Far infrared therapy speeds muscle recovery after a workout, and improves muscle performance during this recovery period.  Delayed onset muscle soreness (DOMS) is the soreness that you feel the day after an intense workout, or after using a new muscle group.  It is not due to the muscle damage itself, but to the inflammation that is triggered by the muscle damage.  Studies have shown that far infrared therapy during the recovery period decreases this inflammation, decreasing pain and soreness, speeding muscle recovery, and increasing muscle performance during the recovery period (1-3).

A study using mice demonstrated that following a period of muscle disuse, after the animals started using the muscles again, adding heat therapy increased muscle regrowth by 30% compared with the control group (8). Heat therapy has even been shown to increase muscle mass and protein content in the absence of physical exercise!  After just one hour of heat therapy, animals had increased muscle weight and protein content seven days later, compared to controls (9). 

Heat treatment prior to exercise has been shown to enhance the effects of exercise on muscle remodeling, increasing the protein content in muscles more than does exercise alone.  This has been demonstrated in an animals study (10) and a study of muscle cells in culture (11).  In the later, one group of muscle cells was put through cyclic stretching (simulating exercise), another group was treated with one hour of heat, and a third group was treated with one hour of heat followed by cyclic stretching.  Not only did the heat and stretching together result in the highest levels of muscle protein, but the effect was cumulative. The combination of heat followed by exercise increased protein production more than did either treatment alone (11).  Sauna alone, or before or after a workout can enhance muscle growth and strength.