Prior Upper Body Exercise Impairs 4-km Cycling Time-Trial Performance Without Altering Neuromuscular Function.

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Understanding the impact of preceding exhaustive exercise on subsequent endurance performance is vital for training and competition strategies.
• Previous upper body exercise may influence lower body performance through central or peripheral fatigue mechanisms.
• Limited research exists on the specific effects of arm-crank exercise on cycling time-trial performance and associated physiological responses.

Purpose of the Study:

• To investigate how prior exhaustive upper body exercise affects performance in a 4-km cycling time-trial (4-km TT).
• To assess the impact of preceding arm-crank exercise on neuromuscular fatigue following a 4-km TT.
• To examine physiological markers, including oxygen uptake, heart rate, EMG, and RPE, during the 4-km TT after arm-crank exercise.

Main Methods:

• Eight recreational cyclists completed a 4-km TT under two conditions: with (ARM_PRE) and without (CONTR) a preceding arm-crank maximal incremental test.
• Neuromuscular fatigue was assessed using maximal voluntary isometric contractions (MVC) and electrically evoked contractions.
• Physiological data, including oxygen uptake (O2), heart rate, electromyographic muscle activity (EMG_RMS), and rating of perceived exertion (RPE), were continuously monitored.

Main Results:

• Cycling performance in the 4-km TT was significantly reduced in the ARM_PRE condition (382 ± 28 s) compared to CONTR (376 ± 27 s).
• Average power output during the 4-km TT was lower in ARM_PRE (299 ± 59 W) versus CONTR (310 ± 59 W).
• No significant differences in neuromuscular fatigue markers (MVC, voluntary activation, twitch force) or physiological responses (O2, EMG_RMS) were observed between conditions; however, the rate of RPE change was higher in ARM_PRE.

Conclusions:

• Impaired cycling performance following exhaustive upper body exercise is primarily attributed to an increased perception of effort, not peripheral neuromuscular fatigue.
• The findings suggest that central factors, such as perceived exertion, play a significant role in performance decrements after concurrent exercise.
• These results have implications for designing training programs that minimize the negative impact of combined upper and lower body exertion on endurance performance.