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The Latest in Water Fitness: Research Update

New science-based program trends are closing the gaps between young and old and between the underactive and the elite athlete.

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Melis “Mel” Edwards, MS, creator of the H.I.T. Method™ (Hydrofit Interval Training), has spent the past 20 years promoting water fitness training both for athletes and as an athlete herself. Edwards, group fitness instructor and director of admissions at Montana State University in Bozeman, Montana, has trained both professional and recreational athletes.

Case in point, Kelcie Nice, a 33-year-old Ironman® athlete and resource engineer, was training for her first Ironman when she developed a hip imbalance. Nice discovered Edwards and trained entirely in the water for 2 months until the problem was corrected. For the next 4 months until the race, she continued hydrotraining 2—3 times per week. “I’m now a lifetime proponent of water running and walking proof that it is not only a legitimate alternative to land running but could possibly even be the way to go,” she says. “There’s no doubt that [land] running, with the constant impact it delivers, is not easy on the body, no matter how addicting those endorphins may be.”

Water fitness has come a long way from its origin story of older women in shower caps having fun in the local pool. Ken Baldwin, director of education at Perform Better Australia, in Brisbane, says, “In Australia, aqua is the ‘go–to’ method of recovery for all Australian Football Rules teams—rugby and soccer. If they can’t get to a cold-water beach, they’ll go to an ice pool to do their walking and regeneration and recovery moves. All professional sporting teams are using water training from that perspective.” Experts agree that interest in deep water running and aquatic boot camp is increasing.

This article examines what’s new in aquatic training research, what’s changing in water fitness class demographics and which program trends are growing. Higher-intensity training and recovery continue to be popular throughout the fitness industry, and aquatic exercise provides options for both. If you’re looking to expand your training repertoire, check out this new wave of possibilities.

Research Update

Mounting research on the benefits of aquatic exercise is changing its image and supporting the claim that it helps people of all ages and ability levels. Before diving into the research, it’s good to review why water is a complementary training medium to weight-bearing, land-based activities. For more on this, see the sidebar “The Properties of Water.”

The gold standard in research is the randomized controlled trial, but owing to lack of funding, few such trials exist in aquatic research, according to experts. Mary E. Sanders, PhD, FACSM, adjunct professor/specialist in internal medicine at the University of Nevada, Reno, school of medicine, and adjunct professor at the university’s school of community health sciences, says, “Many of us would like to see [research] protocols described better by investigators, with more emphasis on studies that extend for longer periods of time… If a study is published in a scientific journal or presented at a scientific meeting with peer review, then it needs to be considered. Many studies have low numbers of exercisers, examine unrealistic exercises or do not take into consideration the properties of water, which perhaps may have changed their conclusions.”

Here are some of the newer findings related to aquatic training, as identified by researchers involved in peer-reviewed studies.

Aquatic training improves ability to perform activities of daily living (ADL). The effectiveness of functional aquatic training for older adults seems well-established. Older women who participated in 60–minute shallow–water exercise classes 3 days a week for 12 weeks performed better in land-based ADL, but did not improve balance (Sanders et al. 2016). The Golden Waves® program, used in this and other studies, has proved effective in all variables except for balance, which has had inconsistent results. Sanders notes that for balance improvement, water depth is critical and shallower is better. “When water is armpit depth, it seems there’s not enough gravity ground-force reaction to challenge balance somatosensory systems (feet),” she says. See the “Resources” sidebar for additional information.

Water fitness enhances muscular strength and endurance, and increases lean body mass. Evidence shows that people of all ages and ability levels can improve strength, endurance and body composition through effective aquatic training. Postmenopausal women who trained with aquatic resistance equipment twice a week for 10 weeks gained strength, reduced fat and increased lean body mass as effectively as women who used weight machines and exercise bands in equivalent land programs (Colado et al. 2012).

Fit young men who did a periodized strength training program 3 times a week for 12 weeks significantly improved muscular strength and power and increased lean body mass (Colado et al. 2009). Healthy, untrained older women who did 60 minutes of shallow–water exercise (including 20 minutes of upper- and lower-body resistance training with equipment) 3 days a week for 24 weeks increased lean body mass by 3.4% and significantly improved muscular strength (Tsourlou et al. 2006).

Water exercise can meet cardiovascular fitness metrics. New research is settling the debate about whether upright water training is an effective way to cross-rain for better cardiovascular fitness. Sanders points to recent research (she was a co-author) that showed that cardiovascular training in water is effective when appropriate protocols, speed and movements are employed. Unskilled healthy young women met ACSM ranges for cardiovascular training in a 40-minute shallow–water session while using resistance gloves. The “hover jog” achieved the greatest average intensity, at 7.3 METs (Nagle et al. 2013).

There’s a correlation between rating of perceived exertion and cardio variables. The properties of water affect heart rate. If you compare water training with land training at the same intensity, heart rate may be as much as 20% lower in the water and will vary from person to person (Haff 2008). Findings from multiple studies in both deep water and shallow water show a significant correlation between overall RPE and cardiorespiratory and neuromuscular variables (Pinto et al. 2015). For some people, RPE may be higher because they use anaerobic energy systems to power their arms and legs through water. Researchers note that it’s important to introduce and explain the RPE scale clearly to participants to ensure effective results.

Aquatic training improves balance and core stability. Balance and walking ability improved among older adults who trained in shallow water with resistance equipment for 90 minutes 3 times a week for 8 weeks (Katsura et al. 2009).

Water ameliorates running performance. In a study that compared electromyography (EMG) activity between dry–land and deep–water runners, researchers found similar but not identical muscle recruitment and concluded that, for healthy individuals, maximal velocity optimized neuromuscular responses in the legs (Alberton et al. 2015). Researchers noted that deep-water running (DWR) reduced ground-force impact by up to 85%.

Another study found that NCAA Division III cross-country athletes who wore aquatic training shoes during DWR achieved intensities closer to land–based runners than those who ran in the water barefoot. To complement land-based training, researchers also recommend wearing an aquatic training shoe to “heighten the perceptual and kinesthetic sense of running on land” (Killgore et al. 2010).

Water properties lead to less muscle soreness and damage. A study comparing high–intensity land- and water-based plyometrics programs found that training in water produced less inflammation and muscle soreness (Robinson et al. 2004).

A study designed to identify the mechanisms underlying this result compared the effects of resistance exercise in water and on land in young male subjects and found significantly less increase in creatine kinase—an indirect marker of muscle damage—from the water workout. Researchers concluded that water–based exercise is an appropriate choice for those who want to limit muscle damage (Pantoja et al. 2009).

Aquatic exercise lowers blood pressure. Postmenopausal women with hypertension who participated in a water aerobics training group for 12 weeks significantly reduced systolic blood pressure in an amount equal to women who participated in a comparable land-based training group. Control group members saw no drop in blood pressure (Arca et al. 2014).

Water fitness lowers blood sugar levels for people with type 2 diabetes. A recent study of 35 people with type 2 diabetes compared land-based training with aquatic exercise. All participants trained for 45 minutes 3 times a week for 12 weeks. Participants in both groups experienced a significant reduction in A1C levels—a measure of glucose control (Delevatti et al. 2016).

Exercise in the pool improves knee and hip osteoarthritis (OA). A Cochrane review of six randomized controlled studies found moderate-quality evidence that aquatic exercise may have small, short-term but clinically relevant effects on pain, disability and quality of life in people with knee and hip OA (Bartels et al. 2016).

More Participants and Changing Demographics

Program directors report that most water fitness classes still serve active older adults. At the same time, programs for young and middle-aged adults, special populations, and recreational and elite athletes are increasing. This reflects the expanded interest in water exercise. Julie See, director of education for the Aquatic Exercise Association in Nokomis, Florida, says, “AEA has seen a 20% increase in membership since 2012 and a 30% increase in education, live and online educational programs since 2012.”

Experts agree that, like land-based programming, water fitness is not “one size fits all,” and niche programs are stimulating transformation by appealing to specific interests and demographic groups. Social media campaigns are also raising awareness among younger generations.

Younger and Middle-Aged Adults

Historically a group fitness schedule may have offered water aerobics and a “Twinges in the Hinges” class, but today’s water fitness program exhibits the same variety you find in land–based programming. Ann Gilbert, master trainer for WATERinMOTION®, in Tampa Bay, Florida, says, “The aquatic student today is younger than in the past . . . and thrives on the variety of class formats offered. [He or she wants] to train in all aspects of fitness—including cardio, dynamic strength, boot camps, martial arts and the mind-body connection.”

Recreational and Elite Athletes

Athletes typically enter the pool only when they need rehabilitation from an injury. However, while in–pool rehab and prehab therapeutic trainings continue to grow, more collegiate and professional athletic coaches are seeing value in cross–training in water as a regular off- and on-season method. In addition, as events like triathlons, marathons, biathlons and Tough Mudder® competitions expand in popularity, more recreational athletes are looking to the pool to cross-train. See the sidebar “Why Healthy Athletes Need Water Training” for more.

Manuel Velasquez, movement lead instructor and department coordinator at Rancho La Puerta Resort & Spa, Tecate, Mexico, says, “Coaches that post pictures and stat results [on Facebook and Instagram] about combining water training with other HIIT land-based programs to increase agility, performance and strength are raising awareness among young fitness enthusiasts and athletes.” The “Resources” sidebar includes links to equipment options that target more athletic enthusiasts.

Special Populations

Research continues to substantiate the benefits of aquatic training for people with chronic conditions, and more people are coping with these issues. Consequently, allied medical organizations and healthcare professionals are recommending water exercise as a disease management tool.

“The AEA is now managing the Arthritis Foundation Aquatic Program to train program leaders to offer this structured program within the community and assist those living with arthritis and related conditions to include exercise as part of a healthy lifestyle,” says See.

Other special populations for whom water exercise is popular include people with type 2 diabetes, people with fibromyalgia, and those coping with disabilities that impair walking or balance—and therefore make land-based activities more challenging. “Our disabled participants improved their cardiovascular fitness and ADL to the point where their new mobility skills allowed them to live more independently,” says Sanders. “Time in water using the WaterFit® program led to significant quality–of–life changes that have persisted.”

Pool-based training is ideal for those who want to avoid excessive impact, overheating or elevated heart rates. These participants include people who’ve had joint replacements, those dealing with heart disease, prenatal and postpartum mothers, and aging athletes who are coping with a lifetime of wear and tear on joints.

Program Trends and New Training Options

Across the fitness industry, the focus is on higher-intensity trainings and recovery. Technological improvements are also expanding training options and equipment. Here’s a sampling of these influences on water fitness trends.

Aquatic bootcamp, HIIT and boxing. Experts note an increase in both deep– and shallow-water high-intensity interval training classes, as well as boxing and kickboxing formats. Irene Lewis–McCormick, MS, SCW certification faculty, of Des Moines, Iowa, says, “Aqua boot–camp circuit is my favorite time–based station workout.” She also teaches deep-water Tabata™. Carrie Haines, a personal trainer in Truckee, California, teaches aqua Tabata, an offering that draws a younger crowd, while deep-waterfitness attracts more men and athletes. See the sidebar “Adapt HIIT to the Water” for more.

Dance and barre. Land-based trends like yoga and Pilates continue to cross over and proliferate in the pool. Aqua Zumba® and barre-based classes are spreading, too. “I took barre to the water,” says Haines, a master trainer for Barre Above™. “Initially, it drew an older crowd, but now, since barre is so hot, it’s becoming more popular in general.”

Surf and turf. Sanders notes that more programs are blending water and land. “Mixing activities to avoid injury and burnout is good for long-term adherence,” she says. “People can increase the volume of exercise without increasing injury risk, and they can perform cardio-resistive exercises in one time-efficient HIIT session. Our studies showed that even when only one water session was added to a regular exercise program, ADL improved significantly. More sessions were better, but even one made a difference.”

Gilbert coached a local marathon walking team that included 18 weeks of on-road training and 4-week offseason pool trainings that consisted of water walking and aquatic strength training. Velasquez offered a “Mindful Triathlon” combining 30 minutes of hiking, 30 minutes of indoor cycling and 30 minutes of water fitness, to expose participants to activities they might not otherwise have tried.

Personal training. Both Baldwin and Edwards see an increase in demand for personal training and combine land- and water-based protocols to help clients succeed. “What’s missing is an explanation of ‘why’ people need to do the exercises,” says Baldwin. “If you can show clients that they can get the results they want with less strain and impact [in the water], they will do it.”

Edwards gives water exercise more credibility by emphasizing her own athletic experience—this helps clients accept what water workout can do. “Otherwise, I do not see the person again, as the first workout is usually not as intense [as it would be on land, because people first need to] learn how to do the moves.”

Equipment options. Training tools such as waterproof kettlebells and medicine balls, underwater treadmills, hot and cold plunge pools, and small pools with movable floors that allow for different training depths and have jets to create currents for overload are prompting more coaches to cross–train athletes in water.

In a HydroWorx® white paper, Alberto Salazar, head coach of the Nike Oregon Project, writes, “We don’t consider [using an underwater treadmill] an alternative to running outside. We consider it as important as running outside. It helps us become stronger by running against the resistance of the water, and it helps us recover from our dry land training.”

“Trending equipment-focused classes include trampolines, vertical poles for supporting the body in dance as well as strength moves, in-water boxing bags, underwater bikes and indoor standup paddleboards,” says See.

The Future of Water Fitness

Experts agree that water fitness is positioned for significant growth owing to changing demographics, improved equipment options and greater public awareness. “With renewed interest in HIIT, CrossFit® and other types of intense workouts, the time is ripe for program directors and fitness pros to give deep-water interval training another look,” Edwards observes.

Velasquez adds: “When attention is given to programming, scheduling and instructor education, [water fitness] turns around retention, referrals and overall customer satisfaction.” Since pool training offers a friendly, fun environment that promotes relationships, Lewis-McCormick thinks more fitness pros should tap into the strength of the “fitness tribe” that naturally emerges in pool classes. Instructors should bring successful classes to the attention of directors and managers.

At the same time, experts agree that education is key. “To bridge into medical fitness and broaden programs to include athletes and special pops, instructor education should be designed with respect to evidence–supported protocols,” says Sanders. As usual, personal trainers should conduct pre-; and posttraining assessments to encourage participants and validate progress. More allied healthcare professionals and athletic trainers will refer clients for aquatic training, and fitness pros need to be ready. A new era of water fitness is here.


Fitness professionals need to understand water’s unique properties in order to design effective training programs for the pool. Exercises that work on land do not translate directly to water. Factors affecting results include not only water’s distinct properties but also training depth and temperature. Here’s a brief review of the physiological effects of vertical immersion in water:

Buoyancy. Water exerts an upward thrust on immersed objects equal to the weight of fluid displaced. Depending on a person’s body composition, shape, bone density and immersion depth, this force varies. At xiphoid level, gravity decreases approximately 60%. In deep water, total body weight may drop by 85%—90%.

Hydrostatic pressure. Immersion exerts pressure on all surface areas below water, making lung expansion and breathing more difficult. This pressure enhances venous return and stimulates the lymphatic system. Cardiac volume increases up to 30% with neck–level immersion, leading to a 35% mean stroke–volume increase at rest. In neutral temperatures (33.5°—35.5°C), the heart rate response is typically 12%—15% less; in warm water (36°—38°C), the response is higher. At chest depth, the total work of breathing increases by approximately 60%, especially during inhalation.

Viscosity. Water is approximately 800 times “thicker” than air, and movement creates resistance. Drag forces, movement speed, turbulence, lever length and equipment can all be used to manipulate resistance levels. Resistance increases exponentially as more force is applied. Resistance to an average speed in water is approximately 12—15 times that of the same movement in air. Varying movement speed and surface area in water facilitates progressions as skill and fitness levels improve.

Thermodynamics. Water transfers heat 25 times faster than air. This affects heart rate and oxygen consumption. Warm–water (30°—35.5°C) training and land training produce similar heart rate responses. Cycling or running in cool to cold water (18°—25°C) results in heart rates that are 10—15 beats per minute lower than on land. For higher–intensity workouts, water temperature needs to be considered.

Sources: Alberton et al. 2015; Nagle, Sanders & Franklin 2015; Sanders 2000.


Studies show that HIIT workouts can be effective for clinical, apparently healthy and athletic participants. Mary Sanders, PhD, FACSM, offers the following research–based tips on how to modify HIIT for the pool to create safe, effective workouts:

  1. Use RPE, rather than HR, to determine exercise intensity.
  2. Increase intensity by changing body positions, changing upper– and lower–limb actions, increasing the speed and surface area of movements, or adding equipment such as gloves, paddles, bands or other resistive devices.
  3. Try intervals based on the 15:15:15 system, using speed and range of motion. During the first 15 seconds, develop the movement size and start the currents; go hard for the next 15 seconds; then, go slowly during the last 15 seconds. Recover and change the move.
  4. Have healthy and athletic populations perform shorter intervals (10—15 seconds) at extremely high intensities, followed by longer rest periods, to target the ATP and anaerobic glycolytic systems. Use longer intervals (30 seconds—2 minutes) performed at >70%—95% of heart rate maximum, with brief rest periods (1:1 or less), to challenge the aerobic system and increase energy expenditure in these populations.
  5. Prescreen clinical populations before they engage in any high–intensity activities. Make sure they have the skills to align and stabilize their bodies in water.

Source: Nagle et al. 2013.


Experts agree that more athletes are turning to the pool. Melissa Layne, MEd, assistant professor of kinesiology at the University of North Georgia, Dahlonega, Georgia, says, “The UNG [women’s] basketball team trains in water. During preseason, the aqua environment is used for cross–training to prevent overuse injuries during an intense training period. Currently, during season, it’s used for rehabilitation only.” Experts note that pool training can also be effective in the offseason. Alert your athletes to the many ways they can benefit from water training:


  • Reduce overuse injuries.


    1. The repetitive stress of intense, specialized training contributes to overuse injuries. Depending on water depth, aquatic training can reduce impact up to 85%, resulting in less stress and reducing the likelihood of injury.


    1. Supplement land training. Many land moves can be mimicked in water, and clients can practice movement patterns without worrying about impact. Shallow water is beneficial for vertical jump training; transitional depths are good for racquet sports training; and deep water is valuable for long–distance run training.


    1. Add variety or overcome training plateaus. Water provides resistance in multiple planes of movement, allowing for new types of overload. Working in a different environment reduces boredom and adds fresh challenges.


    1. Increase muscle strength. Cardiovascular and muscle endurance training can occur concurrently in the water. Correct training techniques and equipment make it possible to build strength.


    1. Supplement speed and sports training. Coaches can teach sport–specific moves in the water. Aquatic training improves core muscle recruitment to stabilize the body against the water’s forces.


  1. Facilitate postworkout recovery. The hydrostatic pressure from immersion increases circulation, reduces swelling and enhances recovery. Water training provides a comfortable environment for active–rest workouts.

Sources: Coutts & Sirotic 2004; Haff 2008; HydroWorx (undated).


To learn more, check out the following resources:


Edwards, M., & Wight, K. 2017. Deep End of the Pool Workouts: No–Impact Interval Training and Strength Exercises. Berkeley, CA: Ulysses Press.

Layne, M. 2015. Water Exercise. Champaign, IL: Human Kinetics.


Available at http://www.healthylearning.com:

Sanders, M., 2017. WaterFit® Shallow Water Training.

Sanders, M., & Maloney–Hills, C. 1998. The Golden Waves®, Functional Water Training for Health.


Aquatic Exercise Association, http://www.aeawave.com/.

Aquatic Therapy University, http://aquatic–therapy–university.com/.

International Council on Active Aging, www.icaa.cc.

National Swimming Pool Foundation, www.nspf.org/.

WaterFit™, www.waterfit.com/.


Acquapole®, www.acquapole.com/en/.

Aqua Stand Up®, www.aquastandup.com/.

Hydrorider®, www.hydroriderusa.com/.

HydroWorx®, includes many research links, www.hydroworx.com.


Alberton, C., et al. 2015. Kinesiological analysis of stationary running performed in aquatic and dry land environments. Journal of Human Kinetics, 49, 5–14.

Arca, E., et al. 2014. Aquatic exercise is as effective as dry land training to blood pressure reduction in postmenopausal hypertensive women. Physiotherapy Research International, 19 (2), 93–98.

Bartels, E., et al. 2016. Aquatic exercise for the treatment of knee and hip osteoarthritis. Cochrane Database of Systematic Reviews. doi: 10.1002/14651858.CD005523.pub3.

Colado, J., et al. 2009. Effects of a short–term aquatic resistance program on strength and body composition in fit young men. Journal of Strength & Conditioning Research, 23 (2), 549–59.

Colado, J., et al. 2012. Effects of aquatic and dry land resistance training devices on body composition and physical capacity in postmenopausal women. Journal of Human Kinetics, 32 (May), 185–95.

Coutts, A., & Sirotic, A. 2004. Post–match recovery for team sport athletes. Sports Coach, 27 (2), 1–4.

Delevatti, R., et al. 2016. Glucose control can be similarly improved after aquatic or dry–land aerobic training in patients with type 2 diabetes: A randomized clinical trial. Journal of Science and Medicine in Sport, 19 (8), 688–93.

Haff, G. 2008. Athletic cross training for athletes: Part 11. Strength & Conditioning Journal, 30 (3), 67–73.

HydroWorx. Undated. How to Use Hydrotherapy to Train Your Athletes. Accessed Feb. 25, 2017. www.hydroworx.com/research–education/research/.

Katsura, Y., et al. 2009. Effects of aquatic exercise training using water–resistance equipment in elderly. European Journal of Applied Physiology, 108 (5), 957–64.

Killgore, G., et al. 2010. A comparison of the physiological exercise intensity differences between shod and barefoot submaximal deep–water running at the same cadence. Journal of Strength and Conditioning Research, 24 (12), 3302–12.

Nagle, E., et al. 2013. Energy expenditure, cardiorespiratory, and perceptual responses to shallow–water aquatic exercise in young adult women. The Physician and Sportsmedicine, 41 (3), 67–76.

Nagle, E., Sanders, M., & Franklin, B. 2015. Aquatic high intensity interval training for cardiometabolic health: Benefits and training design. American Journal of Lifestyle Medicine, 11 (1).

Pantoja, P., et al. 2009. Effect of resistive exercise on muscle damage in water and on land. Journal of Strength and Conditioning Research, 23 (3), 1051–54.

Pinto, S., et al. 2015. Rating of perceived exertion and physiological responses in water–based exercise. Journal of Human Kinetics, 46, 99–108.

Robinson, L., et al. 2004. The effects of land vs. aquatic plyometrics on power, torque, velocity, and muscle soreness in women. Journal of Strength and Conditioning Research, 18 (1), 84–91.

Sanders, M. (Ed.). 2000. YMCA Water Fitness for Health. Champaign, IL: Human Kinetics for the YMCA of the USA.

Sanders, M., et al. 2016. Aquatic exercise for better living on land: Impact of shallow–water exercise on older women for performance of activities of daily living (ADL). International Journal of Aquatic Research and Education, 10 (1), 1–19.

Tsourlou, T., et al. 2006. The effects of a twenty–four–week aquatic training program on muscular strength performance in healthy elderly women. Journal of Strength and Conditioning Research, 20 (4), 811–18.

Shirley Archer-Eichenberger, JD, MA

Shirley Archer, JD, MA, is an internationally acknowledged integrative health and mindfulness specialist, best-selling author of 16 fitness and wellness books translated into multiple languages and sold worldwide, award-winning health journalist, contributing editor to Fitness Journal, media spokesperson, and IDEA's 2008 Fitness Instructor of the Year. She's a 25-year industry veteran and former health and fitness educator at the Stanford Prevention Research Center, who has served on multiple industry committees and co-authored trade books and manuals for ACE, ACSM and YMCA of the USA. She has appeared on TV worldwide and was a featured trainer on America's Next Top Model.

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