Effects of Caffeine on Voluntary Force Estimation During Isometric Exercises

Area of Science:

• Exercise Physiology
• Sports Science
• Nutritional Supplementation

Background:

• Caffeine is a common ergogenic aid for strength.
• Its impact on perceptual accuracy in submaximal isometric force regulation is not well understood.
• This is especially true for complex, multi-joint isometric exercises.

Purpose of the Study:

• To investigate caffeine's effect on maximal isometric force production.
• To determine if caffeine influences the accuracy of voluntary submaximal force estimation.
• To examine these effects during multi-joint isometric exercises like the squat and mid-thigh pull.

Main Methods:

• A randomized, double-blind, placebo-controlled crossover design.
• Seventeen recreationally trained participants ingested caffeine (4 mg·kg^-1) or placebo.
• Maximal voluntary contractions and submaximal efforts (50%, 75% perceived maximal force) were assessed during isometric squat and mid-thigh pull tests.

Main Results:

• Caffeine did not significantly alter maximal isometric force production.
• Caffeine ingestion did not enhance the accuracy of submaximal force estimation.
• Participants tended to overproduce force, especially at lower intensities, indicating consistent estimation errors.

Conclusions:

• A 4 mg·kg^-1 dose of caffeine does not improve maximal isometric strength or perceptual accuracy in multi-joint tasks.
• Reliance on perceived effort alone for prescribing isometric exercise intensity may be unreliable, particularly at lower levels.
• The isometric mid-thigh pull demonstrated better force regulation accuracy compared to the isometric squat.