You Should Wear A Rash Guard
If you participate in combat sports or martial arts involving body-on-body contact, you should wear a rash guard. Why? A rash guard provides a skin-to-object barrier and transports moisture away from the skin so it can evaporate. As such, wearing a rash guard is a matter of hygiene and common courtesy.
Hygiene
Moisture trapped on the skin can cause rashes, irritation, and harbor bacteria. Sweat is a culture medium that fosters the growth and transmission of bacteria, fungi, and viruses easily transferred through skin-to-skin contact, with high transmissibility through open wounds (Mayo Clinic, 2022). While sweat transfer between grapplers is unavoidable, a quality rash guard is an additional barrier to prevent abrasions and open wounds, reducing the risk of transmitting pathogens. A properly constructed rash guard, described below, also transports moisture away from the skin where it can evaporate, reducing foul odors. The science is abundant and clear, and countless sports medicine professionals agree that athletes should wear moisture-wicking apparel to prevent the spread of pathogens (Bracker, 2012; Rippe, 2019; Schwellnus, 2008).
Common Courtesy
Despite the prevalence and transmissibility of pathogens, many grapplers refuse to take proper precautions. No serious jiu-jitsu student wants other students’ sweaty bodies rubbed on them in a way that could be easily prevented if students wore rash guards. Believing otherwise is selfish and disrespectful, regardless of whether the class is gi or no-gi. This applies to women, as well. Contrary to some of the most prominent female jiu-jitsu influencers, a sports bra, worn alone or under a gi, is no substitute for a rash guard.
Furthermore, many gyms, if not most, have children observing the training and young teenagers participating in the class. Would a parent want their 13-year-old boy grappling with an adult female wearing nothing but a sports bra? Would a parent want their 13-year-old girl grappling with an adult male without a shirt? Some parents would be unbothered, but many, if not most, would be uncomfortable. Wearing a rash guard is a simple and appropriate correction that would make everyone feel comfortable and welcome.
Moreover, men, do you really want to rub your nipples all over another grappler’s face in class? If so, plenty of activities would be appropriate for you; perhaps jiu-jitsu is not one of them.
Pro Tip: Cotton t-shirts are no substitute for a rash guard.
Although a t-shirt satisfies the visual and physical barrier requirements, cotton is a very poor textile fiber choice for grapplers. Cotton fabric is highly hydrophilic; in other words, it absorbs and holds moisture efficiently and capably. This is because cotton has a high “regain value,” a percentage rate of absorption increasing the mass of the fabric. Cotton has a regain value of 8.5%, whereas polyester has a regain value of only 0.4%. In practice, a dry, 100-gram layer of cotton fabric would gain 8.5 grams of moisture if saturated and a 100-gram layer of polyester material would gain less than half of a gram (Rohrig, 2022; Priyalatha & Raja, 2018). Since sweat is a culture medium, a cotton shirt is nothing more than a wearable petri dish and a poor choice for grapplers.
Buyer’s Guide
Rash guards are not cheap and the market is flooded with options. Before purchasing, grapplers must understand the importance of composition and construction features.
Pro Tip: Purchase rash guards that are an 80% polyester blend with either nylon or spandex.
If grapplers seek to minimize the amount of moisture on the skin, 100% polyester fabric is best, right? Not exactly. A fabric that is too hydrophobic, having a very low regain value like polyester, will not transport moisture (Rohrig, 2022). In other words, while polyester will not absorb moisture, it does not move it either. Therefore, the best material for grapplers is a blend of textiles, with a strong bias towards fabrics with a low regain value. A polyester blend, with 80-95% polyester fabric combined with 5 - 20% nylon or spandex, creates a garment that will pull moisture from the skin and transport it away from the body, a process commonly marketed as “wicking.” The hydrophobic fabric pushes the sweat outward to the hydrophilic fabric, where it evaporates.
Performance apparel such as a rash guard must enable the athlete or trainee, not impede. In combat sports, the garment must be tight-fitting and stretched across the skin to conform to the contours of the body to prevent finger injuries and keep the garment in place. Once stretched, most fabrics cannot move moisture as efficiently; however, polyester blends retain consistent moisture movement properties when relaxed and stretched (Matusiak & Sukhbat, 2023).
Pro Tip: The GSM of a rash guard is an important number; to a point, bigger is usually better.
The weight of a garment is measured in grams per square meter (GSM), which reflects the amount of fabric used in the garment and not necessarily its thickness. Most rash guards are 150 to 250 GSM. In most cases, a higher GSM fabric will be more durable but that durability will come at a cost: weight. While higher GSM fabrics weigh more, especially when saturated, rash guards crafted from polyester blends manage moisture so efficiently that the perceived weight difference is negligible. As noted above, this is because polyester does not absorb sweat and polyester blends move sweat away from the body where it can evaporate.
Pro Tip: Rash guards with elastic waistbands and rubber hem are the S-Class Mercedes-Benz of rash guard design.
A skin-to-object barrier that protects the wearer from pathogens common to grappling is only effective if it remains in place during rigorous training. The elastic waistband reinforced with a rubber bead allows the rash guard to stay in place while training.
Pro Tip: Flatlock seams are essential.
A flatlock seam prevents chaffing and skin irritation. While a quality, good-fitting rash guard should not move excessively, flatlock stitching prevents irritation caused by seams rubbing on the skin. Since conventional seams require the two sections of fabric to overlap, the top layer of fabric acts as an abrasive on the skin. Flatlock seams require no such overlap, allowing the connected sections to glide freely.
Final Thoughts
- Think about yourself and others when selecting your training apparel.
- Rubbing nipples and dripping armpit sweat on people during training is unnecessary and gross.
- Rash guards are superior to cotton t-shirts in every way
- The composition and construction are critical knowledge prior to purchase. If a company is not fully transparent, shop elsewhere.
About the Author
Professor Brian Bowers is a Brazilian Jiu-Jitsu black belt under Professor Chris Popdan with over 13 years of experience. He is the professor of The Hangout Jiu-Jitsu Club in Indianapolis, Indiana, and a coach at the Franklin, Indiana, Jiu-Jitsu Club. Brian is a federal law enforcement officer and a physical tactics and firearms instructor for his agency. He was also a firearm, physical tactics, and search and seizure instructor at the Federal Law Enforcement Training Center, where he continues to serve as an adjunct instructor.
Having personally relied on jiu-jitsu techniques to protect his life, Brian advocates jiu-jitsu as essential knowledge for all law enforcement personnel. His dedication to this cause is evident in his involvement with the Federal Law Enforcement Officers Association 111 Project, a non-profit organization dedicated to the safety of law enforcement personnel through support, education, training, and information sharing.
Brian's commitment to his students goes beyond the mat. With a Master of Science in Business Management, he leverages his formal education to cultivate deep, meaningful relationships with his students. His selfless dedication to serving their needs is evident in his use of research from psychology and neuroscience to optimize learning in any discipline he teaches. Brian uses science-based principles to educate jiu-jitsu practitioners, law enforcement students, law enforcement instructors, and jiu-jitsu instructors through The Hangout Journal.
References
Bracker, M. D. (2012). The 5-minute sports medicine consult. Lippincott Williams & Wilkins.
Matusiak, M., & Sukhbat, O. (2023). Influence of stretching on liquid transport in knitted fabrics. Materials (Basel, Switzerland), 16(5), 2126.
Mayo Clinic. (2022, May 25). Staph infections - Symptoms & causes. Mayo Clinic.
Priyalatha, S., & Raja, D. (2018). A multi directional wicking instrument to measure wicking characteristics of fabrics under dynamic movements. Journal of The Institution of Engineers (India): Series E, 99(2), 209–218.
Rippe, J. M. (2019). Lifestyle medicine, third edition. CRC Press.
Rohrig, B. (2022). Don’t Sweat It: How Moisture-Wicking Fabrics Keep You Cool and Dry. ChemMatters Magazine.
Schwellnus, M. P. (2008). The Olympic Textbook of Medicine in Sport. Wiley-Blackwell.
