Which of the following is a benefit of regular massage therapy?

Regular massage therapy offers a wide range of benefits that contribute to overall physical and mental well-being. One of the key advantages is improved flexibility. The techniques used in massage, such as stretching and manipulation of soft tissues, can help to lengthen muscles and improve the range of motion in joints. This can be particularly beneficial for athletes or individuals engaging in regular physical activity.

Another notable benefit is reduced stress levels. Massage therapy promotes relaxation by stimulating the body's parasympathetic nervous system, which counteracts the stress response. This can lead to a decrease in levels of the stress hormone cortisol, as well as an increase in feelings of well-being through the release of endorphins.

Increased muscle mass, while not typically the primary focus of massage therapy, can also result indirectly from the improved circulation and muscle recovery that massage facilitates, thus allowing for better performance in resistance training and subsequent growth.

Considering all these benefits together, regular massage therapy indeed contributes positively to flexibility, stress reduction, and potentially even muscle mass. Thus, the option stating all of the above encapsulates the comprehensive benefits that come from regular massage sessions, making it the correct choice.