated by reduced maximal voluntary contraction and twitch force, was less pronounced in HIIT 1min compared to HIIT 3min and CL.
• Perceived effort, pain, and dyspnea were lower in both HIIT protocols compared to CL, with HIIT 1min showing less voluntary activation decline at task failure.

Conclusions:

• Shorter work intervals within a matched work-to-rest ratio (HIIT 1min) enhance exercise tolerance by mitigating physiological and perceptual stress.
• These findings suggest that manipulating work interval duration, while keeping intensity and overall work-to-rest ratio constant, can significantly influence performance and fatigue development during HIIT.