Bruce Becker, a physician and research professor at Washington State University, recently remarked about warm-water immersion with an analogy. “You know when you come home from a long day at work and you’re stressed out?” he asks. “You want to sink into a hot bathtub and go, ‘Ahhh.’ I’m trying to figure out what the hell that ‘Ahhh’ is all about.”
Becker’s efforts focus on the benefits to the autonomic nervous system of soaking in water with a temperature of 102 degrees Fahrenheit. An individual’s autonomic nervous system helps him or her adapt to changes in environment and affects such vital functions as heart rate, digestion, respiration, salivation, circulation and even sexual arousal. While in a constant state of flux, its two subsystems — the sympathetic nervous system (which escalates under stress) and the parasympathetic nervous system (which promotes calm) — fall into balance when the body is immersed in warm water, according to Becker’s findings.
Hot Tubs Bring a “Balanced State”
That balanced state has been associated with a reduction in the risk of cardiovascular disease, improved memory, enhanced cognitive processes and increased concentration. “The autonomic nervous system responds to warm water immersion the same way it responds to meditation or a number of other relaxed states,” Becker says.
While such claims seem logical on the surface, there has been little scientific evidence to support them before now. “Spas have a perception of being used for fun and socializing,” says Chris Robinson, a division director for the Hot Tub Council. “That seems to be limiting their demographics and not promoting their full utility. We know, empirically, that spas make people feel better. They relax you, help you sleep better and provide benefits for sore muscles. But there has been no proof of that medically.”
That’s why Becker’s research at WSU’s National Aquatic & Sports Medicine Institute — funded with grants from the Hot Tub Council, the National Swimming Pool Foundation and AQUA’s parent company Athletic Business — is considered so important. Most of the current literature on immersion focuses on subjects in a supine floating position, rather than in the seated position that is more common in a spa.
Becker presented the initial results of his research at the World Aquatic Health Conference last October and expects to conduct related studies throughout 2010. Specifically, he plans to explore how long the autonomic nervous system remains balanced after warm-water immersion, as well as the effects of immersion on moods, cognitive function and memory.
“The technology to look at this easily, non invasively and in an aquatic environment has not been around all that long,” says Becker, NASMI’s director, whose interest in aquatic therapy dates back to the 1980s, when he started working with elite athletes through Nike’s Olympic Development Program.
“I’m a rehab doc by training, so I’ve used water as a rehab and recovery environment through much of my professional career and have been frustrated by the lack of supporting research to really document what’s happening. Do I know that it works? Yeah. Do I know why it works? No.”
The Hot Tub Experiment
In Becker’s experiment, three tubs filled with water — each large enough to hold as many as four adults — were housed in one of the research laboratories at NASMI headquarters. One by one, 16 college-age students and 16 adults between the ages of 45 and 64 took turns sitting for 24 minutes in each of the tubs during evaluation sessions conducted by Becker and his team of researchers in 2008 and 2009. Resting measurements of heart rate and blood pressure were taken to establish a baseline, and participants’ core body temperature, heart rate, blood pressure, pulse, circulatory functions and respiratory status were monitored during their immersion time in each tub. In between his or her immersions, the test subject would sit for 12 minutes outside of the water in order to reestablish the baseline.
The first tub was filled with 87-degree water. Any cooler than that, and people would start shivering, Becker says, “so we settled on a temperature that most people certainly wouldn’t define as cold. When you get into it, it doesn’t feel cold, but you’re sitting immobile. I participated in the study, and my teeth were chattering in about six minutes.”
The second tub contained what researchers referred to as a “neutral” temperature of 94 degrees, and the “hot” tub registered at 102 degrees, “which isn’t hot by the way some people set their hot tubs,” Becker says. “If you set the hot tub at 104 degrees, which is what most commercial facilities do, people are not able to stay in long enough to get the therapeutic benefits out of it that they could if you set it to a cooler temperature. In our study, most people really were pretty anxious to get out after 24 minutes. We tried going warmer than 102, and they just couldn’t stay in, or they got really lightheaded when they got out — if they managed to stay in for the entire time.”
The two age groups analyzed were chosen because of their healthy youthfulness, in the case of college students, and because middle-age adults have sympathetic and parasympathetic nervous systems that typically remain in a greater state of flux.
At his research’s most basic level, Becker and his colleagues found that immersion in warm water tends to reduce stress levels for all participants. The degree of stress reduced varied from subject to subject, but all of them responded in the same way.
Robinson, who also is the business manager for Lucite Acrylic Sheet, the division of Lucite International that makes surface material for residential spas, is simply pleased that Becker has gotten this far. “I’d like to think this is the beginning of a paradigm shift in the way people think about spas,” he says. “This promotes hot tub use for general therapy, and I think we can use that to help people realize how they can benefit more from the experience. The more of these general studies we can do, the better off the industry will be.”
Bruce Becker’s research at Washington State University may be the first of its kind to focus on how warm water affects the autonomic nervous system. But several other projects are seeking to help facility operators and users better understand water’s healing power.
Among the most significant development is a new aquatic rehabilitation component of the U.S. Army’s Wounded Warriors program. Mary Wykle, a Northern Virginia Community College professor who believes soldiers and athletes have similar rehab needs, is coordinating the program at Wounded Warrior Transition Units, which provide critical support to wounded soldiers and their families. Currently piloted at Fort Lewis, Wash., and Virginia-based Fort Eustis and Fort Belvoir, the aquatic element is expected to eventually involve as many as 10,000 soldiers and will include two phases. One will prepare the wounded for recovery from injuries, and the other will help them return to active duty or civilian life. Projected results include pain reduction, enhanced fitness, and improved range of motion, balance, and core and extremity strength.
While the program isn’t formally a research project, data will be gathered on participants’ progress by location, gender, age, rank and injury, and then compared to that of soldiers in traditional rehabilitation programs. “It’ll be interesting to see, as the results of that program begin to come in, whether or not there is an enhanced level of potential funding,” says Becker, a physician and WSU research professor who helped design the aquatics component for the Wounded Warriors program. “Obviously, the things that we’ve found with warm-water immersion may be profoundly helpful in post-traumatic stress disorder.”