Passive thigh heating improves isokinetic but not isotonic muscle function

Area of Science:

• Exercise Physiology
• Muscle Physiology
• Therapeutic Interventions

Background:

• Optimal skeletal muscle function is temperature-dependent, with elevated tissue temperatures above resting levels enhancing performance.
• Understanding the efficacy and reliability of passive heating interventions is crucial for optimizing muscle function.

Purpose of the Study:

• To examine the effects of passive thigh heating on muscle torque production and maximal velocity.
• To determine the reliability of using passive heating as an intervention to improve muscle function.

Main Methods:

• Twenty active young adults (10 female) underwent two identical experimental sessions.
• One thigh was heated using a water-perfused garment circulating 50°C water for 90 minutes.
• Muscle function (isokinetic and isotonic) was assessed at various speeds every 30 minutes, alongside vastus lateralis muscle temperature measurements.

Main Results:

• Passive heating significantly increased muscle temperature from baseline (32.2°C to 36.8°C at 30 min).
• Peak torque increased during moderate and fast isokinetic contractions (p < .05) from 30 min onwards in the heated limb.
• Rate of force and early force production during slow contractions increased by 14% and 15% respectively in the heated leg, with excellent reliability (ICC > 0.9) observed for muscle function.

Conclusions:

• Passive heating is an effective intervention for improving skeletal muscle peak torque during moderate and fast contractions.
• The intervention reliably enhances early force production in slow-speed contractions.
• Elevating muscle temperature through passive heating can optimize muscle function for performance.