Research indicates that for injuries, you should not keep heat on an area for more than 15-20 minutes. For muscle recovery, 10 minutes is closer to the ideal timeframe.
Conceptual framework for the mechanistic basis underlying the
Ice or Heat: How to Determine the Best Way to Treat an Injury
Ice Pack - Hot and Cold Therapy Reusable Gel Packs Helps Alleviate
Listed with ExportYourStore.com
SomaCare Sport & Back Hot Pack - Pain Relief, Reusable for Neck, Shoulders & Joint Pain, Ease to Use, Click to Activate, Advanced Hot Therapy - Muscle
A hot tub for bigger muscles?
Ice vs. Heat - Muscle Pain - Which is Best?
Benefits of heat and cold therapy
Weiyou Cryo Heating Iceless Therapy System Machine for Recovery
Key benefits of heat therapy for back pain
Exploring the Science of Muscle Recovery - NASM
Recovery Wrap with Ice/Heat/Compression – by Spand-Ice
Is hot or cold better for sore muscles? - CNET
Hot or Cold Shower Post-Workout? There Are Benefits to Each - GoodRx